I have two almost identical circuits (a switching regulator), the main diff is that I move the eprom cells at one level higher hier in circuit A, for the ease of accessing the eprom cells. However, doing so, and running with Ultrasim, I couldn't make the circuit A to work but circuit B work though the results is not as accurate, found out that one schmitt trigger not function, increase the accuracy, speed=4 for that schmitt trigger, it work. For comparison, I also make speed=4 for schmitt trigger in the original circuit B, both results come out good, but circuit A takes like 3-4 times longer than B !
My question : to debug this issue, is there something in the log file I should be looking such as the number of partitioning or number of analog devices to make such significant diff in sim timing ? Has anyone come across this, making a small change and causing big timing difference ?