ESD. Two serious issues: GPS-ext-antenna and Touchscreen outer resistive foil

joerg joerg.twinklephone at gmx.de
Tue Mar 4 10:32:29 CET 2008


Am Di  4. März 2008 schrieben Sie, Andy Green:
> I just woke up -- and talk about GTA02 only -- but JACK_INSERT at least
> has 10K series resistor and a 1K to 0V I believe from the audio amp
> side, so this should be no problems.  HOLD I would have to check.

Hold has 10k. JACK-INS even has a suppressor diode D4402 on GTA01, sorry here.


> 
> Debug connector is probably OK since it is normally NC and does not come
> out of the case.

Ok. So special care should be taken on how to connect it, in case. First 
connect USB?


> 
> BATTEMP IIRC also has a series resistor as part of the network and one
> to 0V so it should be OK.

No series R for GTA01! But not a CPU-IO, just 50606, which i assume is 
a "tough" one.


> Touchscreen is a good point, although again I think it is inherently a
> high impedence path.

For GTA01: U6003 U6004 have no protection (maybe built in?)
******** GTA02: direct connect to CPU! No ESD protection! ***********


> GPS I will look at later, I guess there is some matching network at
> least between it and the chip.

Nope, nothing in the path there, just phantom, which is L and so is useless.
******** GTA02: the same. No ESD protection! ****************
Make GND before signal connector might help, assuming external dev is low imp


> The impedence matters because it affects what is actually seen by the
> protection diodes in the chips it connects to.  It is a lot easier for
> them to shrug off an ESD event via 10K than directly.

ACK.


jOERG




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