UCC2946: UCC2649 Reset Behaviour

Jörn Katzorke

Part Number: UCC2946
Other Parts Discussed in Thread: TPS35, TPS3435

Hi,

i could not find the reset behaviour description in the datasheet of the UCC2946.

My question: How does the reset behave in case of missind WDI?

In case of a failure WDI will not be triggered and after a time WDO and Reset will be asserted.

Will the reset be held forever (latched) or will the reset be released after the reset period?

Thank you!

0 Jesse Villanueva 4 months ago

Hi Jörn,

Figure 4 of the datasheet illustrates. During RESET assertion, the watchdog functionality is disabled and WDO will go high impedance.

Jesse

0 Jörn Katzorke 4 months ago in reply to Jesse Villanueva

Hi Jesse,

thank you for your reply!

I saw figure 4 already.

Does that mean that RESET assertion ends automatically after TRP ends?

Another question: if i use WDO instead to put a microprozessor into reset, does it latch that microprozessor reset?

At t5 TWP expires and WDO asserts low.

If WDO is connected to processor RESET the processor will be in reset and cannot toggle WDI again.

Will WDO stay low forvever in that case?

Thank you!

+1 Jesse Villanueva 4 months ago in reply to Jörn Katzorke

Hi Jörn,

The RESET is the output of the voltage monitor, RTH, so the RESET de-assert after TRP when the voltage at the RTH goes above 1.235V.

Jörn Katzorke said:
Another question: if i use WDO instead to put a microprozessor into reset, does it latch that microprozessor reset?

The WDO is a latched output that requires a falling or rising edge to de-assert. So in your case, yes the WDO will hold LOW.

I would recommend switching over to TPS35 if a voltage monitor + watchdog is needed or TPS3435 if only watchdog is needed.

Jesse

0 Jörn Katzorke 4 months ago in reply to Jesse Villanueva

Thank you very much!

That solves my question.

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