SBAS825 April   2017 ADS8578S

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Family Comparison Table
  6. 6 Pin Configuration and 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: CONVST Control
    7. 7.7  Timing Requirements: Data Read Operation
    8. 7.8  Timing Requirements: Parallel Data Read Operation, CS and RD Tied Together
    9. 7.9  Timing Requirements: Parallel Data Read Operation, CS and RD Separate
    10. 7.10 Timing Requirements: Serial Data Read Operation
    11. 7.11 Timing Requirements: Byte Mode Data Read Operation
    12. 7.12 Timing Requirements: Oversampling Mode
    13. 7.13 Timing Requirements: Exit Standby Mode
    14. 7.14 Timing Requirements: Exit Shutdown Mode
    15. 7.15 Switching Characteristics: CONVST Control
    16. 7.16 Switching Characteristics: Parallel Data Read Operation, CS and RD Tied Together
    17. 7.17 Switching Characteristics: Parallel Data Read Operation, CS and RD Separate
    18. 7.18 Switching Characteristics: Serial Data Read Operation
    19. 7.19 Switching Characteristics: Byte Mode Data Read Operation
    20. 7.20 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Analog Inputs
      2. 8.3.2 Analog Input Impedance
      3. 8.3.3 Input Clamp Protection Circuit
      4. 8.3.4 Programmable Gain Amplifier (PGA)
      5. 8.3.5 Third-Order, Low-Pass Filter (LPF)
      6. 8.3.6 ADC Driver
      7. 8.3.7 Digital Filter and Noise
      8. 8.3.8 Reference
        1. 8.3.8.1 Internal Reference
        2. 8.3.8.2 External Reference
        3. 8.3.8.3 Supplying One VREF to Multiple Devices
      9. 8.3.9 ADC Transfer Function
    4. 8.4 Device Functional Modes
      1. 8.4.1 Device Interface: Pin Description
        1. 8.4.1.1  REFSEL (Input)
        2. 8.4.1.2  RANGE (Input)
        3. 8.4.1.3  STBY (Input)
        4. 8.4.1.4  PAR/SER/BYTE SEL (Input)
        5. 8.4.1.5  CONVSTA, CONVSTB (Input)
        6. 8.4.1.6  RESET (Input)
        7. 8.4.1.7  RD/SCLK (Input)
        8. 8.4.1.8  CS (Input)
        9. 8.4.1.9  OS[2:0]
        10. 8.4.1.10 BUSY (Output)
        11. 8.4.1.11 FRSTDATA (Output)
        12. 8.4.1.12 DB15/BYTE SEL
        13. 8.4.1.13 DB14/HBEN
        14. 8.4.1.14 DB[13:9]
        15. 8.4.1.15 DB8/DOUTB
        16. 8.4.1.16 DB7/DOUTA
        17. 8.4.1.17 DB[6:0]
      2. 8.4.2 Device Modes of Operation
        1. 8.4.2.1 Power-Down Modes
          1. 8.4.2.1.1 Standby Mode
          2. 8.4.2.1.2 Shutdown Mode
        2. 8.4.2.2 Conversion Control
          1. 8.4.2.2.1 Simultaneous Sampling on All Input Channels
          2. 8.4.2.2.2 Simultaneous Sampling Two Sets of Input Channels
        3. 8.4.2.3 Data Read Operation
          1. 8.4.2.3.1 Parallel Data Read
          2. 8.4.2.3.2 Parallel Byte Data Read
          3. 8.4.2.3.3 Serial Data Read
          4. 8.4.2.3.4 Data Read During Conversion
        4. 8.4.2.4 Oversampling Mode of Operation
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

10 Power Supply Recommendations

The ADS8578S uses two separate power supplies: AVDD and DVDD. The AVDD supply provides power to the ADC and internal circuits, and DVDD is used for the digital interface. AVDD and DVDD can be set independently to voltages within the permissible range.

The AVDD supply can be set in the range of 4.75 V to 5.25 V. A low-noise, linear regulator is recommended to generate the analog supply voltage. The device has four AVDD pins. Each AVDD pin must be decoupled with respect to AGND using a 1-µF capacitor. Place the 1-µF capacitor as close to the supply pins as possible.

The DVDD supply is used to drive the digital I/O buffers and can be set in the range of 2.3 V to a maximum value equal to the AVDD voltage. This range allows the device to interface with most state-of-the-art processors and controllers. Place a 1-µF (minimum 100-nF) decoupling capacitor in close proximity to the DVDD supply to provide the high-frequency digital switching current.

There are no specific requirements with regard to the power-supply sequencing of the device. However, issue a reset after the supplies are powered up and are stable to ensure the device is properly configured.

Figure 88 shows a typical PSRR curve with the decoupling capacitors.

ADS8578S D044_SBAS642.gif Figure 88. PSRR vs Frequency (With Decoupling Capacitor)