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TPS3430: Window watchdog without reset timer?

Other Parts Discussed in Thread: TPS3430

Tool/software:

Hi all,

   Im testing a prototype PCB we have developed and we are using the TPS3430 as part of the circuitry. We send a pulse to the WDI input inside of a 1-10ms window to keep the output enable of a level shifter enabled.

If the pulse arrives too late or too early the output enable is de-asserted to indicate a fault. When we intentionally disable the WDI input pulse to test it works fine however the reset delay kicks in and we get a momentary output of the TPS3430 which is undesireable?

The reset delay is set to around 3.2s (1uF capacitor on CRST) and it gives a ~3.2s delay when the WDI pulses resume (which we like!). 

Ive noticed the app notes to latch the WDO output when de-asserted which looks good but wondered if there was an all in one solution, before I go ahead and look at adding the latching circuit (probably with the D flipflop portion added so the micro can reset it without a power down).

Cheers all.

  • The latch circuit (derived entirely from an earlier search on E2E) ive attached as a screenshot. I inferred the requirement for the open drain buffer on the output of the flipflop since it is a push pull output. Presumably this will work fine and prevent the reset "pulse" occurring but will also ensure we get the reset time delay BEFORE WDO is reset when the incoming pulses resume/restart?

  • Hi Ian,

    Your schematic looks good. Unfortunately we do not have a Window watchdog device with a built in latching out at the moment.

    Jesse