LM25148: LM25148

Ali Khan

Part Number: LM25148
Other Parts Discussed in Thread: LM5148

Hi,

I design a board based on LM25148. I also got PCB review for it.
Now i am testing the board.
I noticed that as i increase the load current, the input voltage at converter start dropping drastically so the output voltages..
The board is designed to output 7.4V and minimum input voltages will be 8.4V.
In the given data, the input supply is setup at 8.4V on supply and 1st column show the voltages measure at input terminals of the converter.

Input Voltages V (drop shown at Meter)	Output Voltages V	Load current A
8.4	7.39	0
7.7	7.38	2
6.9	6.79	4
6.2	5.95	6

If i increase the power supply voltages to maintain input voltages at 8.4V then it give desire output. Now the question is why input voltages are dropping? As input voltage drop so obviously output will be less than input.

11 months ago

0 David Baba 11 months ago

TI__Mastermind 34050 points

Hello Ali,

Need to know what the input voltage is dropping, I suspect the input supply is in current limit, the LM5148 is doing what it needs to do to best regulate VOUT from a lower that expect VIN.

hope this helps,

David.

0 Ali Khan 11 months ago in reply to David Baba

Intellectual 980 points

Hi David Baba

Thanks for your reply. The supply isn't ij current limit. I setup current at 10A on power supply.

When there is 0A load current then the input Voltages are 8.4V but same input start dropping as i increase the load current. The above table 1st column shows the voltage drop in input from 8.4V.

Thanks

0 David Baba 11 months ago in reply to Ali Khan

TI__Mastermind 34050 points

Hello Ali,

Its not our device. There is nothing that would make the input supply drop other than the input supply itself, suggest getting another supply. Hope this helps.

David.

0 Ali Khan 11 months ago in reply to David Baba

Intellectual 980 points

Hi,
I will test it on some other power source. Can you confirm me max current rating of this device?
I remember, on datasheet it was 20A and i designed 8A continues and 12 to 15A peak current for this board

0 David Baba 11 months ago in reply to Ali Khan

TI__Mastermind 34050 points

Hello Ali,

Yes, the device is capable of these output currents, hope this helps,

David.

0 Ali Khan 11 months ago in reply to David Baba

Intellectual 980 points

Hi David Baba

I found the problem. It was power supply cables issues. I recently bought new one that are counterfeit. The issue resolved when i changed the cables.
Thanks for all your help.

Power management

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LM25148: LM25148