Have you looked at the LM18245 -- I picked up some of these some time  
ago, chosen because of their relatively higher current and voltage.   
AFAIR it does bipolar and unipolar.

Cheers,
-Neil.


Quoting Josh Koffman <joshybear@gmail.com>:

> Hi all. The last time I designed a stepper motor into a project was a
> long time ago. I used a ULN2803 darlington array and did the stepping
> in software. It worked ok.
>
> I've just started looking into steppers again, and it seems there are
> a bunch of new chips on the market that take care of a lot of the work
> for you. I'm happy to get one chip that will handle generating steps
> as well as handling the higher power to the windings. That will just
> make things easier on me both in the software and hardware. Setting a
> pin to choose the direction and then just sending pulses seems quite
> simple.
>
> However there seem to be a bewildering array of these chips out there.
> I'd love to standardize on a chip that will drive unipolar and bipolar
> motors and doesn't cost an arm and a leg. Something easily available
> at Digikey would be nice too. The Toshiba TB6560
> (http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=TB6560AHQO-ND)
> seems ok for bipolars. Is there something out there than would handle
> both? These aren't huge motors so I would say anything up to an amp or
> two would be good.
>
> What do you use, and why that particular chip?
>
> Thanks!
>
> Josh
> --
> A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.
>         -Douglas Adams
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