Need help on LDO simulation.

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kumarghz

Joined: 25 Nov 2006
Posts: 48
Helped: 3
Location: Penang, malaysia

04 Aug 2009 3:34 ldo simulation

Dear All,
Attached my screen shot of my simple LDO design. Can some one guide me to simulate following parameters, 1. Phase Margin 2. PSR

Thanks.

regards,
Kumar

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hbk2222

Joined: 09 Sep 2007
Posts: 26
Helped: 1
Location: cairo,egypt

04 Aug 2009 6:38 inurl:viewtopic simulation

u put an iprobe between the opamp and the pass element and use the stability analysis to check the phase margin and for the psr u put 1V Ac on the supply and use ac analysis to get the transfer function from the supply to the output.

kumarghz

Joined: 25 Nov 2006
Posts: 48
Helped: 3
Location: Penang, malaysia

04 Aug 2009 7:05 simulate stability of ldo

Dear essawy,
Thanks for reply.

iprobe did you meant a Current probe? how to do stability analysis in SPICE then?

For PSR, that AC signal, is this should be added together with Vsupply? or AC supply alone?

pls advice. thaks

regadrs,
kumar

LvW

Joined: 07 May 2008
Posts: 1466
Helped: 242
Location: Germany

04 Aug 2009 9:39 pspice ldo phase margin

kumarghz wrote:

iprobe did you meant a Current probe? how to do stability analysis in SPICE then?
kumar

Which simulator engine do you use ?
If the program does not contain a specific stability analysis package you have to apply the stability definition: Simulate the ac response of the loop gain Lo(w) and determine the phase margin at the frequency where the magnitude Lo=1.