LM5121: Initial power on issue with LM5121

SHIJU R

Part Number: LM5121

Hi Garret,

Sorry for the delay

In continue with previous linked question , the schematic and layout of the circuit is attached

In layout C3 capacitor is burned during initial power on twice..green marked are ceramic capacitors and yellow marking is tantalum (IC LM5121 LOCATION IS MARKED IN PINK)

over 5 years ago

0 Richard Fu22 over 5 years ago

TI__Mastermind 31115 points

Hi Shiju R,

Thanks for sending the schematic and layout. Let me review it and get back to you by next week.

Thanks,

Richard

0 Richard Fu22 over 5 years ago in reply to Richard Fu22

TI__Mastermind 31115 points

Hi Shiju R,

Can you check if C3 is not placed backwards? Your schematic and layout seems okay.

Thanks,

Richard

0 SHIJU R over 5 years ago in reply to Richard Fu22

Prodigy 200 points

Hi Richard

C3 capacitor placed with correct polarity only, In the circuit for LO and HO sides iam using two different MOSFET as given below, whether it can make any impact during power on??

LO MOSFET : RJK0301DPB-02#J0

HO MOSFET : PSMN1R3-30YL-115

regards

SHIJU.R

0 Richard Fu22 over 5 years ago in reply to SHIJU R

TI__Mastermind 31115 points

Hi Shiju R,

Your MOSFETs look to be okay, they should not make any impact there.

Can you take a waveform during startup of VIN, VOUT, COMP and SS? This will help debug the converter.

Thanks,

Richard

0 SHIJU R over 5 years ago in reply to Richard Fu22

Prodigy 200 points

Dear Richard,

Kindly find the below electrical characteristics data of the two MOSFETs i was used in my design , Kindly confirm the issue may not due the HO and LO MOSFET parts.

Because in one of my same board i used PSMN1R3-30TL-115 for both HO and LO side, there is no issue regarding power on.

Kindly provide your feedback

regards

SHIJU.R

0 Richard Fu22 over 5 years ago in reply to SHIJU R

TI__Mastermind 31115 points

Hi Shiju,

Thank you for providing the comparison table. Since your LO MOSFET has a much lower rise-time, it is possible that the fast turn on time generates lots of ringing, which may exceed the voltage rating of the SW node and C3 capacitor. Because of this, C3 can be damaged.

Thanks,

Richard

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LM5121: Initial power on issue with LM5121