Need a very high frequency PWM controller with variable setpoint/reference

[mtwieg]

Hello, I'm going to try to make a high-bandwidth class D amp for AM modulating RF amplifiers. For best bandwidth (at least 300KHz), I'm want to use a synchronous buck regulator, with an operating frequency around 2MHz or higher. I need to vary the output voltage setpoint with a control voltage, but most PWM controllers have a fixed setpoint internally, so they won't work. Does anyone know of a high speed controller where the setpoint voltage can be varied? Ideally I'd like something like the UC3824, where all the error amplifier pins are available, but that chip isn't fast enough for my needs. The controller doesn't necessarily need to have current-mode control capabilities.

 

[atripathi]

For fixed reference controoler, you may want to tweak the feedback voltage to get different o/p? This may work for limited range.

 

[mtwieg]

For fixed reference controoler, you may want to tweak the feedback voltage to get different o/p? This may work for limited range.

This works when you want to manually adjust the output voltage with a knob or something, but I need it to be voltage-controlled, and I want it to be linear. Also I don't want the closed loop transfer function to change severely over the operating range, so that method won't work for me.

I've found that some controllers have the feature I'm looking for, and it's often referred to as "tracking," like here: **broken link removed**
But none of the ones I've found so far operate up to 2MHz. Also I should clarify that I don't need any gate drivers built into the controller. I'm planning on using an external half bridge driver anyways. Also I don't need an internal error amplifier.