TPS54560: DC-DC-step down converter

Ulli Braunsteffer

Prodigy 80 points

Part Number: TPS54560

Hi altogether,

first in my application I had used MLCCs at the Input - but they are "singing" and had made music!!!!

Now I had changed to alu-capacitors and everything is fine ....

In the DB TI suggest ceramic-capacitors (low ESR) - but they don't say, that I must not use alu-elkos (higher ESR) ...

So are there other reasons against alu-elkos - because I want to use them for series!!??

Thanks for your feedback in advance.

Greatings,

Ulli

over 6 years ago

0 Timothy Hegarty over 6 years ago

TI__Guru 73522 points

Hi Ulli,

What's the ESR and ESL of these caps?

We normally recommend ceramics with X7R dielectric to filter the switching frequency currents and electrolytics for bulk capacitance.

What cap footprint did you use that created the acoustic noise? Please send the schematic for review.

Regards,
Tim

0 Ulli Braunsteffer over 6 years ago in reply to Timothy Hegarty

Prodigy 80 points

Hi Tim,

thanks for your message!

downside the footprint - but no detailed information towards ESL or ESR ...

The application pulses nearly 5W at the output ...

may this can help you and me ...

Regards,

Ulli

0 Timothy Hegarty over 6 years ago in reply to Ulli Braunsteffer

TI__Guru 73522 points

Hi Ulli,

The caps you circled are ceramic caps (Murata 2.2uF, X7R, 1210). What's the ESR/ESL of the electrolytics?

Regards,
Tim

0 Ulli Braunsteffer over 6 years ago in reply to Timothy Hegarty

Prodigy 80 points

Hi Tim,

2 times the Panasonic EEEHD1J100P: Impedance @ 100kHz ==> 2Ohm (20°C).

Regards,

Ulli

0 Timothy Hegarty over 6 years ago in reply to Ulli Braunsteffer

TI__Guru 73522 points

Hi Ulli,

You may consult with the cap vendors (TDK, Murata, Taiyo Yuden, etc.) for their recommended components to reduce acoustic noise. In general, a smaller footprint should reduce the issue. Are you sure your converter is stable with the ceramics? Note that the electrolytic provide damping of the input filter (resonance of the high-Q, low ESR ceramics with the supply line parasitic inductance).

Regards,
Tim

0 Ulli Braunsteffer over 6 years ago in reply to Timothy Hegarty

Prodigy 80 points

Hi Tim,

maybe I will contact the vendors ...

And if the converter is stable ... I think he is ....

I changed the frequency, the output inductivity, the input capacitors, .... the result was always the same - acustic noise!!!

Perhaps I had to change the converter ;-)

Thanks for your note in response of the electrolytics ... I know ... but now I hear nomore bad music ...

Regards,

Ulli

0 Timothy Hegarty over 6 years ago in reply to Ulli Braunsteffer

TI__Guru 73522 points

Hi Ulli,

Is the converter stable? Check the SW node voltage. Is the schematic available?

Regards,
Tim

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TPS54560: DC-DC-step down converter