SLWS224E August   2010  – January 2016 TRF372017

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 Recommended Operating Conditions
    3. 6.3 Thermal Information
    4. 6.4 Electrical Characteristics
    5. 6.5 Timing Requirements - SPI: Writing Phase
    6. 6.6 Timing Requirements - SPI: Read-Back Phase
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Integer and Fractional Mode Selection
      2. 7.3.2  Description of PLL Structure
        1. 7.3.2.1 Selecting PLL Divider Values
        2. 7.3.2.2 Setup Example for Integer Mode
        3. 7.3.2.3 Setup Example for Fractional Mode
      3. 7.3.3  Fractional Mode Setup
      4. 7.3.4  Selecting the VCO and VCO Frequency Control
      5. 7.3.5  External VCO
      6. 7.3.6  VCO Test Mode
      7. 7.3.7  Lock Detect
      8. 7.3.8  Tx Divider
      9. 7.3.9  LO Divider
      10. 7.3.10 Mixer
      11. 7.3.11 Disabling Outputs
      12. 7.3.12 Power Supply Distribution
      13. 7.3.13 Carrier Feedthrough Cancellation
      14. 7.3.14 Internal Baseband Bias Voltage Generation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Powersave Mode
    5. 7.5 Register Maps
      1. 7.5.1 Serial Interface Programming Registers Definition
        1. 7.5.1.1 PLL SPI Registers
          1. 7.5.1.1.1 Register 1
          2. 7.5.1.1.2 Register 2
          3. 7.5.1.1.3 Register 3
          4. 7.5.1.1.4 Register 4
          5. 7.5.1.1.5 Register 5
          6. 7.5.1.1.6 Register 6
          7. 7.5.1.1.7 Register 7
        2. 7.5.1.2 Readback Mode
          1. 7.5.1.2.1 Readback From the Internal Registers Banks
            1. 7.5.1.2.1.1 Register 0 Write
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 DAC Interfacing With External Baseband Bias Voltage
        2. 8.2.2.2 DAC Interface Using Internal VCM Generation
        3. 8.2.2.3 LO Outputs
        4. 8.2.2.4 Loop Filter
        5. 8.2.2.5 ESD Sensitivity
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7 Detailed Description

7.1 Overview

The TRF372017 is a high-performance, direct up-conversion device, integrating a high-linearity, low-noise IQ modulator and an integer-fractional PLL/VCO. The VCO uses integrated frequency dividers to achieve a wide, continuous tuning range of 300 MHz to 4800 MHz. The LO is available as an output with independent frequency dividers. The device also accepts input from an external LO or VCO. The modulator baseband inputs can be biased either internally or externally. Internal DC offset adjustment enables carrier cancellation. The device is controlled through a 3-wire serial programming interface (SPI). A control pin invokes power-save mode to reduce power consumption while keeping the VCO locked for fast start-up.

7.2 Functional Block Diagram

TRF372017 fbd_lws221.gif

7.3 Feature Description

7.3.1 Integer and Fractional Mode Selection

The PLL is designed to operate in either Integer mode or Fractional mode. If the desired local oscillator (LO) frequency is an integer multiple of the phase frequency detector (PFD) frequency, fPFD, then Integer mode can be selected. The normalized in-band phase noise floor in Integer mode is lower than in Fractional mode. In Integer mode, the feedback divider is an exact integer, and the fraction is zero. While operating in Integer mode, the register bits corresponding to the fractional control are don’t care.

In Fractional mode, the feedback divider fractional portion is non-zero on average. With 25-bit fractional resolution, RF stepsize fPFD/225 is less than 1 Hz with a fPFD up to 33 MHz. The appropriate fractional control bits in the serial register must be programmed.

7.3.2 Description of PLL Structure

TRF372017 PLL_loop_dia_lws221.gif Figure 79. Block Diagram of the PLL Loop

The output frequency is given by Equation 1:

Equation 1. TRF372017 q_fvco_output_fqcy_lws230.gif

The rate at which phase comparison occurs is fREF/RDIV. In Integer mode, the fractional setting is ignored and Equation 2 is applied.

Equation 2. TRF372017 q_fvco_ignored_lws230.gif

The feedback divider block consists of a programmable RF divider, a prescaler divider, and an NF divider. The prescaler can be programmed as either a 4/5 or an 8/9 prescaler. The NF divider includes an A counter and an M counter.

7.3.2.1 Selecting PLL Divider Values

Operation of the PLL requires the LO_DIV_SEL, RDIV, PLL_DIV_SEL, NINT, and NFRAC bits to be calculated. The LO or mixer frequency is related to fVCO according to divide-by-1/-2/-4/-8 blocks and the operating range of fVCO.

  1. LO_DIV_SEL
  2. TRF372017 q_lo_div_sel_matrix_lws230.gif

    Therefore:

    TRF372017 q_fvco_lo_div_sel_lws230.gif
  3. PLL_DIV_SEL
  4. Given fVCO, select the minimum value for PLL_DIV_SEL so that the programmable RF divider limits the input frequency into the prescaler block, fPM, to a maximum of 3000 MHz.

    PLL _ DIV _ SEL = min(1, 2, 4) such that fPM ≤ 3000 MHz

    This calculation can be restated as Equation 3.

    Equation 3. TRF372017 q_pll_ceiling_lws230.gif

    Higher values of fPFD correspond to better phase noise performance in Integer mode or Fractional mode. fPFD, along with PLL_DIV_SEL, determines the fVCO stepsize in Integer mode. Therefore, in Integer mode, select the maximum fPFD that allows for the required RF stepsize, as shown by Equation 4.

    Equation 4. TRF372017 q_pfd_fvco_lws230.gif

    In Fractional mode, a small RF stepsize is accomplished through the Fractional mode divider. A large fPFD should be used to minimize the effects of fractional controller noise in the output spectrum. In this case, fPFD may vary according to the reference clock and fractional spur requirements (for example, fPFD = 20 MHz).

