Gents,
Does anyone know of a non-boutiqueish (meaning available) SCR that can keep its juices flowing with less than 1mA hold current? The usual ones are around 5mA, like this:
Ok, I can make one out of transistors but real estate is critical. Needs to be able to withstand 60V or more when open. Max current is miniscule, probably 5-10x the hold current. Small package, SOT23 or less.
Come on! You can't get two trannies in there? ...Jim Thompson
Nope. Because it would be two transistors and two resistors.
s
ds
e,
does something like this:
get close?
-Lasse
That stuff's not so available generally. Even PUTs never caught on in SMT.
A tiny dual NPN/PNP pair with integrated resistors would be ideal, but they are not very popular with such a high voltage rating.
Best regards, Spehro Pefhany
Is it possible to simply add an R for extra load to maintain it at lower currents beyond the burden R ?
Jamie
Or this one, plus a resistor or two.
About 4 cents ea. @ 1 reel, pretty reasonable.
Best regards, Spehro Pefhany
...fer example, a dual on a SOT23-6. Diodes Inc. ZXTD09N50DE6TA Fairchild FMBM5551 Diodes Inc MMDT5551-7-F, MMDTA42-7-F
There are a few others, in similar packages; just takes some digging.
Two resistors? for what? if you think you need base resistors, there are "pre-biased" transistors available in the same package.
The best PNP/NPN biased pairs seem to be 50V rating: Rohm IMD10AT108, IMD16AT108 in SC-74-6 package; UMD6NTR in their UM-6 package; EMD6T2R in their EMT-6 package; IMD8AT108, IMD6AT108, IMD1AT108 in SC-74-6 package.
Yeah, but they're too expensive for Joerg. ;-)
What isn't? :(
If I have to I'll do it with transistors. But even if I use a dual pack it still needs a couple of resistors to make it an SCR. I was hoping some company had a scaled down SCR. There ought to be enough of a market for that.
That 50V would be a bit of a white-knuckle ride.
an
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8XV6T5-D.PDFmany dual packs with resistors build in
-Lasse
It's higher current one would need, not lower, in order to hold the SCR. The smallest SCRs I could find still need around 5mA and that causes too much battery drain in my application.
This is where I envy IC designers. They just sketch it onto their CAD and it's done. Us board level guys can only have what's on the big buffet table. But when it comes to big inductors they lose and we win :-)
this:
Yes, although nearly always with resistors in series with the base as well. It can work but they are usually for logic stuff and cannot take
60V. At least the ones I have seen. I'll have to check out the PBLS series from NPX some more. The NPN in there is only 50V but the PNP is 60V, and that should be enough.However, only the NPN in there comes with a BE resistor.
No, the concern is marginal breakdown voltage. Believe it or not, cost (within resonable limits) is not an issue on this project. Real estate is.
C106. Typical 0.19mA @ 25 Celsius?
Max is 3mA, so you'd have to select, which probably means you won't like it.
Pushing the envelope a bit? I've always used C106 when I needed a sensitive SCR, but not quite as sensitive as you appear to want.
Nope, don't like it :-)
Must be guaranteed.
There are some nice latching apps for SCRs and the only reason I never used any of those ideas was the hold current. Looks like the same this time :-(
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