I've been using the TPS3824-33QDBVRQ1 for some time now but for some reason on my new board design its doing something it did not do before.
The chip seems to ignore the WDI input until I hold it low for a period of time.
This is the sequence of events
1) Power is applied to the board TPS3824 hold the reset line low as expected
2) Once 3.3V supply is stable I would expect the reset line to go high but this is not happening
3) While my system is running the boot loader the WDI line is being driven at a relatively high rate (25mS)
4) When I transition from the boot loader to the main code the WDI line stays low for 400mS, after about 250mS with the WDI line low the TPS3824 finally releases the reset condition.
After this everything seems to work normally.
If I leave the boot loader running (25mS) WDI interval, the reset will remain low.
In the scope capture below, the green trace is the reset line (Pin 1) and the orange line is the WDI line. I've zoomed in on the transition between the boot loader and the main code.
I don't see anything in the data sheet that explains this operation. Am I missing something?
Why is the reset condition not being removed once the 3.3V power is above the threshold?
Ed Hildebrandt
