SLAS990E January   2014  – October 2017 LM15851

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Internal Characteristics
    8. 6.8 Switching Characteristics
    9. 6.9 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Signal Acquisition
      2. 7.3.2 The Analog Inputs
        1. 7.3.2.1 Input Clamp
        2. 7.3.2.2 AC Coupled Input Usage
        3. 7.3.2.3 DC Coupled Input Usage
        4. 7.3.2.4 Handling Single-Ended Input Signals
      3. 7.3.3 Clocking
      4. 7.3.4 Over-Range Function
      5. 7.3.5 ADC Core Features
        1. 7.3.5.1 The Reference Voltage
        2. 7.3.5.2 Common-Mode Voltage Generation
        3. 7.3.5.3 Bias Current Generation
        4. 7.3.5.4 Full Scale Range Adjust
        5. 7.3.5.5 Offset Adjust
        6. 7.3.5.6 Power-Down
        7. 7.3.5.7 Built-In Temperature Monitor Diode
      6. 7.3.6 Digital Down Converter (DDC)
        1. 7.3.6.1 NCO/Mixer
        2. 7.3.6.2 NCO Settings
          1. 7.3.6.2.1 NCO Frequency Phase Selection
          2. 7.3.6.2.2 NCO_0, NCO_1, and NCO_2 (NCO_x)
          3. 7.3.6.2.3 NCO_SEL Bits (2:0)
          4. 7.3.6.2.4 NCO Frequency Setting (Eight Total)
            1. 7.3.6.2.4.1 Basic NCO Frequency-Setting Mode
            2. 7.3.6.2.4.2 Rational NCO Frequency Setting Mode
          5. 7.3.6.2.5 NCO Phase-Offset Setting (Eight Total)
          6. 7.3.6.2.6 Programmable DDC Delay
        3. 7.3.6.3 Decimation Filters
        4. 7.3.6.4 DDC Output Data
        5. 7.3.6.5 Decimation Settings
          1. 7.3.6.5.1 Decimation Factor
          2. 7.3.6.5.2 DDC Gain Boost
      7. 7.3.7 Data Outputs
        1. 7.3.7.1 The Digital Outputs
        2. 7.3.7.2 JESD204B Interface Features and Settings
          1. 7.3.7.2.1  Scrambler Enable
          2. 7.3.7.2.2  Frames Per Multi-Frame (K-1)
          3. 7.3.7.2.3  DDR
          4. 7.3.7.2.4  JESD Enable
          5. 7.3.7.2.5  JESD Test Modes
          6. 7.3.7.2.6  Configurable Pre-Emphasis
          7. 7.3.7.2.7  Serial Output-Data Formatting
          8. 7.3.7.2.8  JESD204B Synchronization Features
          9. 7.3.7.2.9  SYSREF
          10. 7.3.7.2.10 SYNC~
          11. 7.3.7.2.11 Code-Group Synchronization
          12. 7.3.7.2.12 Multiple ADC Synchronization
    4. 7.4 Device Functional Modes
      1. 7.4.1 DDC Modes
      2. 7.4.2 Calibration
        1. 7.4.2.1 Foreground Calibration Mode
        2. 7.4.2.2 Background Calibration Mode
      3. 7.4.3 Timing Calibration Mode
      4. 7.4.4 Test-Pattern Modes
        1. 7.4.4.1 Serializer Test-Mode Details
        2. 7.4.4.2 PRBS Test Modes
        3. 7.4.4.3 Ramp Test Mode
        4. 7.4.4.4 Short and Long-Transport Test Mode
        5. 7.4.4.5 D21.5 Test Mode
        6. 7.4.4.6 K28.5 Test Mode
        7. 7.4.4.7 Repeated ILA Test Mode
        8. 7.4.4.8 Modified RPAT Test Mode
    5. 7.5 Programming
      1. 7.5.1 Using the Serial Interface
        1. 7.5.1.1 Streaming Mode
    6. 7.6 Register Map
      1. 7.6.1 Memory Map
      2. 7.6.2 Register Descriptions
        1. 7.6.2.1 Standard SPI-3.0 (0x000 to 0x00F)
          1. 7.6.2.1.1 Configuration A Register (address = 0x000) [reset = 0x3C]
          2. 7.6.2.1.2 Configuration B Register (address = 0x001) [reset = 0x00]
          3. 7.6.2.1.3 Device Configuration Register (address = 0x002) [reset = 0x00]
          4. 7.6.2.1.4 Chip Type Register (address = 0x003) [reset = 0x03]
          5. 7.6.2.1.5 Chip Version Register (address = 0x006) [reset = 0x13]
          6. 7.6.2.1.6 Vendor Identification Register (address = 0x00C to 0x00D) [reset = 0x0451]
        2. 7.6.2.2 User SPI Configuration (0x010 to 0x01F)
          1. 7.6.2.2.1 User SPI Configuration Register (address = 0x010) [reset = 0x00]
        3. 7.6.2.3 General Analog, Bias, Band Gap, and Track and Hold (0x020 to 0x02F)
          1. 7.6.2.3.1 Power-On Reset Register (address = 0x021) [reset = 0x00]
          2. 7.6.2.3.2 I/O Gain 0 Register (address = 0x022) [reset = 0x40]
          3. 7.6.2.3.3 IO_GAIN_1 Register (address = 0x023) [reset = 0x00]
          4. 7.6.2.3.4 I/O Offset 0 Register (address = 0x025) [reset = 0x40]
          5. 7.6.2.3.5 I/O Offset 1 Register (address = 0x026) [reset = 0x00]
        4. 7.6.2.4 Clock (0x030 to 0x03F)
          1. 7.6.2.4.1 Clock Generator Control 0 Register (address = 0x030) [reset = 0xC0]
          2. 7.6.2.4.2 Clock Generator Status Register (address = 0x031) [reset = 0x07]
          3. 7.6.2.4.3 Clock Generator Control 2 Register (address = 0x032) [reset = 0x80]
          4. 7.6.2.4.4 Analog Miscellaneous Register (address = 0x033) [reset = 0xC3]
          5. 7.6.2.4.5 Input Clamp Enable Register (address = 0x034) [reset = 0x2F]
        5. 7.6.2.5 Serializer (0x040 to 0x04F)
          1. 7.6.2.5.1 Serializer Configuration Register (address = 0x040) [reset = 0x04]
        6. 7.6.2.6 ADC Calibration (0x050 to 0x1FF)
          1. 7.6.2.6.1 Calibration Configuration 0 Register (address = 0x050) [reset = 0x06]
          2. 7.6.2.6.2 Calibration Configuration 1 Register (address = 0x051) [reset = 0xF4]
          3. 7.6.2.6.3 Calibration Background Control Register (address = 0x057) [reset = 0x10]
          4. 7.6.2.6.4 ADC Pattern and Over-Range Enable Register (address = 0x058) [reset = 0x00]
          5. 7.6.2.6.5 Calibration Vectors Register (address = 0x05A) [reset = 0x00]
          6. 7.6.2.6.6 Calibration Status Register (address = 0x05B) [reset = undefined]
          7. 7.6.2.6.7 Timing Calibration Register (address = 0x066) [reset = 0x02]
        7. 7.6.2.7 Digital Down Converter and JESD204B (0x200-0x27F)
          1. 7.6.2.7.1  Digital Down-Converter (DDC) Control Register (address = 0x200) [reset = 0x10]
          2. 7.6.2.7.2  JESD204B Control 1 Register (address = 0x201) [reset = 0x0F]
          3. 7.6.2.7.3  JESD204B Control 2 Register (address = 0x202) [reset = 0x00]
          4. 7.6.2.7.4  JESD204B Device ID (DID) Register (address = 0x203) [reset = 0x00]
          5. 7.6.2.7.5  JESD204B Control 3 Register (address = 0x204) [reset = 0x00]
          6. 7.6.2.7.6  JESD204B and System Status Register (address = 0x205) [reset = Undefined]
          7. 7.6.2.7.7  Overrange Threshold 0 Register (address = 0x206) [reset = 0xF2]
          8. 7.6.2.7.8  Overrange Threshold 1 Register (address = 0x207) [reset = 0xAB]
          9. 7.6.2.7.9  Overrange Period Register (address = 0x208) [reset = 0x00]
          10. 7.6.2.7.10 DDC Configuration Preset Mode Register (address = 0x20C) [reset = 0x00]
          11. 7.6.2.7.11 DDC Configuration Preset Select Register (address = 0x20D) [reset = 0x00]
          12. 7.6.2.7.12 Rational NCO Reference Divisor Register (address = 0x20E to 0x20F) [reset = 0x0000]
          13. 7.6.2.7.13 NCO Frequency (Preset x) Register (address = see ) [reset = see ]
          14. 7.6.2.7.14 NCO Phase (Preset x) Register (address = see ) [reset = see ]
          15. 7.6.2.7.15 DDC Delay (Preset x) Register (address = see ) [reset = see ]
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 RF Sampling Receiver
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
    3. 8.3 Initialization Set-Up
      1. 8.3.1 JESD204B Startup Sequence
    4. 8.4 Dos and Don'ts
      1. 8.4.1 Common Application Pitfalls
  9. Power Supply Recommendations
    1. 9.1 Supply Voltage
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Management
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
      3. 11.1.3 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Community Resource
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Detailed Description

Overview

The LM15851 device is an ultra-wideband sampling and digital tuning subsystem. The device combines a very-wideband and high sampling-rate ADC front-end with a configurable digital-down conversion block. This combination provides the necessary features to facilitate the development of flexible software-defined radio products for a wide range of communications applications.

The LM15851 device is based on an ultra high-speed ADC core. The core uses an interleaved calibrated folding and interpolating architecture that results in very high sampling rate, very good dynamic performance, and relatively low-power consumption. This ADC core is followed by a configurable DDC block which is implemented on a small geometry CMOS. The DDC block provides a range of decimation settings that allow the product to work in ultra-wideband, wideband, and more-narrow-band receive systems. The output data from the DDC block is transmitted through a JESD204B-compatible multi-lane serial-output system. This system minimizes the number of data pairs required to convey the output data to the downstream processing circuitry.

Functional Block Diagram

LM15851 fbd_slas990.gif
LM15851 30180114.gif Figure 31. DDC Details Block Diagram

Feature Description

Signal Acquisition

The analog input is sampled on the rising edge of CLK and the digital equivalent of that data is available in the serialized datastream t(LAT) or t(LAT_DDC) input clock cycles later.

The LM15851 device converts as long as the input clock signal is present. The fully-differential comparator design and the innovative design of the sample-and-hold amplifier, together with calibration, enables very good performance at input frequencies beyond 3 GHz. The LM15851 data is output on a high-speed serial JESD204B interface.

The Analog Inputs

A differential input signal must be used to drive the LM15851 device. Operation with a single-ended signal is not recommended as performance suffers. The input signals can be either be AC coupled or DC coupled. The analog inputs are internally connected to the VCMO bias voltage. When DC-coupled input signals are used, the common mode voltage of the applied signal must meet the device Input common mode requirements. See VCMI in the Recommended Operating Conditions table.

The full-scale input range for each converter can be adjusted through the serial interface. See the Full Scale Range Adjust section.

The buffered analog inputs simplify the task of driving these inputs and the RC pole that is generally used at sampling ADC inputs is not required. If an amplifier circuit before the ADC is desired, use care when selecting an amplifier with adequate noise and distortion performance and adequate gain at the frequencies used for the application. If gain is not required, a balun (balanced-to-unbalanced transformer) is generally used to provide single ended (SE) to differential conversion.

The input impedance of VIN± consists of two 50-Ω resistors in series between the inputs and a capacitance from each of these inputs to ground. A resistance of approximately 20 kΩ exists from the center point of the 50-Ω resistors to the on-chip VCMO providing self-biasing for AC-coupled applications.

Performance is good in both DC-coupled mode and AC coupled mode, provided the common-mode voltage at the analog input is within specifications.

Input Clamp

The LM15851 maximum DC input voltage is limited to the range 0 to 2 V to prevent damage to the device. To help maintain these limits, an active input clamping circuit is incorporated which sources or sinks input currents up to ±50 mA. The clamping circuit is enabled by default and is controlled via the Input_Clamp_EN bit (register 0x034, bit 5). The protection provided by this circuit is limited as follows:

  • Shunt current-clamping is only effective for non-zero source impedances.
  • At frequencies above 3 GHz the clamping is ineffective because of the finite turn-on and turn-off time of the switch.

With these limitations in mind, analysis has been done to determine the allowable input signal levels as a function of input frequency when the Input Clamp is enabled, assuming the source impedance matches the input impedance of the device (100-Ω differential). This information is incorporated in the Absolute Maximum Ratings table.

AC Coupled Input Usage

The easiest way to accomplish SE-to-differential conversion for AC-coupled signals is with an appropriate balun.

LM15851 30180143.gif Figure 32. Single-Ended-to-Differential Signal Conversion With a Balun

Figure 32 shows a generic depiction of a SE-to-differential signal conversion using a balun. The circuitry specific to the balun depends on the type of balun selected and the overall board layout. TI recommends that the system designer contact the manufacturer of the selected balun to aid in designing the best performing single-ended to differential conversion circuit using that particular balun.

When selecting a balun, understanding the input architecture of the ADC is important. Specific balun parameters must be considered. The balun must match the impedance of the analog source to the on-chip 100-Ω differential input termination of the LM15851 device. The range of this input termination resistor is described in the Electrical Characteristics table as the specification RID.

