On Sat, 05 Sep 2009 14:08:54 -0700, Jim Thompson wrote:

On Sat, 05 Sep 2009 12:43:20 -0700, Jim Thompson
wrote:

On Sat, 05 Sep 2009 14:01:59 -0500, Tim Wescott
wrote:

On Sat, 05 Sep 2009 11:03:51 -0700, life imitates life wrote:

On Sat, 05 Sep 2009 12:48:41 -0500, John Fields
wrote:

On Sat, 05 Sep 2009 09:41:06 -0700, Jim Thompson
wrote:

I haven't done a relay driver circuit for, literally, eons.

Where do I look for reed relays that work on 3.3V supplies with
specications for the coil inductance?

Thanks!

---
That's a toughie.

I can't recall ever seeing inductance data on a spec sheet; I think
you'll probably have to go to the manufacturer for that one.

JF

Would not the real question be why would someone concern himself with
the solenoid inductance of a miniature relay? I could see it if it
were huge.

Jim designs custom IC's, so (I assume) he's concerning himself with it
so he can make the output stage of his circuit both economical and
robust. He may even care about making the relay turn off quickly.

It seems like a perfectly valid concern to me, even if the circuit in
question _isn't_ custom -- what if you're powering the relay from
logic, and want to insure fast & safe turn-off?

Dead-on, Tim!

...Jim Thompson

Like this...

http://www.analog-innovations.com/SE...elayDriver.pdf

In the discrete world, with more voltage tolerance available, you can
scale this to larger controlled flyback potentials, for fast turn-off.

...Jim Thompson

Clever. I assume that the gate threshold of MP1 guarantees that the
drain of MN1 never exceeds your max voltage?

I could see a potential for this to oscillate on turn-off, with the
inductor working against the delays in the two FETS, but if it did it may
well not matter, and your relay coil is probably sluggish enough to keep
it from happening anyway.

Do you get to tune the gate thresholds of the individual parts, or is
that usually locked in by the process?

--
www.wescottdesign.com