SNAS192G April   2003  – May 2016 ADCS7476 , ADCS7477 , ADCS7478

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 - ADCS7476
    6. 6.6 Electrical Characteristics - ADCS7477
    7. 6.7 Electrical Characteristics - ADCS7478
    8. 6.8 Timing Requirements
    9. 6.9 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Transfer Function
      2. 7.4.2 Power-Up Timing
      3. 7.4.3 Modes of Operation
        1. 7.4.3.1 Normal Mode
        2. 7.4.3.2 Start-Up Mode
        3. 7.4.3.3 Shutdown Mode
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Analog Inputs
      2. 8.1.2 Digital Inputs and Outputs
    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 Noise
    2. 9.2 Digital Output Effect Upon Noise
    3. 9.3 Power Management
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

10 Layout

10.1 Layout Guidelines

Capacitive coupling between noisy digital circuitry and sensitive analog circuitry can lead to poor performance. The solution is to keep the analog and digital circuitry separated from each other and the clock line as short as possible.

Digital circuits create substantial supply and ground current transients. This digital noise could have significant impact upon system noise performance. To avoid performance degradation of the ADCS747x due to supply noise, do not use the same supply for the ADCS747x that is used for digital logic.

Generally, analog and digital lines must cross each other at 90° to avoid crosstalk. However, to maximize accuracy in high resolution systems, avoid crossing analog and digital lines altogether. It is important to keep clock lines as short as possible and isolated from ALL other lines, including other digital lines. In addition, the clock line must also be treated as a transmission line and be properly terminated.

The analog input must be isolated from noisy signal lines to avoid coupling of spurious signals into the input. Any external component (that is, a filter capacitor) connected between the input pins and ground of the converter or to the reference input pin and ground must be connected to a very clean point in the ground plane.

TI recommends the use of a single, uniform ground plane and the use of split power planes. The power planes must be placed within the same board layer. All analog circuitry (input amplifiers, filters, reference components, and so on) must be placed over the analog power plane. All digital circuitry and I/O lines must be placed over the digital power plane. Furthermore, all components in the reference circuitry and the input signal chain that are connected to ground must be connected together with short traces and enter the analog ground plane at a single, quiet point.

10.2 Layout Example

ADCS7476 ADCS7477 ADCS7478 Layout_Example_SNAS192.png Figure 36. Layout Example