Also, as a result of the ADC architecture, the phase and amplitude balance are important. The lowest possible phase and amplitude imbalance is desired when selecting a balun. The phase imbalance must be no more than ±2.5° and the amplitude imbalance must be limited to less than 1 dB at the desired input frequency range.

Finally, when selecting a balun, the voltage standing-wave ratio (VSWR), bandwidth, and insertion loss of the balun must also be considered. The VSWR aids in determining the overall transmission line termination capability of the balun when interfacing to the ADC input. The insertion loss must be considered so that the signal at the balun output is within the specified input range of the ADC as described in the Electrical Characteristics table as the specification VID.

Table 1 lists the recommended baluns for specific signal frequency ranges.

Table 1. Balun Recommendations

MINIMUM FREQUENCY (MHz) MAXIMUM FREQUENCY (MHz) IMPEDANCE RATIO PART NUMBER MANUFACTURER
4.5 3000 1:1 TC1-1-13MA+ Mini-Circuits
400 3000 1:2 B0430J50100AHF Anaren
30 1800 1:2 ADTL2-18+ Mini-Circuits
10 4000 1:2 TCM2-43X+ Mini-Circuits

DC Coupled Input Usage

When a DC-coupled signal source is used, the common mode voltage of the applied signal must be within a specified range (VCMI). To achieve this range, the common mode of the driver should be based on the VCMO output provided for this purpose.

Full-scale distortion performance degrades as the input common-mode voltage deviates from VCMO. Therefore, maintaining the input common-mode voltage within the VCMI range is important.

Table 2 lists the recommended amplifiers for DC-coupled usage or if AC-coupling with gain is required.

Table 2. Amplifier Recommendations

–3-dB BANDWIDTH (MHz) MIN GAIN (dB) MAX GAIN (dB) GAIN TYPE PART NUMBER
7000 16 16 Fixed LMH3401
2800 0 17 Resistor set LMH6554
2400 6 26 Digital programmable LMH6881
900 –1.16 38.8 Digital programmable LMH6518

Handling Single-Ended Input Signals

The LM15851 device has no provision to adequately process single-ended input signals. The best way to handle single-ended signals is to convert these signals to balanced differential signals before presenting the signals to the ADC.

Clocking

The LM15851 device has a differential clock input, DEVCLK+ and DEVCLK–, that must be driven with an AC-coupled differential clock-signal. The clock inputs are internally terminated and biased. The input clock signal must be capacitively coupled to the clock pins as shown in Figure 33.

LM15851 30180147.gif Figure 33. Differential Sample-Clock Connection

The differential sample-clock line pair must have a characteristic impedance of 100 Ω and must be terminated at the clock source of that 100-Ω characteristic impedance. The input clock line must be as short and direct as possible. The LM15851 clock input is internally terminated with an untrimmed 100-Ω resistance.

Insufficient input clock levels results in poor dynamic performance. Excessively-high input-clock levels can cause a change in the analog-input offset voltage. To avoid these issues, maintain the input clock level within the range specified in the Electrical Characteristics table.

The low times and high times of the input clock signal can affect the performance of any ADC. The LM15851 device features a duty-cycle clock-correction circuit which maintains performance over temperature. The ADC meets the performance specification when the input clock high times and low times are maintained as specified in the Electrical Characteristics table.

High-speed high-performance ADCs such as the LM15851 device require a very-stable input clock-signal with minimum phase noise or jitter. ADC jitter requirements are defined by the ADC resolution or ENOB (effective number of bits), maximum ADC input frequency, and the input signal amplitude relative to the ADC input full-scale range. Use Equation 1 to calculate the maximum jitter (the sum of the jitter from all sources) allowed to prevent a jitter-induced reduction in SNR.

Equation 1. LM15851 eq_01_slas989.gif

where

  • RMStot(J) is the RMS total of all jitter sources in seconds
  • VI(PP) is the peak-to-peak analog input signal
  • VFSR is the full-scale range of the ADC
  • n is the ADC resolution in bits
  • FIN is the maximum input frequency, in Hertz, at the ADC analog input

Note that the maximum jitter previously described is the root sum square (RSS) of the jitter from all sources, including that from the clock source, the jitter added by noise coupling at board level and that added internally by the ADC clock circuitry, in addition to any jitter added to the input signal. Because the effective jitter added by the ADC is beyond user control, the best option is to minimize the jitter from the clock source, the sum of the externally-added input clock jitter and the jitter added by any circuitry to the analog signal.

Input clock amplitudes above those specified in the Recommended Operating Conditions table can result in increased input-offset voltage. Increased input-offset voltage causes the converter to produce an output code other than the expected 2048 when both input pins are at the same potential.

Over-Range Function

To ensure that system-gain management has the quickest-possible response time, a low-latency configurable over-range function is included. The over-range function works by monitoring the raw 12-bit samples exiting the ADC module. The upper 8 bits of the magnitude of the ADC data are checked against two programmable thresholds, OVR_T0 and OVR_T1. The following table lists how a raw ADC value is converted to an absolute value for a comparison of the thresholds.

ADC SAMPLE
(OFFSET BINARY)
ADC SAMPLE
(2's COMPLEMENT)
ABSOLUTE VALUE UPPER 8 BITS USED FOR COMPARISON
1111 1111 1111 (4095) 0111 1111 1111 (+2047) 111 1111 1111 (2047) 1111 1111 (255)
1111 1111 0000 (4080) 0111 1111 0000 (+2032) 111 1111 0000 (2032) 1111 1110 (254)
1000 0000 0000 (2048) 0000 0000 0000 (0) 000 0000 0000 (0) 0000 0000 (0)
0000 0001 0000 (16) 1000 0001 0000 (-2032) 111 1111 0000 (2032) 1111 1110 (254)
0000 0000 0000 (0) 1000 0000 0000 (-2048) 111 1111 1111 (2047) 1111 1111 (255)

If the upper 8 bits of the absolute value equal or exceed the OVR_T0 or OVR_T1 threshold during the monitoring period, then the over-range bit associated with the threshold is set to 1, otherwise the over-range bit is 0. The resulting over-range bits are embedded into the complex output data samples and output on OR_T0 and OR_T1. Table 3 lists the outputs, related data samples, threshold settings and the monitoring period equation.

Table 3. Threshold and Monitor Period for Embedded OR Bits

EMBEDDED OVER-RANGE OUTPUTS ASSOCIATED THRESHOLD ASSOCIATED SAMPLES MONITORING PERIOD
(ADC SAMPLES)
OR_T0 OVR_T0 In-Phase (I) samples 2OVR_N(1)
OR_T1 OVR_T1 Quadrature (Q) samples
OVR_N is the monitoring period register setting.

Table 4. Over-Range Monitoring Period

OVR_N MONITORING PERIOD
0 1
1 2
2 4
3 8
4 16
5 32
6 64
7 128

Typically, the OVR_T0 threshold can be set near the full-scale value (228 for example). When the threshold is triggered, a typical system can turn down the system gain to avoid clipping. The OVR_T1 threshold can be set much lower. For example, the OVR_T1 threshold can be set to 64 (−12 dBFS). If the input signal is strong, the OVR_T1 threshold is tripped occasionally. If the input is quite weak, the threshold is never tripped. The downstream logic device monitors the OVR_T1 bit. If OVR_T1 stays low for an extended period of time, then the system gain can be increased until the threshold is occasionally tripped (meaning the peak level of the signal is above −12 dBFS).

The OR_T0 threshold is embedded as the LSB along with the upper 15 bits of every complex I sample. The OR_T1 threshold is embedded as the LSB along with the upper 15 bits of every complex Q sample.

ADC Core Features

The Reference Voltage

The reference voltage for the LM15851 device is derived from an internal bandgap reference. A buffered version of the reference voltage is available at the VBG pin for user convenience. This output has an output-current capability of ±100 μA. The VBG output must be buffered if more current is required. No provision exists for the use of an external reference voltage, but the full-scale input voltage can be adjusted through the full-scale-range register settings.

Common-Mode Voltage Generation

The internal reference voltage is used to generate a stable common-mode voltage reference for the analog Inputs and the DEVCLK and SYSREF differential-clock inputs.

Bias Current Generation

An external bias resistor, in combination with the on-chip voltage reference is used to provide an accurate and stable source of bias currents for internal circuitry. Using an external accurate resistor minimizes variation in device power consumption and performance.

Full Scale Range Adjust

The ADC input full-scale range can be adjusted through the GAIN_FS register setting (registers 0x022 and 0x023). The adjustment range is approximately 500 mVPP to 950 mVPP. The full-scale range adjustment is useful for matching the input-signal amplitude to the ADC full scale, or to match the full-scale range of multiple ADCs when developing a multi-converter system.

Offset Adjust

The ADC-input offset voltage can be adjusted through the OFFSET_FS register setting (registers 0x025 and 0x026). The adjustment range is approximately 28 mV to –28 mV differential.

NOTE

Offset adjust has no effect when background calibration mode is enabled.

Power-Down

The power-down bit (PD) allows the LM15851 device to be entirely powered down. The serial data output drivers are disabled when PD is high. When the device returns to normal operation, the JESD204 link must be re-established, and the ADC pipeline and decimation filters contain meaningless information and must be flushed.

Built-In Temperature Monitor Diode

A built-in thermal monitoring diode junction is made available on the TDIODE+ and TDIODE– pins. This diode facilitates temperature monitoring and characterization of the device in higher ambient temperature environments. While the on-chip diode is not highly characterized, the diode can be used effectively by performing a baseline measurement at a known ambient or board temperature with the device in power-down (PD) mode. Recommended monitoring ICs include the LM95233 device and similar remote-diode temperature monitoring products from Texas Instruments.

Digital Down Converter (DDC)

The digitized data is the input to the digital down-converter block. This block provides frequency conversion and decimation filtering to allow a specific range of frequencies to be selected and output in the digital data stream.

NCO/Mixer

The DDC contains a complex numerically-controlled oscillator and a complex mixer. The oscillator generates a complex exponential sequence shown in Equation 2.

Equation 2. x[n] = ejωn

The frequency (ω) is specified by the a 32-bit register setting. The complex exponential sequence is multiplied by the real input from the ADC to mix the desired carrier down to 0 Hz.

NCO Settings

NCO Frequency Phase Selection

Within the DDC, eight different frequency and phase settings are always available for use. Each of the eight settings uses a different phase accumulator within the NCO. Because all eight phase accumulators are continuously running independently, rapid switching between different NCO frequencies is possible allowing rapid tuning of different signals.

The specific frequency-phase pair in use is selected through either the NCO_x input pins, or the NCO_SEL configuration bits (register 0x20D, bits 2:0). The CFG_MODE bit (register 0x20C, bit 0) is used to choose whether the input pins or selection bits are used. When the CFG_MODE bit is set to 0, the NCO_x input pins select the active NCO frequency and phase setting. When the CFG_MODE bit is set to 1, the NCO_SEL register settings select the active NCO frequency and phase setting.

The frequency for each phase accumulator is programmed independently through the NCO_FREQn (and optionally NCO_RDIV) settings. The phase offset for each accumulator is programmed independently through the NCO_PHASEn register settings.

NCO_0, NCO_1, and NCO_2 (NCO_x)

When the CFG_MODE bit is set to 0, the state of these three inputs determines the active NCO frequency and phase accumulator settings.

NCO_SEL Bits (2:0)

When the CFG_MODE bit is set to 1, the state of these register bits determines the active NCO frequency and phase accumulator settings.

NCO Frequency Setting (Eight Total)

Basic NCO Frequency-Setting Mode

In basic NCO frequency-setting mode, the NCO frequency setting is set by the 32-bit register value, NCO_FREQn (n = preset 0 trough 7, see the NCO Frequency (Preset x) Register section).

Equation 3. (n = 0 – 7) ƒ(NCO) = NCO_FREQn × 2–32 × ƒ(DEVCLK)

NOTE

Changing the register setting after the JESD204B interface is running results in non-deterministic NCO phase. If deterministic phase is required, the JESD204B link must be re-initialized after changing the register setting. See the Multiple ADC Synchronization section.

Rational NCO Frequency Setting Mode

In basic NCO frequency mode, the frequency step size is very small and many frequencies can be synthesized, but sometimes an application requires very specific frequencies that fall between two frequency steps. For example with ƒS equal to 2457.6 MHz and a desired ƒ(NCO) equal to 5.02 MHz the value for NCO_FREQ is 8773085.867. Truncating the fractional portion results in an ƒ(NCO) equal to 5.0199995 MHz, which is not the desired frequency.

To produce the desired frequency, the NCO_RDIV parameter is used to force the phase accumulator to arrive at specific frequencies without error. First, select a frequency step size (ƒ(STEP)) that is appropriate for the NCO frequency steps required. The typical value of ƒ(STEP) is 10 kHz. Next, program the NCO_RDIV value according to Equation 4.

Equation 4. LM15851 eq_02_slas989.gif

The result of Equation 4 must be an integer value. If the value is not an integer, adjust either of the parameters until the result in an integer value.

For example, select a value of 1920 for NCO_RDIV.

NOTE

NCO_RDIV values larger than 8192 can degrade the NCO SFDR performance and are not recommended.

Now use Equation 5 to calculate the NCO_FREQ register value.

