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From: "Frank Bemelman"
Subject: Re: Resistor proetection for the PIC16F874
Date: Sun, 8 Sep 2002 19:12:48 +0200
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Organization: EuroNet Internet
NNTP-Posting-Date: 08 Sep 2002 17:13:59 GMT
"Spehro Pefhany" schreef in bericht
> The renowned Danny wrote:
> > I am using the PIC16F874 for a project, and I need to know how to
> > the input current protection resistors, and also the output protection
> > resistors. I mean like parallel or serial/series.
> As in the snarky reply ;-), you can use George Simon Ohm's law to
> determine series resistance that won't cause latchup. Limiting the current
> to a few mA is typical (the latchup limit is much higher). The chip will
> survive this, but correct operation in all respects is not guaranteed.
> > And do you have a formula to calculate the resistance?
> > any help would be very much so appreciated
> However, you may wish to clamp the voltage inside the power supply
> rails to prevent side effects of running current through the protection
> diodes, particularly if you are using the 10-bit A/D in this part. You can
> do this with 2 dual transistors and a resistor per input, which will clamp
> the input to within about 100mV of the rails, well within the 300mV
2 dual transistors and a resistor. Without a diagram I'm lost here ;)
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