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Help with Exposed pins protection

Started by Sink0 December 14, 2012
I am designing a project that is very similar to TI MSP-WDS430BT2000D kit.
My design would need rechargeable battery, be Water-resistant and to have
some way to talk to external world without opening it, and be rugged to
external enviroment (shower, swiming poll and so on). The current version
is using a push-pull transformer in order to create a isolated interface to
recharge the battery and iRDA interface to communicate with the external
world. That is working and got a good level of isolation and protection.
However looking at  MSP-WDS430BT2000D specifications, it seems to have a
spy-by-wire interface exposed to connect to the clip and exposed pins to
charge the battery. 

I was looking at some photos at this website
(http://sensorseverywhere.wordpress.com/2011/10/04/metawatch-platform-warranty-voided/),
and it seems to have not real isolation from the external world. Just
clamping diodes as i a can see in the picture. Is that a proper protection
for the internal circuit considering that the watch will be used in all
enviroments a person can go?

Am i over protecting my circuit? My big concern about not isolating the
external pins is due to the ground. If a big surge happens i am afraid my
MSP430 can get reseted.

One more question if is not a problem. One possible solution is to use USB
as my external interface and some ESD protection IC as TPD4S012 or MAX4987.
Does these ICs would be able to protect my USB lines if they are totally
exposed to the enviroment. 

PS: The product is suposed to be a high-reliability circuit. So it must not
fail easily. Not life support, but users really hates when it fails as it
is used as a long term datalogger.

Regards,	   
					
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