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TPS3828-Q1: Reset output behavior and internal watchdog transition after WDI timeout

Yuxi Liu(Tony)
Expert 4310 points

Part Number: TPS3828-Q1
Other Parts Discussed in Thread: TPS3828

Hi Team,
A customer is asking for clarification on the TPS3828-33 watchdog operation, specifically regarding the RESET recovery behavior when the watchdog input (WDI) stops.
Customer Scenario:
The customer is monitoring the RESET pin behavior when they stop providing a trigger signal to the WDI pin. They observed that the RESET output goes high (inactive) after a timeout, but they want to confirm if the device can "self-recover" or toggle the RESET state back to low automatically if the external WDI remains missing.
Technical Questions:
  1. If the external WDI signal stops, will the TPS3828 eventually switch to an internal watchdog timing mode and pull RESET back to low?
  2. Can the RESET output return to a low level on its own after a watchdog fault if no further external WDI signals are provided?
Please help clarify the logic transition between external WDI monitoring and the RESET output state when the WDI pin is left floating or static.
Best regards,
Tony Liu
  • 0
    TI__Genius 12560 points

    Hi Tony, 

    If WDI input left floating, the device generates pulses internally to prevent watchdog reset event. WDI must be driven low or high for watchdog error to assert output.
    They can add a small pull-down resistor at WDI pin to make sure the watchdog is enabled when they don't apply the WDI signal. 

    Best,

    Sila 

  • 0 in reply to Sila Atalar
    TI__Expert 4310 points

    Hi Sila

    If the chip is being controlled by the MCU with the WDI input stopping normal feeding of the dog, the RESET pin will pull low, this no problem.

    So what happens to the TPS3828 when the MCU will put the WDI pin in a high-Z state, or WDI is floating, due to MCU reset or some other reason, and if RESET is held high or low, Will it transition to the internal feeding dog to continue starting a new cycle?

  • +1 in reply to Yuxi Liu(Tony)
    TI__Genius 12560 points

    Hi Yuxi, 

    If they don't provide the WDI signal, when the MCU will put the WDI pin in a high-Z state, or WDI is floating, the device won't be resetting. The RESET will be high. 
    Hope this clarify!

    Best,

    Sila