Re: DDS, again

On 11-12-2024 17:49, john larkin wrote:

On Wed, 11 Dec 2024 14:07:45 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:
 

On 11-12-2024 03:38, john larkin wrote:

I have been unsuccessful in getting LT Spice to simulate a DDS
frequency generator. It's bad enough trying to make the NCO part, but
whenever I get close it stalls or throws convergence errors.
>

>
I think you have the funds to buy Cadence Pspice. It has auto
convergence build in. It's seldom I see problems with convergence after
they added that feature.

 LT Spice is usually pretty good. It just didn't like my trying to make
a 32-bit phase accumulator with an analog circuit.
 I once fixed a convergence problem by adding one resistor to the
circuit. 1K, one ended grounded, the other end open.
 LT is horrible with digital stuff. Imagine making a 32-bit phase
accumulator with its parts. There isn't a screen big enough.
 Qspice is I hear better at mixed-signal sims.
 I can always have one of my kids Matlab the hard stuff.
 

If you buy Pspice Advanced, you can run c++ code in each time step, or whatever timestep you like. I am doing that to simulate a digital SMPS in spice