  5. RDIV, NINT, NFRAC, PRSC_SEL
  6. TRF372017 q_rdiv_lws230.gif
    TRF372017 q_nint_floor_lws230.gif
    TRF372017 q_nfrac_floor_lws230.gif

    The P/(P+1) programmable prescaler is set to 8/9 or 4/5 through the PRSC_SEL bit. To allow proper fractional control, set PRSC_SEL according to Equation 5.

    Equation 5. TRF372017 q_prsc_sel_lws230.gif

    The PRSC_SEL limit at NINT < 75 applies to Fractional mode with third-order modulation. In Integer mode, the PRSC_SEL = 8/9 should be used with NINT as low as 72. The divider block accounts for either value of PRSC_SEL without requiring NINT or NFRAC to be adjusted. Then, calculate the maximum frequency to be input to the digital divider at fN. Use the lower of the possible prescaler divide settings, P = (4,8), as shown by Equation 6.

    Equation 6. TRF372017 q_fn_max_lws230.gif

    Verify that the frequency into the digital divider, fN, is less than or equal to 375 MHz. If fN exceeds 375 MHz, choose a larger value for PLL_DIV_SEL and recalculate fPFD, RDIV, NINT, NFRAC, and PRSC_SEL.

7.3.2.2 Setup Example for Integer Mode

Suppose the following operating characteristics are desired for Integer mode operation:

  • fREF = 40 MHz (reference input frequency)
  • Step at RF = 2 MHz (RF channel spacing)
  • fRF = 1600 MHz (RF frequency)

The VCO range is 2400 MHz to 4800 MHz. Therefore:

  • LO_DIV_SEL = 2
  • fVCO = LO_DIV_SEL × 1600 MHz = 3200 MHz

To keep the frequency of the prescaler less than 3000 MHz:

  • PLL_DIV_SEL = 2

The desired stepsize at RF is 2 MHz, so:

  • fPFD = 2 MHz
  • fVCO, stepsize = PLL_DIV_SEL × fPFD = 4 MHz

Using the reference frequency along with the required fPFD gives:

  • RDIV = 20
  • NINT = 800

NINT ≥ 75; therefore, select the 8/9 prescaler.

where

This example shows that Integer mode operation gives sufficient resolution for the required stepsize.

7.3.2.3 Setup Example for Fractional Mode

Suppose the following operating characteristics are desired for Fractional mode operation:

  • fREF = 40 MHz (reference input frequency)
  • Step at RF = 5 MHz (RF channel spacing)
  • fRF = 1,600,000,045 Hz (RF frequency)

The VCO range is 2400 MHz to 4800 MHz. Therefore:

  • LO_DIV_SEL = 2
  • fVCO = LO_DIV_SEL × 1,600,000,045 Hz = 3,200,000,090 Hz

To keep the frequency of the prescaler less than 3000 MHz:

  • PLL_DIV_SEL = 2

Using a typical fPFD of 20 MHz:

  • RDIV = 2
  • NINT = 80
  • NFRAC = 75

NINT ≥ 75; therefore, select the 8/9 prescaler.

where

The actual frequency at RF is:

  • fRF = 1600000044.9419 Hz

Which yields a frequency error of –0.058 Hz.

7.3.3 Fractional Mode Setup

Optimal operation of the PLL in fractional mode requires several additional register settings. Recommended values are listed in Table 1. Optimal performance may require tuning the MOD_ORD, ISOURCE_SINK, and ISOURCE_TRIM values according to the chosen frequency band.

Table 1. Fractional Mode Register Settings

REGISTER BIT REGISTER ADDRESSING RECOMMENDED VALUE
EN_ISOURCE Reg4B18 1
EN_DITH Reg4B25 1
MOD_ORD Reg4B[27..26] B[27..26] = [10]
DITH_SEL Reg4B28 0
DEL_SD_CLK Reg4B[30..29] B[30..29] = [10]
EN_LD_ISOURCE Reg5B31 0
ISOURCE_SINK Reg7B19 0
ISOURCE_TRIM Reg7B[22..20] B[22..20] = [100]

7.3.4 Selecting the VCO and VCO Frequency Control

To achieve a broad frequency tuning range, the TRF372017 includes four VCOs. Each VCO is connected to a bank of capacitors that determine its valid operating frequency. For any given frequency setting, the appropriate VCO and capacitor array must be selected.

The device contains logic that automatically selects the appropriate VCO and capacitor bank. Set bit EN_CAL to initiate the calibration algorithm. During the calibration process, the device selects a VCO and a capacitor state so that VTune matches the reference voltage set by VCO_CAL_REF_n. Accuracy of the tune is increased through bits CAL_ACC_n. Because a calibration begins immediately when EN_CAL is set, all registers must contain valid values before initiating calibration.

Calibration logic is driven by a CAL_CLK clock derived from the phase frequency detector frequency scaled according to the setting in CAL_CLK_SEL. Faster CAL_CLK frequency enables faster calibration, but the logic is limited to clock frequencies around 1 MHz. Table 2 provides suggested CAL_CLK_SEL scaling recommendations for several phase frequency detector frequencies. The flag R_SAT_ERR is evaluated during the calibration process to indicate calibration counter overflow errors, which occurs if CAL_CLK runs too fast. If R_SAT_ERR is set during a calibration, the resulting calibration is not valid and CAL_CLK_SEL must be used to slow the CAL_CLK. CAL_CLK frequencies should not be set to less than 0.1 MHz.

