psrr frequency
In a PMOS LDO, the Cgd is a killer. You cannot add
enough gate (Cgs) shunt to settle down the output
device. When the supply moves and the load doesn't,
Cgd dumps charge into the gate.
Get away from small signal and look at transient
behavior. You want to see where the gate perturbation
really comes in, is it in phase or antiphase? Where is
it entering and where it is being gained up?
You may have to try compensating with an inverted
image current but this can be a nastiness all its own.