The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> Circuit Simulators >> How to simulate the loop gain in switch cap.?
https://designers-guide.org/forum/YaBB.pl?num=1049765367

Message started by sch on Apr 7^th, 2003, 6:29pm

Title: How to simulate the loop gain in switch cap.?
Post by sch on Apr 7^th, 2003, 6:29pm

If I am running a switch capacitor sigma-delta converter, and
want to see how about the on resistance of the switch affect
the loop gain by simulator (Spectre RF or Spice). How should I do ?

Title: Re: How to simulate the loop gain in switch cap.?
Post by Jitter Man on Apr 8^th, 2003, 3:13pm

Which loop gain are you referring to?
1. The loop gain of a single integrator?
2. The loop gain of the filter alone (generally multiple loops)?
3. The loop gain of the converter?
In the last case, at any instant, the loop is open, so you must be thinking of the loop gain in some average sense.

[glb]Jitter Man[/glb]

Title: Re: How to simulate the loop gain in switch cap.?
Post by sch on Apr 8^th, 2003, 6:59pm

If I am referring to the single integrator loop gain , what command in SpectreRF that I can use to find out the loop gain
vs. frequency?

Title: Re: How to simulate the loop gain in switch cap.?
Post by Jitter Man on Apr 8^th, 2003, 9:27pm

Spectre has a conventional small signal analysis, stb, that computes the loop gain. That will work fine if you believe you can turn off the clock while measuring loop gain. Otherwise you will need to use the techniques described in Section 3.4.1 of Kundert's book. Of course, with the clock being active, you will have to substitute SpectreRF's PAC analysis for the AC analysis used in the book.

[glb]Jitter Man[/glb]