LM27761: Can I change PFM operation current?

Downey Kim

Expert 2675 points

Part Number: LM27761

Hi Ti team,

My customer is designing the Hi-Fi Audio DAC.

there are using LM27761 to supply Volume IC Vcc(-5V). current output of LM27761 is 60~70mA.

Issue : we can hear noise in the 5-10khz band from the headphone out.

Resolve : Increasing the load to the output of the LM27761 to 150mA eliminates noise.

Increasing the output load eliminates noise, but we cannot add load.

I think the cause of the problem is PFM mode. Can I change PFM operation current? I didn't find any related formulas in the datasheet.

Please check that.

Thanks.

over 5 years ago

0 Excel Regidor over 5 years ago

TI__Mastermind 37001 points

Hi Downey,

I believe no possibility to force the device away from PFM mode. However, it is worth to try to decrease the CFLY (ex. 0.47uF), but this might increase the ripple voltage. The buck-boost converter is another alternative.

Best regards,

Excel

0 Tanvee over 5 years ago in reply to Excel Regidor

TI__Genius 17401 points

Hi Downey,

If you don't have further questions, I will close the thread. You can contact us through the thread for further queries.

Best regards,

Tanvee

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LM27761: Can I change PFM operation current?