cool part

Nice, thanks.

Price is right too!

Cheers

I think the dual is 17 cents by the reel.

I like the input pulldown, for before uP ports are configured.

John

Sort of 1/4 of a ULN2803 or 28% of a ULN2003 (at several times the price) for low voltage output applications.

Best regards, Spehro Pefhany

I've always dreaded the infamous -8V drain transient on a mosfet.

What were they thinking?

RL

Everything except the pinout, which could have been improved had pins 3 & 4 been swapped.

Does that mean that there is no body diode in those parts? That could be an interesting feature.

Best regards, Spehro Pefhany

I'm driving tiny relays and don't want the 0.6 volt drop of a Darlington. I also want them to drop out fast, so the zener is better than a clamp diode.

Cute little gadget.

John

Looks like two identical, isolated chips inside. I'll break one open and see.

John

Yup, although the clamp diode will work just as well, depending on what you clamp it to.

So far I've managed to avoid 5V relays most of the time. Last gadget with 5V latching relays used emitter-follower drive on the coils (so no diodes required and no base resistors). There was enough margin with a regulated supply.

Best regards, Spehro Pefhany

I think you're asking too much of this data sheet, if you want to know things like inter-device isolation (drawn as seperate sources) or actual surge capability in any direction. I don't know what the author was using for brains.

The SOA chart doesn't extend operation to the zener clamping voltage, so who's to know what the hell it does.

It's a good attempt to reduce parts count in an application that most designers would try to avoid altogether ie use of electromechanical parts.

RL

Well, I have a 3.3 volt cpu and 5-volt relays here! I'm using some cute little Fujitsu dpdt telecom relays. They pull in and drop out in under a millisecond.

John

The tiny dpdt relays we're using here have 30 milliohm on resistance,

signal response, 1 amp capacity, and 0.25 pF open capacitance. Find me a semiconductor that will do that for $3!

John

snip

I always liked these

Quote "The company owns the freehold of its main two acre site and factory, with no mortgages or borrowings, so we have a very strong financial base."

Martin

That's novel, to not be deep in debt.

I avoid reeds. They seem to fail a lot more often, in real life, than they're supposed to.

These are nice:

The latching ones are great for microvolt stuff... no thermal emf's.

John

Hmm, were you using DC relays with internal diodes? Some have them which stands for the reason of the + & - marking found on some. Other wise, I don't see how the transistors would have survived unless the bias control was ramping?

Think about it.. emitter follower.

Best regards, Spehro Pefhany

Yes, I have.. and still..