LM5122: LO FET fails

Amy Sanvido

Part Number: LM5122

I currently used webbench to create a design for the LM5122. I have taken that design and modified the eval board to test the design. I currently have been blowing up the LO FET. The regulator draws a lot of current as soon as it powers on with no load. I am wondering if there is something that I have wrong in the design.

over 4 years ago

0 Yinsong Cai1 over 4 years ago

TI__Expert 7450 points

Hi Amy,

Thank you for using LM5122. I can review the schematic for you but does this issue happen with multiple LM5122 ICs and MOSFETs?

Thanks,

Yinsong

0 Amy Sanvido over 4 years ago in reply to Yinsong Cai1

Prodigy 10 points

Thank you. That would be helpful. I have replaced the LM5122 and the Fets and have had the same issue reoccur. I wanted to have the schematics checked before replacing the parts again.

0 Yinsong Cai1 over 4 years ago in reply to Amy Sanvido

TI__Expert 7450 points

Hi Amy,

Thank you for the confirmation. I'll review the schematic and let you know.

Thanks,

Yinsong

0 Yinsong Cai1 over 4 years ago in reply to Amy Sanvido

TI__Expert 7450 points

Hi Amy,

I have reviewed the schematic and here are some general comments.

1. the full load steady state peak current will be about 1.5A, please make sure the inductor will not be saturated
2. the 50mhom sensing resistor is too large, you will need some margin to account for the peak current
3. It is usually recommended to reserve the place for a current sense filter

Regarding the problem you had, we may need some waveform to further investigate.

Thanks,

Yinsong

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LM5122: LO FET fails