problem on compensation of a LDO?

[ken_cn]

Hi, all
I am designing a LDO. But when I simulated the open loop gain and phase, I found that the dc gain, unity gain frequency and phase margin are different in different loading condition.
How can I deal with it? Could you give me some suggestions?

Thank you!


Ken
2007/08/0.6

 

[paley]

yes, dc gain, unity gain frequency and phase margin are different in different loading condition.

because the load res will changed the output pole,and the ESR will add a zero,if your regulator have a large output cap,you must simulation the condition of max output current

 

[szekit]

if your load is the second pole, worst case stability is at min output current and max output cap.

 

[iamxo]

i think you need to compensate your LDO to insure your LDO will be stable under all load condition!

good luck.

 

[edwintsu]

Ken, u can refer to the below patent.

B/R
Edwin

 

[txdydhr]

hi, szekit! u say worst case stability is at min output current and max output cap,
why the worst case stability is at these case? could u plz give a detailed commentate, thanks!

 

[liuyonggen_1]

put the dominant pole at the output, and consider the worst case, everything is OK

 

[lokay]

put the dominant pole at the output, and consider the worst case, everything is OK

But it's hard to do that? How can you achieve?