Using a TVS as a zener, bad idea?

Question

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?

Glenn · Accepted Answer

A very active and good group, where you should ask is: nntp:// /Glenn

Rob Gaddi · Answer

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 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.

mike · Answer

Using ANY device for a purpose other than what it was designed (AND SPECIFIED) for is a problem.

Sometimes, it's genius. But most of the time, it's a problem waiting to happen. Most of us are NOT geniuses.

John Devereux · Answer

Yes, there's a guy called Larkin who may be able to help :) --  John Devereux

Using a TVS as a zener, bad idea?

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