Re: [CAD_CAM_EDM_DRO] Xylotex or Gecko step driver for my Mill/Drill?

Dave Rigotti wrote:

>Jon,
> This chip doesn't use resistors!
>http://www.allegromicro.com/sf/97060/
>Now what?
>
>

Well, sure, they leave the protection of the transistors up to the
engineer that designs the board. You need something to keep
the transistors from being destroyed when they turn off. A clamp
doide to the power supply will do that, but it will recirculate
the current for a very long time. You want to add a little resistance
to the circuit to allow the field to collapse faster. This increases
the voltage on the transistors on turnoff, though. So, if your
power supply is already near the limit, you have very little room
to work with. These are the compromises that are forced upon
you with the unipolar scheme.

Jon