TPS6124x / TPS6125x minimum PFM mode switching frequency

Keith Keller

Other Parts Discussed in Thread: TPS61240, TPS61253, TPS61241, TPS61259, TPS61258, TPS61254, TPS61256

Hello,

My customer is concerned with audio band noise of TPS61240 or TPS61253 in PFM mode switching frequency.

From the datasheet waveforms, it looks like both of these converters will operate down to 20kHz in no load configuration.

[ please see attached .DOCX file ]

Is there any Lout/Cout configuration which could guarantee switching frequency greater than 30kHz?

[ For instance looking at attached TPS61253 datasheet with Cout = 22uF, could we decrease to 10uF and achieve double the switching freq?]

Ideally the customer would like minimum switching frequency greater than 48kHz, but greater than 30kHz should be ok.

Related converters TPS61240 TPS61241 TPS61253 TPS61254 TPS61256 TPS61258 TPS61259

Thank you very much. Keith

PFM-E2E-forum.docx

over 11 years ago

0 Chris Glaser over 11 years ago

TI__Guru*** 144230 points

We'll need to know your Vin, Vout, and minimum load to take some data. But even then, we may not be able to take data soon. Perhaps you can move your post to the internal forum and share the opportunity.

It will come down to measuring what it does in the lab. There are no equations with these devices. But yes, reducing the Cout is the way to start. Make sure you keep the datasheet minimum for stability.

0 Keith Keller over 11 years ago in reply to Chris Glaser

TI__Expert 6480 points

Attached are measurments I made on the TPS61256 and TPS61240 at ~ 2.5Vin & 4.3Vin.

At 0mA load the switching frequency does fall into the audio range. By 10mA load the switching > 160kHz.

A table of data is included for TPS61256 from no load to 60mA load including screen captures and screen captures for TPS61240 at 30mA & 60mA output.

Boost-Converter-PFM-mode-captures.docx

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TPS6124x / TPS6125x minimum PFM mode switching frequency