LM25118-Q1: stability of overall gain loop

Rana LM-S

Prodigy 210 points

Part Number: LM25118-Q1
Other Parts Discussed in Thread: LM25118

Hello Dears,

I'm using the LM25118 DCDC Converter, I need to verify the stability of the circuit.

As mentioned in the datasheet, the overall loop gain is the product of the modulator gain and the error amplifier gain.

this is what I have :

I need to Know , did I should measured the phase margin relatively to -180° or the 0° line?

Best Regards,

Rana

over 7 years ago

0 Garrett Roecker over 7 years ago

TI__Mastermind 21720 points

Hi Rana,

Please measure the phase margin relative to the 0 degree line.

Thanks,

Garrett

0 Rana LM-S over 7 years ago in reply to Garrett Roecker

Prodigy 210 points

Dear Garrett,

Thank you for your replay

could you please clarify more why I need to measure the phase margin relative to the 0 line .?

Many thanks,
Rana

0 Garrett Roecker over 7 years ago in reply to Rana LM-S

TI__Mastermind 21720 points

It is due to the way the graph is plotted. The plot is showing phase margin, to plot the phase angle just multiply by -1.

-Garrett

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LM25118-Q1: stability of overall gain loop