LM3481: Part selection for 15-30V input with 20V 0.1A output

Jingyuan Zhao1

Part Number: LM3481
Other Parts Discussed in Thread: LM3478, , LM5155, LM5156, LM5118

Dear team,

My customer is looking for low cost DCDC solutions with 15-30V input and 20V 0.1A output. I've checked using webench, it seems that SEPIC controller LM3481/LM3478 gives the lowest cost.

I wonder is this the right topology or is this the right part to use? Any recommendation on substitute solutions?

Thanks and best regards,

Charles

over 5 years ago

0 Yinsong Cai1 over 5 years ago

TI__Expert 7450 points

Hi Charles,

SEPIC is the right topology. For the part selection, please consider LM5155/LM5156 which is the upgrade of LM3481. (LM5156 has spread spectrum feature added on LM5155.)

Please let me know if you have any questions.

Thanks,

Yinsong

0 Jingyuan Zhao1 over 5 years ago in reply to Yinsong Cai1

TI__Prodigy 440 points

Hi Yinsong,

Thanks a lot for your reply!

I do not see much customers use this topology, so I wonder are there any design considerations I need to pay attention to in advance? How is the total BOM cost of SEPIC again 4 switches buck-boost?

BR,

Charles

0 Yinsong Cai1 over 5 years ago in reply to Jingyuan Zhao1

TI__Expert 7450 points

Hi Charles,

The special things about SEPIC are the two inductors or coupled inductor and the AC capacitor. You can refer to this note https://www.ti.com/lit/an/snva168e/snva168e.pdf.

You can refer to LM5118 EVM www.ti.com/.../snva334 and LM5155 SEPIC EVM www.ti.com/.../snvu628 for the BOM details.

Basically, 4 switch buck boost doubles the number of switch devices and also the controller is more expensive.

Please let me know if you have any questions.

Thanks,

Yinsong

0 Yinsong Cai1 over 5 years ago in reply to Yinsong Cai1

TI__Expert 7450 points

Sorry the two links are bad.

LM5118 EVM

https://www.ti.com/lit/pdf/snva334

LM5155 EVM

https://www.ti.com/lit/pdf/snvu628

0 Jingyuan Zhao1 over 5 years ago in reply to Yinsong Cai1

TI__Prodigy 440 points

Hi Yinsong,

Solved my problems perfectly.

Thanks a lot for your reply!

Best regards,

Charles

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LM3481: Part selection for 15-30V input with 20V 0.1A output