Table 2. Example CAL_CLK_SEL Scaling

PFD FREQUENCY
(MHz)
CAL_CLK_SEL
SCALING
CAL_CLK FREQUENCY
(MHz)
20 1/32 0.625
1 1 1
0.1 8 0.8

When VCOSEL_MODE is 0, the device automatically selects both the VCO and capacitor bank within 23 CAL_CLK cycles. When VCOSEL_MODE is 1, the device uses the VCO selected in VCO_SEL_0 and VCO_SEL_1 and automatically selects the capacitor array within 17 CAL_CLK cycles. The VCO and capacitor array settings resulting from calibration cannot be read from the VCO_SEL_n and VCO_TRIM_n bits in registers 2 and 7. They can only be read from register 0.

Automatic calibration can be disabled by setting CAL_BYPASS to 1. In this manual cal mode, the VCO is selected through register bits VCO_SEL_n, while the capacitor array is selected through register bits VCO_TRIM_n. Calibration modes are summarized in Table 3. After calibration is complete, the PLL is released from calibration mode to reach an analog lock.

During the calibration process, the TRF372017 scans through many frequencies. RF and LO outputs should be disabled until calibration is complete. At power up, the RF and LO output are disabled by default.

Once a calibration has been performed at a given frequency setting, the calibration is valid over all operating temperature conditions.

Table 3. VCO Calibration Modes

CAL_BYPASS VCOSEL_MODE MAX CYCLES CAL_CLK VCO CAPACITOR ARRAY
0 0 46 Automatic
0 1 34 VCO_SEL_n automatic
1 don't care na VCO_SEL_n VCO_TRIM_n

7.3.5 External VCO

An external LO or VCO signal may be applied. EN_EXTVCO powers the input buffer and selects the buffered external signal instead of an internal VCO. Dividers, the pfd, and the charge pump remain enabled and may be used to drive an external VCO. NEG_VCO must correspond to the gain of the external VCO.

7.3.6 VCO Test Mode

Setting VCO_TEST_MODE forces the currently selected VCO to the edge of its frequency range by disconnecting the charge pump input from the pfd and loop filter and forcing its output high or low. The upper or lower edge of the VCO range is selected through COUNT_MODE_MUX_SEL.

VCO_TEST_MODE also reports the value of a frequency counter in COUNT, which can be read back in register 0. COUNT reports the number of digital N divider cycles in the PLL, directly related to the period of fN, that occur during each CAL_CLK cycle. Counter operation is initiated through the bit EN_CAL.

Table 4. VCO Test Mode

VCO_TEST_MODE COUNT_MODE_MUX_SEL VCO OPERATION REGISTER 0 B[30..13]
0 don't care Normal B[30..24] = undefined
B[23..22] = VCO_SEL selected during autocal
B21 = undefined
B[20..13] = VCO_TRIM selected during autocal
1 0 Max frequency B[30..13] = Max frequency counter
1 1 Min frequency B[30..13] = Min frequency counter

7.3.7 Lock Detect

The lock detect signal is generated in the phase frequency detector by comparing the VCO target frequency against the VCO actual frequency. When the phase of the two compared frequencies remains aligned for several clock cycles, an internal signal goes high. The precision of this comparison is controlled through the LD_ANA_PREC bits. This internal signal is then averaged and compared against a reference voltage to generate the LD signal. The number of averages used is controlled through LD_DIG_PREC. Therefore, when the VCO is frequency locked, LD is high. When the VCO frequency is not locked, LD may pulse high or exhibit periodic behavior.

By default, the internal lock detect signal is driven on the LD terminal. Register bits MUX_CTRL_n can be used to control a mux to output other diagnostic signals on the LD output. The LD control signals are shown in Table 5.

Table 5. LD Control Signals

ADJUSTMENT REGISTER BITS BIT ADDRESSING
Lock detect precision LD_ANA_PREC_0 Register 4 Bit 19
Unlock detect precision LD_ANA_PREC_1 Register 4 Bit 20
LD averaging count LD_DIG_PREC Register 4 Bit 24
Diagnostic Output MUX_CTRL_n Register 7 Bits 18..16

Table 6. LD Control Signal Mode Settings

CONDITION RECOMMENDED SETTINGS
Integer Mode LD_ANA_PREC_0 = 0
LD_ANA_PREC_1 = 0
LD_DIG_PREC = 1
Fractional Mode LD_ANA_PREC_0 = 1
LD_ANA_PREC_1 = 1
LD_DIG_PREC = 1

7.3.8 Tx Divider

The Tx divider, illustrated in Figure 80, converts the differential output of the VCO into differential I and Q mixer components. The divide by 1 differential quadrature phases are provided through a polyphase. Divide by 2, 4, and 8 differential quadrature phases are provided through flip-flop dividers. Only one of the dividers operates at a time, and the appropriate output is selected by a mux. DIVn bits are controlled through TX_DIV_SELn.

TX_DIV_I determines the bias level for the divider blocks. The SPEEDUP control is used to bypass a stabilization resistor and reach the final bias level faster after a change in the divider selection. SPEEDUP should be disabled during normal operation.

TRF372017 tx_divider_lws221.gif Figure 80. Tx Divider

7.3.9 LO Divider

The LO divider is shown in Figure 81. It frequency divides the VCO output. Only one of the dividers operates at a time, and the appropriate output is selected by a mux. DIVn bits are controlled through LO_DIV_SELn. The output is buffered and provided on output pins LO_OUT_P and LO_OUT_N. The output level is controlled through BUFOUT_BIASn.

LO_DIV_I determines the bias level for the divider blocks. The SPEEDUP control is used to bypass a stabilization resistor and reach the final bias level faster after a change in the divider selection. SPEEDUP should be disabled during normal operation. Although SPEEDUP controls both the Tx and LO divider biases, the Tx and LO divider biases are generated independently.

TRF372017 lo_divider_lws221.gif Figure 81. LO Divider

7.3.10 Mixer

A diagram of the mixer is shown in Figure 82. The mixer is followed by a differential to single-ended converter and buffer for output.

