Re: Lets talk about input protection against ESD (human body).

"At which qties? 17c is a lot of money if you are talking about a few
million units a year. Also, make sure that whatever LDO you are using
will not go on allocation. Or at least that your company is high up in
the pecking order should that happen. And check it out for stability
inside out. These things can be rather fickle."

Qty = 800K (for now)

You think this part is expensive? Geesh, I looked long and hard for
this regulator. It's very precise, has tons of built in stuff that
eliminates external circuitry, etc...

Do you think a switcher could be implemented for anywhere near this
price? I don't think so. But then again, I've never really looked :).

I picked a device that can be sourced from 3 different vendors if need
be.

The regulator is stable given the loading vs. capacitance used on its
output. I've tested it to death and have never had a failure.

"Ok, you can use 12V if it's before the 100K like you have in your
drawing. But when the switch is open you'll see 7mA or so flowing at
all
times, more if the switch is pressed, of course. If the circuit is
powered down when not in use that may be ok. Else the valuable customer

sits there one winter day in his fancy vehicle and the engine won't
turn
over :-("

The 12V source switches off with vehicle IGN. Key off load current is
about 90uA. The acceptable limit is 300uA. I'm safe.

"Freescale? HC parts? Mine are spec'd from ONSemi, not Freescale. I'd
be
surprised if they sold any. From a specsmanship point of view (familiy
specs, ESD etc.) Philips is really good but their web site is a pain.

Anyway, HC is a regular plain clothes CMOS process. Look at the family
specs."

I think there is a little confusion here. The device is a
microcontroller manufactured by Freescale (Motorola). Not a common
logic gate. True, the HC in the part number MC68HC908kX8does stand for
CMOS, but the microcontroller implementation goes a little further with
its input scheme than a general logic gate. Or so I am lead to
believe.

"That MLV cap is suspicious. Could fry on ESD."

This multi layered varistor (MLV) is made to absorb transient engergy
from ESD. I would only hope it can stand up to a strike without
frying. Take a look at its data *** here:

http://www.epcos.com/inf/70/db/var_01/01170130.pdf

.

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