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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8.3.1.4 SET Pin Behavior

The TPS3435 offers one or two SET pins based on the pinout option selected. SET pins offer flexibility to the user to program the tWD timer on the fly to meet various application requirements. Typical use cases where SET pin can be used are:

  • Use wide timeout timer when host is in sleep mode, change to small timeout operation when host is operational. Watchdog can be used to wake up the host after long duration to perform the application related activities before going back to sleep.
  • Change to wide timeout timer when performing system critical tasks to make sure the watchdog does not interrupt the critical task. Change timer to application specified interval after the critical task is complete.

The tWD timer value for the device is combination of timer selection based on the CWD pin or fixed timer value along with SET pin logic level. The base tWD timer value is decided based on the Watchdog Time selector in the Section 5 section. The SET pin logic level is decoded during the device power up. The SET pin value can be changed any time during the operation. SETx pin change which leads to change of watchdog timer value or enable disable state, terminates the ongoing watchdog frame immediately. SETx pins can be updated when WDO output is asserted as well. The updated tWD timer value will be applied after output is deasserted and the tSD timer is over or terminated.

For a pinout which offers only SET0 pin to the user, the tWD multiplier value is decided based on the Watchdog Time Scaling selector in the Section 5 section. Table 8-1 showcases an example of the tWD values for different SET0 logic levels when using Watchdog Time setting as option D = 10 msec.

Table 8-1 tWD Scaling with SET0 Pin Only
WATCHDOG TIME SCALING SELECTIONtWD
SET0 = 0SET0 = 1
A10 msec20 msec
B10 msec40 msec
C10 msec80 msec
D10 msec160 msec
E10 msec320 msec
F10 msec640 msec
G10 msec1280 msec

For pinouts which offer both SET0 & SET1 pins to the user, the tWD multiplier value is decided based on the Watchdog Time Scaling selector in the Section 5 section. Two SETx pins offer 3 different time scaling options. The SET[1:0] = 0b'01 combination disables the watchdog operation. Table 8-2 showcases an example of the tWD values for different SET[1:0] logic levels when using Watchdog Time setting as option G = 100 msec. The package pin out selected does not offer WD-EN pin.

Table 8-2 tWD Scaling with SET0 & SET1 Pins, WD-EN Pin Not Available
WATCHDOG TIME SCALING SELECTIONtWD
SET[1:0] = 0b'00SET[1:0] = 0b'01SET[1:0] = 0b'10SET[1:0] = 0b'11
A100 msecWatchdog disable200 msec400 msec
B100 msecWatchdog disable400 msec800 msec
C100 msecWatchdog disable800 msec1600 msec
D100 msecWatchdog disable1600 msec3200 msec
E100 msecWatchdog disable3200 msec6400 msec
F100 msecWatchdog disable6400 msec12800 msec
G100 msecWatchdog disable12800 msec25600 msec

Selected pinout option can offer WD-EN pin along with SET[1:0] pins. With this pinout, the WD-EN pin controls watchdog enable and disable operation. The SET[1:0] = 0b'01 combination operates as SET[1:0] = 0b'00.

Make sure the tWD value with SETx multiplier does not exceed 640 sec. If a selection of timer and multiplier results in tWD > 640 sec, the timer value will be restricted to 640 sec.

Figure 8-9 to Figure 8-11 diagrams show the timing behavior with respect to SETx status changes.

Figure 8-9 Watchdog Behavior with SETx Pin Status
Figure 8-10 Watchdog Operation with 2 SET Pins
Figure 8-11 Watchdog Operation with 1 SET Pin
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