Equation 5. LM15851 eq_03_slas989.gif

Alternatively, the following equations can be used:

Equation 6. LM15851 eq_04_slas989.gif
Equation 7. LM15851 eq_05_slas989.gif

Table 5. Common NCO_RDIV Values (For 10-kHz Frequency Steps)

ƒ(DEVCLK) (MHz) NCO_RDIV
3686.4 2880
3072 2400
2949.12 2304
2457.6 1920
1966.08 1536
1474.56 1152
1228.8 960

NCO Phase-Offset Setting (Eight Total)

The NCO phase-offset setting is set by the 16-bit register value NCO_PHASEn (n = preset 0 trough 7, see the NCO Phase (Preset x) Register section). The value is left-justified into a 32-bit field and then added to the phase accumulator.

Use Equation 8 to calculate the phase offset in radians.

Equation 8. NCO_PHASEn × 2–16 × 2 × π

NOTE

Changing the register setting after the JESD204B interface is running results in non-deterministic NCO phase. If deterministic phase is required, the JESD204B link must be re-initialized after changing the register setting. See Multiple ADC Synchronization.

Programmable DDC Delay

The DDC Filter elements incorporate a programmable sample delay. The delay can be programmed from 0 to (decimation setting – 0.5) ADC sample periods. The delay step-size is 0.5 ADC sample periods. The delay settings are programmed through the DDC_DLYn parameter.

Table 6. Programmable DDC Delay Range

D (Decimation Setting) Min Delay (t(DEVCLK)) Max Delay (t(DEVCLK))
4 0 3.5
8 0 7.5
10 0 9.5
16 0 15.5
20 0 19.5
32 0 31.5

Decimation Filters

The decimation filters are arranged to provide a programmable overall decimation of 4, 8, 10, 16, 20, or 32. The input and output of each filter is complex. The output data consists of 15-bit complex baseband information. Table 7 lists the effective output sample rates.

Table 7. Output Sample Rates

DECIMATION SETTING COMPLEX SAMPLE OUTPUT RATE AND RESULTING BANDWIDTH
(OUTPUT SAMPLE = 15-BIT I + 15-BIT Q + 2-BIT OR)
ƒ(DEVCLK) ƒ(DEVCLK) = 4000 MHz
OUTPUT RATE (MSPS) RAW OUTPUT BANDWIDTH (MHz) ALIAS PROTECTED BANDWIDTH (MHz) OUTPUT RATE (MSPS) RAW OUTPUT BANDWIDTH
(MHz)
ALIAS PROTECTED BANDWIDTH
(MHz)
4 ƒ(DEVCLK) / 4 ƒ(DEVCLK) / 4 0.8 × ƒ(DEVCLK) / 4 1000 1000 800
8 ƒ(DEVCLK) / 8 ƒ(DEVCLK)N / 8 0.8 × ƒ(DEVCLK) / 8 500 500 400
10 ƒ(DEVCLK) / 10 ƒ(DEVCLK) / 10 0.8 × ƒ(DEVCLK) / 10 400 400 320
16 ƒ(DEVCLK) / 16 ƒ(DEVCLK) / 16 0.8 × ƒ(DEVCLK) / 16 250 250 200
20 ƒ(DEVCLK) / 20 ƒ(DEVCLK) / 20 0.8 × ƒ(DEVCLK) / 20 200 200 160
32 ƒ(DEVCLK) / 32 ƒ(DEVCLK) / 32 0.8 × ƒ(DEVCLK) / 32 125 125 100

For maximum efficiency a group of high speed filter blocks are implemented with specific blocks used for each decimation setting. The first table below describes the combination of filter blocks used for each decimation setting. The next table lists the coefficient details and decimation factor of each filter block.

Table 8. Decimation Mode Filter Usage

Decimation Setting Filter Blocks Used
4 CS19, CS55
8 CS11, CS15, CS55
10 CS11, CS139
16 CS7, CS11, CS15, CS55
20 CS7, CS11, CS139
32 CS7, CS7, CS11, CS15, CS55

Table 9. Filter Coefficient Details

Filter Coefficient Set (Decimation Factor of Filter)
CS7 (2) CS11 (2) CS15 (2) CS19 (2) CS55 (2) CS139 (5)
–65 –65 109 109 –327 –327 22 22 –37 –37 –5 –5
0 0 0 0 0 0 0 0 0 0 –9 –9
577 577 –837 –837 2231 2231 –174 –174 118 118 –9 –9
1024 0 0 0 0 0 0 0 0 –5 –5
4824 4824 –8881 –8881 744 744 –291 –291 0 0
8192 0 0 0 0 0 0 20 20
39742 39742 –2429 –2429 612 612 33 33
65536 0 0 0 0 33 33
10029 10029 –1159 –1159 21 21
16384 0 0 0 0
2031 2031 –54 –54
0 0 –88 –88
–3356 –3356 –89 –89
0 0 –56 –56
5308 5308 0 0
0 0 119 119
–8140 –8140 196 196
0 0 199 199
12284 12284 125 125
0 0 0 0
–18628 –18628 –234 –234
0 0 –385 –385
29455 29455 –393 –393
0 0 –248 –248
–53191 –53191 0 0
0 0 422 422
166059 166059 696 696
262144 711 711
450 450
0 0
–711 –711
–1176 –1176
–1206 –1206
–766 –766
0 0
1139 1139
1893 1893
1949 1949
1244 1244
0 0
–1760 –1760
–2940 –2940
–3044 –3044
–1955 –1955
0 0
2656 2656
4472 4472
4671 4671
3026 3026
0 0
–3993 –3993
–6802 –6802
–7196 –7196
–4730 –4730
0 0
6159 6159
10707 10707
11593 11593
7825 7825
0 0
–10423 –10423
–18932 –18932
–21629 –21629
–15618 –15618
0 0
24448 24448
52645 52645
78958 78958
97758 97758
104858

DDC Output Data

The DDC output data consist of 15-bit complex data plus the two over-range threshold-detection control bits. The following table lists the data format:

16-BIT OUTPUT WORD
CHANNEL 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
I DDC Output In-Phase (I) 15 bit OR_T0
Q DDC Output Quadrature (Q) 15 bit OR_T1

Decimation Settings

Decimation Factor

The decimation setting is adjustable over the following settings:

  • Decimate-by-4
  • Decimate-by-8
  • Decimate-by-10
  • Decimate-by-16
  • Decimate-by-20
  • Decimate-by-32

NOTE

Because the output format is complex I+Q, the effective output bandwidth is approximately two-times the value for a real output with the same decimation factor.

DDC Gain Boost

The DDC gain boost (register 0x200, bit 4) provides additional gain through the DDC block. With a setting of 1 the final filter has 6.02-dB gain. With a setting of 0, the final filter has a 0-dB gain. This setting is recommended when the NCO is set near DC.

Data Outputs

The data outputs (DSx±) are very high-speed differential outputs and conform to the JESD204B JEDEC standard. A CML (current-mode logic)-type output driver is used for each output pair. Output pre-emphasis is adjustable to compensate for longer PCB-trace lengths.

The Digital Outputs

The LM15851 output data is transmitted on up to five high-speed serial-data lanes. The output data from the DDC is formatted to the five lanes, 8b10b encoded, and serialized. Up to four different serial output rates are possible depending on the decimation mode setting: 1x, 1.25x, 2x, and 2.5x. In 1x mode, the output serializers run at the same bit rate as the frequency of the applied DEVCLK. In 1.25x mode, the output serializers run at a bit rate that is 1.25-times that of the applied DEVCLK, and so on. For example, for a 1.6-GHz input DEVCLK, the output rates are 1.6 Gbps in 1x mode, 2 Gbps in 1.25x mode, 3.2 Gbps in 2x mode and 4 Gbps in 2.5x mode.

JESD204B Interface Features and Settings

Scrambler Enable

Scrambling randomizes the 8b10b encoded data, spreading the frequency content of the data interface. This reduces the peak EMI energy at any given frequency reducing the possibility of feedback to the device inputs impacting performance. The scrambler is disabled by default and is enabled via SCR (register 0x201, bit 7).

Frames Per Multi-Frame (K-1)

The frames per multi-frame (K) setting can be adjusted within constraints that are dependant on the selected decimation (D) and serial rate (DDR) settings. The K-minus-1 (KM1) register setting (register 0x201, bits 6:2) must be one less than the desired K setting.

DDR

The serial rate can be either 1ƒ(CLK) (DDR = 0) or 2ƒ(CLK) (DDR = 1).

JESD Enable

The JESD interface must be disabled (JESD_EN is set to 0) while any of the other JESD parameters are changed. While JESD_EN is set 0 the block is held in reset and the serializers are powered down. The clocks for this section are also gated off to further save power. When the parameters have been set as desired the JESD block can be enabled (JESD_EN is set to 1).

JESD Test Modes

Several different JESD204B test modes are available to assist in link verification and debugging. The list of modes follows.

NOTE

PRBS test signals are output directly, without 8b10b encoding.

  • Normal operation
  • PRBS7 test mode
  • PRBS15 test mode
  • PRBS23 test mode
  • Ramp test mode
  • Short or long transport-layer test mode
  • D21.5 test mode
  • K28.5 test mode
  • Repeated ILA test mode
  • Modified RPAT test mode
  • Serial-outputs differential 0 test mode
  • Serial-outputs differential 1 test mode

Configurable Pre-Emphasis

The high-speed serial-output drivers incorporate a configurable pre-emphasis feature. This feature allows the output drive waveform to be optimized for different PCB materials and signal transmission distances. The pre-emphasis setting is adjusted through the serializer pre-emphasis setting in register 0x040, bits 3 to 0. The default setting is 4d. Higher values will increase the pre-emphasis to compensate for more lossy PCB materials. This adjustment is best used in conjunction with an eye-diagram analysis capability in the receiver. The pre-emphasis setting should be adjusted to optimize the eye-opening for the hardware configuration and line rates needed.

Serial Output-Data Formatting

Output data is generated by the DDC then formatted according to the selected decimation and output rate settings. When less than the maximum of five lanes are active, lanes are disabled beginning with the highest numerical lanes. For example when only two lanes are active, lanes 0 and 1 are active, while all higher lanes are inactive.

Table 10. Parameter Definitions

PARAMETER DESCRIPTION USER CONFIGURED OR DERIVED STANDARD JESD204B LINK PARAMETER
D Decimation factor, determined by DMODE register User No
DDR Serial line rate: 1 = DDR rate (2x), 0 = SDR rate (1x) User No
P54 Enable 5/4 PLL to increase line rate by 1.25x. User No 
0 = no PLL (1x), 1 = enable PLL (1.25x)
K Number of frames per multiframe User Yes
N Bits per sample (before adding control bits and tails bits) Derived Yes
CS Control bits per sample Derived Yes
N’ Bits per sample (after adding control bits and tail bits). Must be a multiple of 4. Derived Yes
L Number of serial lanes Derived Yes
F Number of octets (bytes) per frame (per lane) Derived Yes
M Number of (logical) converters Derived Yes
S Number of samples per converter per frame Derived Yes
CF Number of control words per frame Derived Yes
HD 1=High density mode (samples may be broken across lanes), 0 = normal mode (samples may not be broken across lanes) Derived Yes
KS Legal adjustment step for K, to ensure that the multi-frame clock is a sub-harmonic of other internal clocks Derived No

Table 11. Serial Link Parameters(1)

USER SPECIFIED PARAMETERS DERIVED PARAMETERS OTHER INFORMATION
DECIMATION FACTOR (D) DDR P54 N CS N’ L F M S KS LEGAL K RANGE BIT RATE / ADC CLOCK(2)
4 1 0 15 1 16 5 4 2 5 4 8-32 2x
4 1 1 15 1 16 4 2 2 2 2 10-32 2.5x 
8 0 0 15 1 16 5 4 2 5 2 6-32 1x
8 0 1 15 1 16 4 2 2 2 1 9-32 1.25x 
8 1 0 15 1 16 3 8 2 5 2 4-32 2x
8 1 1 15 1 16 2 2 2 1 2 10-32 2.5x 
10 0 0 15 1 16 4 2 2 2 4 12-32 1x
10 1 0 15 1 16 2 2 2 1 8 16-32 2x
16 0 0 15 1 16 3 8 2 5 1 3-32 1x
16 0 1 15 1 16 2 2 2 1 1 9-32 1.25x 
16 1 0 15 1 16 2 16 2 5 1 2-32 2x
16 1 1 15 1 16 1 4 2 1 1 5-32 2.5x 
20 0 0 15 1 16 2 2 2 1 4 12-32 1x
20 1 0 15 1 16 1 4 2 1 4 8-32 2x
32 0 0 15 1 16 2 16 2 5 1 2-32 1x
32 0 1 15 1 16 1 4 2 1 1 5-32 1.25x 
32 1 0 15 1 16 1 32 2 5 1 1-32 2x
In all modes: HD = 0 and CF = 0
x = times (for example, 2x = 2-times)

Output data is formatted in a specific optimized fashion for each decimation and DDR setting combination. The following tables list the specific mapping formats. In all mappings the T or tail bits are 0 (zero).

