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eia-485 signal levels

Posted: Sun May 09, 2004 5:50 pm
by sklords
what is the output voltage swing of
an eia-485 typical driver chip? and
what is a good inexpensive one.

Re: eia-485 signal levels

Posted: Mon May 10, 2004 3:02 am
by dyarker
monopolar-differential 3 Volts.<p>Differential is two wires (a pair) per signal. Neither wire is ground. (Sometimes an extra wire is run for a ground reference. Half-duplex one pair, full duplex two pairs.) When one wire goes down, the other goes up.<p>Monopolar is all voltages on same side of ground. (RS-232 is bi-polar) When run on a 5V supply a high is 4V to 4.5V, a low is 0.5V to 1V. So about a 3V difference between wires. I think receiver chips will work with a 0.5V difference to allow for long cables. Cat 3, or better, cable works well; or any ole cable for a couple yards/meters.<p>Go to Digikey/Mouser/your favorite parts place, search on 485, select ICs and take your pick.<p>Cheers,<p>[ May 10, 2004: Message edited by: Dale Y ]</p>