LM5121-Q1: Input Bulk capacitor after series disconnection switch

selvam perumal

Intellectual 515 points

Part Number: LM5121-Q1
Other Parts Discussed in Thread: LM5121, LM5069, LM5122

Hi,

In LM5121,Shall I put bulk capacitor after disconnection switch?

So that I can limit my input inrush current due to Filter capacitors.

By doing so,Will it affect current loop or performance?

Refer attached image.

With regards,

Selvam.

over 3 years ago

0 Richard Fu22 over 3 years ago

TI__Genius 17540 points

Hi Selvam,

You should not put bulk capacitor after disconnection switch. I'm afraid that by doing so, you will have bypassed the current limit protection, which is placed before the disconnection switch.

Please refer to the reference designs here in the design and development section:

https://www.ti.com/product/LM5121?keyMatch=LM5121&tisearch=Search-EN-everything#design-development

Thanks,

Richard

0 selvam perumal over 3 years ago in reply to Richard Fu22

Intellectual 515 points

Hi Richard,

I am using Inrush current controller using LM5069 before EMI Filter?

To reduce power dissipation and component count,Shall I bypass series disconnection switch in Boost converter?

Over current and short circuit protection will be taken care in LM5069.

With regards,

Selvam.

0 Richard Fu22 over 3 years ago in reply to selvam perumal

TI__Genius 17540 points

Hi Selvam,

If you do not wish to use the disconnection switch, you can leave DG and DS open, and remove Qd and Df.

However, please place LM5069 before LM5122 input in order to make sure inductor current is still sensed across CSP and CSN pin.

Thanks,

Richard

Power management

Power management forum

LM5121-Q1: Input Bulk capacitor after series disconnection switch