Table 12. Decimate-by-4, DDR = 1, P54 = 0, LMF = 5,2,4

TIME →
CHAR NUMBER 0 1 2 3
Lane 0 I0 I1
Lane 1 I2 I3
Lane 2 I4 Q0
Lane 3 Q1 Q2
Lane 4 Q3 Q4
Frame n

Table 13. Decimate-by-4, DDR = 1, P54 = 1, LMF = 4,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5
Lane 0 I0 I2 I4
Lane 1 I1 I3 I5
Lane 2 Q0 Q2 Q4
Lane 3 Q1 Q3 Q5
Frame
n
Frame
n + 1
Frame
n + 2

Table 14. Decimate-by-8, DDR = 0, P54 = 0, LMF = 5,2,4

TIME →
CHAR NUMBER 0 1 2 3
Lane 0 I0 I1
Lane 1 I2 I3
Lane 2 I4 Q0
Lane 3 Q1 Q2
Lane 4 Q3 Q4
Frame n

Table 15. Decimate-by-8, DDR = 0, P54 = 1, LMF = 4,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5
Lane 0 I0 I2 I4
Lane 1 I1 I3 I5
Lane 2 Q0 Q2 Q4
Lane 3 Q1 Q3 Q5
Frame
n
Frame
n + 1
Frame
n + 2

Table 16. Decimate-by-8, DDR = 1, P54 = 0, LMF = 3,2,8

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 I1 I2 I3
Lane 1 I4 Q0 Q1 Q2
Lane 2 Q3 Q4 T T
Frame n

Table 17. Decimate-by-8, DDR = 1, P54=1, LMF = 2,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5
Lane 0 I0 I1 I2
Lane 1 Q0 Q1 Q2
Frame
n
Frame
n + 1
Frame
n + 2

Table 18. Decimate-by-10, DDR = 0, P54 = 0, LMF = 4,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 I2 I4 I6
Lane 1 I1 I3 I5 I7
Lane 2 Q0 Q2 Q4 Q6
Lane 3 Q1 Q3 Q5 Q7
Frame
n
Frame
n + 1
Frame
n + 2
Frame
n + 3

Table 19. Decimate-by-10, DDR = 1, P54 = 0, LMF = 2,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 I1 I2 I3
Lane 1 Q0 Q1 Q2 Q3
Frame
n
Frame
n + 1
Frame
n + 2
Frame
n+3

Table 20. Decimate-by-16, DDR = 0, P54 = 0, LMF = 3,2,8

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 I1 I2 I3
Lane 1 I4 Q0 Q1 Q2
Lane 2 Q3 Q4 T T
Frame n

Table 21. Decimate-by-16, DDR = 0, P54 = 1, LMF = 2,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5
Lane 0 I0 I1 I2
Lane 1 Q0 Q1 Q2
Frame
n
Frame
n + 1
Frame
n + 2

Table 22. Decimate-by-16, DDR = 1, P54 = 0, LMF = 2,2,16

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lane 0 I0 I1 I2 I3 I4 Q0 Q1 Q2
Lane 1 Q3 Q4 T T T T T T
Frame n

Table 23. Decimate-by-16, DDR = 1, P54 = 1, LMF = 1,2,4

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7 8 9 10 11
Lane 0 I0 Q0 I1 Q1 I2 Q2
Frame n Frame n + 1 Frame n + 2

Table 24. Decimate-by-20, DDR = 0, P54 = 0, LMF = 2,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 I1 I2 I3
Lane 1 Q0 Q1 Q2 Q3
Frame
n
Frame
n + 1
Frame
n + 2
Frame
n + 3

Table 25. Decimate-by-20, DDR = 1, P54 = 0, LMF = 1,2,2

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7
Lane 0 I0 Q0 I1 Q1
Frame n Frame n + 1

Table 26. Decimate-by-32, DDR = 0, P54 = 0, LMF = 2,2,16

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Lane 0 I0 I1 I2 I3 I4 Q0 Q1 Q2
Lane 1 Q3 Q4 T T T T T T
Frame n

Table 27. Decimate-by-32, DDR = 0, P54 = 1, LMF = 1,2,4

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7 8 9 10 11
Lane 0 I0 Q0 I1 Q1 I2 Q2
Frame n Frame n + 1 Frame n + 2

Table 28. Decimate-by-32, DDR = 1, P54 = 0, LMF = 1,2,32

TIME →
CHAR NUMBER 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Lane 0 I0 I1 I2 I3 I4 Q0 Q1 Q2 Q3 Q4 T T T T T T
Frame n

The formatted data is 8b10b encoded and output on the serial lanes. The 8b10b encoding provides a number of specific benefits, including:

  • Standard encoding format. Therefore the IP is readily available in off-the-shelf FPGAs and ASIC building blocks.
  • Inherent DC balance allows AC coupling of lanes with small on-chip capacitors
  • Inherent error checking

JESD204B Synchronization Features

The JESD204B standard defines methods for synchronization and deterministic latency in a multi-converter system. This device is a JESD204B Subclass 1 device and conforms to the various aspects of link operation as described in section 5.3.3 of the JESD204B standard. The specific signals used to achieve link operation are described briefly in the following sections.

SYSREF

The SYSREF is a periodic signal which is sampled by the device clock, and is used to align the boundary of the local multi-frame clock inside the data converter. SYSREF

is required to be a sub-harmonic of the LMFC internal timing. To meet this requirement, the timing of SYSREF is dependent on the device clock frequency and the LMFC frequency as determined by the selected DDC decimation and frames per multi-frame settings. This clock is typically in the range of 10 MHz to 300 MHz. See the Multiple ADC Synchronization section for more details on SYSREF timing requirements.

SYNC~

SYNC~ is asserted by the receiver to initiate a synchronization event.

Single ended and differential SYNC~ inputs are provided. The SYNC_DIFFSEL bit (register 0x202, bit 6) is used to select which input is used. . To assert SYNC~, a logic low is applied. To deassert SYNC~ a logic high is applied.

Code-Group Synchronization

Code-group synchronization is achieved using the following process:

  • The receiver issues a synchronization request through the SYNC~ input
  • The transmitter issues a stream of K28.5 symbols
  • The receiver synchronizes and waits for correct reception of at least 4 consecutive K symbols
  • The receiver deactivates the synchronization request
  • Upon detecting that the receiver has deactivated the SYNC~ pin, the transmitter continues emitting K symbols until the next LMFC boundary (or optionally a later LMFC boundary)
  • On the first frame following the selected LMFC boundary the transmitters emit an initial lane-alignment sequence

The initial-lane alignment sequence transmitted by the ADC device is defined in additional detail in JESD204B section 5.3.3.5.

Multiple ADC Synchronization

The second function for the SYSREF input is to facilitate the precise synchronization of multiple ADCs in a system.

One key challenge is to ensure that this synchronization works is to ensure that the SYSREF inputs are repeatedly captured by the input CLK. Two key elements must occur for the SYSREF inputs to be captured. First, the SYSREF input must be created so that it is synchronous to the input DEVCLK, be an integer sub-harmonic of the multi-frame (K × t(FRAME)) and a repeatable and fixed-phase offset. When this constraint is achieved, repeatedly capturing SYSREF is easier. To further ease this task, the SYSREF signal is routed through a user-adjustable delay which eases the timing requirements with respect to the input DEVCLK signal. The SYSREF delay RDEL is adjusted through bits 3 through 0 in register 0x032.

As long as the SYSREF signal has a fixed timing relationship to DEVCLK, the internal delay can be used to maximize the setup and hold times between the internally delayed SYSREF and the internal DEVCLK signal. These timing relationships are listed in the Timing Requirements table. To find the proper delay setting, the RDEL value is adjusted from minimum to maximum while applying SYSREF and monitoring the SysRefDet and Dirty Capture detect bits. The SysRefDet bit is set whenever a rising edge of SYSREF is detected. The Dirty Capture bit is set whenever the setup or hold time between DEVCLK and the delayed SYSREF is insufficient. The SysRefDetClr bit is used to clear the SysRefDet bit. The Clear Dirty Capture bit is used to clear that bit.

This procedure should be followed to determine the range of delay settings where a clean SYSREF capture is achieved. The delay value at the center of the clean capture range must be loaded as the final RDEL setting. Table 29 lists a summary of the control bits that are used and the monitor bits that are read.

Table 29. SYSREF Capture Control and Status

BIT NAME REGISTER ADDRESS REGISTER BIT FUNCTION
RDEL 0x032 3:0 Adjust relative delay between DEVCLK and SYSREF
SysRefDet 0x031 7 Detect if a SYSREF rising edge has been captured (not self clearing)
Dirty Capture 0x031 6 Detect if SYSREF rising edge capture failed setup/hold (not self clearing)
SysRefDetClr 0x030 5 Clear SYSREF detection bit
Clear Dirty Capture 0x030 4 Clear Dirty Capture detection bit
SysRef_Rcvr_En 0x030 7 Enable SYSREF receiver. See the CLKGEN_0 descriptions in the Clock Generator Control 0 Register section for more information.
SysRef_Pr_En 0x030 6 Enable SYSREF processing. See the CLKGEN_0 descriptions in the Clock Generator Control 0 Register section for more information.

One final aspect of multi-device synchronization relates to phase alignment of the NCO phase accumulators when DDC modes are enabled. The NCO phase accumulators are reset during the ILA phase of link startup which means that for multiple ADCs to have NCO phase alignment, all links must be enabled in the same LMFC period. Enabling all links in the same LMFC period requires synchronizing the SYNC~ de-assertion across all data receivers in the system, so that all of the SYNC~ signals are released during the same LMFC period. Using large K values and resulting longer LMFC periods will ease this task, at the expense of potentially higher latency in the receiving device.

Device Functional Modes

DDC Modes

In the DDC modes (decimation > 1) complex (I,Q) data is output at a lower sample rate as determined by the decimation factor (4, 8, 10, 16, 20, and 32).

Calibration

Calibration adjusts the ADC core to optimize the following device parameters:

  • ADC core linearity
  • ADC core-to-core offset matching
  • ADC core-to-core full-scale range matching
  • ADC core 4-way interleave timing

All calibration processes occur internally. Calibration does not require any external signals to be present and works properly as long as the device is maintained within the values listed in the Recommended Operating Conditions table.

Foreground Calibration Mode

In foreground mode the calibration process interrupts normal ADC operation and no output data is available during this time (the output code is forced to a static value). The calibration process should be repeated if the device temperature changes by more than 20ºC to ensure rated performance is maintained. Foreground calibration is initiated by setting the CAL_SFT bit (register 0x050, bit 3) which is self clearing. The foreground calibration process finishes within t(CAL) number of DEVCLK cycles. The process occurs somewhat longer when the timing calibration mode is enabled.

NOTE

Initiating a foreground calibration asynchronously resets the calibration control logic and may glitch internal device clocks. Therefore after setting the CAL_SFT bit clearing and then setting JESD_EN is necessary. If resetting the JESD204B link is undesirable for system reasons, background calibration mode may be preferred.

Background Calibration Mode

In background mode an additional ADC core is powered-up for a total of 5 ADC cores. At any given time, one core is off-line and not used for data conversion. This core is calibrated in the background and then placed on-line simultaneous with another core going off-line for calibration. This process operates continuously without interrupting data flow in the application and ensures that all cores are optimized in performance regardless of any changes of temperature. The background calibration cycle rate is fixed and is not adjustable by the user.

Because of the additional circuitry active in background calibration mode, a slight degradation in performance occurs in comparison to foreground calibration mode at a fixed temperature. As a result of this degradation, using foreground calibration mode is recommended if the expected change in operating temperature is <30°C. Using background calibration mode is recommended if the expected change in operating temperature is >30°C. The exact difference in performance is dependent on the DEVCLK (sampling clock) frequency, and the analog input signal frequency and amplitude. For this reason, device and system performance should be evaluated using both calibration modes before finalizing the choice of calibration mode.

To enable the background calibration feature, set the CAL_BCK bit (register 0x057, bit 0) and the CAL_CONT bit (register 0x057, bit 1). The value written to the register 0x057 to enable background calibration is therefore 0x013h. After writing this value to register 0x057, set the CAL_SFT bit in register 0x050 to perform the one-time foreground calibration to begin the process.

NOTE

The ADC offset-adjust feature has no effect when background calibration mode is enabled.

Timing Calibration Mode

The timing calibration process optimizes the matching of sample timing for the 4 internally interleaved converters. This process minimize the presence of any timing related interleaving spurs in the captured spectrum. The timing calibration feature is disabled by default, but using this feature is highly recommended. To enable timing calibration, set the T_AUTO bit (register 0x066, bit 0). When this bit is set, the timing calibration performs each time the CAL_SFT bit is set.

Table 30. Calibration Cycle Timing for Different Calibration Modes and Options

CAL_CONT, CAL_BCK T_AUTO LOW_SIG_EN INITIAL ONE-TIME CALIBRATION
CAL_SFT 0 → 1 (tDEVCLK)
BACKGROUND CALIBRATION CYCLE(1)
(ALL CORES)
(tDEVCLK)
0 0 0 102 E+6 N/A
0 0 1 64 E+6 N/A
0 1 0 227 E+6 N/A
0 1 1 189 E+6 N/A
1 0 0 127.5 E+6 816 E+6
1 0 1 80 E+6 512 E+6
1 1 0 283.75 E+6 816 E+6
1 1 1 236.25 E+6 512 E+6
N/A = not applicable

Test-Pattern Modes

A number of device test modes are available. These modes insert known patterns of information into the device data path for assistance with system debug, development, or characterization.

Serializer Test-Mode Details

Test modes are enabled by setting the appropriate configuration of the JESD204B_TEST setting (Register 0x202, Bits 3:0). Each test mode is described in detail in the following sections. Regardless of the test mode, the serializer outputs are powered up based on the configuration decimation and DDR settings. The test modes should only be enabled while the JESD204B link is disabled.

LM15851 JESD204_Test_Modes_Flow.gif Figure 34. Test-Mode Insertion Points

PRBS Test Modes

The PRBS test modes bypass the 8B10B encoder. These test modes produce pseudo-random bit streams that comply with the ITU-T O.150 specification. These bit streams are used with lab test equipment that can self-synchronize to the bit pattern and therefore the initial phase of the pattern is not defined.

