LMR36510: High Quiescent Current

Greg Reynolds

Part Number: LMR36510

Tool/software:

Hi,

I have a circuit that uses the LMR36510 to generate +5V from a power input that can be anywhere from +12V to +48V. It appears that even when there is no load, the circuit draws 7mA when supplied with +12V, which is much more than I was expecting. Circuit is shown below:

The inductor is a Bourns SRP7028C-220M.

The input and output capacitors are all MLCCs, output is X6S, input is X7R.

I have to say that the circuit seems to work fine, but it seems to enter PWM straight away, and not PFM mode which I was expecting when not loaded. In this product, the quiescent current is very important.

Any thoughts/comments much appreciated.

Greg

1 month ago

0 Richard Fu22 1 month ago

TI__Mastermind 31075 points

Hi Greg,

What's the OPN of the device?

I believe the Auto-mode device OPN is LMR36510ADDAR.

I also noted that there doesn't seem to be a device comparison table, which led to the confusion. Thanks for bringing this to our attention.

Thanks,

Richard

0 Greg Reynolds 1 month ago in reply to Richard Fu22

Prodigy 40 points

Hi Richard,

I've just checked my records and it appears that I've purchased the variant that doesn't have PFM mode, which is a bit frustrating!

Thanks for pointing it out. I did noticed that the datasheet talked about "variants", but because they weren't listed, I assumed it was text copied from another similar part.

Actually I'm quite relieved that the problem isn't more fundamental, I've designed this part into quite a few designs where the quiescent current doesn't matter and it seems to work very reliably.

Best wishes,

Greg

0 Greg Reynolds 20 days ago in reply to Richard Fu22

Prodigy 40 points

Hi Richard,

I have now bought the alternative variant of the device (from DigiKey) and it exhibits exactly the same behaviour - no auto-mode and the quiescent current is still about 7-8mA.

For clarity, I have tried:

LMR36510ADDAR (direct from TI)

LMR36510FADDAR (from DigiKey)

Any more suggestions?

Thanks,

Greg

0 Greg Reynolds 20 days ago in reply to Greg Reynolds

Prodigy 40 points

Please ignore this, I ordered the wrong part again the second time - I have not tried the LMR36510ADDAR yet.

0 Richard Fu22 20 days ago in reply to Greg Reynolds

TI__Mastermind 31075 points

Hi Greg,

Thanks for clarifying. Hope it works out better with the LMR36510ADDAR.

Cheers,

Richard

0 Greg Reynolds 16 days ago in reply to Richard Fu22

Prodigy 40 points

Hi Richard,

I can now confirm that with the correct part, LMR36510ADDAR, the quiescent current is now where I'd expect it to be, i.e. less than 1mA.

Many thanks,

Greg

P.S. Any idea when the datasheet will be updated?

0 Richard Fu22 16 days ago in reply to Greg Reynolds

TI__Mastermind 31075 points

Hi Greg,

Great, glad it works out- we'll note it as something to be added on the datasheet. The modification may take a bit of time due to internal processes.

Thanks,

Richard

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LMR36510: High Quiescent Current