LM2642: 12V 33A backup output power supply for PC mother board

Jiang Boqian

Part Number: LM2642
Other Parts Discussed in Thread: LM27403, LM27402

Hi there,

I want to add a 12V backup power supply for my PC mother board. My target output power is 12V 33A, input from a suitable battery from 10-14.4V.

Because there's no multi-phase buck-boost controller I think, so my proposal is to use cascaded boost and buck controller to derive a 12V output from 10-14.4V input. Do you have better recommendations?

Right now, I am considering LM2642 for the multi-phase buck controller (boost controller is not selected yet), however, space(inductor size and input capacitor size) is not too critical in my application. Do you really recommend multi-phase converter? Or just single phase is OK? My output current is "only" 33A, not crazy values like 56A or so...

Thank you.

over 6 years ago

0 Mathew Jacob1 over 6 years ago

TI__Expert 5910 points

Jiang,

I think your selection is okay considering the high current need. There have been instances where customers have designed LM27402/LM27403 for your exact situation as single phase and used parallel fets for thermal management.

Regards,

Mathew

0 Jiang Boqian over 6 years ago in reply to Mathew Jacob1

Intellectual 655 points

Thank you Mathew.
Can you share a little bit more about the topology your customer used for the exact situation, also pre-boost and post-buck?
I read the LM2642 datasheet, its maximum duty cycle may down to 85% for 600kHz switch frequency, which put a low limit on pre-boost output voltage. I may have to boost to 15V(instead of maybe 13V) for the buck the output 12V.

0 Mathew Jacob1 over 6 years ago in reply to Jiang Boqian

TI__Expert 5910 points

Jiang,

I was referring to a standard single phase buck topology with parallel fets.

Regards,

Mathew

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LM2642: 12V 33A backup output power supply for PC mother board