TPS3820: Unexpected Reset signal

Ruixin Feng

Part Number: TPS3820

Tool/software:

Hi team,

customer has a application that customer feedback TPS3820 occasionally output an unexpected reset signal.

I'd like to clarify the application first. Customer use TPS3820 to reset M0 as below schematics shown. The signal path is that MCU will give a high voltage pulse of DWdog to disable output of U45, and then pull down resistor on output pin of U45 will give a low voltage to enable output of U46. input of U46 is the watchdog pulse.

then probing the DWdog(green), WDI (yellow), RESET active-low(blue)

For normal device, after DWdog pull high, after around 50ms, WDI has watchdog pulse and there isn't reset. M0 can wake up normally.

For failed device, after DWdog pull high around 40ms, TPS3820 output a reset signal to reset MCU, then cause WDI signal output after a long time.

before DWdog pull high, WDI pin of TPS3820 should be high-impedance, then the internal WDI pulse is working. After DWdog pull high, WDI pin is active. I'm suspecting if this issue is related internal WDI pulse. could you pls help to review this issue and share some suggestions?

Besides, I got several questions that hope you could help to support:

1. what's the time interval of internal WDI pulse?

2. What's the watchdog time out for internal WDI pulse?

3. Does external WDI pulse use same timer with internal WDI pulse?

Thanks!

Rayna

30 days ago

0 Anusha Adira 29 days ago

TI__Intellectual 780 points

Hi Rayna,

In order to get a better understanding, could you provide another scope capture of both devices where VDD_STB is also being monitored? As for your questions on the internal WDI, we cannot release that information since it is not in the datasheet.

Regards,

Anusha

0 Ruixin Feng 29 days ago

TI__Intellectual 2395 points

HI Anusha,

VDD is always there as a fixed voltage. why you think VDD_STB matters here?

From your side, what's the possible reason of this kind of issue?

Thanks!

Rayna

0 Anusha Adira 28 days ago in reply to Ruixin Feng

TI__Intellectual 780 points

Hi Rayna,

It seems that there is a dip in the voltage before RESET asserts, which could indicate a UV condition causing the fault, not the watchdog. Without all of the information, I wouldn't be able to give a reason.

Regards,

Anusha

0 Jesse Villanueva 28 days ago in reply to Anusha Adira

TI__Mastermind 18710 points

Hi Rayna,

I have let's continue this discussion of the email thread.

Jesse

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TPS3820: Unexpected Reset signal