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TPS62125: Power

Matt Karaerik

Intellectual 360 points

Part Number: TPS62125

Hello,

We use the TPS62125 buck converter in a few designs, we are having some noise issues in one of the batch of the boards and wondering any suggestion to fix and any reason for the cause would be very much appreciated.
All PCB guidelines are observed and attached are the design and the noise output and PCB layout.

over 4 years ago

0 JohnTucker over 4 years ago

TI__Guru**** 191445 points

Matt,

i suppose it is not really noise you are concerned with but rather large ripple on your 3.3 V output, correct? Can you tell me your load condition? Doe the ripple decrease when your low current increases? Can you provide a zoomed in waveform That shows Out as well as the SW node voltage? Two periods of the ripple should be sufficient. Also, I would like to see your layout and schematic in high resolution. I cannot read what you have included.

0 Matt Karaerik over 4 years ago in reply to JohnTucker

Intellectual 360 points

Hello John,

thank you for your answer. I have included the schematic and the scope reading below. Can you see it now?

0 Matt Karaerik over 4 years ago in reply to JohnTucker

Intellectual 360 points

Hello John,

thank you for your answer. I have included the schematic and the scope reading below. Can you see it now?

3617.Design.docx

0 Kumar Vale over 4 years ago

Intellectual 270 points

The typical current draw is 1.89mA, but with this fault it measures 6.55mA

0 Kumar Vale over 4 years ago in reply to Kumar Vale

Intellectual 270 points

As we load more, the amplitude didn't change but the frequency increases.

0 JohnTucker over 4 years ago in reply to Kumar Vale

TI__Guru**** 191445 points

Matt and Kumar,

I need to see the SW node waveform as well as the output voltage. Zoom in so individual switching pulses can be discerned.

0 Kumar Vale over 4 years ago in reply to JohnTucker

Intellectual 270 points

John

Basically with this fault the SW out(pin7) and the v out are having the same waveforms !

0 Kumar Vale over 4 years ago in reply to Kumar Vale

Intellectual 270 points

The mystery has been solved!

The signal on the switching pin(SW) and the voltage output are the same and this leads to the discovery!

The inductor was placed in the wrong way causing a short between switching signal to the output voltage!

All boards are working well after placing the same inductors in the correct way!

Thanks