A strange phenomenon during LDO stability analysis

[mjun0mjun]

Hey guys.I am doing a LDO stability analysis with corners. In most cases, the loop gain bode curves seem fine except @30mA load current, high temperature & strong device. The strange phenomenon is that "the loop gain phase margin curve" starts from 0 degree instead of 180 degree. The strange curve is attached in the "pic_stb". The red curve shows the strange phenomenon, while the green one is normal. And 30mA is in the middle range of the LDO working current. Very pleased to hear your advice. Many thanks!

 

[yuvan]

Have you tried out a transient simulation? But surprised that you a couple of low frequency zeros, interesting arch

 

[mjun0mjun]

Yeah, I've tried transient simulation, which is fine without oscillation.

Have you tried out a transient simulation? But surprised that you a couple of low frequency zeros, interesting arch