Looking for synchronous average current mode buck regulator IC

[[email protected]]

Hello,

I am designing a synchronous buck regulator with average current-mode
control (not
ramp-compensated peak mode control) that must be able to source and
sink 10 amps
at varying output voltages (capacitive load). I'm looking for an IC
that would
work for this purpose. Unfortunately, most PWM IC's seem to operate on
peak current-mode
control and expect a unipolar current signal. I can sense current on
the low side of the
load, giving me a continuous current signal suitable for average
current-mode control
with a small common mode range, but nonetheless a bipolar signal.

I have a design with two LM3478 PWM IC's and a gate driver, but the
challenge is getting
suitable ramp compensation when the output voltage is swinging. I'd
like something
more elegant.

I'd prefer an IC because I'll be switching at 500kHz and would like as
much noise
immunity as possible. Am I stuck rolling my own? Would a "beyond the
rails" op amp
be a good choice for level shifting the current signal into the
single-supply realm?

Thanks

Justin

 

[Joerg]

Hello Justin,

I'd prefer an IC because I'll be switching at 500kHz and would like as
much noise
immunity as possible. Am I stuck rolling my own? ...

Did you look at the UC3849? An expensive but nifty chip.

Would a "beyond the rails" op amp be a good choice for level shifting
the current signal into the single-supply realm?

Just be careful. I only did peak current mode so far but there the
bandwidth had to be really high. It's just a matter of microseconds
between something going wrong and the trigger of a major kaboom, leaving
a crater where the switching device was.

Regards, Joerg