The sequences are defined by a recursive equation. For example, the PRBS7 sequence is defined as shown in Equation 9.

Equation 9. y[n] = y[n – 6]y[n – 7]

where

  • Bit n is the XOR of bit [n – 6] and bit [n – 7] which are previously transmitted bits

Table 31. PBRS Mode Equations

PRBS TEST MODE SEQUENCE SEQUENCE LENGTH (bits)
PRBS7 y[n] = y[n – 6]y[n – 7] 127
PRBS15 y[n] = y[n – 14]y[n – 15] 32767
PRBS23 y[n] = y[n – 18]y[n – 23] 8388607

The initial phase of the pattern is unique for each lane.

Ramp Test Mode

In the ramp test mode, the JESD204B link layer operates normally, but the transport layer is disabled and the input from the formatter is ignored. After the ILA sequence, each lane transmits an identical octet stream that increments from 0x00 to 0xFF and repeats.

Short and Long-Transport Test Mode

The long-transport test mode is available in all DDC modes (decimation > 1). Patterns are generated in accordance with the JESD204B standard and are different for each output format.

Table 32 lists one example of the long transport test pattern:

Table 32. Long Transport Test Pattern - Decimate-by-4, DDR = 1, P54 = 1, K=10

TIME →
CHAR NO. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Lane 0 0x0003 0x0002 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x0003
Lane 1 0x0002 0x0005 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x0002
Lane 2 0x0004 0x0002 0x8001 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x0004
Lane 3 0x0004 0x0004 0x8000 0x8001 0x8000 0x8000 0x8000 0x8000 0x8000 0x8000 0x0004
Frame
n
Frame
n + 1
Frame
n + 2
Frame
n + 3
Frame
n + 4
Frame
n + 5
Frame
n + 6
Frame
n + 7
Frame
n + 8
Frame
n + 9
Frame
n + 10

If multiple devices are all programmed to the transport layer test mode (while JESD_EN = 0), then JESD_EN is set to 1, and then SYSREF is used to align the LMFC of the devices, the patterns will be aligned to the SYSREF event (within the skew budget of JESD204B). For more details see JESD204B, section 5.1.6.3.

D21.5 Test Mode

In this test mode, the controller transmits a continuous stream of D21.5 characters (alternating 0s and 1s).

K28.5 Test Mode

In this test mode, the controller transmits a continuous stream of K28.5 characters.

Repeated ILA Test Mode

In this test mode, the JESD204B link layer operates normally with one exception: when the ILA sequence completes, the sequence repeats indefinitely. Whenever the receiver issues a synchronization request, the transmitter will initiate code group synchronization. Upon completion of code group synchronization, the transmitter will repeatedly transmit the ILA sequence. If there is no active code group synchronization request at the moment the transmitter enters the test mode, the transmitter will behave as if it received one.

Modified RPAT Test Mode

A 12-octet repeating pattern is defined in INCITS TR-35-2004. The purpose of this pattern is to generate white spectral content for JESD204B compliance and jitter testing. Table 33 lists the pattern before and after 8b10b encoding.

Table 33. Modified RPAT Pattern Values

OCTET NUMBER Dx.y NOTATION 8-BIT INPUT TO 8b10b ENCODER 20b OUTPUT OF 8b10b ENCODER
(2 CHARACTERS)
0 D30.5 0xBE 0x86BA6
1 D23.6 0xD7
2 D3.1 0x23 0xC6475
3 D7.2 0x47
4 D11.3 0x6B 0xD0E8D
5 D15.4 0x8F
6 D19.5 0xB3 0xCA8B4
7 D20.0 0x14
8 D30.2 0x5E 0x7949E
9 D27.7 0xFB
10 D21.1 0x35 0xAA665
11 D25.2 0x59

Programming

Using the Serial Interface

The serial interface is accessed using the following four pins: serial clock (SCLK), serial-data in (SDI), serial-data out (SDO), and serial-interface chip-select (SCS). Registers access is enabled through the SCS pin.

    SCSThis signal must be asserted low to access a register through the serial interface. Setup and hold times with respect to the SCLK must be observed.
    SCLKSerial data input is accepted at the rising edge of this signal. SCLK has no minimum frequency requirement.
    SDIEach register access requires a specific 24-bit pattern at this input. This pattern consists of a read-and-write (R/W) bit, register address, and register value. The data is shifted in MSB first. Setup and hold times with respect to the SCLK must be observed (see Figure 2).
    SDOThe SDO signal provides the output data requested by a read command. This output is high impedance during write bus cycles and during the read bit and register address portion of read bus cycles.

Each register access consists of 24 bits, as shown in Figure 2. The first bit is high for a read and low for a write.

The next 15 bits are the address of the register that is to be written to. During write operations, the last 8 bits are the data written to the addressed register. During read operations, the last 8 bits on SDI are ignored, and, during this time, the SDO outputs the data from the addressed register. The serial protocol details are illustrated in Figure 35.

LM15851 serial_protocol_standard_slas989.gif Figure 35. Serial Interface Protocol - Single Read / Write

Streaming Mode

The serial interface supports streaming reads and writes. In this mode, the initial 24 bits of the transaction specifics the access type, register address, and data value as normal. Additional clock cycles of write or read data are immediately transferred, as long as the SCS input is maintained in the asserted (logic low) state. The register address auto increments (default) or decrements for each subsequent 8 bit transfer of the streaming transaction. The ADDR_ASC bit (register 000h, bits 5 and 2) controls whether the address value ascends (increments) or descends (decrements). Streaming mode can be disabled by setting the ADDR_STATIC bit (register 010h, bit 0). The streaming mode transaction details are shown in Figure 36.

LM15851 serial_protocol_streaming_slas989.gif Figure 36. Serial Interface Protocol - Streaming Read / Write

See the Register Map section for detailed information regarding the registers.

NOTE

The serial interface must not be accessed during calibration of the ADC. Accessing the serial interface during this time impairs the performance of the device until the device is calibrated correctly. Writing or reading the serial registers also reduces dynamic performance of the ADC for the duration of the register access time.

Register Map

Several groups of registers provide control and configuration options for this device. Each following register description also shows the power-on reset (POR) state of each control bit.

NOTE

All multi-byte registers are arranged in little-endian format (the least-significant byte is stored at the lowest address) unless explicitly stated otherwise.

Memory Map

Address Reset Type Register
Standard SPI-3.0 (0x000 to 0x00F)
0x000 0x3C R/W Configuration A Register
0x001 0x00 R Configuration B Register
0x002 0x00 R/W Device Configuration Register
0x003 0x03 R Chip Type Register
0x004-0x005 Undefined R RESERVED
0x006 0x13 R Chip Version Register
0x007-0x00B Undefined R RESERVED
0x00C-0x00D 0x0451 R Vendor Identification Register
0x00E-0x00F Undefined R RESERVED
User SPI Configuration (0x010 to 0x01F)
0x010 0x00 R/W User SPI Configuration Register
0x011-0x01F Undefined R RESERVED
General Analog, Bias, Band Gap, and Track and Hold (0x020 to 0x02F)
0x020 0x9D R/W RESERVED
0x021 0x00 R/W Power-On Reset Register
0x022 0x40 R/W I/O Gain 0 Register
0x023 0x00 R/W I/O Gain 1 Register
0x024 0x00 R/W RESERVED
0x025 0x40 R/W I/O Offset 0 Register
0x026 0x00 R/W I/O Offset 1 Register
0x027 0x06 R/W RESERVED
0x028 0xBA R/W RESERVED
0x029 0xD4 R/W RESERVED
0x02A 0xEA R/W RESERVED
0x02B-0x02F Undefined R RESERVED
Clock (0x030 to 0x03F)
0x030 0xC0 R/W Clock Generator Control 0 Register
0x031 0x07 R Clock Generator Status Register
0x032 0x80 R/W Clock Generator Control 2 Register
0x033 0xC3 R/W Analog Miscellaneous Register
0x034 0x2F R/W Input Clamp Enable Register
0x035 0xDF R/W RESERVED
0x036 0x00 R/W RESERVED
0x037 0x45 R/W RESERVED
0x038-0x03F Undefined R/W RESERVED
Serializer (0x040 to 0x04F)
0x040 0x04 R/W Serializer Configuration Register
0x041-0x04F Undefined R RESERVED
ADC Calibration (0x050 to 0x1FF)
0x050 0x06 R/W Calibration Configuration 0 Register
0x051 0xF4 R/W Calibration Configuration 1 Register
0x052 0x00 R/W RESERVED
0x053 0x5C R/W RESERVED
0x054 0x1C R/W RESERVED
0x055 0x92 R/W RESERVED
0x056 0x20 R/W RESERVED
0x057 0x10 R/W Calibration Background Control Register
0x058 0x00 R/W ADC Pattern and Over-Range Enable Register
0x059 0x00 R/W RESERVED
0x05A 0x00 R/W Calibration Vectors Register
0x05B Undefined R Calibration Status Register
0x05C 0x00 R/W RESERVED
0x05D-0x05E Undefined R/W RESERVED
0x05F 0x00 R/W RESERVED
0x060 Undefined R RESERVED
0x061 Undefined R RESERVED
0x062 Undefined R RESERVED
0x063 Undefined R RESERVED
0x064 Undefined R RESERVED
0x065 Undefined R RESERVED
0x066 0x02 R/W Timing Calibration Register
0x067 0x01 R/W RESERVED
0x068 Undefined R RESERVED
0x069 Undefined R RESERVED
0x06A 0x00 R/W RESERVED
0x06B 0x20 R/W RESERVED
0x06C-0x1FF Undefined R RESERVED
Digital Down Converter and JESD204B (0x200-0x27F)
0x200 0x10 R/W Digital Down-Converter (DDC) Control
0x201 0x0F R/W JESD204B Control 1
0x202 0x00 R/W JESD204B Control 2
0x203 0x00 R/W JESD204B Device ID (DID)
0x204 0x00 R/W JESD204B Control 3
0x205 Undefined R/W JESD204B and System Status Register
0x206 0xF2 R/W Overrange Threshold 0
0x207 0xAB R/W Overrange Threshold 1
0x208 0x00 R/W Overrange Period
0x209-0x20B 0x00 R/W RESERVED
0x20C 0x00 R/W DDC Configuration Preset Mode
0x20D 0x00 R/W DDC Configuration Preset Select
0x20E-0x20F 0x0000 R/W Rational NCO Reference Divisor
PRESET 0
0x210-0x213 0xC0000000 R/W NCO Frequency (Preset 0)
0x214-0x215 0x0000 R/W NCO Phase (Preset 0)
0x216 0xFF R/W DDC Delay (Preset 0)
0x217 0x00 R/W RESERVED
PRESET 1
0x218-0x21B 0xC0000000 R/W NCO Frequency (Preset 1)
0x21C-0x21D 0x0000 R/W NCO Phase (Preset 1)
0x21E 0xFF R/W DDC Delay (Preset 1)
0x21F 0x00 R/W RESERVED
PRESET 2
0x220-0x223 0xC0000000 R/W NCO Frequency (Preset 2)
0x224-0x225 0x0000 R/W NCO Phase (Preset 2)
0x226 0xFF R/W DDC Delay (Preset 2)
0x227 0x00 R/W RESERVED
PRESET 3
0x228-0x22B 0xC0000000 R/W NCO Frequency (Preset 3)
0x22C-0x22D 0x0000 R/W NCO Phase (Preset 3)
0x22E 0xFF R/W DDC Delay (Preset 3)
0x22F 0x00 R/W RESERVED
PRESET 4
0x230-0x233 0xC0000000 R/W NCO Frequency (Preset 4)
0x234-0x235 0x0000 R/W NCO Phase (Preset 4)
0x236 0xFF R/W DDC Delay (Preset 4)
0x237 0x00 R/W RESERVED
PRESET 5
0x238-0x23B 0xC0000000 R/W NCO Frequency (Preset 5)
0x23C-0x23D 0x0000 R/W NCO Phase (Preset 5)
0x23E 0xFF R/W DDC Delay (Preset 5)
0x23F 0x00 R/W RESERVED
PRESET 6
0x240-0x243 0xC0000000 R/W NCO Frequency (Preset 6)
0x244-0x245 0x0000 R/W NCO Phase (Preset 6)
0x246 0xFF R/W DDC Delay (Preset 6)
0x247 0x00 R/W RESERVED
PRESET 7
0x248-0x24B 0xC0000000 R/W NCO Frequency (Preset 7)
0x24C-0x24D 0x0000 R/W NCO Phase (Preset 7)
0x24E 0xFF R/W DDC Delay (Preset 7)
0x24F-0x251 0x00 R/W RESERVED
0x252-0x27F Undefined R RESERVED
Reserved
0x0280-0x7FFF Undefined R RESERVED

Register Descriptions

Standard SPI-3.0 (0x000 to 0x00F)

Table 34. Standard SPI-3.0 Registers

Address Reset Acronym Register Name Section
0x000 0x3C CFGA Configuration A Register Go
0x001 0x00 CFGB Configuration B Register Go
0x002 0x00 DEVCFG Device Configuration Register Go
0x003 0x03 CHIP_TYPE Chip Type Register Go
0x004-0x005 0x0000 RESERVED RESERVED Go
0x006 0x13 CHIP_VERSION Chip Version Register Go
0x007-0x00B Undefined RESERVED RESERVED
0x00C-0x00D 0x0451 VENDOR_ID Vendor Identification Register Go
0x00E-0x00F Undefined RESERVED RESERVED

Configuration A Register (address = 0x000) [reset = 0x3C]

All writes to this register must be a palindrome (for example: bits [3:0] are a mirror image of bits [7:4]). If the data is not a palindrome, the entire write is ignored.

