How to select a TVS diode?

Discussion in 'General Electronics Chat' started by crypton, Oct 18, 2016.

  1. crypton

    Thread Starter New Member

    Oct 18, 2016
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    Moderator's note: This is a continuation of http://forum.allaboutcircuits.com/threads/how-to-select-a-tvs-diode.61072/#post-1050992z

    Sry for waking up a zombie thread but I did not understand, was this method confirmed ?

    I'd also understand that the TVS working voltage (Vrwm) should be the voltage that you expect the circuit to work on (so below maximum operating voltages of devices on protected rail). In my case this would be up to 4.5V.

    Breakdown (Vbr) voltage should be the voltage when you expect the diode to start conducting - thus wasting exess energy. In my case the absolute maximum ratings of the devices on protected rail. One device is 6V max VCC (some can go up to 10V).

    Clamping voltage would be the voltage drop on the TVS with certain current (since I have seen no graph in any datasheets of how the current relates to this clamping, and I would never experience these high currents, i currently don't worry about it).

    BUT I can't find any TVS that meets these requirements. For an example: I wouldn't use TVS with 3.0V working voltage on 4.5V rail to meet 6V breakdown voltage requirement... Choosing f.i. 5V TVS, its breakdown is too high to protect absolute maximum requirement of the device.
    I thought to use MMBZ6V8AL but breakdown is above 6V.

    How would one proceed in such case (which seems to happen more often than it seems)?

    (Again sry for waking up an old topic, but this bugs me a lot).
     
    Last edited by a moderator: Oct 18, 2016
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