TPS3610: WDI pin function

user5908499

Part Number: TPS3610

Hi.

When the WDI pin of the TPS3610 was left open, I observed a pulse with a period of about 700ms.
Is this the signal the TPS3610 outputs itself to reset the internal watchdog timer?

CH4 is the WDI pin waveform.

When I connected the WDI pin of the TPS3610 to my microcontroller, the WDI pin went to about 2.5V.
At this time, a pulse signal of about 700ms cannot be confirmed, so the internal watchdog timer should not be reset, but the TPS3610 does not enable the reset signal.
Why is this?

over 1 year ago

0 Allison Kuo over 1 year ago

TI__Prodigy 90 points

Hello,

You are correct for the first scope shot. If the WDI pin is left open, the input momentarily pulses high to reset the watchdog timer. The 700 ms period you observe is the watchdog timeout period. Please see page 10 of the TPS3610 datasheet: Battery-Backup Supervisors for RAM Retention datasheet (Rev. B)

For the second scope shot, could you please provide a schematic of your circuit so I can better answer your question?

Best,

Allison Kuo

0 user5908499 over 1 year ago in reply to Allison Kuo

Prodigy 110 points

Hello Allison,

I will send you the circuit diagram.

The GPIO of the MCU is connected to the WDI pin.
However, I made a mistake in the MCU port assignment design. Therefore, the MCU is not outputting normally due to pin contention issues with bus functions.
Nevertheless, the TPS3610 does not output a reset, which is why I am asking this question.

Thanks

0 Allison Kuo over 1 year ago in reply to user5908499

TI__Prodigy 90 points

Hello,

The WDI pin recognizes VIL at 0.3xVDD and VIH at 0.7xVDD as noted in page 11 of the datasheet. Since the input to your WDI pin right now is in between these values, it is in an undefined state and TI cannot guarantee its performance as a watchdog. For the TPS3610 to operate as a watchdog properly, the WDI pin input should be either held at lower than 0.3xVDD and pulsed to above 0.7xVDD or held at higher than 0.7xVDD and pulsed to below 0.3xVDD by the GPIO pin of your MCU.

Please see this E2E page for related information: TPS3610: Unused case of WDI pin - Power management forum - Power management - TI E2E support forums

Best,

Allison Kuo

Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

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TPS3610: WDI pin function