LM2678: Inductor selection guide for wide input rage.

Dexter Choi

Expert 2795 points

Part Number: LM2678

Dear Sir,

My customer is now using LM2678S-ADJ/NOPB.

I have some problem.

When Input voltage is 12V. it is OK.

but when Input voltage is 28V, LM2678S-ADJ is burned.

Could you tell me Why LM2678S-ADJ is burned.

Could you advise me to solve this issue?

If you need more information please let me know that.

Specification are below.

Input Voltage rage : 9V ~ 36V

Output voltage : 9.33V

Output current : 2.5A

please refer to the attached schematic.

0 Samuel Jaffe over 6 years ago

Dexter,

What do you mean by burned? Does it catch on fire? Or does it just get hot?

If it catches on fire, please check each pin to ensure the circuit does not violate the absolute maximum voltage ratings on each pin.

Also try shorting L16 and L12. I have not seen ferrite beads placed in this way before. Why did you place them there?

-Sam

0 Dexter Choi over 6 years ago in reply to Samuel Jaffe

Expert 2795 points

Hi Sam,

Thank you for your reply.

Burned mean is just getting hot and die.

my customer is using L16 and L12 because of EMI.

I will try shorting L16 and L12. could you advise anything else?

Thanks.

0 Samuel Jaffe over 6 years ago in reply to Dexter Choi

Dexter,

Please share the layout as well if shorting L16 and L12 does not help. I'll have more comments once I see the layout.

-Sam

0 Dexter Choi over 6 years ago in reply to Samuel Jaffe

Expert 2795 points

Dear Sam,

It solved that is Shorting L16 and L12.

Thank you so much.

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