Re: MIL-STD-188-114A vs. RS-232

"rickman" <spamgoeshere4@xxxxxxxxx> wrote in news:1143775491.874277.176470
@j33g2000cwa.googlegroups.com:

I need to interface to MIL-STD-188-114A which is electrically similar
to RS-232. But I am finding that while MIL-STD-188-114A specifies a
driver output impedance of 50 Ohms or less, RS-232 does not seem to
spec an output impedance at all and can be met with a fairly high
value. Looking at data sheets for a few parts, it looks like 100 to
200 Ohms is typical.

I have no doubt that I could use any of the many RS-232 converters on
the market and get the job done. But my supervisor is being very
cautious and wants to meet the full MIL-STD-188-114A spec. Since none
of the chips I have seen will meet the output impedance spec, I am
considering using transistors to make my own driver circuit. Anyone
know of a better solution to driving MIL-STD-188-114A?



I did a product many years ago that supported MIL-STD-188-114A (I think).
As I recall the main difference was polarity. They had a few other slew
rate issues I think as well. I'm fairly sure that we just used 189 and 188
type devices anyway and we never had an issue interfacing anything.

A typical 232 driver has something like a 300 ohm series R. This is to
protect it from shorts. You could probably add some Q's then then use a
series R

--
Al Clark
Danville Signal Processing, Inc.
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