UCC28911: Pulse Skip operation when transition from CV to CC

What do you mean "pulse skip is appeared when transition from CV to CC"? Can you provide waveforms to show what happaned?

Hi Hong Huang,

Thank you for your reply.

I confirm the customer and then send to you.

Best regards,

Shinichi

Hi Hong Huang,

I obtained the latest information from the customer.

I was wondering if you could advise.
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The problem was solved if Ripk(1.8kohm) set near UCC28911(1-3pin) as close as possible and add a cap(220pF) in parallel.

Is there any problem of adding a capacitance(220pF) in parallel with Ripk(1.8kohm)?

I think current limit response is delayed, is it correct?

What other effects considered?
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I appreciate your great help.

Best regards,
Shinichi

Based on your description, it looks this is a noise issue. The best way is to make the resistor very close to IPK based on the datasheet number 1 suggestion. A small capacitor can be added but will delay internal thermal protection internally, also real current will be higher than the device sensed which means the device MOSFET can be overloaded while the device does not make protection. So in general we do not recommend solution to add a cap on to IPK. But if you do need a small cap to get going, you need to test to see ok with overload without device damage by test confirmation since the device current sense signal not accurate after the cap addition to IPK pin.