SNVSB66A July   2018  – October 2021 TPS3431

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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
    7. 6.7 Timing Diagrams
    8. 6.8 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable Input (EN) and Enable Output (ENOUT)
      2. 7.3.2 Watchdog Mode
        1. 7.3.2.1 CWD
        2. 7.3.2.2 Watchdog Input WDI
        3. 7.3.2.3 Watchdog Output WDO
        4. 7.3.2.4 SET1
    4. 7.4 Device Functional Modes
      1. 7.4.1 VDD is Below VPOR ( VDD < VPOR)
      2. 7.4.2 Above Power-On-Reset, But Less Than VDD(min) (VPOR ≤ VDD < VDD(min))
      3. 7.4.3 Normal Operation (VDD ≥ VDD(min))
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 CWD Functionality
        1. 8.1.1.1 Factory-Programmed Timing Options
        2. 8.1.1.2 CWD Adjustable Capacitor Watchdog Timeout
    2. 8.2 Typical Application
      1. 8.2.1 Design 1 Requirements
      2. 8.2.2 Detailed Design 1 Procedure
        1. 8.2.2.1 Calculating WDO Pullup Resistor Design 1
        2. 8.2.2.2 Setting the Watchdog Design 1
      3. 8.2.3 Application Curves Design 1
    3. 8.3 Programmable Application
      1. 8.3.1 Design 2 Requirements
      2. 8.3.2 Detailed Design 2 Procedure
        1. 8.3.2.1 Calculating WDO Pullup Resistor Design 2
        2. 8.3.2.2 Setting the Watchdog Design 2
        3. 8.3.2.3 Watchdog Disabled During Initialization Period Design 2
        4. 8.3.2.4 Programmable Disable Feature Design 2
      3. 8.3.3 Application Curves Design 2
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2.2 Setting the Watchdog Design 1

As illustrated in Figure 8-1 there are three options for setting the watchdog timer. The design specifications in this application allow for a factory-programmed timing option by leaving CWD floating. To ensure proper functionality, a falling edge must be issued before tWD(min) with is set for 1.36 seconds when CWD is not connected. Figure 8-8 illustrates that a WDI signal with a period of 1 second keeps WDO from asserting.

Figure 8-4 shows WDO asserting when the WDI signal has a period longer than tWD(max) which is 1.84 seconds when CWD is not connected. Figure 8-5 shows a watchdog fault caused by missing WDI pulse followed by correct timing WDI pulses to deactivate WDO.