TRF372017 mixer_lws221.gif Figure 82. Mixer

7.3.11 Disabling Outputs

RF frequency outputs are generated at the RFOUT and LO* terminals. Unused RF frequency outputs should be disabled to minimize power consumption and noise generation. Table 7 lists settings used to disable the outputs. Power-save mode can also be used to disable outputs.

Table 7. Register Controls for Disabling Outputs

DISABLED OUTPUT REGISTER BIT SETTING
RFOUT PWD_TX_DIV 1
LOP and LON PWD_OUT_BUFF 1
PWD_LO_DIV 1

7.3.12 Power Supply Distribution

Power supply distribution for the TRF372017 is shown in Figure 83. Proper isolation and filtering of the supplies is critical for low noise operation of the device. Each supply pin should be supplied with local decoupling capacitance and isolated with a ferrite bead. VCC_VCO2 is tolerant of 5-V supply voltages to permit additional supply filtering.

TRF372017 pwr_sup_lws221.gif Figure 83. Power Supply Distribution

7.3.13 Carrier Feedthrough Cancellation

The structure of the baseband current DAC is shown in Figure 84. For each input pair, there is a programmable reference current. The reference current for each pair (I and Q) is identical and is programmed through the same register bits, but the reference current source itself is duplicated in the device for both I and Q inputs. This current can be set to change the total current flowing into the P and N nodes, which in turn changes the offset programmability range.

The reference current is then mirrored and multiplied before getting injected into the input node. The total mirrored current is routed into the two sides of the differential pair and routed according to eight programmable bits. As the 8-bit setting is changed, current is shifted from one side of the pair into the other side for each of the I and Q input pairs. In practical usage, the offset current routing distributes the adjustment for each side of the pair, while the reference current sets the range of adjustment. This effect can be seen in Figure 78, which shows that the gain of the current routing is greater when the reference current setting is higher. However the step size also increases with increase in range. Figure 78 shows the effect on common mode voltage of varying the DAC reference current. Adjustment register bits are shown in Table 8.

Offset adjustment may be provided by an external source, such as a DAC QMC block, for DC-coupled systems.

TRF372017 prog_ref_lws221.gif Figure 84. Block Diagram of the Programmable Current DAC

Table 8. Baseband Differential Offset Adjustment Factors

ADJUSTMENT REGISTER BITS BIT ADDRESS
I input differential offset programmability I Offset Ref Curr IOFF_n
Register 6
Bits 12..5
Q input differential offset programmability Q Offset Ref Curr QOFF
Register 6
Bits 20..13
Offset Programmability Range DCoffset_I_n Register 7
Bits 30..29

7.3.14 Internal Baseband Bias Voltage Generation

The TRF372017 has the ability to generate DC voltage levels for its baseband inputs internally. Register settings in the device allow the user to adjust common mode voltage of the I and Q signals separately. There are three adjustment factors for the baseband inputs. These are described in Table 9.

Table 9. Baseband Adjustment Factors

ADJUSTMENT REGISTER BITS BIT ADDRESSING
VCM setting VREF_SEL_n Register 6 Bits 23..21
VCM Enable PWD_BB_VCM Register 4 Bit 15
Bias select IB_VCM_SEL Register 7 Bit 25

Each baseband input pair includes the circuitry depicted in Figure 85. The Vref set voltage impacts all four terminals: IP, IN, QP, and QN. The effect of changing the reference voltage is shown in Figure 77. Each node also includes a programmable current DAC that injects current into the positive and negative terminals of each input.

TRF372017 baseband_lws221.gif Figure 85. Block Diagram of the Baseband I Input Nodes

Table 10. Frequency Range Operation

VCO FREQUENCY DIV BY 2 DIV BY 4 DIV BY 8
Fmin Fmax Fmin Fmax Fmin Fmax Fmin Fmax
2400 4800 1200 2400 600 1200 300 600

7.4 Device Functional Modes

7.4.1 Powersave Mode

Powersave mode can be used to put the device into a low power consumption mode. The PLL block remains active in Powersave mode, reducing the time required for start-up. However, the modulator, dividers, output buffers, and baseband common mode generation blocks are powered down. The SPI block remains active, and registers are addressable. Use the PS pin to activate powersave mode.

7.5 Register Maps

7.5.1 Serial Interface Programming Registers Definition

The TRF372017 features a 3-wire serial programming interface (SPI) that controls an internal 32-bit shift register. There are a total of 3 signals that must be applied: the clock (CLK, pin 47), the serial data (DATA, pin 46) and the latch enable (LE, pin 45). The TRF372017 has an additional pin (RDBK, pin 2) for read-back functionality. This pin is a digital pin and can be used to read-back values of different internal registers.

The DATA (DB0-DB31) is loaded LSB first and is read on the rising edge of the CLOCK. The LE is asynchronous to the CLOCK and at its rising edge the data in the shift register gets loaded onto the selected internal register. The 5 LSB of the Data field are the address bits to select the available internal registers.

