Watchdog Timer application

[kadam]

Hello Team,

We are considering STM6822SWY6F Watchdog IC for our design.

We have query regarding WDI input pulse for time out condition. 

What is status of Reset pin, if WDI pin is fixed to High or Low voltage level even after 1.6 sec of time out period?

Regards,

Kadam Shah

[Peter BENSCH]

Welcome @kadam, to the community!

After the timeout of 1.6s, the Reset is activated, which is described for the STM6822 in the  data sheet, section 1.1.2:

Active low, open drain reset output (RST) - STM6321/6322/6822
Pulses low when triggered, and stays low whenever VCC is below the reset threshold or when MR is a logic low. It remains low for trec after either VCC rises above the reset threshold, the watchdog triggers a reset, or MR goes from low to high. Connect a pull-up resistor to supply voltage.

Hope that helps?

Regards
/Peter

[kadam]

Hello Peter,

Thanks for your reply.

If WDI pin is fixed to High or Low voltage level after completing timeout period (1.6sec) + trec (200ms), what will be voltage level of Reset pin? Is Reset pin will be high continuously or after 1.6sec time out peroid it become low again?

Regards,

Kadam Shah

[Peter BENSCH]

Well, I can't verify this at the moment because I don't have the device on a board. However, I strongly assume that /RST changes back to inactive after the time has elapsed, i.e. is no longer switched to GND. Whether this state corresponds to high depends on the load, as /RST is an open drain output.

Regards
/Peter