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Original question:

TPS3828: How to handle the chip during development/ debugging?

TPS3828: How to deal with WDI when MCU in low power mode

Lin_Charles
Expert 4260 points
Part Number: TPS3828

Hi team,

My customer is using TPS3828-33 to monitor MCU. They met below issue,

when customer let MCU work in low power mode, WDI cannot go to high ipedance state. This will trigger the reset pin to low output. Whta they do now is to pull WDI pin with 50k resistor to 3.3V, this can solve their probelm.I want to check with team that if this is ok to use?

I also see the same issue in below thread, I am thing to let the WDI pin of the MCU into input IO to let TPS3828 into Auto-Reset Oscillator state. Can this method solve this issue? Thank you for your help here.

BR,

CL

https://e2e.ti.com/support/power-management/f/196/p/734710/2713411?tisearch=e2e-sitesearch

  • 0
    TI__Genius 9375 points

    Hi CL,

    I will get somebody who has worked on this issue in the past to help you out.

    Thanks,

    Abhinav.

  • 0 in reply to Abhinav.Sharma
    TI__Expert 4260 points

    Hi Abinav,

    Thank you for your help here. Would appreciate it if you can share team’s feedback by May 1st. Thanks.

    BR,

    CL

  • 0 in reply to Lin_Charles
    TI__Genius 12630 points

    CL,

    Using a pull-up or pull-down resistor on WDI prevents WDI from being high-impedance state meaning the device will continue to trigger a watchdog fault reset because there is no transitions on WDI. Using a pull-up or pull-down resistor is Ok to use, there is no problem there except the device still requires an external high or low transition pulse on WDI to prevent reset.

    It is best to configure the WDI pin to high-z mode (instead of output) to allow the device to generate internal WDI pulse. If you set the MCU pin to input, this may also work if the input impedance is high enough to allow the TPS3828 device to still make an internal pulse on WDI.

    Lastly, you can also use a pass FET at the /RESET output and turn off the FET when a reset is not desired, and then turn on when the /RESET signal should be passed to the connecting device.

    Please let me know if this answers your questions. Let me know if you need additional support. Thanks