TPS3851-Q1: watchdog timeout

Arie Li

Part Number: TPS3851-Q1

Hi experts,

My customer set the watchdog timeout of TPS3851-Q1 as 200ms with below configuration(CWD pulled up to VDD through 10k pullup resistor). In theory, if there is no WDI signal, the WDO timeout should be 200ms, but customer found that the first timeout after watchdog enabled is a little longer than 200ms(around 250ms) as the waveform shows. Is it a normal phenomenon? I didn't find any description of this from the datasheet. Could you please help to explain it? Thank you.

over 3 years ago

0 Abhinav.Sharma over 3 years ago

TI__Genius 9375 points

Hi Arie,

The watchdog pulses on WDO are based on the falling edge of the input on WDI. Can you show the WDI waveform relative to the WDO rather than SET1?

Thanks,
Abhinav.

0 Arie Li over 3 years ago in reply to Abhinav.Sharma

TI__Expert 3390 points

Hi Abhinav,

There's no WDI signal because the watchdog starts up without WDI in this measurement. So in theory, after watchdog is enabled, WDO should wait for 200ms defined by CWD and then reset for 200ms and then pull up again to wait WDI signal...The waveform customer measured seems correct but only the first timeout is not consistent with datasheet. It should be 200ms, but the waveform shows nealy 250ms. Is there any delay here?

0 Abhinav.Sharma over 3 years ago in reply to Arie Li

TI__Genius 9375 points

Arie,

Closing to continue this discussion over email.

Thanks,
Abhinav.

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TPS3851-Q1: watchdog timeout