7.5.1.1 PLL SPI Registers

7.5.1.1.1 Register 1

Table 1. Register 1

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address Reference Clock Divider
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
…. RSV REF INV VCO NEG Charge Pump Current CP DOUBLE VCO Cal CLK div/Mult RSV

Table 11. Register 1 Field Descriptions

REGISTER 1 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 1 Register address bits
Bit1 ADDR_1 0
Bit2 ADDR_2 0
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 RDIV_0 1 13-bit Reference Divider value
(minimum value Rmin= 1, B[17..5] = [00 0000 0000 001];
maximum value Rmax=8191, B[17..5] = [11 1111 1111 111];
Bit6 RDIV_1 0
Bit7 RDIV_2 0
Bit8 RDIV_3 0
Bit9 RDIV_4 0
Bit10 RDIV_5 0
Bit11 RDIV_6 0
Bit12 RDIV_7 0
Bit13 RDIV_8 0
Bit14 RDIV_9 0
Bit15 RDIV_10 0
Bit16 RDIV_11 0
Bit17 RDIV_12 0
Bit18 RSV 0
Bit19 REF_INV 0 Invert Reference Clock polarity; 1 = use falling edge
Bit20 NEG_VCO 1 VCO polarity control; 1= negative slope (negative Kv)
Bit21 ICP_0 0 Program Charge Pump DC current, ICP
1.94mA, B[25..21] = [00 000]
0.47mA, B[25..21] = [11 111]
0.97mA, default value, , B[25..21] = [01 010]
Bit22 ICP_1 1
Bit23 ICP_2 0
Bit24 ICP_3 1
Bit25 ICP_4 0
Bit26 ICPDOUBLE 0 1 = set ICP to double the current
Bit27 CAL_CLK_SEL_0 0 Multiplication or division factor to create VCO calibration clock from PFD frequency
Bit28 CAL_CLK _SEL_1 0
Bit29 CAL_CLK _SEL_2 0
Bit30 CAL_CLK _SEL_3 1
Bit31 RSV 0

CAL_CLK_SEL[3..0]: Set the frequency divider value used to derive the VCO calibration clock from the phase detector frequency.

Table 12. Scaling Factors

CAL_CLK_SEL SCALING FACTOR
1111 1/128
1110 1/64
1101 1/32
1100 1/16
1011 1/8
1010 1/4
1001 ½
1000 1
0110 2
0101 4
0100 8
0011 16
0010 32
0001 64
0000 128

ICP[4..0]: Set the charge pump current.

Table 13. ICP and Current

ICP[4..0] CURRENT (mA)
00 000 1.94
00 001 1.76
00 010 1.62
00 011 1.49
00 100 1.38
00 101 1.29
00 110 1.21
00 111 1.14
01 000 1.08
01 001 1.02
01 010 0.97
01 011 0.92
01 100 0.88
01 101 0.84
01 110 0.81
01 111 0.78
10 000 0.75
10 001 0.72
10 010 0.69
10 011 0.67
10 100 0.65
10 101 0.63
10 110 0.61
10 111 0.59
11 000 0.57
11 001 0.55
11 010 0.54
11 011 0.52
11 100 0.51
11 101 0.5
11 110 0.48
11 111 0.47

7.5.1.1.2 Register 2

Table 2. Register 2

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address N-Divider Value
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
... PLL divider setting Prescaler Select RSV RSV VCO select FCO sel mode Cal accuracy CAL

Table 14. Register 2 Field Descriptions

REGISTER 2 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 0 Register address bits
Bit1 ADDR_1 1
Bit2 ADDR_2 0
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 NINT_0 0 PLL N-divider division setting
Bit6 NINT_1 0
Bit7 NINT_2 0
Bit8 NINT_3 0
Bit9 NINT_4 0
Bit10 NINT_5 0
Bit11 NINT_6 0
Bit12 NINT_7 1
Bit13 NINT_8 0
Bit14 NINT_9 0
Bit15 NINT_10 0
Bit16 NINT_11 0
Bit17 NINT_12 0
Bit18 NINT_13 0
Bit19 NINT_14 0
Bit20 NINT_15 0
Bit21 PLL_DIV_SEL0 1 Select division ratio of divider in front of prescaler
Bit22 PLL_DIV_SEL1 0
Bit23 PRSC_SEL 1 Set prescaler modulus (0 → 4/5; 1 → 8/9)
Bit24 RSV 0
Bit25 RSV 0
Bit26 VCO_SEL_0 0 Selects between the four integrated VCOs
00 = lowest frequency VCO; 11 = highest frequency VCO
Bit27 VCO_SEL_1 1
Bit28 VCOSEL_MODE 0 Single VCO auto-calibration mode (1 = active)
Bit29 CAL_ACC_0 0 Error count during the cap array calibration
Recommended programming [00]
Bit30 CAL_ACC_1 0
Bit31 EN_CAL 0 Execute a VCO frequency auto-calibration. Set to 1 to initiate a calibration. Resets automatically.

PLL_DIV<1,0>: Select division ratio of divider in front of prescaler.

Table 15. Frequency Divider

PLL DIV FREQUENCY DIVIDER
00 1
01 2
10 4

VCOSEL_MODE<0>: When it is 1, the cap array calibration is run on the VCO selected through bits VCO_SEL<2,1>.

7.5.1.1.3 Register 3

Table 3. Register 3

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address Fractional N-Divider Value
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
... RSV RSV

Table 16. Register 3 Field Descriptions

REGISTER 3 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 1 Register address bits
Bit1 ADDR_1 1
Bit2 ADDR_2 0
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 NFRAC<0> 0 Fractional PLL N divider value 0 to 0.99999.
Bit6 NFRAC<1> 0
Bit7 NFRAC<2> 0
Bit8 NFRAC<3> 0
Bit9 NFRAC<4> 0
Bit10 NFRAC<5> 0
Bit11 NFRAC<6> 0
Bit12 NFRAC<7> 0
Bit13 NFRAC<8> 0
Bit14 NFRAC<9> 0
Bit15 NFRAC<10> 0
Bit16 NFRAC<11> 0
Bit17 NFRAC<12> 0
Bit18 NFRAC<13> 0
Bit19 NFRAC<14> 0
Bit20 NFRAC<15> 0
Bit21 NFRAC<16> 0
Bit22 NFRAC<17> 0
Bit23 NFRAC<18> 0
Bit24 NFRAC<19> 0
Bit25 NFRAC<20> 0
Bit26 NFRAC<21> 0
Bit27 NFRAC<22> 0
Bit28 NFRAC<23> 0
Bit29 NFRAC<24> 0
Bit30 RSV 0
Bit31 RSV 0

