Using a TVS as a zener, bad idea?

Oct 02, 2012 4 Replies

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Rob Gaddi

A TVS diode is basically just a zener optimized for for surge power handling rather than continuous low-current use. So you're not using a TVS as a zener diode, you're using a zener diode as a zener diode. My only question would be "Why?". In my experience, TVSs are physically…

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Rob 14 years ago

Been doing some experimentation with TVS's and have found that they seem to be usable as a zener diode when their clamp voltage has been achieved but with a very low current.

Eg. If I have a TVS with a clamp voltage of 14V with a current flow of less than 1 mA, say from some circuitry that is acting as a constant current source, then it seems to be quite happy to be left on / clamping / (zenering?). Power dissipation is less than 5mW. The clamp / zener voltage doesn't have to be that accurate, just approximately 14V.

Can anyone see a problem with this?

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Glenn 14 years ago

A very active and good group, where you should ask is: nntp://sci.electronics.design

/Glenn

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Rob Gaddi 14 years ago

My only question would be "Why?". In my experience, TVSs are physically larger and more expensive. On a lark I pulled up any old datasheet I had on file, the MAZ3140. It's a SOT-23 14V Zener with a breakover voltage that doesn't barely twitches between 1 and 10 mA, and in fact remains at 13.1V at only 60uA. Less than 30 cents a piece at 25 piece quantities, 8 cents a pop by the reel.

Rob Gaddi, Highland Technology -- www.highlandtechnology.com Email address domain is currently out of order. See above to fix.

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