Figure 37. Configuration A Register (CFGA)
7 6 5 4 3 2 1 0
SWRST RESERVED ADDR_ASC RESERVED RESERVED ADDR_ASC RESERVED SWRST
R/W-0 R/W-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-0 R/W-0

Table 35. CFGA Field Descriptions

Bit Field Type Reset Description
7 SWRST R/W 0 Setting this bit causes all registers to be reset to their default state. This bit is self-clearing.
6 RESERVED R/W 0
5 ADDR_ASC R/W 1 This bit is NOT reset by a soft reset (SWRST)
0 : descend – decrement address while streaming (address wraps from 0x0000 to 0x7FFF)
1 : ascend – increment address while streaming (address wraps from 0x7FFF to 0x0000) (default)
4 RESERVED R/W 1 Always returns 1
3 RESERVED R/W 1100 Palindrome bits
  bit 3 = bit 4, bit 2 = bit 5, bit 1 = bit 6, bit 0 = bit 7
2 ADDR_ASC R/W
1 RESERVED R/W
0 SWRST R/W

Configuration B Register (address = 0x001) [reset = 0x00]

Figure 38. Configuration B Register (CFGB)
7 6 5 4 3 2 1 0
RESERVED
R - 0x00h

Table 36. CFGB Field Descriptions

Bit Field Type Reset Description
7:0 RESERVED R 0000 0000

Device Configuration Register (address = 0x002) [reset = 0x00]

Figure 39. Device Configuration Register (DEVCFG)
7 6 5 4 3 2 1 0
RESERVED MODE
R/W-000000 R/W-00

Table 37. DEVCFG Field Descriptions

Bit Field Type Reset Description
7-2 RESERVED R/W 0000 00
1-0 MODE R/W 00 SPI 3.0 specification has 1 as low power functional mode and 2 as low power fast resume. This chip does not support these modes.
0: Normal Operation – full power and full performance (default)
1: Normal Operation – full power and full performance (default)
2: Power Down – Everything powered down
3: Power Down – Everything powered down

Chip Type Register (address = 0x003) [reset = 0x03]

Figure 40. Chip Type Register (CHIP_TYPE)
7 6 5 4 3 2 1 0
RESERVED CHIP_TYPE
R-0000 R-0011

Table 38. CHIP_TYPE Field Descriptions

Bit Field Type Reset Description
7-4 RESERVED R 0000
3-0 CHIP_TYPE R 0011 Always returns 0x3, indicating that the part is a high speed ADC.

Chip Version Register (address = 0x006) [reset = 0x13]

Figure 41. Chip Version Register (CHIP_VERSION)
7 6 5 4 3 2 1 0
CHIP_VERSION
R-0001 0011

Table 39. CHIP_VERSION Field Descriptions

Bit Field Type Reset Description
7-0 CHIP_VERSION R 0001 0011 Chip version, returns 0x13

Vendor Identification Register (address = 0x00C to 0x00D) [reset = 0x0451]

Figure 42. Vendor Identification Register (VENDOR_ID)
15 14 13 12 11 10 9 8
VENDOR_ID
R-0x04h
7 6 5 4 3 2 1 0
VENDOR_ID
R-0x51h

Table 40. VENDOR_ID Field Descriptions

Bit Field Type Reset Description
15-0 VENDOR_ID R 0x0451h Always returns 0x0451 (TI Vendor ID)

User SPI Configuration (0x010 to 0x01F)

Table 41. User SPI Configuration Registers

Address Reset Acronym Register Name Section
0x010 0x00 USR0 User SPI Configuration Register Go
0x011-0x01F Undefined RESERVED RESERVED

User SPI Configuration Register (address = 0x010) [reset = 0x00]

Figure 43. User SPI Configuration Register (USR0)
7 6 5 4 3 2 1 0
RESERVED ADDR_STATIC
R/W-0000 000 R/W-0

Table 42. USR0 Field Descriptions

Bit Field Type Reset Description
7-1 RESERVED R/W 0000 000
0 ADDR_STATIC R/W 0 0 : Use ADDR_ASC bit to define what happens to address during streaming (default).
1 : Address stays static throughout streaming operation. Useful for reading/writing calibration vector information at CAL_VECTOR register.

General Analog, Bias, Band Gap, and Track and Hold (0x020 to 0x02F)

Table 43. General Analog, Bias, Band Gap, and Track and Hold Registers

Address Reset Acronym Register Name Section
0x020 0x9D RESERVED RESERVED
0x021 0x00 POR Power-On Reset Register Go
0x022 0x40 IO_GAIN_0 I/O Gain 0 Register Go
0x023 0x00 IO_GAIN_1 I/O Gain 1 Register Go
0x024 0x00 RESERVED RESERVED
0x025 0x40 IO_OFFSET_0 I/O Offset 0 Register Go
0x026 0x00 IO_OFFSET_1 I/O Offset 1 Register Go
0x027 0x06 RESERVED RESERVED
0x028 0xBA RESERVED RESERVED
0x029 0xD4 RESERVED RESERVED
0x02A 0xAA RESERVED RESERVED
0x02B-0x02F Undefined RESERVED RESERVED

Power-On Reset Register (address = 0x021) [reset = 0x00]

Figure 44. Power-On Reset Register (POR)
7 6 5 4 3 2 1 0
RESERVED SPI_RES
R/W-0000 000 R/W-0

Table 44. POR Field Descriptions

Bit Field Type Reset Description
7-1 RESERVED R/W 0000 000
0 SPI_RES R/W 0 Reset all digital. Emulates a power on reset (not self-clearing).
Write a 0 and then write a 1 to emulate a reset. Transition from 0—>1 initiates reset.
Default: 0

I/O Gain 0 Register (address = 0x022) [reset = 0x40]

Figure 45. I/O Gain 0 Register (IO_GAIN_0)
7 6 5 4 3 2 1 0
RESERVED GAIN_FS[14] GAIN_FS[13] GAIN_FS[12] GAIN_FS[11] GAIN_FS[10] GAIN_FS[9] GAIN_FS[8]
R/W-0 R/W-1 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Table 45. IO_GAIN_0 Field Descriptions

Bit Field Type Reset Description
7 RESERVED R/W 0
6-0 GAIN_FS[14:8] R/W 100 0000 MSB Bits for GAIN_FS[14:0]. (See the IO_GAIN_1 description in General Analog, Bias, Band Gap, and Track and Hold (0x020 to 0x02F))

IO_GAIN_1 Register (address = 0x023) [reset = 0x00]

Figure 46. IO_GAIN_1 Register (IO_GAIN_1)
7 6 5 4 3 2 1 0
GAIN_FS[7] GAIN_FS[6] GAIN_FS[5] GAIN_FS[4] GAIN_FS[3] GAIN_FS[2] GAIN_FS[1] GAIN_FS[0]
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Table 46. IO_GAIN_1 Field Descriptions

Bit Field Type Reset Description
7-0 GAIN_FS[7:0] R/W 0000 0000 LSB bits for GAIN_FS[14:0]
GAIN_FS[14:0] Value
0x0000 500 mVp-p
0x4000 725 mVp-p (default)
0x7FFF 950 mVp-p

I/O Offset 0 Register (address = 0x025) [reset = 0x40]

Figure 47. I/O Offset 0 Register (IO_OFFSET_0)
7 6 5 4 3 2 1 0
RESERVED OFFSET_FS[14] OFFSET_FS[13] OFFSET_FS[12] OFFSET_FS[11] OFFSET_FS[10] OFFSET_FS[9] OFFSET_FS[8]
R/W-0 R/W-1 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Table 47. IO_OFFSET_0 Field Descriptions

Bit Field Type Reset Description
7 RESERVED R/W 0
6-0 OFFSET_FS[14:8] R/W 100 0000 MSB Bits for OFFSET_FS[14:0].
The ADC offset adjust feature has no effect when Background Calibration Mode is enabled. (See IO_OFFSET_1 description in the General Analog, Bias, Band Gap, and Track and Hold (0x020 to 0x02F) section).

I/O Offset 1 Register (address = 0x026) [reset = 0x00]

Figure 48. I/O Offset 1 Register (IO_OFFSET_1)
7 6 5 4 3 2 1 0
OFFSET_FS[7] OFFSET_FS[6] OFFSET_FS[5] OFFSET_FS[4] OFFSET_FS[3] OFFSET_FS[2] OFFSET_FS[1] OFFSET_FS[0]
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Table 48. IO_OFFSET_1 Field Descriptions

Bit Field Type Reset Description
7-0 OFFSET_FS[7:0] R/W 0000 0000 LSB bits for OFFSET_FS[14:0]. OFFSET_FS[14:0] adjusts the offset of the entire ADC (all banks are impacted).
OFFSET_FS[14:0] Value
0x0000 –28-mV offset
0x4000 no offset (default)
0x7FFF 28-mV offset
The ADC offset adjust feature has no effect when Background Calibration Mode is enabled.

Clock (0x030 to 0x03F)

Table 49. Clock Registers

Address Reset Acronym Register Name Section
0x030 0xC0 CLKGEN_0 Clock Generator Control 0 Register Go
0x031 0x07 CLKGEN_1 Clock Generator Status Register Go
0x032 0x80 CLKGEN_2 Clock Generator Control 2 Register Go
0x033 0xC3 ANA_MISC Analog Miscellaneous Register Go
0x034 0x2F IN_CL_EN Clamp Enable Register Go
0x035 0xDF RESERVED RESERVED
0x036 0x00 RESERVED RESERVED
0x037 0x45 RESERVED RESERVED
0x038-0x03F Undefined RESERVED RESERVED

Clock Generator Control 0 Register (address = 0x030) [reset = 0xC0]

Figure 49. Clock Generator Control 0 Register (CLKGEN_0)
7 6 5 4 3 2 1 0
SysRef_Rcvr_En SysRef_Pr_En SysRefDetClr Clear Dirty Capture RESERVED DC_LVPECL_CLK_en DC_LVPECL_SYSREF_en DC_LVPECL_SYNC_en
R/W-1 R/W-1 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

Table 50. CLKGEN_0 Field Descriptions

Bit Field Type Reset Description
7 SysRef_Rcvr_En R/W 1 Default: 1
0 : SYSREF receiver is disabled.
1 : SYSREF receiver is enabled (default)
6 SysRef_Pr_En R/W 1 To power down the SYSREF receiver, clear this bit first, then clear SysRef_Rcvr_En. To power up the SYSREF receiver, set SysRef_Rcvr_En first, then set this bit.
Default: 1
0 : SYSREF Processor is disabled.
1 : SYSREF Processor is enabled (default)
5 SysRefDetClr R/W 0 Default: 0
Write a 1 and then a 0 to clear the SysRefDet status bit.
4 Clear Dirty Capture R/W 0 Default: 0
Write a 1 and then a 0 to clear the DC status bit.
3 RESERVED R/W 0 Default: 0
2 DC_LVPECL_CLK_en R/W 0 Default: 0
Set this bit if DEVCLK is a DC-coupled LVPECL signal through a 50-Ω resistor.
1 DC_LVPECL_SYSREF_en R/W 0 Default: 0
Set this bit if SYSREF is a DC-coupled LVPECL signal through a 50-Ω resistor.
0 DC_LVPECL_SYNC_en R/W 0 Default: 0
Set this bit if SYNC~ is a DC-coupled LVPECL signal through a 50-Ω resistor.

Clock Generator Status Register (address = 0x031) [reset = 0x07]

Figure 50. Clock Generator Status Register (CLKGEN_1)
7 6 5 4 3 2 1 0
SysRefDet Dirty Capture RESERVED
R-0 R-0 R-00 0111

Table 51. CLKGEN_1 Field Descriptions

Bit Field Type Reset Description
7 SysRefDet R 0 When high, indicates that a SYSREF rising edge was detected.
To clear this bit, write SysRefDetClr to 1 and then back to 0.
6 Dirty Capture R 0 When high, indicates that a SYSREF rising edge occurred very close to the device clock edge, and setup or hold is not ensured (dirty capture). To clear this bit, write CDC to1 and then back to 0.
NOTE: When sweeping the timing on SYSREF, it may jump across the clock edge without triggering this bit. The REALIGNED status bit must be used to detect this (see the JESD_STATUS register description in Digital Down Converter and JESD204B (0x200-0x27F))
5-0 RESERVED R 00 0111 Reserved register. Always returns 000111b

Clock Generator Control 2 Register (address = 0x032) [reset = 0x80]

Figure 51. Clock Generator Control 2 Register (CLKGEN_2)
7 6 5 4 3 2 1 0
RESERVED RDEL
R/W-1000 R/W-0000

Table 52. CLKGEN_2 Field Descriptions

Bit Field Type Reset Description
7-4 RESERVED R/W 1000 Default: 1000b
3-0 RDEL R/W 0000 Adjusts the delay of the SYSREF input signal with respect to DEVCLK.
Each step delays SYSREF by 20 ps (nominal)
Default: 0
Range: 0 to 15 decimal

Analog Miscellaneous Register (address = 0x033) [reset = 0xC3]

Figure 52. Analog Miscellaneous Register (ANA_MISC)
7 6 5 4 3 2 1 0
RESERVED SYNC_DIFF_PD RESERVED
R/W-1100 0 R/W-0 R/W-11

