On 8/20/13 8:20 AM, Brian Inglis wrote:
On 2013-08-20 02:45, "Björn" wrote:
[email protected] said:
The PTTI 1PPS is defined in
http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf
It is 20us long and common in some applications. However the voltage
levels
are a bit high...
The section I saw said 10 V nominal, +1, -2. That's 8-11 V.
I think that would work fine with a RS-232 receiver.
Yes, but driving 10V into _50ohms_ is a lot of power for a modern
receiver...
/Björn
RS-232 transmitter output impedance is 50 ohms,
Not in the sense of what the spec calls for nor in terms of a "matched
transmission line".
The RS-232 standard says the transmitter has to tolerate shorts to any
voltage -25V to 25V. Then, there's also a "shall source 30mA or sink
30mA" (or maybe it's 20 mA)
max slew rate is 30V/microsecond, which folks regularly bust to run
faster than the notional 20kbps max for RS232.
The standard capacitance of the load is 2500pF.
Driving 12 or 15V at 20 mA is 600 ohms..
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