LM2674: Buck regulate a positive and negative Vout

Hello

The LM2674 is OK for your application.

Other devices you might consider are the LM22674, LMR33610, LMR50410

I have attached some information about using a uC as a DAC to adjust your Vout. (you may need a filter if you are using PWM from the uC)

If you have a -24V rail, then the simplest thing to do is to use a negative linear regulator for your negative Vout.

You can use an ordinary buck as an inverting converter (IBB).  You would use your +24V rail and convert to your negative Vout.

However, it is somewhat tricky to do the DAC with an IBB.  You will need level shifting.

I have attached some information on the IBB that may be helpful.

Thanks

3733.snva856a.pdf

8358.DAC_calc5.xlsx

Frank

Excellent inputs on this. A few comments:

a) I prefer not to use +24v to also generate the negative output rail. I prefer to use the -24v rail to generate the negative Vout. I have a lot of these regulators in the system, and I want to balance current loads on the +24v and -24v supplies (if possible).

b) Regulating the negative voltage with a microprocessor should be easy since I plan to use PWM from the micro, and this can be AC coupled. I prefer to stay away from a DAC to control the output. Also, I will probably implement a feedback loop to the micro (which has a lot of 10-bit ADC inputs) to tightly control +Vout and -Vout (using perhaps an inverting op-amp).

Thanks.