7.5.1.1.4 Register 4

Table 4. Register 4

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address PD PLL Power-Down PLL blocks PD VCM
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
PD DC off EXT VCO PLL Test Control ΣΔ Mode order ΣΔ Mode controls EN Fract mode

Table 17. Register 4 Field Descriptions

REGISTER 4 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 0 Register address bits
Bit1 ADDR_1 0
Bit2 ADDR_2 1
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 PWD_PLL 0 Power-down all PLL blocks (1 = off)
Bit6 PWD_CP 0 When 1, charge pump is off
Bit7 PWD_VCO 0 When 1, VCO is off
Bit8 PWD_VCOMUX 0 Power-down the 4 VCO mux block (1 = Off)
Bit9 PWD_DIV124 0 Power-down programmable RF divider in PLL feedback path (1 = off)
Bit10 PWD_PRESC 0 Power-down programmable prescaler (1 = off)
Bit11 RSV 0
Bit12 PWD_OUT_BUFF 1 Power-down LO output buffer (1 = off).
Bit13 PWD_LO_DIV 1 Power-down frequency divider in LO output chain 1 (1 = off)
Bit14 PWD_TX_DIV 1 Power-down frequency divider in modulator chain (1 = off)
Bit15 PWD_BB_VCM 1 Power-down baseband input DC common block (1 = off)
Bit16 PWD_DC_OFF 1 Power-down baseband input DC offset control block (1 = off)
Bit17 EN_EXTVCO 0 Enable external LO/VCO input buffer (1 = enabled)
Bit18 EN_ISOURCE 0 Enable offset current at Charge Pump output (to be used in fractional mode only, 1 = on).
Bit19 LD_ANA_PREC_0 0 Control precision of analog lock detector (1 1 = low; 0 0 = high). See Lock Detect section of Application Information for usage details.
Bit20 LD_ANA_PREC_1 0
Bit21 CP_TRISTATE_0 0 Set the charge pump output in Tristate mode.
Normal, B[22..21] = [00]
Down, B[22..21] = [01]
Up, B[22..21] = [10]
Tristate, B[22..21] = [11]
Bit22 CP_TRISTATE_1 0
Bit23 SPEEDUP 0 Speed up PLL and Tx blocks by bypassing bias stabilizer capacitors.
Bit24 LD_DIG_PREC 0 Lock detector precision (increases sampling time if set to 1)
Bit25 EN_DITH 1 Enable ΔΣ modulator dither (1=on)
Bit26 MOD_ORD_0 0 ΔΣ modulator order (1 through 4). Not used in integer mode.
1st order, B[27..26] = [00]
2nd order, B[27..26] = [01]
3rd order, B[27..26] = [10]
4th order, B[27..26] = [11]
Bit27 MOD_ORD_1 1
Bit28 DITH_SEL 0 Select dither mode for ΔΣ modulator (0 = const; 1 = pseudo-random)
Bit29 DEL_SD_CLK_0 0 ΔΣ modulator clock delay. Not used in integer mode.
Min delay = 00
Max delay = 11
Bit30 DEL_SD_CLK_1 1
Bit31 EN_FRAC 0 Enable fractional mode (1 = fractional enabled)

7.5.1.1.5 Register 5

Table 5. Register 5

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address VCO_R Trim PLL_R_Trim VCO Current VCOBUF BIAS
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
VCOMUX BIAS OUTBUF BIAS RSV BIAS SEL VCO CAL REF VCOMUX AMPL VCO Bias Voltage RSV EN_LD ISRC

Table 18. Register 5 Field Descriptions

REGISTER 5 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 1 Register address bits
Bit1 ADDR_1 0
Bit2 ADDR_2 1
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 VCOBIAS_RTRIM_0 0 VCO bias resistor trimming. Recommended programming [100].
Bit6 VCOBIAS_RTRIM_1 0
Bit7 VCOBIAS_RTRIM_2 1
Bit8 PLLBIAS_RTRIM_0 0 PLL bias resistor trimming. Recommended programming [10].
Bit9 PLLBIAS_RTRIM_1 1
Bit10 VCO_BIAS_0 0 VCO bias reference current.
300 µA, B[13..10] = [00 00]
600 µA, B[13..10] = [11 11]
Bias current varies directly with reference current
Recommended programming
400 µA, B[13..10] = [0101] with VCC_VCO2 = 3.3 V
600 µA, B[13..10] = [1111] with VCC_VCO2 = 5 V
Bit11 VCO_BIAS_1 0
Bit12 VCO_BIAS_2 0
Bit13 VCO_BIAS_3 1
Bit14 VCOBUF_BIAS_0 0 VCO buffer bias reference current.
300 µA, B[15..14] = [00]
600 µA, B[15..14] = [11]
Bias current varies directly with reference current
Recommended programming [10]
Bit15 VCOBUF_BIAS_1 1
Bit16 VCOMUX_BIAS_0 0 VCO’s muxing buffer bias reference current.
300 µA, B[17..16] = [00]
600 µA, B[17..16] = [11]
Bias current varies directly with reference current
Recommended programming [11]
Bit17 VCOMUX_BIAS_1 1
Bit18 BUFOUT_BIAS_0 0 PLL output buffer bias reference current.
300 µA, B[19..18] = [00]
600 µA, B[19..18] = [11]
Bias current varies directly with reference current
Bit19 BUFOUT_BIAS_1 1
Bit20 RSV 0
Bit21 RSV 1
Bit22 VCO_CAL_IB 0 Select bias current type for VCO calibration circuitry
0 = PTAT; 1 = constant over temperature
Recommended programming [0]
Bit23 VCO_CAL_REF_0 0 VCO calibration reference voltage trimming.
0.9 V, B[25..23] = [000]
1.4 V, B[25..23] = [111]
Recommended programming [010]
Bit24 VCO_CAL_REF_1 0
Bit25 VCO_CAL_REF_2 1
Bit26 VCO_AMPL_CTRL_0 0 Adjust the signal amplitude at the VCO mux input
Recommended programming [11]
Bit27 VCO_AMPL_CTRL_1 1
Bit28 VCO_VB_CTRL_0 0 VCO core bias voltage control
1.2 V, B[29..28] = [00]
1.35 V, B[29..28] = [01]
1.5 V, B[29..28] = [10]
1.65 V, B[29..28] = [11]
Recommended programming [00]
Bit29 VCO_VB_CTRL _1 1
Bit30 RSV 0
Bit31 EN_LD_ISOURCE 1 Enable monitoring of LD to turn on Isource when in frac-n mode (EN_FRAC=1).
0 = ISource set by EN_ISOURCE.
1 = ISource set by LD.
Recommended programming [0]

