SBASAP8A december   2022  – august 2023 ADS131B23

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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 Diagram
    9. 6.9 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Offset Drift Measurement
    2. 7.2 Gain Drift Measurement
    3. 7.3 Noise Performance
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Naming Conventions
      2. 8.3.2 Precision Voltage References (REFA, REFB)
      3. 8.3.3 Clocking (MCLK, OSCM, OSCD)
      4. 8.3.4 ADC1y
        1. 8.3.4.1 ADC1y Input Multiplexer
        2. 8.3.4.2 ADC1y Programmable Gain Amplifier (PGA)
        3. 8.3.4.3 ADC1y ΔΣ Modulator
        4. 8.3.4.4 ADC1y Digital Filter
        5. 8.3.4.5 ADC1y Offset and Gain Calibration
        6. 8.3.4.6 ADC1y Conversion Data
      5. 8.3.5 ADC2y
        1. 8.3.5.1 ADC2y Input Multiplexer
        2. 8.3.5.2 ADC2y Programmable Gain Amplifier (PGA)
        3. 8.3.5.3 ADC2y ΔΣ Modulator
        4. 8.3.5.4 ADC2y Digital Filter
        5. 8.3.5.5 ADC2y Offset and Gain Calibration
        6. 8.3.5.6 ADC2y Sequencer
        7. 8.3.5.7 VCMy Buffers
        8. 8.3.5.8 ADC2y Measurement Configurations
        9. 8.3.5.9 ADC2y Conversion Data
      6. 8.3.6 General-Purpose Digital Inputs and Outputs (GPIO0 to GPIO4)
        1. 8.3.6.1 GPIOx PWM Output Configuration
        2. 8.3.6.2 GPIOx PWM Input Readback
      7. 8.3.7 General-Purpose Digital Inputs and Outputs (GPIO0A, GPIO1A, GPIO0B, GPIO1B)
      8. 8.3.8 Monitors and Diagnostics
        1. 8.3.8.1  Supply Monitors
        2. 8.3.8.2  Clock Monitors
        3. 8.3.8.3  Digital Monitors
          1. 8.3.8.3.1 Register Map CRC
          2. 8.3.8.3.2 Memory Map CRC
          3. 8.3.8.3.3 GPIO Readback
        4. 8.3.8.4  Communication Monitors
        5. 8.3.8.5  Fault Flags and Fault Masking
        6. 8.3.8.6  FAULT Pin
        7. 8.3.8.7  Diagnostics and Diagnostic Procedure
        8. 8.3.8.8  Indicators
        9. 8.3.8.9  Conversion and Sequence Counters
        10. 8.3.8.10 Supply Voltage Readback
        11. 8.3.8.11 Temperature Sensor (TSA)
        12. 8.3.8.12 Test DACs (TDACA, TDACB)
        13. 8.3.8.13 Open-Wire Detection
        14. 8.3.8.14 Missing Host Detection and MHD Pin
        15. 8.3.8.15 Overcurrent Comparators (OCCA, OCCB)
          1. 8.3.8.15.1 OCCA and OCCB Pins
          2. 8.3.8.15.2 Overcurrent Indication Response Time
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Up and Reset
        1. 8.4.1.1 Power-On Reset (POR)
        2. 8.4.1.2 RESETn Pin
        3. 8.4.1.3 RESET Command
      2. 8.4.2 Operating Modes
        1. 8.4.2.1 Active Mode
        2. 8.4.2.2 Standby Mode
        3. 8.4.2.3 Power-Down Mode
      3. 8.4.3 ADC Conversion Modes
        1. 8.4.3.1 ADC1y Conversion Modes
          1. 8.4.3.1.1 Continuous-Conversion Mode
          2. 8.4.3.1.2 Single-Shot Conversion Mode
          3. 8.4.3.1.3 Global-Chop Mode
            1. 8.4.3.1.3.1 Overcurrent Indication Response Time in Global-Chop Mode
        2. 8.4.3.2 ADC2y Sequencer Operation and Sequence Modes
          1. 8.4.3.2.1 Continuous Sequence Mode
          2. 8.4.3.2.2 Single-Shot Sequence Mode
          3. 8.4.3.2.3 Synchronized Single-Shot Sequence Mode Based on ADC1y Conversion Starts
    5. 8.5 Programming
      1. 8.5.1 Serial Interface
        1. 8.5.1.1 Serial Interface Signals
          1. 8.5.1.1.1 Chip Select (CSn)
          2. 8.5.1.1.2 Serial Data Clock (SCLK)
          3. 8.5.1.1.3 Serial Data Input (SDI)
          4. 8.5.1.1.4 Serial Data Output (SDO)
          5. 8.5.1.1.5 Data Ready (DRDYn)
        2. 8.5.1.2 Serial Interface Communication Structure
          1. 8.5.1.2.1 SPI Communication Frames
          2. 8.5.1.2.2 SPI Communication Words
          3. 8.5.1.2.3 STATUS Word
          4. 8.5.1.2.4 Communication Cyclic Redundancy Check (CRC)
          5. 8.5.1.2.5 Commands
            1. 8.5.1.2.5.1 NULL (0000 0000 0000 0000b)
            2. 8.5.1.2.5.2 RESET (0000 0000 0001 0001b)
            3. 8.5.1.2.5.3 LOCK (0000 0101 0101 0101b)
            4. 8.5.1.2.5.4 UNLOCK (0000 0110 0101 0101b)
            5. 8.5.1.2.5.5 WREG (011a aaaa aaa0 0nnnb)
            6. 8.5.1.2.5.6 RREG (101a aaaa aaan nnnnb)
          6. 8.5.1.2.6 SCLK Counter
          7. 8.5.1.2.7 SPI Timeout
          8. 8.5.1.2.8 Reading ADC1A, ADC1B, and ADC2A Conversion Data
          9. 8.5.1.2.9 DRDYn Pin Behavior
    6. 8.6 Register Map
      1. 8.6.1 Registers
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Unused Inputs and Outputs
      2. 9.1.2 Minimum Interface Connections
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Current-Shunt Measurement
        2. 9.2.2.2 Battery-Pack Voltage Measurement
        3. 9.2.2.3 Shunt Temperature Measurement
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
      1. 9.3.1 Power-Supply Options
        1. 9.3.1.1 Single Unregulated External 4-V to 16-V Supply (3.3-V Digital I/O Levels)
        2. 9.3.1.2 Single Regulated External 3.3-V Supply (3.3-V Digital IO Levels)
        3. 9.3.1.3 Single Regulated External 5-V Supply (5-V Digital I/O Levels)
      2. 9.3.2 Power-Supply Sequencing
      3. 9.3.3 Power-Supply Decoupling
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.4.5 ADC1y Offset and Gain Calibration

