Big zeners are rarely used these days, at least by me. Need to dump several watts this time. Other than the ghastly DO5 "long bolt" style, are there any in modern heatsink-able packages such as TO220?
-- Regards, Joerg http://www.analogconsultants.com/
Might not it be cheaper to use a dinky zener (or heavens! a TL431) and a power MOSFET?
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et |
Cost is not much of a factor (ain't that nice!) but real estate is. Must be simple, just something that can be bolted on. I don't want to have to machine down a DO5 package ...
-- Regards, Joerg http://www.analogconsultants.com/
Microsemi.
John
According to their web site they only have TO3, like this series:
Power-wise that would be ok but too fat (yeah, sorry, I should have said TO-220 or smaller). Can't really machine down a TO3, only DO5 and the like. We'll do it if needed but it would be a chore.
-- Regards, Joerg http://www.analogconsultants.com/
What's wrong with a ~1W zener and a TO-220 BJT?
Isn't there some kind of shunt regulator/zener "booster" circuit that uses a zener and a mongo transistor?
Thanks, Rich
One more part :-)
Seriously, there is literally no room, I can barely get a TO-220 with a crew cut in there.
If there really isn't any TO-220 or similar zener I'll go for a TO-220 FET and a SOD-523 zener on the board since that's only 1.5mm long and
0.7mm in width and height.-- Regards, Joerg http://www.analogconsultants.com/
Sure, but no space. The other stuff would have to go on a circuit board which is already full to the brim.
-- Regards, Joerg http://www.analogconsultants.com/
You seem to have an awful lot of "blue-wire" problems ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et |
What's a blue-wire problem?
-- Regards, Joerg http://www.analogconsultants.com/
Patches to fix unanticipated bugs. Called "blue-wire" because it's common to use blue Teflon jumpers ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et |
So, what about anticipated bugs?
Ah, yes, got some of that here. But this circuit isn't even done yet so it can't have no bugs. And the schedule says there better ain't gonna be no bugs ...
-- Regards, Joerg http://www.analogconsultants.com/
Oops, they used to exist, apparently gone now.
How about a transzorb in an SMB package?
John
That would be resulting in a loud bang and engine company 89 roaring down Cameron Park Drive. Under extreme circumstances I'll have to dump several watts average into this thing.
But I better do it with a FET. Means more parts but then things don't go obsolete on my client years down the road.
-- Regards, Joerg http://www.analogconsultants.com/
won't it be eaisier to get a controlled voltage with a bjt?
somthing like tip121 with a 0805 zener would fit on the pads/legs of the transistor
-Lasse
It's not to generate a controlled voltage but to dump unwanted spike energy. Without creating smoke :-)
But it looks like it will have to be a FET. Machining a DO-5 package to a smaller size isn't exactly my favorite method.
-- Regards, Joerg http://www.analogconsultants.com/
what voltage ~?
-Lasse
Not sure yet but probably around 70V.
-- Regards, Joerg http://www.analogconsultants.com/
That's TO262, SC83, SOT404 - D2pak for a mosfet.
Assuming you have somewhere for the heat to go.....
As for real estate, have you considered wave-side smd component use?
RL
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