TVS datasheets: transil or zener?

Eeyore wrote:

Matt wrote:

I'm switching a 5VDC relay coil using a FET and a microcontroller.

I'm comfortable using a bidirectional transient voltage suppressor
(which functions like two zener diodes back-to-back) across the
coil---except for a little issue with the stand-off voltage. I think
that that is supposed to be the normal operating voltage of the device
(in this case 5V). The stand-off leakage current seems to be the
current when the device is run at the stand-off voltage (800uA for the
5V device).
(cf. http://www.fairchildsemi.com/ds/SM%2FSMBJ20A.pdf)
That doc also mentions a "test current" of 10mA. I'm guessing that that
is what defines the clamping voltage.

It looks like it.

The Fairchild and Vishay datasheets I found are silent about the technology of the devices. The ST data*** below is better in that it states that the TVS devices are made with transils. It also makes clearer the meanings of stand-off, breakdown, and clamp voltages. Those are the voltages at 800uA, 10mA, and peak-pulse currents respectively.

http://www.stmicroelectronics.com/stonline/products/literature/ds/5617.pdf
.

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