aaron_do wrote on Jun 27th, 2012, 6:09am:I'm not sure if there's any simulation to see if a circuit has start-up issues, but if there is one, its probably a transient analysis with step input on the power supply (start from zero initial conditions).
Cap coupling can provide startup current so ramping supply can miss issues. However, you do want to make sure that a glitch on the power supply won't shut it off -- a friend had that happen to him. This is the reason I don't use por-type startup circuits. DC sims also don't tell you that it might start up in real life from parasitic leakage, but it could take an extremely long time because the inherent startup currents from leakage are very small - and may even be overcome by leakages not modeled.
The best sim I've found is a power up sim without ramping the supply. Make sure all mosfets are off. Even if you have to add extra circuitry to power it down this is the sim you want to look at.
The second extremely important simulation is mismatch (with the power up sim). You need to overcome the offsets in the opamp (or mos pair, etc) to activate the positive feedback part of the loop.
So power-up with mismatch is what you want to look at.