This reminds me of a guy I talked to who was trying to put a Pentium II
in an oceanographic probe.  He insisted that to get a "good" processor
reset it was not enough to ground the /reset pin.  He connected the
/reset pin to a negative current source with a Schottkey clamp to pull
the pin below ground and flood the die with carriers to avoid a
"marginal" processor reset.
        I though he was nuts, but I have never worked with anything bigger than
an 8086.

Sherpa Doug

> -----Original Message-----
> From: Spehro Pefhany [mailto:speff@INTERLOG.COM]
> Sent: Tuesday, August 07, 2001 5:06 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Input protection V-I curve
>
>
> At 05:32 PM 8/7/01 +1000, you wrote:
>
> >PS. Based on their max 20mA spec, and your measured
> >0.887v, Microchip seem to be speccing the clamp diodes
> >at max of 18mW... Death to the infidels. ;o)
>
> Remember that the diodes may work perfectly at 20mA and at
> 100mA, BUT the current injected due to the diode action
> can trigger the BIG PARASITIC SUICIDE SCR (tm) that lives
> inside every PIC (connected from Vdd to Vss) just
> _waiting_ for a "gate" pulse to cause it to TURN ON AND
> KILL THE PIC (sufficient power supply current being
> available).
>
> This is the reason not to exceed the data sheet limits
> (and de BIG PARASITIC SUICIDE SCR, he like to turn on
> even better when it be hot, hot, hot*).
>
> Microchip have done a fine job in guaranteeing the 20mA
> minimum current, IMHO, early CMOS circuits would
> practically do this if you looked at them sideways too hard.
>
> * Caribana weekend, mon.
>
> Best regards,
>
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> =-=-=-=-=-=-=-=
> Spehro Pefhany --"it's the network..."            "The
> Journey is the reward"
> speff@interlog.com             Info for manufacturers:
http://www.trexon.com
Embedded software/hardware/analog  Info for designers:
http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at:
http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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