Negative input negative output DC/DC buck converter

Eliahu Pekel 

Did you try searching the E2E forums for Negative Input, Negative Output BUCK converter? 

There are other posts with a switching (BUCK) solution using the LM5001 and a non-switching (Linear) using the LM2991 

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/367158/negative-input-negative-output-with-buck-converter 

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1058496/negative-input-negative-output-with-buck-converter 

Eliahu Pekel 

Yes.  Unfortunately, most of our BUCK converters are designed for Quadrant 1 (Positive Input / Positive Output) Operation.  We have application circuits to operate them in Quadrant 4 (Positive Input, Negative Output) but they are not well suited for Quadrant 3 (Negative Input, Negative Output) operation.

You could use a Boost controller, like the TPS40210 to build a non-synchronous converter.  The power circuitry would look much like the LM5001, but it would still need to have the output voltage level shifted to the negative rai for feedback.

Peter hello, thank you for your reply.

In a meanwhile, as an alternative solution, I will use an isolated power supply ic / module.

Thank you.