SBAS633E February   2016  – August 2022 ADS8681 , ADS8685 , ADS8689

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: Conversion Cycle
    7. 6.7  Timing Requirements: Asynchronous Reset
    8. 6.8  Timing Requirements: SPI-Compatible Serial Interface
    9. 6.9  Timing Requirements: Source-Synchronous Serial Interface (External Clock)
    10. 6.10 Timing Requirements: Source-Synchronous Serial Interface (Internal Clock)
    11. 6.11 Timing Diagrams
    12. 6.12 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Analog Input Structure
      2. 7.3.2 Analog Input Impedance
      3. 7.3.3 Input Protection Circuit
      4. 7.3.4 Programmable Gain Amplifier (PGA)
      5. 7.3.5 Second-Order, Low-Pass Filter (LPF)
      6. 7.3.6 ADC Driver
      7. 7.3.7 Reference
        1. 7.3.7.1 Internal Reference
        2. 7.3.7.2 External Reference
      8. 7.3.8 ADC Transfer Function
      9. 7.3.9 Alarm Features
        1. 7.3.9.1 Input Alarm
        2. 7.3.9.2 AVDD Alarm
    4. 7.4 Device Functional Modes
      1. 7.4.1 Host-to-Device Connection Topologies
        1. 7.4.1.1 Single Device: All multiSPI Options
        2. 7.4.1.2 Single Device: Standard SPI Interface
        3. 7.4.1.3 Multiple Devices: Daisy-Chain Topology
      2. 7.4.2 Device Operational Modes
        1. 7.4.2.1 RESET State
        2. 7.4.2.2 ACQ State
        3. 7.4.2.3 CONV State
    5. 7.5 Programming
      1. 7.5.1 Data Transfer Frame
      2. 7.5.2 Input Command Word and Register Write Operation
      3. 7.5.3 Output Data Word
      4. 7.5.4 Data Transfer Protocols
        1. 7.5.4.1 Protocols for Configuring the Device
        2. 7.5.4.2 Protocols for Reading From the Device
          1. 7.5.4.2.1 Legacy, SPI-Compatible (SYS-xy-S) Protocols with a Single SDO-x
          2. 7.5.4.2.2 Legacy, SPI-Compatible (SYS-xy-S) Protocols With Dual SDO-x
          3. 7.5.4.2.3 Source-Synchronous (SRC) Protocols
            1. 7.5.4.2.3.1 Output Clock Source Options
            2. 7.5.4.2.3.2 Output Bus Width Options
    6. 7.6 Register Maps
      1. 7.6.1 Device Configuration and Register Maps
        1. 7.6.1.1 DEVICE_ID_REG Register (address = 00h)
        2. 7.6.1.2 RST_PWRCTL_REG Register (address = 04h)
        3. 7.6.1.3 SDI_CTL_REG Register (address = 08h)
        4. 7.6.1.4 SDO_CTL_REG Register (address = 0Ch)
        5. 7.6.1.5 DATAOUT_CTL_REG Register (address = 10h)
        6. 7.6.1.6 RANGE_SEL_REG Register (address = 14h)
        7. 7.6.1.7 ALARM_REG Register (address = 20h)
        8. 7.6.1.8 ALARM_H_TH_REG Register (address = 24h)
        9. 7.6.1.9 ALARM_L_TH_REG Register (address = 28h)
  8. 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
      3. 8.2.3 Application Curves
    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
  9. 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
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • PW|16
Thermal pad, mechanical data (Package|Pins)
Orderable Information
7.5.4.2.1 Legacy, SPI-Compatible (SYS-xy-S) Protocols with a Single SDO-x

As shown in Table 7-9, the host controller can use any of the four legacy, SPI-compatible protocols (SPI-00-S, SPI-01-S, SPI-10-S, or SPI-11-S) to read data from the device.

Table 7-9 SPI Protocols for Reading From the Device
PROTOCOL SCLK POLARITY
(At CS Falling Edge)		 SCLK PHASE
(Capture Edge)		 MSB BIT LAUNCH EDGE SDI_CTL_REG SDO_CTL_REG DIAGRAM
SPI-00-S Low Rising CS falling 00h 00h Figure 7-32
SPI-01-S Low Falling 1st SCLK rising 01h 00h Figure 7-32
SPI-10-S High Falling CS falling 02h 00h Figure 7-33
SPI-11-S High Rising 1st SCLK falling 03h 00h Figure 7-33

On power-up or after coming out of any asynchronous reset, the device supports the SPI-00-S protocol for data read and data write operations. To select a different SPI-compatible protocol for both the data transfer operations:

  1. Program the SDI_MODE[1:0] bits in the SDI_CTL_REG register. This first write operation must adhere to the SPI-00-S protocol. Any subsequent data transfer frames must adhere to the newly-selected protocol.
  2. Set the SDO_MODE[1:0] bits = 00b in the SDO_CTL_REG register.

Note:

The SPI transfer protocol selected by configuring the SDI_MODE[1:0] bits in the SDI_CTL_REG register determines the data transfer protocol for both write and read operations. Either data can be read from the device using the selected SPI protocol by configuring the SDO_MODE[1:0] bits = 00b in the SDO_CTL_REG register, or one of the SRC protocols can be selected for data read, as explained in the Section 7.5.4.2.3 section.

When using any of the SPI-compatible protocols, the RVS output remains low throughout the data transfer frame; see the Section 6.8 table for associated timing parameters.

Figure 7-32 and Figure 7-33 explain the details of the four protocols. As explained in the Section 7.5.1 section, the host controller can use a short data transfer frame to read only the required number of MSB bits from the 32-bit output data word.

If the host controller uses a long data transfer frame with SDO_CNTL_REG[7:0] = 00h, then the device exhibits daisy-chain operation (see the Section 7.4.1.3 section).

GUID-9BB82B70-BAA3-4B53-94EB-8E97879C00C5-low.gifFigure 7-32 Standard SPI Timing Protocol
(CPHA = 0, Single SDO-x)
GUID-01B0067C-2096-4D48-9ACB-544FBE02F5EB-low.gifFigure 7-33 Standard SPI Timing Protocol
(CPHA = 1, Single SDO-x)