ZHCSRF8 December   2022 TPS3435

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 器件比较
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Switching Characteristics
    8. 7.8 Timing Diagrams
    9. 7.9 Typical Characteristics
  8. 8 详细说明
    1. 8.1 Overview
    2. 8.2 Functional Block Diagrams
    3. 8.3 Feature Description
      1. 8.3.1 Timeout Watchdog Timer
        1. 8.3.1.1 tWD Timer
        2. 8.3.1.2 Watchdog Enable Disable Operation
        3. 8.3.1.3 tSD Watchdog Start Up Delay
        4. 8.3.1.4 SET Pin Behavior
      2. 8.3.2 Manual RESET
      3. 8.3.3 WDO Output
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Output Assert Delay
        1. 9.1.1.1 Factory-Programmed Output Assert Delay Timing
        2. 9.1.1.2 Adjustable Capacitor Timing
      2. 9.1.2 Watchdog Timer Functionality
        1. 9.1.2.1 Factory-Programmed Timing Options
        2. 9.1.2.2 Adjustable Capacitor Timing
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1: Monitoring a Standard Microcontroller for Timeouts
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Setting the Watchdog Timeout Period
          2. 9.2.1.2.2 Setting Output Assert Delay
          3. 9.2.1.2.3 Setting the Startup Delay
          4. 9.2.1.2.4 Calculating the WDO Pullup Resistor
        3. 9.2.1.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 接收文档更新通知
    2. 12.2 支持资源
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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8.3.1.2 Watchdog Enable Disable Operation

The TPS3435 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 TPS3435 supports watchdog enable or disable functionality through either WD-EN pin or SET[1:0] = 0b'01 logic combination or by keeping WDI pin in the floating state. For a given pinout only one of these three 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 8-7 diagram shows timing behavior with WD-EN pin control.

Figure 8-7 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 8.3.1.4 section for additional details regarding SET[1:0] pin behavior.

A pinout which does not offer WD-EN or SET[1:0] pins uses WDI float pin status to disable the watchdog operation. Users can float the WDI pin during normal operation to disable the watchdog. To enable watchdog, drive the WDI pin and apply a valid edge to trigger the watchdog. It is recommended to drive HIGH and then LOW when exiting the WDI float state.

Pinout options A, B, K 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. Note, capacitance value is detected and latched during start-up or after an error event. Changing capacitance on the fly does not enable or disable watchdog operation. A power supply recycle is needed to detect change in capacitance.

When watchdog is disabled the ongoing frame will be terminated and WDO will stay deasserted. When enabled the device will immediately enter tWD frame and start watchdog monitoring operation.
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