LM5148: Use LM5148 to have a PD board design, need to change 48V to 5V,9V,15V,20V,28V,36V, but the output can't go to 15V.

Kuno Wu

Part Number: LM5148

Tool/software:

Hi Team,

I use the LM5148 to finish the 48V to 5V,9V,15V,20V,28V,36V transfer, but the output can't go to 15V. When I short the SYNC to GND to use the FPWM, the output can go to 15V, but the power loss too high, about 48V@0.3A in no load, seems to work in some abnormal condition, could you please help me to check it? Thank you.

(The SW pin, it’s my fault, I have used one line to connect to SW1 now.)

Best Regards,

Kunyue

21 days ago

+1 Timothy Hegarty 21 days ago

TI__Guru 74052 points

Hi Kunyue,

This is a standard-level MOSFET, so its Miller plateau is too high for a 5V gate drive:

Choose a logic-level FET with Rdson rated at Vgs = 4.5V. Also, no need for such low Rdson, especially the high-side FET. This is what's causing the high no-load input current, especially with paralleled FETs.

Please use the LM5148 quickstart calculator to optimize your design.

Regards,

Tim

0 Kuno Wu 19 days ago in reply to Timothy Hegarty

Prodigy 80 points

Hi Tim,

Appreciate so much, it will be useful.

Best Regards,

Kunyue

0 Timothy Hegarty 18 days ago in reply to Kuno Wu

TI__Guru 74052 points

Thank you, Kunyue.

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LM5148: Use LM5148 to have a PD board design, need to change 48V to 5V,9V,15V,20V,28V,36V, but the output can't go to 15V.