LM25184-Q1: Loop Stability Test

Keith Li

Part Number: LM25184-Q1
Other Parts Discussed in Thread: LM25184

Hi, Ti team, I want to test the performance of the LM25184's loop response. According to past experience, I put the interference injection resistor in series on the voltage feedback loop, but we can't get the correct Bode diagram. The measured waveform is very bad, I don't know Is it a problem with my test method, I hope to get your help, thank you.（Below is a schematic diagram of my resistor locations）

over 1 year ago

0 Richard Fu22 over 1 year ago

TI__Genius 17560 points

Hi Keith,

I think the reason for your trouble is that you're injecting noise into the switch node. Can you place the injection resistor in series with Rfb, such that it looks like this?

Regards,

Richard

0 Keith Li over 1 year ago in reply to Richard Fu22

Prodigy 50 points

Hi,Richard

I followed your suggestion to keep the injection resistor away from the noise source, but still can't test a valid waveform.Do you have the loop stability test report of the demo board? Thanks.

Keith.

0 Richard Fu22 over 1 year ago in reply to Keith Li

TI__Genius 17560 points

Hi Keith,

I apologize for the recommendation. I dug into this a bit more and found out that it is not possible to obtain loop measurement with the PSR flyback. You may need to run simulation results, or try another method- such as load-transient tests.

Regards,

Richard

0 Keith Li over 1 year ago in reply to Richard Fu22

Prodigy 50 points

Hi,Richard

Thank you so much for your reply, you don't have to apologize for it. So your suggestion is to demonstrate the stability of the loop response from the resulting performance by testing the dynamic load, right? thanks

Regards,

Keith.

0 Richard Fu22 over 1 year ago in reply to Keith Li

TI__Genius 17560 points

Hi Keith,

Yes, that is correct.

Regards,

Richard

0 Keith Li over 1 year ago in reply to Richard Fu22

Prodigy 50 points

Hi,Richard.

Thanks for the suggestion, I have done it and its dynamic performance is solid and my problem is solved.

Regards,

Keith.

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LM25184-Q1: Loop Stability Test