SBAS705B June   2015  – April 2020 ADS131E08S

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
    1.     Power Application: Three-Phase Voltage and Current Connection
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin 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 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Noise Measurements
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Electromagnetic Interference (EMI) Filter
      2. 9.3.2  Input Multiplexer
        1. 9.3.2.1 Device Noise Measurements
        2. 9.3.2.2 Test Signals (TestP and TestN)
        3. 9.3.2.3 Temperature Sensor (TempP, TempN)
        4. 9.3.2.4 Power-Supply Measurements (MVDDP, MVDDN)
      3. 9.3.3  Analog Input
      4. 9.3.4  PGA Settings and Input Range
        1. 9.3.4.1 Input Common-Mode Range
      5. 9.3.5  ΔΣ Modulator
      6. 9.3.6  Clock
      7. 9.3.7  Digital Decimation Filter
      8. 9.3.8  Voltage Reference
      9. 9.3.9  Input Out-of-Range Detection
      10. 9.3.10 General-Purpose Digital I/O (GPIO)
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power-Down
      2. 9.4.2 Reset
      3. 9.4.3 Conversion Mode
        1. 9.4.3.1 START Pin Low-to-High Transition or START Command Sent
        2. 9.4.3.2 Input Signal Step
        3. 9.4.3.3 Continuous Conversion Mode
    5. 9.5 Programming
      1. 9.5.1 SPI Interface
        1. 9.5.1.1 Chip Select (CS)
        2. 9.5.1.2 Serial Clock (SCLK)
        3. 9.5.1.3 Data Input (DIN)
        4. 9.5.1.4 Data Output (DOUT)
        5. 9.5.1.5 Data Ready (DRDY)
      2. 9.5.2 Data Retrieval
        1. 9.5.2.1 Status Word
        2. 9.5.2.2 Readback Length
        3. 9.5.2.3 Data Format
      3. 9.5.3 SPI Command Definitions
        1. 9.5.3.1  WAKEUP: Exit STANDBY Mode
        2. 9.5.3.2  STANDBY: Enter STANDBY Mode
        3. 9.5.3.3  RESET: Reset Registers to Default Values
        4. 9.5.3.4  START: Start Conversions
        5. 9.5.3.5  STOP: Stop Conversions
        6. 9.5.3.6  OFFSETCAL: Channel Offset Calibration
        7. 9.5.3.7  RDATAC: Start Read Data Continuous Mode
        8. 9.5.3.8  SDATAC: Stop Read Data Continuous Mode
        9. 9.5.3.9  RDATA: Read Data
        10. 9.5.3.10 RREG: Read from Register
        11. 9.5.3.11 WREG: Write to Register
        12. 9.5.3.12 Sending Multibyte Commands
    6. 9.6 Register Map
      1. 9.6.1 Register Descriptions
        1. 9.6.1.1 ID: ID Control Register (Factory-Programmed, Read-Only) (address = 00h) [reset = D2h]
          1. Table 11. ID: ID Control Register Field Descriptions
        2. 9.6.1.2 CONFIG1: Configuration Register 1 (address = 01h) [reset = 94h]
          1. Table 12. CONFIG1: Configuration Register 1 Field Descriptions
        3. 9.6.1.3 CONFIG2: Configuration Register 2 (address = 02h) [reset = 00h]
          1. Table 14. CONFIG2: Configuration Register 2 Field Descriptions
        4. 9.6.1.4 CONFIG3: Configuration Register 3 (address = 03h) [reset = E0h]
          1. Table 15. CONFIG3: Configuration Register 3 Field Descriptions
        5. 9.6.1.5 FAULT: Fault Detect Control Register (address = 04h) [reset = 00h]
          1. Table 16. FAULT: Fault Detect Control Register Field Descriptions
        6. 9.6.1.6 CHnSET: Individual Channel Settings (address = 05h to 0Ch) [reset = 10h]
          1. Table 17. CHnSET: Individual Channel Settings Field Descriptions
        7. 9.6.1.7 FAULT_STATP: Fault Detect Positive Input Status (address = 12h) [reset = 00h]
          1. Table 18. FAULT_STATP: Fault Detect Positive Input Status Field Descriptions
        8. 9.6.1.8 FAULT_STATN: Fault Detect Negative Input Status (address = 13h) [reset = 00h]
          1. Table 19. FAULT_STATN: Fault Detect Negative Input Status Field Descriptions
        9. 9.6.1.9 GPIO: General-Purpose IO Register (address = 14h) [reset = 0Fh]
          1. Table 20. GPIO: General-Purpose IO Register Field Descriptions
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Multiple Device Configuration
        1. 10.1.1.1 Synchronizing Multiple Devices
        2. 10.1.1.2 Standard Configuration
        3. 10.1.1.3 Daisy-Chain Configuration
      2. 10.1.2 Power Monitoring Specific Applications
      3. 10.1.3 Current Sensing
      4. 10.1.4 Voltage Sensing
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
      3. 10.2.3 Application Curves
    3. 10.3 Initialization Set Up
      1. 10.3.1 Setting the Device Up for Basic Data Capture
  11. 11Power Supply Recommendations
    1. 11.1 Power-Up Timing
    2. 11.2 Recommended External Capacitor Values
    3. 11.3 Device Connections for Unipolar Power Supplies
    4. 11.4 Device Connections for Bipolar Power Supplies
  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 Support Resources
    3. 13.3 Trademarks
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.1.1.3 Daisy-Chain Configuration

