SBASAY5 June   2024 ADS8681W

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Timing Diagrams
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Analog Input Structure
      2. 6.3.2 Analog Input Impedance
      3. 6.3.3 Input Protection Circuit
      4. 6.3.4 Programmable Gain Amplifier (PGA)
      5. 6.3.5 Second-Order, Low-Pass Filter (LPF)
      6. 6.3.6 ADC Driver
      7. 6.3.7 Reference
        1. 6.3.7.1 Internal Reference
        2. 6.3.7.2 External Reference
      8. 6.3.8 ADC Transfer Function
      9. 6.3.9 Alarm Features
        1. 6.3.9.1 Input Alarm
        2. 6.3.9.2 AVDD Alarm
    4. 6.4 Device Functional Modes
      1. 6.4.1 Host-to-Device Connection Topologies
        1. 6.4.1.1 Single Device: All multiSPI Options
        2. 6.4.1.2 Single Device: Standard SPI Interface
        3. 6.4.1.3 Multiple Devices: Daisy-Chain Topology
      2. 6.4.2 Device Operational Modes
        1. 6.4.2.1 RESET State
        2. 6.4.2.2 ACQ State
        3. 6.4.2.3 CONV State
    5. 6.5 Programming
      1. 6.5.1 Data Transfer Frame
      2. 6.5.2 Input Command Word and Register Write Operation
      3. 6.5.3 Output Data Word
      4. 6.5.4 Data Transfer Protocols
        1. 6.5.4.1 Protocols for Configuring the Device
        2. 6.5.4.2 Protocols for Reading From the Device
          1. 6.5.4.2.1 Legacy, SPI-Compatible (SYS-xy-S) Protocols With a Single SDO-x
          2. 6.5.4.2.2 Legacy, SPI-Compatible (SYS-xy-S) Protocols With Dual SDO-x
          3. 6.5.4.2.3 Source-Synchronous (SRC) Protocols
            1. 6.5.4.2.3.1 Output Clock Source Options
            2. 6.5.4.2.3.2 Output Bus Width Options
  8. 7 Register Maps
    1. 7.1 Device Configuration and Register Maps
      1. 7.1.1 DEVICE_ID_REG Register (address = 00h)
      2. 7.1.2 RST_PWRCTL_REG Register (address = 04h)
      3. 7.1.3 SDI_CTL_REG Register (address = 08h)
      4. 7.1.4 SDO_CTL_REG Register (address = 0Ch)
      5. 7.1.5 DATAOUT_CTL_REG Register (address = 10h)
      6. 7.1.6 RANGE_SEL_REG Register (address = 14h)
      7. 7.1.7 ALARM_REG Register (address = 20h)
      8. 7.1.8 ALARM_H_TH_REG Register (address = 24h)
      9. 7.1.9 ALARM_L_TH_REG Register (address = 28h)
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Alarm Function
      3. 8.2.3 Application Curve
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Power Supply Decoupling
      2. 8.3.2 Power Saving
        1. 8.3.2.1 NAP Mode
        2. 8.3.2.2 Power-Down (PD) Mode
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2 Detailed Design Procedure

This design combines the single-channel, 16-bit ADS8681W SAR ADC with the eight-channel MUX36D08 differential multiplexer. The ADS8681W provides the fast-settling, high-bandwidth performance necessary to support an external discrete multiplexer for responsive channel-to-channel operation.

The ADS868xW is settles to 1% accuracy at under 5µs (Figure 8-2) because of the device high-bandwidth input of up to 400kHz at −3dB. The ADS868xW also includes an internal programmable gain amplifier, ADC driver, and reference. Thus, making the device incredibly simple to connect a signal with an amplitude of up to ±12.288V on a single analog supply. This device also includes a variety of safety features, such as overvoltage protection, an input alarm, and AVDD alarm.

ADS8681W ADS8685W ADS8689W Step Settling Response Time Figure 8-2 Step Settling Response Time

The MUX36D08 is a differential multiplexer. This multiplexer enables using up to eight differential inputs to perform fast and accurate voltage, current, or temperature sensing across a wide input voltage range. This device accepts three digital control lines to select the analog inputs.

The ADS8681W interfaces with a controller through an enhanced SPI communication protocol, simplifying the controller speed requirements. Overall, this system simplifies connecting a wide range of single-ended or differential signals, and includes features to safely monitor these signals in an industrial environment.