SBAS853A January   2020  – April 2021 ADS131M02

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 Switching Characteristics
    8. 6.8 Timing Diagrams
    9. 6.9 Typical Characteristics
  7. 7 Parameter Measurement Information
    1. 7.1 Noise Measurements
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input ESD Protection Circuitry
      2. 8.3.2  Input Multiplexer
      3. 8.3.3  Programmable Gain Amplifier (PGA)
      4. 8.3.4  Voltage Reference
      5. 8.3.5  Clocking and Power Modes
      6. 8.3.6  ΔΣ Modulator
      7. 8.3.7  Digital Filter
        1. 8.3.7.1 Digital Filter Implementation
          1. 8.3.7.1.1 Fast-Settling Filter
          2. 8.3.7.1.2 SINC3 and SINC3 + SINC1 Filter
        2. 8.3.7.2 Digital Filter Characteristic
      8. 8.3.8  DC Block Filter
      9. 8.3.9  Internal Test Signals
      10. 8.3.10 Channel Phase Calibration
      11. 8.3.11 Calibration Registers
      12. 8.3.12 Communication Cyclic Redundancy Check (CRC)
      13. 8.3.13 Register Map CRC
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
        1. 8.4.1.1 Power-On Reset
        2. 8.4.1.2 SYNC/RESET Pin
        3. 8.4.1.3 RESET Command
      2. 8.4.2 Fast Startup Behavior
      3. 8.4.3 Conversion Modes
        1. 8.4.3.1 Continuous-Conversion Mode
        2. 8.4.3.2 Global-Chop Mode
      4. 8.4.4 Power Modes
      5. 8.4.5 Standby Mode
      6. 8.4.6 Current-Detect Mode
    5. 8.5 Programming
      1. 8.5.1 Interface
        1. 8.5.1.1  Chip Select (CS)
        2. 8.5.1.2  Serial Data Clock (SCLK)
        3. 8.5.1.3  Serial Data Input (DIN)
        4. 8.5.1.4  Serial Data Output (DOUT)
        5. 8.5.1.5  Data Ready (DRDY)
        6. 8.5.1.6  Conversion Synchronization or System Reset (SYNC/RESET)
        7. 8.5.1.7  SPI Communication Frames
        8. 8.5.1.8  SPI Communication Words
        9. 8.5.1.9  ADC Conversion Data
          1. 8.5.1.9.1 Collecting Data for the First Time or After a Pause in Data Collection
        10. 8.5.1.10 Commands
          1. 8.5.1.10.1 NULL (0000 0000 0000 0000)
          2. 8.5.1.10.2 RESET (0000 0000 0001 0001)
          3. 8.5.1.10.3 STANDBY (0000 0000 0010 0010)
          4. 8.5.1.10.4 WAKEUP (0000 0000 0011 0011)
          5. 8.5.1.10.5 LOCK (0000 0101 0101 0101)
          6. 8.5.1.10.6 UNLOCK (0000 0110 0110 0110)
          7. 8.5.1.10.7 RREG (101a aaaa annn nnnn)
            1. 8.5.1.10.7.1 Reading a Single Register
            2. 8.5.1.10.7.2 Reading Multiple Registers
          8. 8.5.1.10.8 WREG (011a aaaa annn nnnn)
        11. 8.5.1.11 Short SPI Frames
      2. 8.5.2 Synchronization
    6. 8.6 ADS131M02 Registers
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Unused Inputs and Outputs
      2. 9.1.2 Antialiasing
      3. 9.1.3 Minimum Interface Connections
      4. 9.1.4 Multiple Device Configuration
      5. 9.1.5 Power Metrology Applications
      6. 9.1.6 Code Example
      7. 9.1.7 Troubleshooting
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Voltage Measurement Front-End
        2. 9.2.2.2 Current Measurement Front-End
        3. 9.2.2.3 ADC Setup
        4. 9.2.2.4 Calibration
        5. 9.2.2.5 Formulae
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 CAP Pin Behavior
    2. 10.2 Power-Supply Sequencing
    3. 10.3 Power-Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.11 Calibration Registers

The calibration registers allow for the automatic computation of calibrated ADC conversion results from pre-programmed values. The host can rely on the device to automatically correct for system gain and offset after the error correction terms are programmed into the corresponding device registers. The measured calibration coefficients must be store in external non-volatile memory and programmed into the registers each time the ADS131M02 powers up because the ADS131M02 registers are volatile.

The offset calibration registers are used to correct for system offset error, otherwise known as zero error. Offset error corresponds to the ADC output when the input to the system is zero. The ADS131M02 corrects for offset errors by subtracting the contents of the OCALn[23:0] register bits in the CHn_OCAL_MSB and CHn_OCAL_LSB registers from the conversion result for that channel before being output. There are separate CHn_OCAL_MSB and CHnOCAL_LSB registers for each channel, which allows separate offset calibration coefficients to be programmed for each channel. The contents of the OCALn[23:0] bits are interpreted by the device as 24-bit two's complement values, which is the same format as the ADC data.

The gain calibration registers are used to correct for system gain error. Gain error corresponds to the deviation of gain of the system from its ideal value. The ADS131M02 corrects for gain errors by multiplying the ADC conversion result by the value given by the contents of the GCALn[23:0] register bits in the CHn_GCAL_MSB and CHn_GCAL_LSB registers before being output. There are separate CHn_GCAL_MSB and CHn_GCAL_LSB registers for each channel, which allows separate gain calibration coefficients to be programmed for each channel. The contents of the GCALn[23:0] bits are interpreted by the device as 24-bit unsigned values corresponding to linear steps ranging from gains of 0 to 2 – (1 / 223). Table 8-6 describes the relationship between the GCALn[23:0] bit values and the gain calibration factor.

Table 8-6 GCALn[23:0] Bit Mapping
GCALn[23:0] VALUE GAIN CALIBRATION FACTOR
000000h 0
000001h 1.19 × 10–7
800000h 1
FFFFFEh 2 – 2.38 × 10–7
FFFFFFh 2 – 1.19 × 10–7

The calibration registers do not need to be enabled because they are always in use. The OCALn[23:0] bits have a default value of 000000h resulting in no offset correction. Similarly, the GCALn[23:0] bits default to 800000h resulting in a gain calibration factor of 1.

Figure 8-12 depicts a block diagram illustrating the mechanics of the calibration registers on one channel of the ADS131M02.

GUID-8237203A-7DA3-4392-8812-493A846EC5C5-low.gifFigure 8-12 Calibration Block Diagram