Problems simulating isolated voltage to frequency converter

[MateusHG]

Hello everyone! I'm trying to simulate a circuit of an isolated voltage-to-frequency converter using the LM331 in LTspice, but I'm having issues with the "Time step too slow" error. I'm using a third-party LM331 model since it's not available in LTspice. How can I try to solve this problem? Attached are my file and the LM331 model I'm using.

 

[KlausST]

Hi,

The error message says "time step too SMALL"
If it is too small --> simply set it to a higher value.

Usually you are asked to input this value when you start the simulation (for the first time). You have to option to adjust simulation parameter at any time.

Klaus

 

[FvM]

The error message says "time step too SMALL"
If it is too small --> simply set it to a higher value.

No, that doesn't help. The error occurs if the model has unusual non-linearity or simulation circuit is unsuitable. Adjusting simulation parameters or selecting a different solver can help but not always.

I notice that simulation circuit is considerably different from data sheet application, I guess unintentionally. C2 = 1Meg (10e6) should be 1u (10e-6), also R5 value is far off. This may affect simulation convergence.

 

[KlausST]

No, that doesn't help.

I´m sure I once had the same error message and setting the min time step to a higher value helped.

Maybe not in every case.

Klaus