[SOLVED] stability assessment for LDO using nested Miller Compensation

[minhchau]

Hello,
I am learning nested Miller Compensation to design LDO.
This image show the block diagram for a three-stage op amp with nested Miller compensation.

If I use nested Miller Compensation to design LDO the system will have about 3 negative feedback loops,
when I evaluate the system's stability (by stb simulation in cadence, do i need to consider phase margin
and gain margin in 2 negative feedback loop, Cm1 and Cm2?
or I just evaluate the outer loop from Vout back to Vin.
Thanks you,
Chau

 

[MahmoudHassan]

You will need to evaluate the outer loop from Vout to one of the inputs (make sure it is negative)
the other input will be the reference voltage.
The effect of CM1 and CM2 -poles and feedforward zeros - will affect this loop stability and PM.