Re: Allegro 3977 with separate H bridge

>
> One suggestion was to use the Allegro 3977 chip with the outlets
> driving a separate H bridge (via some simple logic) and using the
> sense inputs (with appropriate resistors/capacitors) to give the
> current control.
>

I am trying to visualize the output of an H bridge driving another H
bridge and the logic needed to sort things out. I stikes me as being
easier to use a PWM chip with the correct outputs and drive a
descrete bridge once. You need to find the front end chip that will
drive the half bridge hybrid chips. Since current limit would have
to be external you start to loose a lot of the advantages of having
everything on one chip.

Take a look at:

http://209.41.165.153/stepper/fet3.htm

This is a three axis high current bipolar stepper controller for 125
bucks.....they somehow use the allegro unipolar stepper controller so
maybe there is a possibility there. All things considered with the
price of this assembled and tested card so low it's hard to justify
going through the pain of doing your own design (and there WILL be
pain).