Daisy-chain mode is enabled by setting the DAISY_IN bit in the CONFIG1 register. Figure 55b shows the daisy-chain configuration. In this mode SCLK, DIN, and CS are shared across multiple devices. The DOUT pin of device 1 is connected to the DAISY_IN pin of device 0, thereby creating a daisy-chain for the data. Connect the DAISY_IN pin of device 1 to DGND if not used. The daisy-chain timing requirements for the SPI interface are illustrated in Figure 2. Data from the ADS131E08S device 0 appear first on DOUT, followed by a don’t care bit, and then the status and data words from the ADS131E08S device 1.

The internal oscillator output cannot be enabled because all devices in the chain operate by sharing the same DIN pin, thus an external clock must be used.

ADS131E08S ai_daisy_connex_sbas705.gif
1. To reduce pin count, set the START pin low and use the START command to synchronize and start conversions.
Figure 55. Multiple Device Configurations

There are several items to be aware of when using daisy-chain mode:

  1. One extra SCLK must be issued between each data set (see Figure 56)
  2. All devices are configured to the same register values because the CS signal is shared
  3. Device register readback is only valid for device 0 in the daisy-chain. Only ADC conversion data can be read back from device 1 through device N, where N is the last device in the chain.

The more devices in the chain, the more challenging adhering to setup and hold times becomes. A star-pattern connection of SCLK to all devices, minimizing the trace length of DOUT, and other printed circuit board (PCB) layout techniques helps to mitigate this challenge with signal delays. Placing delay circuits (such as buffers) between DOUT and DAISY_IN are options to help reduce signal delays. One other option is to insert a D flip-flop between DOUT and DAISY_IN clocked on an inverted SCLK. Figure 56 shows a timing diagram for daisy-chain mode.

ADS131E08S ai_tim_daisy_sbas705.gif

NOTE:

n = (number of channels) × (resolution) + 24 bits. The number of channels is 8. Resolution is 16 bits or 24 bits.
Figure 56. Daisy-Chain Data Word

The maximum number of devices that can be daisy-chained depends on the data rate that the devices are operated at. The maximum number of devices can be calculated with Equation 10.

Equation 10. ADS131E08S q_ndevices_bas561.gif

where

  • NBITS = device resolution (depends on DR[2:0] setting)
  • NCHANNELS = number of channels powered up in the device

For example, when the ADS131E08S is operated in 24-bit, 8-kSPS data rate with fSCLK = 10 MHz, up to six devices can be daisy-chained together.