SLVSGE8B November   2022  – August 2024 TPS35-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Voltage Supervisor
      2. 7.3.2 Timeout Watchdog Timer
        1. 7.3.2.1 tWD Timer
        2. 7.3.2.2 Watchdog Enable Disable Operation
        3. 7.3.2.3 tSD Watchdog Start Up Delay
        4. 7.3.2.4 SET Pin Behavior
      3. 7.3.3 Manual RESET
      4. 7.3.4 RESET and WDO Output
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 CRST Delay
        1. 8.1.1.1 Factory-Programmed watchdog Timing
        2. 8.1.1.2 Adjustable Capacitor Timing
      2. 8.1.2 Watchdog Timer Functionality
        1. 8.1.2.1 Factory-Programmed watchdog Timing
        2. 8.1.2.2 Adjustable Capacitor Timings
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Monitoring a Microcontroller Supply Voltage and Watchdog Timer
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Setting the Voltage Threshold
          2. 8.2.1.2.2 Meeting the Watchdog Timeout Period
          3. 8.2.1.2.3 Setting the Reset Delay
          4. 8.2.1.2.4 Setting the Startup Delay and Output Topology
          5. 8.2.1.2.5 Calculating the RESET Pullup Resistor
        3. 8.2.1.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

7.3.2.2 Watchdog Enable Disable Operation

The TPS35-Q1 supports watchdog enable or disable functionality. This functionality is critical for different use cases as listed below.

  • Disable watchdog during firmware update to avoid host RESET.
  • Disable watchdog during software step-by-step debug operation.
  • Disable watchdog when performing critical task to avoid watchdog error interrupt.
  • Keep watchdog disabled until host boots up.

The TPS35-Q1 supports watchdog enable or disable functionality through either WD-EN pin (pin configuration C) or SET[1:0] = 0b'01 (pin configuration B) logic combination. For a given pinout only one of these two methods is available for the user to disable watchdog operation.

For a pinout which offers a WD-EN pin, the watchdog enable disable functionality is controlled by the logic state of WD-EN pin. Drive WD-EN = 1 to enable the watchdog operation or drive WD-EN = 0 to disable the watchdog operation. The WD-EN pin can be toggled any time during the device operation. The Figure 7-7 diagram shows timing behavior with WD-EN pin control.

TPS35-Q1 Watchdog Enable: WD-EN Pin Control Figure 7-7 Watchdog Enable: WD-EN Pin Control

SET[1:0] = 0b'01 combination can be used to disable watchdog operation with a pinout which offers SET1 and SET0 pins, but does not include WD-EN pin. The SET pin logic states can be changed at any time during watchdog operation. Refer Section 7.3.2.4 section for additional details regarding SET[1:0] pin behavior.

Pinout options A, B offer watchdog timer control using a capacitance connected between CWD and GND pin. A capacitance value higher than recommended or connect to GND leads to watchdog functionality getting disabled. Capacitance based disable operation overrides the other two options mentioned above. Changing capacitance on the fly does not enable or disable watchdog operation. A power supply recycle or device recovery after UV fault, MR low event is needed to detect change in capacitance.

Ongoing watchdog frame is terminated when watchdog is disabled. WDO stays deasserted when watchdog operation is disabled. For a pinout with only RESET output, the RESET can assert if supply supervisor error occurs. When enabled the device immediately enters tWD frame and start watchdog monitoring operation.