LM5145: Capacitive Load Capabilities

John Fagerlund38

Part Number: LM5145

I'm planning on using the LM5145 as my input buck step-down supply from 40V-60V input to 12V output at 6.5A. Following this I have several buck regulators generating the various voltage rails needed for my design. each on of those step-down bucks have input caps. Heaviest of the rails is 0.9V output at 35A.

My question is can the LM5154 function with a large capacitive load? I've seen regulators function fine until a large capacitive load is applied, then not be able to come up when power is applied.

Thanks,

-j

over 5 years ago

0 Marshall_Beck over 5 years ago

TI__Mastermind 35210 points

You are right that is one of the challenges faced with DCDCs, with highly capacitve loads at startup.

LM5145 has soft start (SS) pin. You can calculate for the given Css cap you need based on the required soft start time you need to avoid current limit of the device.

Please reference the application note below for deeper understanding, as well, the LM5145 datasheet for equations.

http://www.ti.com/lit/an/slyt669/slyt669.pdf

0 John Fagerlund38 over 5 years ago in reply to Marshall_Beck

Intellectual 260 points

Good info. I'll look at my actual capacitive load and ramp requirements, and play with it.

Thanks,

John Fagerlund

Power management

Power management forum

LM5145: Capacitive Load Capabilities