multiple LM5175's : single control

Chris,

I've moved your post to the DC/DC forum.

I'm not clear about what you are asking. Can you elaborate?

Suppose I want to control several power-supplies using a single control, perhaps variable, like in my case. My choice now is only to gang the external feed-back resistors. This is troublesome.

If I had control over the reference voltage to the Error Amplifier I could simply change this voltage. The feedback resistors could be sub-1% parts. Linearity matching of ganged pots reeks.

I had in mind to use at least four of these DC/DC controllers, they all need separate feed back, but has to have a single control. They share common ground.

If I have to add power supplies to the system all have to do is tap into the common Vref. So simple.

What you are probably looking for is a part with PMBus such as TPS549A20. Will that type of device work for you?

No, it also has its Vref hardwired to the Error Amplifiers + input. (p.16 in the .pdf) It will not buck-boost, just buck. Adding a micro controller for the PMBus (12C?) is more work than using a single pot. The PMBus does not seem to be able to affect the either the feed-back or the reference(?)
IF it could affect the Vref thru the PMBus then I would need a micro to digitize a pot, kinda hokey.