Loop Stability Analysis

masashi.nogawa · January 16, 2024, 1:30pm

Zout to NISM: Output Impedance to Non-Invasive Stability Measurement

There are a couple of very interesting posts evaluating control loop stability on this forum.

Fast FRA implementation (perhaps not as fast as .bode) posted by @physicboy
- FRA using .meas vs .bode
Winslow Impedance Probe posted by @frank.wiedmann
Stb analysis like Cadence Virtouso posted by @Heisenberg

…and let me add one more.

My new article (part-9) is live now, at Microwave Journal, by using PyQSPICE shown in this post, that explains output impedance Zout to non-invasive stability measurement NISM.

The beauty of this method is that we can execute an actual measurement, in the same way we simulate, when our PCB is ready on the bench.
==> That’s the naming of “non-invasive” on your board.

FYI, the Part-8 and Part-9 of my posts are summarized on my Jupyter Lab notebook and this illustrates power of Python scripting for an entire engineering report writing .

masashi.nogawa · April 24, 2024, 4:16pm

I introduced my time-domain-base loop analysis article in another thread.

This is my 1st part of total 2-part mini-series. In the 2nd part (I’m writing now), I’ll use this method on a switching regulator model.

masashi.nogawa · July 8, 2024, 12:44pm

I just published one strong loop analysis method with QSPICE.
Please check my latest article (part-11), at Microwave Journal, featuring the SEPIA technology.

The 3rd example simulation in the article illustrates we can extract the loop info directly from one step-response simulation, thus no need to think about AC-models.