7.5.1.1.6 Register 6

Table 6. Register 6

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address BB DC OFFSET
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
BB DC OFFSET VREF SEL TXDIV SEL LODIV SEL TXDIV BIAS LODIV BIAS

Table 19. Register 6 Field Descriptions

REGISTER 6 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 0 Register address bits
Bit1 ADDR_1 1
Bit2 ADDR_2 1
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 IOFF_0 0 Adjust Iref current used for defining I DC offset.
Full range, 2 × Iref, B[12..5] = [1 1111 111]
Mid scale, Iref B[12..5] = [1 0000 000]
Bit6 IOFF_1 0
Bit7 IOFF_2 0
Bit8 IOFF_3 0
Bit9 IOFF_4 0
Bit10 IOFF_5 0
Bit11 IOFF_6 0
Bit12 IOFF_7 1
Bit13 QOFF_0 0 Adjust Iref current used for defining Q DC offset.
Full range, 2 × Iref, B[20..13] = [1 1111 111]
Mid scale, Iref B[20..13] = [1 0000 000]
Bit14 QOFF_1 0
Bit15 QOFF_2 0
Bit16 QOFF_3 0
Bit17 QOFF_4 0
Bit18 QOFF_5 0
Bit19 QOFF_6 0
Bit20 QOFF_7 1
Bit21 VREF_SEL_0 0 Adjust Vref in baseband common mode generation circuit.
0.65 V, B[23..21] = [000]
1 V, B[23..21] = [111]
Modulator common mode is Vref + Vbe.
Recommended programming [100]
Bit22 VREF_SEL_1 0
Bit23 VREF_SEL_2 1
Bit24 TX_DIV_SEL_0 0 Adjust Tx path divider.
Div1, [B25..24] = [00]
Div2, [B25..24] = [01]
Div4, [B25..24] = [10]
Div8, [B25..24] = [11]
Bit25 TX_DIV_SEL_1 0
Bit26 LO_DIV_SEL_0 0 Adjust LO path divider
Div1, [B28..27] = [00]
Div2, [B28..27] = [01]
Div4, [B28..27] = [10]
Div8, [B28..27] = [11]
Bit27 LO_DIV_SEL_1 0
Bit28 TX_DIV_BIAS_0 0 TX divider bias reference current
25 µA, [B29..28] = [00]
37.5 µA, [B29..28] = [01]
50 µA, [B29..28] = [10]
62.5 µA, [B29..28] = [11]
Bias current varies directly with reference current
Bit29 TX_DIV_BIAS_1 1
Bit30 LO_DIV_BIAS_0 0 LO divider bias reference current
25 µA, [B29..28] = [00]
37.5 µA, [B29..28] = [01]
50 µA, [B29..28] = [10]
62.5 µA, [B29..28] = [11]
Bias current varies directly with reference current
Bit31 LO_DIV_BIAS_1 1

7.5.1.1.7 Register 7

Table 7. Register 7

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12 Bit13 Bit14 Bit15
Register address VCO CAP ARRAY CONTROL RSV VCO test mode CAL bypass
Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30 Bit31
MUX CONTROL ISRC SINK OFFSET CURRENT ADJUST LP PD TimeConst VCM Bias MIX LO VCM DC OFF REF VCO BIAS SEL

Table 20. Register 7 Field Descriptions

REGISTER 7 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 1 Register address bits
Bit1 ADDR_1 1
Bit2 ADDR_2 1
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 RSV 0
Bit6 RSV 0
Bit7 VCO_TRIM_0 0 VCO capacitor array control bits, used in manual cal mode
Bit8 VCO_TRIM_1 0
Bit9 VCO_TRIM_2 0
Bit10 VCO_TRIM_3 0
Bit11 VCO_TRIM_4 0
Bit12 VCO_TRIM_5 1
Bit13 RSV 0
Bit14 VCO_TEST_MODE 0 Counter mode: measure max/min frequency of each VCO
Bit15 CAL_BYPASS 0 Bypass of VCO auto-calibration. When 1, VCO_TRIM and VCO_SEL bits are used to select the VCO and the cap array setting
Bit16 MUX_CTRL_0 1 Select signal for test output (pin 5, LD).
[000] = Ground
[001] = Lock detector
[010] = NDIV counter output
[011] = Ground
[100] = RDIV counter output
[101] = Ground
[110] = A_counter output
[111] = Logic high;
Bit17 MUX_CTRL_1 0
Bit18 MUX_CTRL_2 0
Bit19 ISOURCE_SINK 0 Charge pump offset current polarity.
Bit20 ISOURCE_TRIM_0 0 Adjust isource bias current in frac-n mode.
Bit21 ISOURCE_TRIM_1 0
Bit22 ISOURCE_TRIM_2 1
Bit23 PD_TC_0 0 Time constant control for PWD_OUT_BUFF
[00] = Minimum time constant
[11] = Maximum time constant
Bit24 PD_TC_1 0
Bit25 IB_VCM_SEL 0 Select constant/ptat current for Common mode bias generation block
0 = PTAT
1 = const
Bit26 RSV 0
Bit27 RSV 0
Bit28 RSV 1
Bit29 DCOFFSET_I_0 0 Adjust BB input DC offset Iref
50 µA, B[27..26] = [00]
100 µA, B[27..26] = [01]
150 µA, B[27..26] = [10]
200 µA, B[27..26] = [11]
Bit30 DCOFFSET_I_1 1
Bit31 VCO_BIAS_SEL 0 Select VCO_BIAS trim settings stored in EEPROM
0 = Use EEPROM settings if parity check is 1; otherwise, use SPI settings
1 = Use SPI settings
Recommended programming [1]