ADC1y provides the ability to compute offset and gain corrected conversion data using user-programmable offset and gain correction registers. As shown in Figure 8-8, the 24-bit offset correction value (OCAL1y[23:0]) is subtracted from the conversion data before being multiplied by the 16-bit gain correction factor (GCAL1y[15:0]). Output data are rounded to the final resolution and clipped to +FS and –FS code values after the scaling operation. The offset and gain calibration coefficients must be stored in external nonvolatile memory and programmed into the offset and gain calibration registers each time the device powers up or resets because the ADS131B23 registers are volatile.

GUID-20221012-SS0I-DZWB-FMTX-4KDKFMGRL5TW-low.svg Figure 8-5 Calibration Logic Block Diagram

The 24-bit offset calibration value is provided in two's-complement format and programmed into the OCAL1y[23:0] bit field that spans across the ADC1y_OCAL_MSB and ADC1y_OCAL_LSB registers. Table 8-9 shows example offset calibration values. The LSB size of the offset calibration value is calculated using Equation 6.

Equation 6. LSB size = (2 × VREFy) / (GAIN1y × 224)
Table 8-4 Offset Calibration Value Examples
OCAL1y[23:0] VALUE APPLIED OFFSET CORRECTION
000010h –16 LSB
000001h –1 LSB
FFFFFFh 1 LSB
FFFFF0h 16 LSB

The 16-bit gain calibration value is provided in two's-complement format and programmed into the GCAL1y[15:0] bit field. One LSB of the gain calibration value equals a gain correction factor of 1/216 = 0.000015. Table 8-10 shows example gain calibration values.

Table 8-5 Gain Calibration Value Examples
GCAL1y[15:0] VALUE APPLIED GAIN CORRECTION
7FFFh 1.499985
0001h 1.000015
0000h 1
FFFFh 0.999985
8000h 0.5

The recommended calibration procedure is as follows:

  1. Preset the offset and gain calibration registers to OCAL1y[23:0] = 000000h and GCAL1y[15:0] = 0000h, respectively.
  2. Perform an offset calibration by shorting the ADC1y inputs internally using the respective input multiplexer setting (MUX1y[1:0] = 10b), or short the inputs externally at the system level to include the offset error of the external filter stages. Acquire multiple conversion data and write the average value of the data into the offset calibration registers. Averaging the data reduces conversion noise to improve calibration accuracy.
  3. Perform a gain calibration by applying a precision calibration signal to the ADC1y inputs or at the system level to include the gain error of the external filter stages. Choose the calibration voltage to be less than the full-scale input range to avoid clipping the output code. Clipped output codes result in inaccurate calibration. For example, use a 150-mV calibration signal when using gain = 8. Acquire multiple conversion data and average the results. Use Equation 7 to calculate the gain calibration value.
    Equation 7. Gain Calibration Value = (expected output code / actual output code)
    The expected output code for a 150-mV calibration voltage using gain = 8 is: (150 mV / LSB size) = 7AE148h, where LSB size = (2 × 1.25 V) / (8 × 224). If the actual measured output code is 6FB587h for example, then the gain calibration factor calculates to 1.1. The resulting gain calibration value to write into the GCAL1y[15:0] bit field is: (1.1 – 1) / (1 / 216) = 199Ah.