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Transient-voltage-suppression (TVS) diodes to protect IO Pins

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mribble:
I'm working on a project which will be in an enclosure, but will have many connectors that expose either pins from the Atmel SAM3x8 (http://www.mouser.com/ProductDetail/Atmel/ATSAM3X8EA-AU/?qs=sGAEpiMZZMtQuSbTnHsVtm6dgCW59dFS) or an LTV827 optoisolator (http://www.digikey.com/product-detail/en/LTV-827S-TA1/160-2040-2-ND/388468).

I'm wondering if people with more experience than me have any opinions on using transient-voltage-suppression (TVS) diodes on pins exposed to the user via plugs.  Most projects I've looked at don't have these (such as the Arduino boards), and my past projects have not used them.  I had few few unexplained failures (1%-ish), but I'm not sure if it was this or something else.  However, I've had a person say I should really consider adding them to be safe.  The problem is to protect all my external pins would require about 80 of these diodes which is a considerable expense to the project.  Do you think the SAM3x8 or optoisolator pins should really have this sort of protection?

My gut is that there is already enough protection in the microcontroller and optoisoltor either via dedicated protection or just naturally protect via the silicon geometries.  I know certain types of transistors like mosfets are sensitive to ESD, but none of my external pins connect to mosfets.  So basically I'm looking for people with experience to say whether they think the added protection of TVS diodes is worth it to them in this kind of case.

Thanks!

Simon:
The thing with a TVS is that it will have a cut in voltage and a clamping voltage which is usually twice the cut in making it hard to actually protect fully in such a restricted range

olsenn:
Transient voltage supressing diodes, as far as I am aware, typically only supress voltages in the kilovolt range. Perhaps even as low as a few hundred volts, but not 6V. A zener diode is most likely what you want... these are diodes intended to be operated in the breakdown region and are trimmed to a user-specified breakdown voltage.

Take a look at the attached image for example. Note that the resistor may be replaced by a PTC

Simon:
I think you can buy TVS diodes specifically for IO pins a zener i was told is not as fast as a TVS

sleemanj:

--- Quote from: olsenn on May 24, 2014, 02:07:28 pm ---Transient voltage supressing diodes, as far as I am aware, typically only supress voltages in the kilovolt range. Perhaps even as low as a few hundred volts,

--- End quote ---

TVS are available in low clamping voltages no problem.
Sent from my HTC Dream using Tapatalk 2

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