how to chose TVS diode?

[chico]

I was wondering if anyone knew how to choose a TVS diode.
They have spec'd "reverse standoff voltage", "breakdown voltage" and "direction" (uni or bi directional).

If I have a 5V Vcc do i want "reverse standoff voltage" or "breakdown voltage" above 5V?
Why would I ever want a bidirectional diode? that sounds like a horrible idea.

 

[crutschow]

The reverse standoff voltage is the normal operating voltage which in your case would be 5V.

The breakdown voltage is self explanatory.

Bidirectional diodes are used to protect AC circuits.