LM5155: Alternate Layout Guide using 2 Separate Non-Coupled Inductors

Deniel Go

Part Number: LM5155
Other Parts Discussed in Thread: LM5157, , LM5156

Hello TI Engineers,

Currently the LM5155, LM5156 as well as the LM5157/5158 SEPIC EVMs use coupled inductors in the layout. Based on the TI article "Benefits of a coupled-inductor SEPIC converter", the SEPIC can be designed with

2 individual non-coupled inductors. Does TI have a guide on how to layout the LM5155/6/7/8 SEPIC using 2 individual inductors? Can we follow the LM5155/6/7/8 SEPIC EVM and replace the L1 footprint with the 2 individual inductors next to each other in the same area as the current L1 coupled inductors.

Another question: What are the other parameters for the selecting the MOSFET for the LM5155 SEPIC design?

The current MOSFET in the LM5155 SEPIC EVM is ON Semiconductor NVMFS5C645NLWFAFT1G

If we were to find an alternate part to use, what are the most important parameters to match?

Thanks,

Deniel

8 months ago

0 Feng Ji 8 months ago

TI__Genius 12365 points

Hi Deniel,

You should determine the hot loop which should be minimized.

https://www.analog.com/en/technical-articles/minimizing-emissions-of-a-sepic-converter.html

You can replace the coupled inductor with two individual inductors, as inductor will not appear in the hot loop.

You may find SPEIC with two individual inductor here: https://www.ti.com/tool/LM5171EVM-BIDIR

There are a lot of important parameters in a MOSFET datasheet. You need to check the voltage stress, Rds(on), and so on.

Best Regards,

Feng Ji

0 Deniel Go 8 months ago in reply to Feng Ji

Intellectual 340 points

Hello Feng Ji,

Thanks for this response and resource links.

Power management

Power management forum

LM5155: Alternate Layout Guide using 2 Separate Non-Coupled Inductors