LM25184: Using LM25184 with -12V as ground and 0V as Vin

Hi,

Do you want to make a buck or a boost from negative pressure to negative pressure? What is the output voltage? 

Aurora

Hi,

Yes, I want a -15V/-42V to -3.3 v with LM25184.

I am Expecting -3.3V on the output of Flyback w.r.t 0v or GND.

Thanks 

Sai Kumar

Hi Sai,

I just see the solution use boost to achieve this. I put this solution below. (Use LM5122, Vin=-48V, Vo=-24V) Thanks.

Aurora

Hi Aurora

Thanks for the reply.

but i am already using oLM2518 as buck in my requirement, i do not want to go for another IC(booster), Can't we use same LM25184 as buck and generate -3.3V?

Thanks 
Sai Kumar

Hi Sai,

For the chip, the voltage of the VIN pin must be higher than the voltage of the GND pin. So you cannot directly give the chip a -15V input. I have never used flyback for this application before. Maybe I can ask other colleagues for you, but I need to give you an answer next Monday. Pls wait patiently. Thanks.

Aurora

Hi Aurora

sorry, I did a mistake in the first image I attached.

I want to connect -15V to GND pin of IC and 0V/GND of supply to Vin pin of IC.

Will it work in this way?

Thanks 

Sai Kumar

Hi Sai,

This is okay, but it should be noted that the withstand voltage value marked on the datasheet is the withstand voltage between each pin relative to the GND pin. Thanks.

Aurora