LM5051 surge protection

Mark Sun

Other Parts Discussed in Thread: LM5051

Hi Sir,

We use LM5051 as 48Vdc input Oring FETs drive and have 100V MOV at input terminal to suppress the surge. We apply negative 1.1kv surge voltage on input side and find LM5051 fails. The pin 4 is shorted. Can you recommend a way to protect LM5051?

Thanks,

Mark

over 9 years ago

0 Brian Daugherty over 9 years ago

TI__Expert 5940 points

Hi Mark,

The quick answer is that a 100v MOV is designed to operate on a 100v line steady state and will clamp somewhere above this level as a variable resistor. So if you put a 1.1kv surge (you didn't mention the duration or source impedance), it will not begin to clamp until over the 100v rating of the LM5051 and failure would be expected. You may be able to do a resistor/zener/cap on the Line pin to limit the max voltage it sees here with the surge, but you probably need a lower voltage rated MOV also.

Brian Daugherty

0 Mark Sun over 9 years ago in reply to Brian Daugherty

Prodigy 130 points

Hi Brain,

We add 1k resistor at INN pin (pin6) and it pass 1.1kv surge test. This modification is from TI LM5051 datasheet in Figure 32. Does this 1k resistor will affect LM5051 any function? Can someone call me to discuss this?

Thanks,

Mark

9729487931

0 Brian Daugherty over 9 years ago in reply to Mark Sun

TI__Expert 5940 points

Mark,I will call tomorrow. I think we know each other.........Brian

0 Mark Sun over 9 years ago in reply to Brian Daugherty

Prodigy 130 points

Hi Brain,

You work for Lucent Tech and Intersil before, right? I am ex-lucent engineer and good to meet you again. Hope to talk to you later.

regards,

Mark

0 Brian Daugherty over 9 years ago in reply to Mark Sun

TI__Expert 5940 points

small world. Will call you in a few min. If I miss you, will call in the AM.

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LM5051 surge protection