PIC based synchronous buck

Did you use this chip before? I once used an STR700 from ST and I've found the peripherals flaky at best.

Yes, I know the ADUC7xxx series quite well, in fact that is what I am replacing! They are great chips, but lacking in CPU horsepower, peripherals and RAM compared to more modern parts.

No, I have not used it before (only played with a development board a little). The peripherals *appear* extremely capable, but we shall see :)

In that case you really should consider switching to NXP. ST is full of surprises. On most parts the CPU cannot run at full speed while executing code from flash.

I found the STM32F2 does seem to run full speed from flash - it can toggle a PIO at 30MHz! (Measured)

I have not encountered any issues with the limited testing done so far (PIOs, UART, clock setup, timers). I use NXP too, they have some good features. But the LPC2000 series did have serious bugs for a long time, some parts did not run at full speed *at all*. I don't know if they ever got the real time clock working reliably...

=2E..say no more...

(with software yet...)

mike

I agree they are pretty old, but they have 4 fast DAC's which is hard to find in a microcontroller (only real reason I'm using them).. how did you find the 12bit ADC/DAC's performance?

cheers, Jamie

Yes, they are unmatched in that area AFAIK. The original product design required the DACS, but I have a new arrangement that does not need them.

In the ADUC7xxx? Very nice. I actually pushed the ADC to 2MHz, still seemed to work fine (just as a test). Another thing I realised recently is the voltage reference is surprisingly accurate for a microcontroller, better than most stand-alone types. They must calibrate each one.

My impression is that the ADUC is a nice analog toolkit with a mediocre ARM microcontroller hanging off it. With other parts you get a state-of-the-art microcontroller with crappy analog functions.

On the STM32F2 I have not tried the ADCs yet. I fully expect them to be poor in terms of accuracy compared to the ADUC. But for my application I believe I can make up for that using the simultaneous sampling feature, using one ADC at low gain and one at high gain. In my application dynamic range, CPU speed and RAM is, now, far more important than absolute accuracy.

Thanks for the input. We'll get going on this as a background project.