LM5118-Q1: Issue with Comp and SS pin

Asghar Shamshir

Part Number: LM5118-Q1

Tool/software:

Hi Stefan,
Hope you are doing well. I am sharing, all the waveforms issues i am facing is on comp and ss on low input 15V the output trips / clamp to 18V which was wrong as i had design it for 23V out however on higher input i-e-Vin = 24V to 30V the behaviour is acceptable.
Please take a look on the waveform.

Will wait for your reply.

Waveforms LM5118.pdf

9 months ago

0 Stefan Schauer 9 months ago

TI__Guru 60001 points

Hi Asghar,

this thread is continuing the discussions from this one - right?

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1462377/power-management-forum

Best regards,

Stefan

0 Asghar Shamshir 9 months ago in reply to Stefan Schauer

Prodigy 30 points

Hi, Stefan,
Yes.

0 Asghar Shamshir 9 months ago in reply to Stefan Schauer

Prodigy 30 points

Did you access the waveforms, can they help me understand why the COMP and SS signals are not behaving as expected?

0 Stefan Schauer 9 months ago in reply to Asghar Shamshir

TI__Guru 60001 points

Hi Asghar,

yes, i could access the waveforms.

For the waveform on the last page, can you do three other measurements:

- probe SS and FB (FB instead of Comp)

- zoom in on the dip of SS to e.g. 500ns

- probe SS during power on to see the full ramp up from 0V to ~ 1.3V.

Note: The dips you see on SS should come from the probing setup and are only injected to the probe as the charging of the SS cap would be much slower.

Best regards,

Stefan

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LM5118-Q1: Issue with Comp and SS pin