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TPS7B63-Q1: why dose WDO pin out to low ?

jinsu kim
Prodigy 80 points
Part Number: TPS7B63-Q1

Hi Team. 

My customer has some question about TPS7B6350-Q1.

My customer set the schematic as below

 1) WTS = Low = Window watchdog mode

 2) FSEL = Low = t(WD) = RROSC × 0.5 × 10-6 (RROSC = 60.4kΩ) = 30.2 mS

 3) t(WD_INI) = 8 × t(WD) = 241.6 mS

 4) WRS = Low = t(OW) = t(CW) = 50% × t(WD) = 15.1mS

 5) t (WD_HOLD) = 20% × t (WD) = 6.04mS

and toggling WD pin every 10mS.

When WD_EN pin  is low, WD pin toggling after 10mS. 

Then WDO pin gose low ( MCU reset ) 

why dose WDO pin out to low ? 

 

Let me know What kind of Fault condition ? 

• Fault 1: The watchdog service signal is received during the closed window. The WDO is triggered once,
receiving a WD rising edge during the closed window.
• Fault 2: The watchdog service signal is not received during the open window. WDO is triggered after the
maximum open-window duration t(WD) / 2.
• Fault 3: The watchdog service signal is not received during the WD initialization. WDO is triggered after the
maximum initialization window duration 8 × t(WD).

thank you.

best regards

  • 0
    TI__Mastermind 23361 points

    Hi Jinsu, 

    As you described, the device is set to window watchdog mode with twd = 30ms. Assuming all the information provided is correct. The only case that may cause the WDO to toggle low is as follows: 

    1. As soon as WD_EN toggles low, there is a WD rising edge immediately that happened to finish the first WD initialization process. 

    2. After the initialization, it's in CW for the next twd/2 = 15ms. So a WD rising happens in 10ms could trigger the WDO to toggle low. 

    I would suggest double check to see if there is any unintentional WD signal that may accidentally happen as soon as WD_EN toggles low. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 80 points

    Hi jason

    As soon as WD_EN toggles low, My customer has checked  WD rising edge. but it isn't happened.

    Additionally after WD pulse went to low My customer gave WD_EN pin delay time for 1ms, but the WDO to toggle low. 

    Let me know Why WDO to toggle low?

    and I have another question.

    Dose the TPS7B6350-Q1 need delay time between WD_EN and WD  ?

    Let me  know What is  related  parameter in datasheet?

    thank you

  • 0 in reply to jinsu kim
    TI__Mastermind 23361 points

    Hi Jinsu, 

    Since the support of this issue has been moved to direct emails. I am closing the post here. 

    Regards, 
    Jason Song