Lpc2000

lhaddix wrote:

>Hi,
>I'm working on an LPC2138 design and just moved
>into ESD testing. After some ESD hits there was
>no damage, but the processor would be left not 
>running.
>
>  
>
I'm wondering why you would subject a board's electronics to a static 
discharge??  When we go through U/L testings, they zap us with an ESD on 
the inputs of the board, but they don't start showering the board with 
static charges.

In our case, it is a matter of going after the source of the problem, 
the EMF wave introduced by the discharge.  I had one design where it 
used an AT style keyboard.  Sometimes when you plugged the keyboard in, 
the 8041 processor would lockup, in that case also, you had to power 
cycle the processor to get it working again.  Our solution had been 
simple, add a couple of silicon (1N4148) diodes to the signal lines in 
question to dump the excess voltage into the power supply bus (low 
impedance).

Other solutions we use is the classic Transorb (gas tube), resistor and 
Transil (high speed zenor).  This works exceptionally well in situations 
where high-voltage may be induced into wiring due to nearby lightning 
storms.

IMHO, you are working towards the solution backwards?  I mean, fixing 
the result rather than the cause?

TomW


-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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