SBASA31B November   2020  – November 2021 ADS131B04-Q1

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  Internal Test Signals
      6. 8.3.6  Clocking
        1. 8.3.6.1 External Clock Using CLKIN Pin
        2. 8.3.6.2 Internal Oscillator
      7. 8.3.7  ΔΣ Modulator
      8. 8.3.8  Digital Filter
        1. 8.3.8.1 Digital Filter Implementation
          1. 8.3.8.1.1 Fast-Settling Filter
          2. 8.3.8.1.2 SINC3 and SINC3 + SINC1 Filter
        2. 8.3.8.2 Digital Filter Characteristic
      9. 8.3.9  Calibration Registers
      10. 8.3.10 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 Start-Up 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 Synchronization
    5. 8.5 Programming
      1. 8.5.1 Serial 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  SPI Communication Frames
        7. 8.5.1.7  SPI Communication Words
        8. 8.5.1.8  Short SPI Frames
        9. 8.5.1.9  Communication Cyclic Redundancy Check (CRC)
        10. 8.5.1.10 SPI Timeout
      2. 8.5.2 ADC Conversion Data Format
      3. 8.5.3 Commands
        1. 8.5.3.1 NULL (0000 0000 0000 0000)
        2. 8.5.3.2 RESET (0000 0000 0001 0001)
        3. 8.5.3.3 STANDBY (0000 0000 0010 0010)
        4. 8.5.3.4 WAKEUP (0000 0000 0011 0011)
        5. 8.5.3.5 LOCK (0000 0101 0101 0101)
        6. 8.5.3.6 UNLOCK (0000 0110 0110 0110)
        7. 8.5.3.7 RREG (101a aaaa annn nnnn)
          1. 8.5.3.7.1 Reading a Single Register
          2. 8.5.3.7.2 Reading Multiple Registers
        8. 8.5.3.8 WREG (011a aaaa annn nnnn)
      4. 8.5.4 Collecting Data for the First Time or After a Pause in Data Collection
    6. 8.6 Register Map
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Troubleshooting
      2. 9.1.2 Unused Inputs and Outputs
      3. 9.1.3 Antialias Filter
      4. 9.1.4 Minimum Interface Connections
      5. 9.1.5 Multiple Device Configuration
    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
        4. 9.2.2.4 Auxiliary Analog Supply Voltage Measurement
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 CAP Pin Capacitor Requirement
    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

8.4.3.2 Global-Chop Mode

The ADS131B04-Q1 incorporates a global-chop mode option to reduce offset error and offset drift inherent to the device resulting from mismatch in the internal circuitry to very low levels. When global-chop mode is enabled by setting the GC_EN bit in the GLOBAL_CHOP_CFG register, the device uses the conversion results from two consecutive internal conversions taken with opposite input polarity to cancel the device offset voltage. Conversion n is taken with normal input polarity. The device then reverses the internal input polarity for conversion n + 1. The average of two consecutive conversions (n and n + 1, n + 1 and n + 2, and so on) yields the final offset compensated result.

Figure 8-12 shows a block diagram of the global-chop mode implementation. The combined PGA and ADC internal offset voltage is modeled as VOFS. Only this device inherent offset voltage is reduced by global-chop mode. Offset in the external circuitry connected to the analog inputs is not affected by global-chop mode.

GUID-20201025-CA0I-RK4T-D9KT-GJDNXQ6MLGRH-low.gif Figure 8-12 Global-Chop Mode Implementation

The conversion period in global-chop mode differs from the conversion time when global-chop mode is disabled (tDATA = OSR × tMOD). Figure 8-13 shows the conversion timing for an ADC channel using global-chop mode.

GUID-20201025-CA0I-DMB0-GQXK-K8BZLMMJTS7P-low.gif Figure 8-13 Conversion Timing With Global-Chop Mode Enabled

Every time the device swaps the input polarity, the digital filter is reset. The ADC then always takes three internal conversions to produce one settled global-chop conversion result.

The ADS131B04-Q1 provides a programmable delay (tGC_DLY) between the end of the previous conversion period and the beginning of the subsequent conversion period after the input polarity is swapped. This delay allows for external input circuitry to settle because the chopping switches interface directly with the analog inputs. The GC_DLY[3:0] bits in the GLOBAL_CHOP_CFG register configure the delay after chopping the inputs. The global-chop delay is selected in terms of modulator clock periods from 2 to 65,536 × tMOD.

The effective conversion period in global-chop mode follows Equation 6. A DRDY falling edge is generated each time a new global-chop conversion becomes available to the host.

The conversion process of all ADC channels in global-chop mode is restarted in the following two conditions so that all channels start sampling at the same time:

  • Falling edge of SYNC/RESET pin
  • Change of OSR setting

The conversion period of the first conversion after the ADC channels are reset is considerably longer than the conversion period of all subsequent conversions mentioned in Equation 6, because the device first must perform two fully settled internal conversions with the input polarity swapped. The conversion period for the first conversion in global-chop mode follows Equation 7.

Equation 6. tGC_CONVERSION = tGC_DLY + 3 × OSR × tMOD
Equation 7. tGC_FIRST_CONVERSION = tGC_DLY + 3 × OSR × tMOD + tGC_DLY + 3 × OSR x tMOD + 44 × tMOD

Using global-chop mode reduces the ADC noise shown in Table 7-1 at a given OSR by a factor of √2 because two consecutive internal conversions are averaged to yield one global-chop conversion result. The dc test signal cannot be measured in global-chop mode.