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Design >> Analog Design >> rtc crystal open-loop simulation
https://designers-guide.org/forum/YaBB.pl?num=1230772170

Message started by trashbox on Dec 31^st, 2008, 5:09pm

Title: rtc crystal open-loop simulation
Post by trashbox on Dec 31^st, 2008, 5:09pm

When I simulate real-time clock crystal's open-loop with ac, there are two cases as attachment:
1)The BLUE result, it uses a ~15meg resisitor as the feedback for setting inverter's operating point. This result is what I need.
2)The PINK result. it uses several switches in series(a switch is a nmos and a pmos in parallel) instead of the 15meg resistor for saving area. The result is strange and not reasonable.

Why? I only find case 2) when temperature is 120 degree. The other situations such as SS/0, SS/60, FF/0, FF/60, TT/0 and TT/60 are all case 1).

Thanks!
Trashbox

Title: Re: rtc crystal open-loop simulation
Post by trashbox on Jan 1^st, 2009, 11:23pm

Hi I've found the root cause. It is because leakage current that result in inverter's operating point shift.