Table 53. ANA_MISC Field Descriptions

Bit Field Type Reset Description
7-3 RESERVED R/W 1100 0
2 SYNC_DIFF_PD R/W 0 Set this bit to power down the differential SYNC~± inputs for the JESD204B interface.
The receiver must be powered up to support the differential SYNC~.
Default: 0b
1-0 RESERVED R/W 11 Default: 11b

Input Clamp Enable Register (address = 0x034) [reset = 0x2F]

Figure 53. Input Clamp Enable Register (IN_CL_EN)
7 6 5 4 3 2 1 0
RESERVED INPUT_CLAMP_EN RESERVED
R/W-00 R/W-1 R/W-0 1111

Table 54. IN_CL_EN Field Descriptions

Bit Field Type Reset Description
7-6 RESERVED R/W 00 Default: 00b
5 INPUT_CLAMP_EN R/W 1 Set this bit to enable the analog input active clamping circuit. Enabled by default.
Default: 1b
4-0 RESERVED R/W 0 1111 Default: 01111b

Serializer (0x040 to 0x04F)

Table 55. Serializer Registers

Address Reset Acronym Register Name Section
0x040 0x04 SER_CFG Serializer Configuration Register Go
0x041-0x04F Undefined RESERVED RESERVED

Serializer Configuration Register (address = 0x040) [reset = 0x04]

Figure 54. Serializer configuration Register (SER_CFG)
7 6 5 4 3 2 1 0
RESERVED SERIALIZER PRE-EMPHASIS
R/W-0000 R/W-0100

Table 56. SER_CFG Field Descriptions

Bit Field Type Reset Description
7-4 RESERVED R/W 0000
3-0 SERIALIZER PRE-EMPHASIS R/W 0100 Control bits for the pre-emphasis strength of the serializer output driver. Pre-emphasis is required to compensate the low pass behavior of the PCB trace.
Default: 4d

ADC Calibration (0x050 to 0x1FF)

Table 57. ADC Calibration Registers

Address Reset Acronym Register Name Section
0x050 0x06 CAL_CFG0 Calibration Configuration 0 Register Go
0x051 0xF4 CAL_CFG1 Calibration Configuration 1 Register Go
0x052 0x00 RESERVED RESERVED
0x053 0x5C RESERVED RESERVED
0x054 0x1C RESERVED RESERVED
0x055 0x92 RESERVED RESERVED
0x056 0x20 RESERVED RESERVED
0x057 0x10 CAL_BACK Calibration Background Control Register Go
0x058 0x00 ADC_PAT_OVR_EN ADC Pattern and Over-Range Enable Register Go
0x059 0x00 RESERVED RESERVED
0x05A 0x00 CAL_VECTOR Calibration Vectors Register Go
0x05B Undefined CAL_STAT Calibration Status Register Go
0x05C 0x00 RESERVED RESERVED
0x05D-0x05E Undefined RESERVED RESERVED
0x05F 0x00 RESERVED RESERVED
0x060 Undefined RESERVED RESERVED
0x061 Undefined RESERVED RESERVED
0x062 Undefined RESERVED RESERVED
0x063 Undefined RESERVED RESERVED
0x064 Undefined RESERVED RESERVED
0x065 Undefined RESERVED RESERVED
0x066 0x02 T_CAL Timing Calibration Register Go
0x067 0x01 RESERVED RESERVED
0x068 Undefined RESERVED RESERVED
0x069 Undefined RESERVED RESERVED
0x06A 0x00 RESERVED RESERVED
0x06B 0x20 RESERVED RESERVED
0x06C-0x1FF Undefined RESERVED RESERVED

Calibration Configuration 0 Register (address = 0x050) [reset = 0x06]

Figure 55. Calibration Configuration 0 Register (CAL_CFG0)
7 6 5 4 3 2 1 0
RESERVED CALIBRATION_READ_WRITE_EN CAL_SFT RESERVED
R/W-00 R/W-0 R/W-0 R/W-0 R/W-110

Table 58. CAL_CFG0 Field Descriptions

Bit Field Type Reset Description
7-5 RESERVED R/W 000
4 CALIBRATION_READ_WRITE_EN R/W 0 Enables the scan register to read or write calibration vectors at register 0x05A.
Default: 0
3 CAL_SFT(1) R/W 0 Software calibration bit. Set bit to initiate foreground calibration.
This bit is self-clearing.
This bit resets the calibration state machine. Most calibration SPI registers are not synchronized to the calibration clock. Changing them may corrupt the calibration state machine. Always set CAL_SFT AFTER making any changes to the calibration registers.
2-0 RESERVED R/W 110 Default: 110
IMPORTANT NOTE: Setting CAL_SFT can glitch internal state machines. The JESD_EN bit must be cleared and then set after setting CAL_SFT. 

Calibration Configuration 1 Register (address = 0x051) [reset = 0xF4]

Figure 56. Calibration Configuration 1 Register (CAL_CFG1)
7 6 5 4 3 2 1 0
RESERVED LOW_SIG_EN RESERVED
R/W-1 R/W-111 R/W-0100

Table 59. CAL_CFG1 Field Descriptions

Bit Field Type Reset Description
7 RESERVED R/W 1
6-4 LOW_SIG_EN R/W 111 Controls signal range optimization for calibration processes.
111: Calibration is optimized for lower amplitude input signals (< –10dBFS).
000: Calibration is optimized for large (-1dBFS) input signals.
Default: 111 but recommend 000 for large input signals.
3-0 RESERVED R/W 0100

Calibration Background Control Register (address = 0x057) [reset = 0x10]

Figure 57. Calibration Background Control Register (CAL_BACK)
7 6 5 4 3 2 1 0
RESERVED CAL_CONT CAL_BCK
R/W-0001 00 R/W-0 R/W-0

Table 60. CAL_BACK Field Descriptions

Bit Field Type Reset Description
7-2 RESERVED R/W 0001 00 Set to 0001 00b
1 CAL_CONT R/W 0 CAL_CONT is the only calibration register bit that can be modified while background calibration is ongoing. This bit must be set to 0 before modifying any of the other bits.
0 : Pause or stop background calibration sequence.
1 : Start background calibration sequence.
0 CAL_BCK R/W 0 Background calibration mode enabled. When pausing background calibration leave this bit set, only change CAL_CONT to 0.
If CAL_BCK is set to 0 after background calibration has been operation the calibration processes may stop in an incomplete condition. Set CAL_SFT to perform a foreground calibration

ADC Pattern and Over-Range Enable Register (address = 0x058) [reset = 0x00]

Figure 58. ADC Pattern and Over-Range Enable Register (ADC_PAT_OVR_EN)
7 6 5 4 3 2 1 0
RESERVED ADC_PAT_EN OR_EN RESERVED
R/W-0000 0 R/W-0 R/W-0 R/W-0

Table 61. ADC_PAT_OVR_EN Field Descriptions

Bit Field Type Reset Description
7-3 RESERVED R/W 0000 0 Set to 00000b
2 ADC_PAT_EN R/W 0 Enable ADC test pattern
1 OR_EN R/W 0 Enable over-range output
0 RESERVED R/W 0 Set to 0

Calibration Vectors Register (address = 0x05A) [reset = 0x00]

Figure 59. Calibration Vectors Register (CAL_VECTOR)
7 6 5 4 3 2 1 0
CAL_DATA
R/W-0000 0000

Table 62. CAL_VECTOR Field Descriptions

Bit Field Type Reset Description
7-0 CAL_DATA R/W 0000 0000 Repeated reads of this register outputs all the calibration register values for analysis if the CALIBRATION_READ_WRITE_EN bit is set.
Repeated writes of this register inputs all the calibration register values for configuration if the CAL_RD_EN bit is set.

Calibration Status Register (address = 0x05B) [reset = undefined]

Figure 60. Calibration Status Register (CAL_STAT)
7 6 5 4 3 2 1 0
RESERVED CAL_CONT_OFF FIRST_CAL_DONE
R-0000 10 R-X R-X

Table 63. CAL_STAT Field Descriptions

Bit Field Type Reset Description
7-2 RESERVED R 0000 10XX
1 CAL_CONT_OFF R X After clearing CAL_CONT, calibration does not stop immediately. Use this register to confirm it has stopped before changing calibration settings.
0: Indicates calibration is running (foreground or background)
1: Indicates that calibration is finished or stopped because CAL_CONT = 0
0 FIRST_CAL_DONE R X Indicates first calibration sequence has been done and ADC is operational.

Timing Calibration Register (address = 0x066) [reset = 0x02]

Figure 61. Timing Calibration Register (T_CAL)
7 6 5 4 3 2 1 0
RESERVED T_AUTO
R/W-0000 001 R/W-0

Table 64. CAL_STAT Field Descriptions

Bit Field Type Reset Description
7-1 RESERVED R/W 0000 001 Set to 0000001b
0 T_AUTO R/W 0 Set to enable automatic timing optimization. Timing calibration will occur once CAL_SFT is set.

Digital Down Converter and JESD204B (0x200-0x27F)

Table 65. Digital Down Converter and JESD204B Registers

Address Reset Acronym Register Name Section
0x200 0x10 DDC_CTRL1 Digital Down-Converter (DDC) Control Go
0x201 0x0F JESD_CTRL1 JESD204B Control 1 Go
0x202 0x00 JESD_CTRL2 JESD204B Control 2 Go
0x203 0x00 JESD_DID JESD204B Device ID (DID) Go
0x204 0x00 JESD_CTRL3 JESD204B Control 3 Go
0x205 Undefined JESD_STATUS JESD204B and System Status Register Go
0x206 0xF2 OVR_T0 Overrange Threshold 0 Go
0x207 0xAB OVR_T1 Overrange Threshold 1 Go
0x208 0x00 OVR_N Overrange Period Go
0x209-0x20B 0x00 RESERVED RESERVED
0x20C 0x00 NCO_MODE DDC Configuration Preset Mode Go
0x20D 0x00 NCO_SEL DDC Configuration Preset Select Go
0x20E-0x20F 0x0000 NCO_RDIV Rational NCO Reference Divisor Go
0x210-0x213 0xC0000000 NCO_FREQ0 NCO Frequency (Preset 0) Go
0x214-0x215 0x0000 NCO_PHASE0 NCO Phase (Preset 0) Go
0x216 0xFF DDC_DLY0 DDC Delay (Preset 0) Go
0x217 0x00 RESERVED RESERVED
0x218-0x21B 0xC0000000 NCO_FREQ1 NCO Frequency (Preset 1) Go
0x21C-0x21D 0x0000 NCO_PHASE1 NCO Phase (Preset 1) Go
0x21E 0xFF DDC_DLY1 DDC Delay (Preset 1) Go
0x21F 0x00 RESERVED RESERVED
0x220-0x223 0xC0000000 NCO_FREQ2 NCO Frequency (Preset 2) Go
0x224-0x225 0x0000 NCO_PHASE2 NCO Phase (Preset 2) Go
0x226 0xFF DDC_DLY2 DDC Delay (Preset 2) Go
0x227 0x00 RESERVED RESERVED
0x228-0x22B 0xC0000000 NCO_FREQ3 NCO Frequency (Preset 3) Go
0x22C-0x22D 0x0000 NCO_PHASE3 NCO Phase (Preset 3) Go
0x22E 0xFF DDC_DLY3 DDC Delay (Preset 3) Go
0x22F 0x00 RESERVED RESERVED
0x230-0x233 0xC0000000 NCO_FREQ4 NCO Frequency (Preset 4) Go
0x234-0x235 0x0000 NCO_PHASE4 NCO Phase (Preset 4) Go
0x236 0xFF DDC_DLY4 DDC Delay (Preset 4) Go
0x237 0x00 RESERVED RESERVED
0x238-0x23B 0xC0000000 NCO_FREQ5 NCO Frequency (Preset 5) Go
0x23C-0x23D 0x0000 NCO_PHASE5 NCO Phase (Preset 5) Go
0x23E 0xFF DDC_DLY5 DDC Delay (Preset 5) Go
0x23F 0x00 RESERVED RESERVED
0x240-0x243 0xC0000000 NCO_FREQ6 NCO Frequency (Preset 6) Go
0x244-0x245 0x0000 NCO_PHASE6 NCO Phase (Preset 6) Go
0x246 0xFF DDC_DLY6 DDC Delay (Preset 6) Go
0x247 0x00 RESERVED RESERVED
0x248-0x24B 0xC0000000 NCO_FREQ7 NCO Frequency (Preset 7) Go
0x24C-0x24D 0x0000 NCO_PHASE7 NCO Phase (Preset 7) Go
0x24E 0xFF DDC_DLY7 DDC Delay (Preset 7) Go
0x24F-0x251 0x00 RESERVED RESERVED
0x252-0x27F Undefined RESERVED RESERVED

Digital Down-Converter (DDC) Control Register (address = 0x200) [reset = 0x10]

Figure 62. Digital Down-Converter (DDC) Control Register (DDC_CTRL1)
7 6 5 4 3 2 1 0
RESERVED DDC GAIN BOOST DMODE
R/W-000 R/W-1 R/W-0000

Table 66. DDC_CTRL1 Field Descriptions

Bit Field Type Reset Description
7-5 RESERVED R/W 000
4 DDC GAIN BOOST R/W 1 0 : Final filter has 0-dB gain (recommended when NCO is set near DC).
1 : Final filter has 6.02-dB gain (default)
3-0 DMODE(1) R/W 0000 0 : decimate-by-4 (default)
1 : Reserved
2 : decimate-by-4
3 : decimate-by-8
4 : decimate-by-10
5 : decimate-by-16
6 : decimate-by-20
7 : decimate-by-32
8..15 : RESERVED
The DMODE setting must only be changed when JESD_EN is 0.

