Major problem fixed!

[Sandy]

I'm not sure, but even on the lm1951 1 amp driver, the uses something like
an internal zener to clamp the voltage, opposed to one of the other parts
lm1921 which uses just an internal diode. I take a stab at it, that the
zener will let the coil move instead of giving it a dead short (back through
the diode), then when the voltage reaches the zener voltage, just clamp it.
This may allow the coil to move off the seat faster. Or this could all be
BS. I'll look in some data books and see what they say. Pretty good question!

Sandy

At 09:16 AM 3/24/97 -0600, you wrote:
>>I have not really looked at it, but I would not expect too much. The
>>recommened approach is to use the zener instead of a regular diode. I can't
>>remember when I stuck the scope on it and watched the input and outputs, but
>>I don't remember seeing anything fishy.
>>
>>Sandy
>>
>>At 10:57 AM 3/24/97 +1200, you wrote:
>>>I finally got my system running reasonably. Problem turned
>>>out to be that, when using a LM1949 (or in my case a 
>>>discrete copy), Using a diode to absorb the inductive kick
>>>lengthens the pulse by about 2.5ms!. Not good when idle requires
>
>why would a zener work better ???  if the coil is clamped with
>a diode, it could saturate and take a while to come back, but
>the zener will clamp it too (after it is a diode also).  The
>zener is slower than a switching diode (all diodes turn ON fast,
>its t-rr that's slow).  The only advantage I can see from a zener
>is that it limits the voltage in BOTH directions, but it's
>t-rr is VERY slow ???
>
>Tom Cloud <cloud at peaches.ph.utexas.edu>
>
>