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From: ftpam1@acad3.alaska.edu (MUNTS PHILLIP A)
Newsgroups: sci.electronics
Subject: Re: RS232 Driver Request
Message-ID: <1990Dec3.054329.5931@hayes.ims.alaska.edu>
Date: 3 Dec 90 05:43:29 GMT
References: <1990Dec2.220302.10794@julius.cs.uiuc.edu>
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In article <1990Dec2.220302.10794@julius.cs.uiuc.edu>, totty@flute.cs.uiuc.edu (Brian Totty) writes...
> 
>	I need an RS232 driver chip to send data to a Sparc station.  The
>	Sparc seems to have data between a range of +5 and -5 volts.  I have
>	a +5/-5 volt power supply here, but my 1488 drivers seem to want a
>	6 or 7 volt supply minimum.  What I want is to take a TTL input,
>	provide +5 and -5 volt supplies and get a -5 to +5 output.  Anyone
>	want to suggest me a chip?
> 
> 
>   /                      Brian Totty              o o
>  /__  __  o       1304 W. Springfield Avenue       o  
> /  / /   /             Urbana, IL 61801           \_/  "We have corn in
>/__/ /   /             totty@cs.uiuc.edu                Massachusetts too!"

     There are a number of possibilities, with tradeoffs between cost and
complexity.

     First, you can use 14C88 drivers from National Semiconductor.  These are
supposed to be able to run off +/- 5V.  They have the advantage of being pin
compatible with the standard 1488.

     Motorola makes a device, the 145406 (I think), which is a new CMOS design
that isn't compatible with anything else.  It has both drivers and receivers
on one chip and runs on +/- 5V.

     Finally, you can use the MAX232 which also has both drivers and receivers
on one chip.  This can run on a single 5V supply but you need to add 4 small
capacitors for the on board voltage generators.  The advantage of the MAX232
is it has many more sources than either of the others.  There is also a MAX233,
my personal favorite, that has the capacitors integrated, but it is single 
sourced from Maxim, as far as I know.

     Digi-Key catalogs the MAX232 (listed as ICL232) at $4.80.  JDR Microdevices
lists it at $7.95.  Jameco lists the 14C88 at $1.19.  I couldn't find a hobbyist
source for the 145406.

Philip Munts N7AHL
NRA Extremist, etc.
University of Alaska, Fairbanks


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