
38 RS-422/485 Application Note
Copyright B&B Electronics -- Revised October 1997
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 434-7094
Appendix A: EIA Specification Summary
EIA RS-422 Specification Summary
Parameter Conditions Min Max Units
Driver Output Voltage
Open Circuit
10
-10
V
V
Driver Output Voltage
Loaded
R
T
= 100 Ω
2
-2
V
V
Driver Output Resistance A to B 100
Ω
Driver Output
Short-Circuit Current
Per output to
common
±150 mA
Driver Output Rise Time
R
T
= 100 Ω
10 % of Bit
Width
Driver Common Mode
Voltage
R
T
= 100 Ω
±3 V
Receiver Sensitivity
Vcm ≤ ±7
±200 mV
Receiver Common-Mode
Voltage Range
-7 +7 V
Receiver Input Resistance 4000
Ω
Differential Receiver
Voltage
Operational:
Withstand:
±10
±12
V
V
EIA RS-485 Specification Summary
Parameter Conditions Min Max Units
Driver Output Voltage
Open Circuit
1.5
-1.5
6
-6
V
V
Driver Output Voltage
Loaded
R
LOAD
= 54Ω
1.5
-1.5
5
-5
V
V
Driver Output Short-
Circuit Current
Per output to
+12V or –7V
±250 mA
Driver Output Rise Time
R
LOAD
= 54Ω
C
LOAD
= 50 pF
30 % of Bit Width
Driver Common Mode
Voltage
R
LOAD
= 54Ω
-1 3 V
Receiver Sensitivity
-7 ≤ Vcm ≤ +12
±200 mV
Receiver Common-Mode
Voltage Range
-7 +12 V
Receiver Input Resistance 12K
Ω
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