Circuit below. The window should be about 1.8ms to 46ms. My pulse train is 4-6ms between edges. I can't see any reason why my input strobe from the micro isn't good enough but on the /RESET output I get a constant pulse train out where the output is high for about 14ms and low for about 25ms. It makes no sense. I measured my 3.3V rail and it looks good. Please help! I can't use my microcontroller because it is getting reset constantly.
HI David,
Your C8 is below the recommended minimum. Assuming this value of C8 can work, this gives you a lower bound of 1.21ms and an upper bound of 56.05ms where you can strobe the WDI pulse.
I recommend increasing C8 to greater than 155pF to get more stable operation.
Regards,
John,
I am using the EP mil temp range part and looking at the datasheet I have it shows a lower of 47pF. Why do you have a different value and why would the minimum cap change? I noticed the automotive/commercial version had a different range too.
I'll try the higher cap but I think the 56ms might be a bit outside my requirement range.
EDIT: I now have 200pF for c8 and I'm getting the exact same output. It's just a constant ~14ms square wave.
