PSpice Switch Convergence

Aug 22, 2005 2 Replies

Hi,



I'm running a long overnight simulation, and I set up some circuitry that would cause the circuit to have a convergence failure if a certain condition was met so that I can save computation time on the system. I used an S switch and configured it so that if the condition occurs the switch would just toggle on and off and then it would hit the iteration limit. However, PSpice finds a solution for this. I was wondering if anyone knows the convergence routine for this switch. I've pasted a simplified version below where I get a constant 1.2 volts at node 2 which when I look at the equations in their manual for this component, I just can't see how that number is reached. Any insights? Thanks, Alex.


  • R1 2 0 1 S1 2 1 2 0 TEST V1 1 0 12
  • ..MODEL TEST VSWITCH (ROFF=1E9 RON=1 VOFF=2 VON=1)
  • ..TEMP 27 ..TRAN 2e-008 1u 0 UIC ..PRINT TRAN V(1) V(2) ..PLOT TRAN V(1) V(2) ..PROBE ..END


"engr4fun" schrieb im Newsbeitrag news: snipped-for-privacy@g43g2000cwa.googlegroups.com...

Hello Alex, you shouldn't believe all the formulas. :) I am sure now that there is a small but important mistake in PSPCREF.pdf.

They defined Vd regardless whether Von is smaller or greater than Voff.

Vd=Von-Voff

In your case Von is lower than Voff. So you get a negative number. I tried with the opposite formula for your case.

Vd=Voff-Von

Now you have also a positive number in this case. The result for Rs from the big formula is then in accordance with the simulation result.

I have used LTspice to figure out this PSPICE documentation error. :)

Best regards, Helmut

Thanks Helmut,

It looks like you're right. Once I make that polarity change, I get the expected results. Thanks for your help.

Alex

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