Electronic – Calculation in LTspice “never” finishes

ltspice

I'm currently using LTspice, and I have a problem with it "never" finishing calculating a certain circuit. When I say "never", I mean that it's still calculating an hour after it started, even though the review-time is less than two periods of the input sine.

In the program status field it says: "Stepping Source: 100% step size=6.8413e-005 N-R iterations: changes frequently between numbers spanning from 0 to 200 fill-ins: 4". It seems to be stuck at this point.

The circuit I'm talking about is this frequency doubler.

Does anybody know a solution to this problem? If there is no solution, can you suggest a program that will not get stuck like this?

Best Answer

When I get those errors, it is usually because the SPICE model from the manufacturer is wrong or broken, or that your SPICE settings are wrong (open the LTspice's Control Panel and click Reset on the SPICE tab).

I tried implementing the circuit from your application note in LTspice and it worked (it is here), but:

  • I used the LT1720 since it was already in the LTspice libraries has a 4.5 ns propagation delay and the MAX9010 has 5 ns;
  • The XOR gate is set to have a 4.8 ns propagation delay (from the datasheet).
  • The clock source is 15 MHz.

enter image description here

This gives me:

enter image description here

As you can see, the pink trace is roughly twice the frequency of the green one (the input signal), working as expected.

I tried using the MAX9010 SPICE model, but had to edit it to put the pins in proper order, and the output looked wrong.

Related Topic