LM5119: HICCUP mode

David Kim6

Part Number: LM5119

I'm testing a dual BUCK(13V,18V) by LM5119.

There is no problem with 13v but 18v start a hiccup at no load.
Looking at the data sheet, there seems to be only an over current related to the hiccup.
Can you be a hiccup for another reason?

-test condition

2-ch Buck(LM5119)

Input: DC 66~100V

Output: DC 13V / DC 18V

DC 18V 1A(typ) / 11A(peak)

over 5 years ago

0 Qian Chen over 5 years ago

TI__Mastermind 24075 points

Hi David,

If the noise on sensing resistor is not filtered well by RCR filter, it is possible that there is false OC condition and make part enter hiccup.
Can you provide the schematic in pdf file?

Thanks
Qian

0 David Kim6 over 5 years ago in reply to Qian Chen

Prodigy 220 points

Thanks for your support.

Refer to attached schematic

2CH BUCK_LM5119.pdf.

0 Qian Chen over 5 years ago in reply to David Kim6

TI__Mastermind 24075 points

Hi David,

Can you change RD902 and RD903 values to 100 ohm and check if it helps?
Just want to check if the issue is related to noise on current sense circuit.
In layout, the CD901 should be close to CS2 and CSG2 pin.

Thanks
Qian

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LM5119: HICCUP mode