SBAS999A June   2019  – January 2021 ADS125H01

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Timing Diagrams
    9. 7.9 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Noise Performance
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Input Voltage Range
      2. 9.3.2 Analog Inputs (AINP, AINN)
        1. 9.3.2.1 ESD Diodes
        2. 9.3.2.2 Input Switch
      3. 9.3.3 Programmable Gain Amplifier (PGA)
        1. 9.3.3.1 PGA Operating Range
        2. 9.3.3.2 PGA Monitors
      4. 9.3.4 Reference Voltage
        1. 9.3.4.1 Reference Monitor
      5. 9.3.5 ADC Modulator
      6. 9.3.6 Digital Filter
        1. 9.3.6.1 Sinc Filter Mode
          1. 9.3.6.1.1 Sinc Filter Frequency Response
        2. 9.3.6.2 FIR Filter
        3. 9.3.6.3 50-Hz and 60-Hz Normal-Mode Rejection
    4. 9.4 Device Functional Modes
      1. 9.4.1 Conversion Control
        1. 9.4.1.1 Continuous-Conversion Mode
        2. 9.4.1.2 Pulse-Conversion Mode
        3. 9.4.1.3 Conversion Latency
        4. 9.4.1.4 Start-Conversion Delay
      2. 9.4.2 Clock Mode
      3. 9.4.3 Reset
        1. 9.4.3.1 Power-On Reset
        2. 9.4.3.2 Reset by RESETPin
        3. 9.4.3.3 Reset by Command
      4. 9.4.4 Calibration
        1. 9.4.4.1 Offset and Full-Scale Calibration
          1. 9.4.4.1.1 Offset Calibration Registers
          2. 9.4.4.1.2 Full-Scale Calibration Registers
        2. 9.4.4.2 Offset Calibration Command (OFSCAL)
        3. 9.4.4.3 Full-Scale Calibration Command (GANCAL)
        4. 9.4.4.4 Calibration Command Procedure
        5. 9.4.4.5 User Calibration Procedure
    5. 9.5 Programming
      1. 9.5.1 Serial Interface
        1. 9.5.1.1 Chip-Select Pins (CS1 and CS2)
        2. 9.5.1.2 Serial Clock (SCLK)
        3. 9.5.1.3 Data Input (DIN)
        4. 9.5.1.4 Data Output/Data Ready (DOUT/DRDY)
      2. 9.5.2 Data Ready (DRDY)
        1. 9.5.2.1 DRDY in Continuous-Conversion Mode
        2. 9.5.2.2 DRDY in Pulse-Conversion Mode
        3. 9.5.2.3 Data Ready by Software Polling
      3. 9.5.3 Conversion Data
        1. 9.5.3.1 Status Byte (STATUS0)
        2. 9.5.3.2 Conversion Data Format
      4. 9.5.4 Cyclic Redundancy Check (CRC)
      5. 9.5.5 Commands
        1. 9.5.5.1  General Command Format
        2. 9.5.5.2  NOP Command
        3. 9.5.5.3  RESET Command
        4. 9.5.5.4  START Command
        5. 9.5.5.5  STOP Command
        6. 9.5.5.6  RDATA Command
        7. 9.5.5.7  OFSCAL Command
        8. 9.5.5.8  GANCAL Command
        9. 9.5.5.9  RREG Command
        10. 9.5.5.10 WREG Command
    6. 9.6 Register Map
      1. 9.6.1  Device Identification (ID) Register (address = 00h) [reset = 4xh]
      2. 9.6.2  Main Status (STATUS0) Register (address = 01h) [reset = 01h]
      3. 9.6.3  Mode 0 (MODE0) Register (address = 02h) [reset = 24h]
      4. 9.6.4  Mode 1 (MODE1) Register (address = 03h) [reset = 01h]
      5. 9.6.5  Reserved (RESERVED) Register (address = 04h) [reset = 00h]
      6. 9.6.6  Mode 3 (MODE3) Register (address = 05h) [reset = 00h]
      7. 9.6.7  Reference Configuration (REF) Register (address = 06h) [reset = 05h]
      8. 9.6.8  Offset Calibration (OFCALx) Registers (address = 07h, 08h, 09h) [reset = 00h, 00h, 00h]
      9. 9.6.9  Full-Scale Calibration (FSCALx) Registers (address = 0Ah, 0Bh, 0Ch) [reset = 00h, 00h, 40h]
      10. 9.6.10 Reserved (RESERVED) Register (address = 0Dh) [reset = FFh]
      11. 9.6.11 Reserved (RESERVED) Register (address = 0Eh) [reset = 00h]
      12. 9.6.12 Reserved (RESERVED) Register (address = 0Fh) [reset = 00h]
      13. 9.6.13 MODE4 (MODE4) Register (address = 10h) [reset = 50h]
      14. 9.6.14 PGA Alarm (STATUS1) Register (address = 11h) [reset = xxh]
      15. 9.6.15 Status 2 (STATUS2) Register (address = 12h) [reset = 0xh]
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Example to Determine the PGA Linear Operating Range
      2. 10.1.2 Input Signal Rate of Change (dV/dt)
      3. 10.1.3 Unused Inputs and Outputs
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 Power-Supply Decoupling
    2. 11.2 Analog Power-Supply Clamp
    3. 11.3 Power-Supply Sequencing
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

9.3.3 Programmable Gain Amplifier (PGA)

The PGA is a low-noise, programmable gain (attenuation), CMOS differential-input, differential-output amplifier. The PGA operates in gain or attenuation mode depending on the selected gain. Typically, the PGA is programmed for gain when the expected input signal voltage is ≤ VREF and is programmed for attenuation when the expected input signal voltage is ≥ VREF.

Figure 9-1 shows the block diagram of the PGA.

GUID-510CCD2F-10DE-4F3C-8125-F5FAA18EDBDA-low.gifFigure 9-1 PGA Block Diagram

The signal inputs are RC filtered to reduce sensitivity to radio frequency interference (RFI) and electromagnetic interference (EMI). The first PGA stage is a high input-impedance, noninverting differential amplifier (amplifiers A1 and A2) and provides gain. Inverse-parallel connected diodes across the inputs of A1 and A2 clamp the amplifier input voltage if they are driven out-of-range. If the amplifier is out-of-range, the diodes can conduct, resulting in current flow through the analog input pins. High dV/dt input signals, such as those generated from the switching of a multiplexer, can lead to transient turn-on of the clamp diodes. In some cases, an RC filter at the PGA inputs may be necessary to limit the dV/dt of the signal to prevent the clamp diodes from turning on.

The second stage (amplifiers A3 and A4) is an inverting, differential amplifier. This stage provides attenuation of high-amplitude signal levels. The common-mode voltage of this stage is AVDD / 2. The second stage drives the modulator input of the ADC and is also connected to the CAPP and CAPN pins. An external 1-nF capacitor filters the modulator input sample pulses and also provides the antialias filter for the ADC. Place the capacitor close to the pins using short, direct traces. Avoid running clock traces or other digital traces underneath or in the vicinity of these pins. Gain is programmed by the GAIN[3:0] bits of the MODE 4 register.

Monitors verify the voltage headroom of the PGA input and output nodes. See the Section 9.3.3.2 section for details.