> Anyone here a pro on these?  Specifically...

No, but here goes ...

>=20
> I usually see regular diodes across the inductive load itself, but I noti=
ce the
> LM1949 fuel injector driver puts a zener across the switching transistor.
> Makes sense to protect the transistor, but wondering if this was just for=
 the
> ease of putting it internally to the controller, or if there's something =
other
> better about this arrangement.

I thought you were going to say it is across the inductive load, because th=
at may help the field collapse faster, and this seems to me to be the sort =
of application where that may be desirable. Across the transistor may do th=
e same as well. It also has a possible side effect of returning energy to t=
he power source, which may be desirable - or not as the case may be.

> Secondarily, how does one calculate the value for these?  I can calculate=
 an
> estimate of the energy held in coil once energized, but with the field
> collapses, what determines the voltage and current produced?  It should b=
e
> the resistance of the load, but that would be a diode in this case.

The resistance of the inductive load becomes the DC current limiting factor=
, and the inductance with the resistance becomes the time constant. In this=
 configuration any power supply impedance will also become a factor.

Don't know if this helps, there will be someone with better knowledge than =
mine.



--=20
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