7.5.1.2 Readback Mode

Register 0 functions as a Readback register. TRF372017 implements the capability to read-back the content of any serial programming interface register by initializing register 0.

Each read-back is composed by two phases: writing followed by the actual reading of the internal data. This is shown in the timing diagram in Figure 2. During the writing phase, a command is sent to TRF372017 register 0 to set it in read-back mode and to specify which register is to be read. In the proper reading phase, at each rising clock edge, the internal data is transferred into the RDBK pin and can be read at the following falling edge (LSB first). The first clock after the LE goes high (end of writing cycle) is idle and the following 32 clocks pulses transfer the internal register content to the RDBK pin.

7.5.1.2.1 Readback From the Internal Registers Banks

TRF372017 integrates 8 registers: Register 0 (000) to Register 7 (111). Registers 1 through 7 are used to set-up and control the TRF372017 functionalities, while register 0 is used for the readback function.

The latter register must be programmed with a specific command that sets TRF372017 in read-back mode and specifies the register to be read:

  • Set B[31] to 1 to put TRF372017 in read-back mode.
  • Set B[30,28] equal to the address of the register to be read (000 to 111).
  • Set B27 to control the VCO frequency counter in VCO test mode.

7.5.1.2.1.1 Register 0 Write

Table 21. Register 0 Write

NAME RESET VALUE DESCRIPTION
ADDRESS BITS B0 ADDR<0> 0 Register 0 to be programmed to set TRF372017 in readback mode.
B1 ADDR<1> 0
B2 ADDR<2> 0
B3 ADDR<3> 1
B4 ADDR<4> 0
DATA FIELD B5 N/C 0
B6 N/C 0
B7 N/C 0
B8 N/C 0
B9 N/C 0
B10 N/C 0
B11 N/C 0
B12 N/C 0
B13 N/C 0
B14 N/C 0
B15 N/C 0
B16 N/C 0
B17 N/C 0
B18 N/C 0
B19 N/C 0
B20 N/C 0
B21 N/C 0
B22 N/C 0
B23 N/C 0
B24 N/C 0
B25 N/C 0
B26 N/C 0
B27 COUNT_MODE_MUX_SEL 0 Select Readback for VCO maximum frequency or minimum frequency.
0 = Max
1 = Min
B28 RB_REG<0> X 3 LSB’s of the address for the register that is being read
Reg 0, B[30..28] = [000]
Reg 7, B[30..28] = [111]
B29 RB_REG<1> X
B30 RB_REG<2> X
B31 RB_ENABLE 1 1 ≥ Put the device in Readback Mode

The contents of any register specified in RB_REG can be read back during the read cycle, including register 0.

Bit0 Bit1 Bit2 Bit3 Bit4 Bit5 Bit6 Bit7 Bit8 Bit9 Bit10 Bit11 Bit12
Register address CHIP_ID NU R_SAT_ERR
Bit13 Bit14 Bit15 Bit16 Bit17 Bit18 Bit19 Bit20 Bit21 Bit22 Bit23 Bit24 Bit25 Bit26 Bit27 Bit28 Bit29 Bit30
COUNT0-7/VCO_TRM COUNT8-10/VCO_SEL COUNT11-17
Bit31
COUNT_MODE-MUX-SEL
REGISTER 0 NAME RESET VALUE DESCRIPTION
Bit0 ADDR_0 0 Register address bits
Bit1 ADDR_1 0
Bit2 ADDR_2 0
Bit3 ADDR_3 1
Bit4 ADDR_4 0
Bit5 CHIP_ID_0 1
Bit6 CHIP_ID_1 1
Bit7 NU x
Bit8 NU x
Bit9 NU x
Bit10 NU x
Bit11 NU x
Bit12 R_SAT_ERR x Error flag for calibration speed
Bit13 count_0/NU x B[30..13] = VCO frequency counter high when COUNT_MODE_MUX_SEL = 0 and VCO_TEST_MODE = 1
Bit14 count_1/NU x
Bit15 count_2/VCO_TRIM_0 x
Bit16 count_3/VCO_TRIM_1 x
Bit17 count_4/VCO_TRIM_2 x
Bit18 count_5/VCO_TRIM_3 x
Bit19 count_6/VCO_TRIM_4 x
Bit20 count_7/VCO_TRIM_5 x
Bit21 count_8/NU x B[30..13] = VCO frequency counter low when COUNT_MODE_MUX_SEL = 1 and VCO_TEST_MODE = 1
Bit22 count_9/VCO_sel_0 x
Bit23 count_10/VCO_sel_1 x
Bit24 count<11> x B[20..15] = Autocal results for VCO_TRIM,
B[23..22] = Autocal results for VCO_SEL when
VCO_TEST_MODE = 0
Bit25 count<12> x
Bit26 count<13> x
Bit27 count<14> x
Bit28 count<15> x
Bit29 count<16> x
Bit30 count<17> x
Bit31 COUNT_MODE_MUX_SEL x 0 = Minimum frequency
1 = Maximum frequency