SBAS404D October   2006  – February 2016 ADS8556 , ADS8557 , ADS8558


  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: General
    6. 6.6  Electrical Characteristics: ADS8556
    7. 6.7  Electrical Characteristics: ADS8557
    8. 6.8  Electrical Characteristics: ADS8558
    9. 6.9  Power Dissipation Characteristics
    10. 6.10 Serial Interface Timing Requirements
    11. 6.11 Parallel Interface Timing Requirements (Read Access)
    12. 6.12 Parallel Interface Timing Requirements (Write Access)
    13. 6.13 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
        1. Analog Inputs
        2. Analog-to-Digital Converter (ADC)
        3. Conversion Clock
        4. CONVST_x
        5. BUSY/INT
        6. Reference
      2. 7.3.2 Digital
        1. Device Configuration
        2. Parallel Interface
        3. Serial Interface
        4. Output Data Format
    4. 7.4 Device Functional Modes
      1. 7.4.1 Hardware Mode
      2. 7.4.2 Software Mode
      3. 7.4.3 Daisy-Chain Mode (in Serial Mode Only)
      4. 7.4.4 Sequential Mode (in Software Mode with External Conversion Clock Only)
      5. 7.4.5 Reset and Power-Down Modes
    5. 7.5 Register Maps
      1. 7.5.1 Control Register (CR); Default Value = 0x000003FF
  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 Curve
  9. Power Supply Recommendations
  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 Related Links
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

9 Power Supply Recommendations

The ADS855x requires four separate supplies: the analog supply for the ADC (AVDD), the buffer I/O supply for the digital interface (BVDD), and the high-voltage supplies driving the analog input circuitry (HVDD and HVSS). Generally, there are no specific requirements with regard to the power sequencing of the device. However, when HVDD is supplied before AVDD, the internal ESD structure conducts, increasing IHVDD beyond the specified value.

The AVDD supply provides power to the internal circuitry of the ADC. AVDD can be set in the range of 4.5 V to 5.5 V. Because the supply current of the device is typically 30 mA, a passive filter cannot be used between the digital board supply of the application and the AVDD pin. A linear regulator is recommended to generate the analog supply voltage. Decouple each AVDD pin to AGND with a 100-nF capacitor. In addition, place a single 10-μF capacitor close to the device but without compromising the placement of the smaller capacitor. Optionally, each supply pin can be decoupled using a 1-μF ceramic capacitor without the requirement for a 10-μF capacitor.

The BVDD supply is only used to drive the digital I/O buffers and can be set in the range of 2.7 V to 5.5 V. This range allows the device to interface with most state-of-the-art processors and controllers. To limit the noise energy from the external digital circuitry to the device, filter BVDD. A 10-Ω resistor can be placed between the external digital circuitry and the device because the current drawn is typically below 2 mA (depending on the external loads). Place a bypass ceramic capacitor of 1-μF (or alternatively, a pair of 100-nF and 10-μF capacitors) between the BVDD pin and pin 8.

The high-voltage supplies (HVSS and HVDD) are connected to the analog inputs. Noise and glitches on these supplies directly couple into the input signals. Place a 100-nF ceramic decoupling capacitor, located as close to the device as possible, between each of pins 30, 31, and AGND. An additional 10-μF capacitor is used that must be placed close to the device but without compromising the placement of the smaller capacitor.