Hi all,
I'm using virtuoso subversion IC6.1.7-64b.500.21 and spectre subversion 18.1.0.143.isr1.
I'm verifying stability in a nested multiloop LDO design, so I've introduced several probes to analyze each of the existing loops individually. The location of poles varies with the load current so two runs are made, one for no load and one for max load condition. One of the loops is showing me -40 degrees PM at high load condition but the transient analysis shows no oscillatory behavior. I know the iprobes from analogLib do not open the loop and should not be affecting the operating point of the circuit, but I'm having a hard time understanding what's the root cause of the different results and how to reconcile them.
How to make sure that stb results are reliable?
Attached you can see the simulation results. Let me know if anything else is needed (I show only a zoom in the transient response from zero to max current and viceversa)
