[Help!!] P-spice Error --> Time step too small..

hi, all I'm lcd engineer who design the electric circuit.

recently, i use spice to pridect my circuit and i'm in trouble now.

there is an error -"Time step too small"

to solve the problem, I add some options. The options are: -. ITL4=100 -. RELTOL=0.01 - change the time step : 1us --> 50us

but error is still with me.

show me the way, Plz...

regards, jason

Reply to
jason KIM
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Off the top of my head, check for something floating. Perhaps you are muxing something and leaving a node undefined. Also a bad model can cause this problem. Is there a section of the circuit with high gain?

Making the time step bigger won't help. The problem is the circuit state is changing rapidly so the internal time step is getting smaller in order to keep the iteration to iteration change within limits.

Sometimes I've got around this problem by using all 4 parameters on the .tran line. The spice gurus can do a better explanation, but basically if you just give spice a time step and time limit, the simulation picks times that it thinks are appropriate given the changing state of the circuit. But for display (print out) purposes, the value at the time step you desire is interpolated from the time steps that spice used. You see this all the time of you are trying to simulate a circuit for THD. That is, for such simulations you need to set the time step to be say 1/100th of the period of the input sine wave. The .tran card goes step stop start max. So you may need to set a small MAX limit.

Reply to
miso

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