SPRS288H May   2008  – October 2021

PRODMIX  

  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 Switching Characteristics
    8. 6.8 Timing Diagrams
    9. 6.9 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 Input Voltage (VDD)
        1. 7.3.1.1 VDD Hysteresis
        2. 7.3.1.2 VDD Glitch Immunity
      2. 7.3.2 Implemented Window-Watchdog Settings
        1. 7.3.2.1 Timing Rules of Window-Watchdog
      3. 7.3.3 Watchdog Software Considerations
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Lower-Boundary Calculation
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Programming Window-Watchdog Using an External Capacitor
      3. 8.2.3 Application Curve
  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
      1. 11.1.1 Device Nomenclature
    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

Package Options

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

8.2.2 Detailed Design Procedure

To configure the window watchdog function, two pins are provided by the TPS3813-Q1family of devices. These pins set the window timeout and ratio.

The window watchdog ratio is a fixed ratio, which determines the lower boundary of the window frame. This ratio can be configured in two different frame sizes.

If the window watchdog ratio pin (WDR) is set to VDD (Position 1 in Figure 8-1) then the lower boundary frame is a value based on a ratio calculation of the overall window timeout size. For the watchdog timeout pin (WDT) connected to GND, the value is a ratio of 1:124.9, for WDT connected to VDD, the value is a ratio of 1:127.7, and for an external capacitor connected to WDT, the value is a ratio of 1:64.5.

If the window watchdog ratio pin (WDR) is set to GND (Position 2) the lower boundary frame is a value based on a ratio calculation of the overall window timeout size. For the watchdog timeout pin (WDT) connected to GND, the value is a ratio of 1:31.8, for WDT connected to VDD the value is a ratio 1:32, and for an external capacitor connected to WDT the value is a ratio of 1:25.8.

The watchdog timeout can be set in two fixed timings of 0.25 s and 2.5 s for the window or can by programmed by connecting a external capacitor with a low leakage current at WDT.

For example, if the watchdog timeout pin (WDT) is connected to VDD, the timeout is 2.5 s. If the window watchdog ratio pin (WDR) is set in this configuration to a ratio of 1:127.7 by connecting the pin to VDD, the lower boundary is 19.6 ms.