SBAS531D December   2010  – February 2016 ADS8555

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 Serial Interface Timing Requirements
    7. 6.7 Parallel Interface Timing Requirements (Read Access)
    8. 6.8 Parallel Interface Timing Requirements (Write Access)
    9. 6.9 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. 7.3.1.1 Analog Inputs
        2. 7.3.1.2 Analog-to-Digital Converter (ADC)
        3. 7.3.1.3 Conversion Clock
        4. 7.3.1.4 CONVST_x
        5. 7.3.1.5 BUSY/INT
        6. 7.3.1.6 Reference
      2. 7.3.2 Digital
        1. 7.3.2.1 Device Configuration
        2. 7.3.2.2 Parallel Interface
        3. 7.3.2.3 Serial Interface
        4. 7.3.2.4 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. Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Measurement of Electrical Variables in a 3-Phase Power System
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 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 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

10 Layout

10.1 Layout Guidelines

All GND pins must be connected to a clean ground reference. This connection must be kept as short as possible to minimize the inductance of this path. TI recommends using vias connecting the pads directly to the ground plane. In designs without ground planes, keep the ground trace as wide as possible. Avoid connections that are too close to the grounding point of a microcontroller or digital signal processor.

Depending on the circuit density on the board, placement of the analog and digital components, and the related current loops, a single solid ground plane for the entire printed-circuit-board (PCB) or a dedicated analog ground area can be used. In case of a separated analog ground area, ensure a low-impedance connection between the analog and digital ground of the ADC by placing a bridge underneath (or next) to the ADC. Otherwise, even short undershoots on the digital interface lower than –300 mV lead to the conduction of ESD diodes causing current flow through the substrate and degrading the analog performance.

During PCB layout, take care to avoid any return currents crossing sensitive analog areas or signals.

Figure 40 illustrates a layout recommendation for the ADS8555 device along with the proper decoupling and reference capacitor placement and connections.

10.2 Layout Example

ADS8555 ai_layout_bas531.gif
1. All 0.1-μF, 0.47-μF, and 1-μF capacitors must be placed as close to the ADS8555 device as possible.
2. All 10-μF capacitors must be close to the device but without compromising the placement of the smaller capacitors.
Figure 40. Layout Recommendation