SBAS780B December   2016  – March 2021 ADS8661 , ADS8665

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. 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. 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
  9. Power Supply Recommendations
    1. 9.1 Power Supply Decoupling
    2. 9.2 Power Saving
      1. 9.2.1 NAP Mode
      2. 9.2.2 Power-Down (PD) Mode
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary

Package Options

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

Layout Guidelines

Figure 10-1 illustrates a PCB layout example for the ADS866x.

  • Partition the PCB into analog and digital sections. Care must be taken to ensure that the analog signals are kept away from the digital lines. This layout helps keep the analog input and reference input signals away from the digital noise. In this layout example, the analog input and reference signals are routed on the lower side of the board and the digital connections are routed on the top side of the board.
  • Using a single dedicated ground plane is strongly encouraged.
  • Power sources to the ADS866x must be clean and well-bypassed. Using a 1-μF, X7R-grade, 0603-size ceramic capacitor with at least a 10-V rating in close proximity to the analog (AVDD) supply pins is recommended. For decoupling the digital supply pin (DVDD), a 1-μF, X7R-grade, 0603-size ceramic capacitor with at least a 10-V rating is recommended. Placing vias between the AVDD, DVDD pins and the bypass capacitors must be avoided. All ground pins must be connected to the ground plane using short, low-impedance paths.
  • There are two decoupling capacitors used for the REFCAP pin. The first is a small, 1-μF, 0603-size ceramic capacitor placed close to the device pins for decoupling the high-frequency signals and the second is a
    10-μF, 0805-size ceramic capacitor to provide the charge required by the reference circuit of the device. A capacitor with an ESR less than 0.2 Ω is recommended for the 10-μF capacitor. Both of these capacitors must be directly connected to the device pins without any vias between the pins and capacitors.
  • The REFIO pin also must be decoupled with a minimum of 4.7-μF ceramic capacitor if the internal reference of the device is used. The capacitor must be placed close to the device pins.