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

7.5.3 Output Data Word

The data read from the device can be synchronized to the external clock on the SCLK pin or to an internal clock of the device by programming the configuration registers (see the Section 7.5.4 section for details).

In any data transfer frame, the contents of the internal output shift register are shifted out on the SDO-x pins. The output data for any frame (F+1) is determined by the command issued in frame F and the status of DATA_VAL[2:0] bits:

  • If the DATA_VAL[2:0] bits in the DATAOUT_CTL_REG register are set to 1xxb, then the output data word for frame (F+1) contains fixed data pattern as described in the DATAOUT_CTL_REG register.
  • If a valid READ command is issued in frame F, the output data word for frame (F+1) contains 8-bit register data, followed by 0's.
  • If a valid READ_HWORD command is issued in frame F, the output data word for frame (F+1) contains 16-bit register data, followed by 0's.
  • For all other combinations, the output data word for frame (F+1) contains the latest 16-bit conversion result. Program the DATAOUT_CTL_REG register to append various data flags to the conversion result. The data flags are appended as per following sequence:
    1. DEVICE_ADDR[3:0] bits are appended if the DEVICE_ADDR_INCL bit is set to 1
    2. ADC INPUT RANGE FLAGS are appended if the RANGE_INCL bit is set to 1
    3. AVDD ALARM FLAGS are appended if the VDD_ACTIVE_ALARM_INCL bit is set to 1
    4. INPUT ALARM FLAGS are appended if the IN_ACTIVE_ALARM_INCL bit is set to 1
    5. PARITY bits are appended if the PAR_EN bit is set to 1
    6. All the remaining bits in the 32-bit output data word are set to 0.

Table 7-6 shows the output data word with all data flags enabled.

Table 7-6 Output Data Word With All Data Flags Enabled
DEVICE_ADDR_INCL = 1b, VDD_ACTIVE_ALARM_INCL = 1b, IN_ACTIVE_ALARM_INCL = 1b, RANGE_INCL = 1b, and PAR_EN = 1b
D[31:16] D[15:12] D[11:8] D[7:6] D[5:4] D[3:2] D[1:0]
Conversion result Device address ADC input range AVDD alarm flags Input alarm flags Parity bits 00b

Table 7-7 shows output data word with only some of the data flags enabled.

Table 7-7 Output Data Word With Only Some Data Flags Enabled
DEVICE_ADDR_INCL = 0b, VDD_ACTIVE_ALARM_INCL = 1b, IN_ACTIVE_ALARM_INCL = 0b, RANGE_INCL = 1b, and PAR_EN = 1b
D[31:16] D[15:12] D[11:10] D[9:8] D[7:0]
Conversion result ADC input range AVDD alarm flags Parity bits 00000000b