JESD204B Control 1 Register (address = 0x201) [reset = 0x0F]

Figure 63. JESD204B Control 1 Register (JESD_CTRL1)
7 6 5 4 3 2 1 0
SCR K_Minus_1 DDR JESD_EN
R/W-0 R/W-000 11 R/W-1 R/W-1

Table 67. JESD_CTRL1 Field Descriptions

Bit Field Type Reset Description
7 SCR R/W 0 0 : Scrambler disabled (default) 
1 : Scrambler enabled
6-2 K_Minus_1 R/W 000 11 K is the number of frames per multiframe, and K – 1 is programmed here.
Default: K = 4, K_Minus_1 = 3.
Depending on the decimation (D) and serial rate (DDR), there are constraints on the legal values of K.
1 DDR R/W 1 0 : SDR serial rate (ƒ(BIT) = ƒS)
1 : DDR serial rate (ƒ(BIT) = 2ƒS) (default)
0 JESD_EN(1) R/W 1 0 : Block disabled
1 : Normal operation (default)
Before altering any parameters in the JESD_CTRL1 register, you must set JESD_EN to 0. When JESD_EN is 0, the block is held in reset and the serializers are powered down. The clocks are gated off to save power.

JESD204B Control 2 Register (address = 0x202) [reset = 0x00]

Figure 64. JESD204B Control 2 Register (JESD_CTRL2)
7 6 5 4 3 2 1 0
P54 SYNC_DIFFSEL RESERVED JESD204B_TEST
R/W-0 R/W-0 R/W-00 R/W-0000

Table 68. JESD_CTRL2 Field Descriptions

Bit Field Type Reset Description
7 P54 R/W 0 0 : Disable 5/4 PLL. Serial bit rate is 1x or 2x based on DDR parameter.
1 : Enable 5/4 PLL. Serial bit rate is 1.25x or 2.5x based on DDR parameter. 
6 SYNC_DIFFSEL R/W 0 0 : Use SYNC_SE_N input for SYNC_N function
1 : Use SYNC_DIFF_N input for SYNC_N function
5-4 RESERVED R/W 00 Set to 00b
3-0 JESD204B_TEST(1) R/W 0000 See
0 : Test mode disabled. Normal operation (default)
1 : PRBS7 test mode
2 : PRBS15 test mode
3 : PRBS23 test mode
4 : Ramp test mode
5 : Short and long transport layer test mode
6 : D21.5 test mode
7 : K28.5 test mode
8 : Repeated ILA test mode
9 : Modified RPAT test mode
10: Serial outputs held low
11: Serial outputs held high
12 through 15 : RESERVED
The JESD_CTRL2 register must only be changed when JESD_EN is 0.

JESD204B Device ID (DID) Register (address = 0x203) [reset = 0x00]

Figure 65. JESD204B Device ID (DID) Register (JESD_DID)
7 6 5 4 3 2 1 0
JESD_DID
R/W-0000 0000

Table 69. JESD_DID Field Descriptions

Bit Field Type Reset Description
7-0 JESD_DID(1) R/W 0000 0000 Specifies the DID value that is transmitted during the second multiframe of the JESD204B ILA.
The DID setting must only be changed when JESD_EN is 0.

JESD204B Control 3 Register (address = 0x204) [reset = 0x00]

Figure 66. JESD204B Control 3 Register (JESD_CTRL3)
7 6 5 4 3 2 1 0
RESERVED FCHAR
R/W-0000 00 R/W-00

Table 70. JESD_CTRL3 Field Descriptions

Bit Field Type Reset Description
7-2 RESERVED R/W 0000 00
1-0 FCHAR(1) R/W 00 Specify which comma character is used to denote end-of-frame. This character is transmitted opportunistically according to JESD204B Section 5.3.3.4.
When using a JESD204B receiver, always use FCHAR=0.
When using a general purpose 8-b or 10-b receiver, the K28.7 character can cause issues. When K28.7 is combined with certain data characters, a false, misaligned comma character can result, and some receivers realign to the false comma. To avoid this, program FCHAR to 1 or 2.
0 : Use K28.7 (default) (JESD204B compliant)
1 : Use K28.1 (not JESD204B compliant)
2 : Use K28.5 (not JESD204B compliant)
3 : Reserved
The JESD_CTRL3 register must only be changed when JESD_EN is 0.

JESD204B and System Status Register (address = 0x205) [reset = Undefined]

See the JESD204B Synchronization Features section for more details.

Figure 67. JESD204B and System Status Register (JESD_STATUS)
7 6 5 4 3 2 1 0
RESERVED LINK_UP SYNC_STATUS REALIGNED ALIGNED PLL_LOCKED RESERVED
R/W-0 R/W-0 R/W-X R/W-X R/W-0 R/W-0 R/W-00

Table 71. JESD_STATUS Field Descriptions

Bit Field Type Reset Description
7 RESERVED R/W 0 Always returns 0
6 LINK_UP R/W 0 When set, indicates that the JESD204B link is in the DATA_ENC state.
5 SYNC_STATUS R/W X Returns the state of the JESD204B SYNC~ signal (SYNC_SE_N or SYNC_DIFF_N).
0 : SYNC~ asserted
1 : SYNC~ deasserted
4 REALIGNED R/W X When high, indicates that the div8 clock, frame clock, or multiframe clock phase was realigned by SYSREF.
Writing a 1 to this bit clears it.
3 ALIGNED R/W 0 When high, indicates that the multiframe clock phase has been established by SYSREF. The first SYSREF event after enabling the JESD204B encoder will set this bit.
Writing a 1 to this bit clears it.
2 PLL_LOCKED R/W 0 When high, indicates that the PLL is locked.
1-0 RESERVED R/W 0 Always returns 0

Overrange Threshold 0 Register (address = 0x206) [reset = 0xF2]

Figure 68. Overrange Threshold 0 Register (OVR_T0)
7 6 5 4 3 2 1 0
OVR_T0
R/W-1111 0010

Table 72. OVR_T0 Field Descriptions

Bit Field Type Reset Description
7-0 OVR_T0 R/W 1111 0010 Over-range threshold 0. This parameter defines the absolute sample level that causes control bit 0 to be set. Control bit 0 is attached to the DDC I output samples. The detection level in dBFS (peak) is
20log10(OVR_T0 / 256)
Default: 0xF2 = 242 → –0.5 dBFS

Overrange Threshold 1 Register (address = 0x207) [reset = 0xAB]

Figure 69. Overrange Threshold 1 Register (OVR_T1)
7 6 5 4 3 2 1 0
OVR_T1
R/W-1010 1011

Table 73. OVR_T1 Field Descriptions

Bit Field Type Reset Description
7-0 OVR_T1 R/W 1010 1011 Overrange threshold 1. This parameter defines the absolute sample level that causes control bit 1 to be set. Control bit 1 is attached to the DDC Q output samples. The detection level in dBFS (peak) is
20log10(OVR_T1 / 256)
Default: 0xAB = 171 → –3.5 dBFS

Overrange Period Register (address = 0x208) [reset = 0x00]

Figure 70. Overrange Period Register (OVR_N)
7 6 5 4 3 2 1 0
RESERVED OVR_N
R/W-0000 0 R/W-000

Table 74. OVR_N Field Descriptions

Bit Field Type Reset Description
7-3 RESERVED R/W 0000 0
2-0 OVR_N(1) R/W 000 This bit adjusts the monitoring period for the OVR[1:0] output bits. The period is scaled by 2OVR_N. Incrementing this field doubles the monitoring period.
Changing the OVR_N setting while JESD_EN=1 may cause the phase of the monitoring period to change.

DDC Configuration Preset Mode Register (address = 0x20C) [reset = 0x00]

Figure 71. DDC Configuration Preset Mode Register (NCO_MODE)
7 6 5 4 3 2 1 0
RESERVED CFG_MODE
R/W-0000 000 R/W-0

Table 75. NCO_MODE Field Descriptions

Bit Field Type Reset Description
7-1 RESERVED R/W 0000 000
0 CFG_MODE R/W 0 The NCO frequency and phase are set by the NCO_FREQx and NCO_PHASEx registers, where x is the configuration preset (0 through 7). The DDC delay setting is defined by the DDC_DLYx register.
0 : Use NCO_[2:0] input pins to select the active DDC and NCO configuration preset.
1 : Use the NCO_SEL register to select the active DDC and NCO configuration preset.

DDC Configuration Preset Select Register (address = 0x20D) [reset = 0x00]

Figure 72. DDC Configuration Preset Select Register (NCO_SEL)
7 6 5 4 3 2 1 0
RESERVED NCO_SEL
R/W-0000 0 R/W-000

Table 76. NCO_SEL Field Descriptions

Bit Field Type Reset Description
7-3 RESERVED R/W 0000 0
2-0 NCO_SEL R/W 000 When NCO_MODE = 1, this register is used to select the active configuration preset.

Rational NCO Reference Divisor Register (address = 0x20E to 0x20F) [reset = 0x0000]

Figure 73. Rational NCO Reference Divisor Register (NCO_RDIV)
15 14 13 12 11 10 9 8
NCO_RDIV
R/W-0x00h
7 6 5 4 3 2 1 0
NCO_RDIV
R/W-0x00h

Table 77. NCO_RDIV Field Descriptions

Bit Field Type Reset Description
15-0 NCO_RDIV R/W 0x0000h Sometimes the 32-bit NCO frequency word does not provide the desired frequency step size and can only approximate the desired frequency. This results in a frequency error. Use this register to eliminate the frequency error. Use this equation to compute the proper value to program:
Equation 10. NCO_RDIV = ƒS / ƒ(STEP) / 128

where

  • ƒS is the ADC sample rate
  • ƒ(STEP) is the desired NCO frequency step size

For example, if ƒS= 3072 MHz, and ƒ(STEP) = 10 KHz then:
Equation 11. NCO_RDIV = 3072 MHz / 10 KHz / 128 = 2400

Any combination of ƒS and ƒ(STEP) that results in a fractional value for NCO_RDIV is not supported. Values of NCO_RDIV larger than 8192 can degrade the NCO’s SFDR performance and are not recommended. This register is used for all configuration presets. 

NCO Frequency (Preset x) Register (address = see Table 65) [reset = see Table 65]

Figure 74. NCO Frequency (Preset x) Register (NCO_FREQ_x)
31 30 29 28 27 26 25 24
NCO_FREQ_x
R/W-0xC0h
23 22 21 20 19 18 17 16
NCO_FREQ_x
R/W-0x00h
15 14 13 12 11 10 9 8
NCO_FREQ_x
R/W-0x00h
7 6 5 4 3 2 1 0
NCO_FREQ_x
R/W-0x00h

Table 78. NCO_FREQ_x Field Descriptions

Bit Field Type Reset Description
31-0 NCO_FREQ_x R/W 0xC0000000h Changing this register after the JESD204B interface is running results in non-deterministic NCO phase. If deterministic phase is required, the JESD204B interface must be re-initialized after changing this register.
The NCO frequency (ƒ(NCO)) is:
Equation 12. ƒ(NCO) = NCO_FREQ_x × 2–32 × ƒS

where

  • ƒS is the sampling frequency of the ADC
  • NCO_FREQ_x is the integer value of this register

  This register can be interpreted as signed or unsigned.
Use this equation to determine the value to program:
Equation 13. NCO_FREQ_x = 232 × ƒ(NCO) / ƒS

If the equation does not result in an integer value, you must choose an alternate frequency step (ƒ(STEP) ) and program the NCO_RDIV register. Then use one of the following equations to compute NCO_FREQ_x:
Equation 14. NCO_FREQ_x = round(232 × ƒ(NCO) / ƒS)
Equation 15. NCO_FREQ_x = round(225 × ƒ(NCO) / ƒ(STEP) / NCO_RDIV) 

NCO Phase (Preset x) Register (address = see Table 65) [reset = see Table 65]

Figure 75. NCO Phase (Preset) Register (NCO_PHASE_x)
15 14 13 12 11 10 9 8
NCO_PHASE_x
R/W-0x00h
7 6 5 4 3 2 1 0
NCO_PHASE_x
R/W-0x00h

Table 79. NCO_PHASE_x Field Descriptions

Bit Field Type Reset Description
15-0 NCO_PHASE_x R/W 0x0000h This value is MSB-justified into a 32−bit field and then added to the phase accumulator. The phase (in radians) is
Equation 16. NCO_PHASE_x × 2–16 × 2π

This register can be interpreted as signed or unsigned.

DDC Delay (Preset x) Register (address = see Table 65) [reset = see Table 65]

Figure 76. DDC Delay (Preset) Register (DDC_DLY_x)
7 6 5 4 3 2 1 0
DDC_DLY_x
R/W-0xFFh

Table 80. DDC_DLY_x Field Descriptions

Bit Field Type Reset Description
7-0 DDC_DLY_x R/W 0xFFh DDC delay for configuration preset 0
This register provides fine adjustments to the DDC group delay. The step size is one half of an ADC sample period (t(DEVCLK) / 2). This is equivalent to Equation 17.
Equation 17. tO / (2 × D)

where

  • tO is the DDC output sample period
  • D is the decimation factor
The legal range for this register is 0 to 2D-1. Illegal values result in undefined behavior.
Example: When D = 8, the legal register range is 0 to 15. The step size is tO / 16 and the maximum delay is 15 × tO / 16.
Programming this register to 0xFF (the default value) powers down and bypasses the fractional delay filter which reduces the DDC latency by 34 ADC sample periods (as compared to the 0 setting).