Sep 30, 2010 #1 S sj95 Member level 1 Joined Oct 4, 2006 Messages 33 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,286 Activity points 1,568 Dear all: The LDO has enough phase margin when no load or light or heavy load. But if I use a pulse current such as Iout vout 0 pulse( 0 2 800u 1n 1n 100u 200u) the circuit will ring And if Iout vout 0 pulse( 10m 2 800u 1n 1n 100u 200u) the circuit will be fine. Why? setting Iout as a zero current when transient simulation is not resonable ? Thanks for your answer.
Dear all: The LDO has enough phase margin when no load or light or heavy load. But if I use a pulse current such as Iout vout 0 pulse( 0 2 800u 1n 1n 100u 200u) the circuit will ring And if Iout vout 0 pulse( 10m 2 800u 1n 1n 100u 200u) the circuit will be fine. Why? setting Iout as a zero current when transient simulation is not resonable ? Thanks for your answer.
Sep 30, 2010 #2 leo_o2 Advanced Member level 4 Joined Sep 3, 2004 Messages 1,322 Helped 278 Reputation 558 Reaction score 241 Trophy points 1,343 Location China Activity points 5,761 The LDO under Iout=0 is unstable. Sometimes phase margin is not trustable.