My customer is currently using the UCC2946D’s Voltage and Watchdog monitoring for their uP. They would like a similar part to this which has an EN pin for the watchdog? There may be potential problems with the timeout required on the watchdog while my uP is downloading code.
If not, they are thinking about attaching a buffer with an enable pin on the WDO output to simulate the required functionality they want as per SLVA145 “Disabling the Watchdog Timer for TI’s Family of Supervisors” (http://www.ti.com/lit/an/slva145/slva145.pdf).
SLVA145 discusses using an EN buffer on WDI. However, actual app note doesn’t list the UCC2946 as one of these devices that has an auto-turn off in high-z mode – does this chip actually have this functionality built in?
An alternative solution, TPS386040’s watchdog timer does not appear to be adjustable.
For your application, since WDO is connected to NMI, it could be solved by putting the buffer with the enable between WDO and NMI, with a pull up at the output of the buffer. When the buffer is disabled, even if WDO is asserted, no NMI occurs.
When boot has finished, you send a WDI transittion (WDO is de asserted) and then you enable the buffer.
Hope this helps
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