UCC28881: High Side Buck Converter D3 location

60532 Siegrist

Prodigy 10 points

Part Number: UCC28881

Tool/software:

We have some circuits on the production line not starting up. Changing the diode in the D3 location seems to help.

How can I tell if the diode in the D3 location (freewheeling diode) is fast/not fast enough?

Does anyone have scope captures to compare the 2 conditions?

5 days ago

0 Ning Tan 4 days ago

TI__Expert 4985 points

What D3 are you referring to? Can you share the schematics?

0 60532 Siegrist 3 days ago in reply to Ning Tan

Prodigy 10 points

The D3 refers to the freewheeling diode shown in the datasheet.

By not starting up, I meant that the ACDC circuit was not producing enough power to start the application.

Expected output for us is between 3.2V - 3.35V. When the condition described above, the output is only around 2.8V. Replacing the D3 diode with a faster device fixes the issue, but I am trying to find supporting evidence as to why. Some diodes from the same manufacturer and PN work, while others do not.

0 Ning Tan 2 days ago in reply to 60532 Siegrist

TI__Expert 4985 points

There is only one D3 in the datasheet. Is this what you refer to?

0 60532 Siegrist 1 day ago in reply to Ning Tan

Prodigy 10 points

My apologies. It is the D1 location in this photo.

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UCC28881: High Side Buck Converter D3 location