Datasheet

3
LT1785/LT1785A
LT1791/LT1791A
DC ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
OD1
Differential Driver Output Voltage (Unloaded) I
O
= 0 ● 4.1 5 V
V
OD2
Differential Driver Output Voltage (With Load) R = 50Ω (RS422), Figure 1 ● 2.0 2.70 V
R = 27Ω (RS485), Figure 1
● 1.5 2.45 V
R = 18Ω
● 1.2 2.2 V
∆V
OD
Change in Magnitude of Driver Differential Output R = 27Ω or R = 50Ω, Figure 1 ● 0.2 V
Voltage for Complementary Output States
V
OC
Driver Common Mode Output Voltage R = 27Ω or R = 50Ω, Figure 1 ● 2 2.5 3 V
∆V
OC
 Change in Magnitude of Driver Common Mode R = 27Ω or R = 50Ω, Figure 1 ● 0.2 V
Output Voltage for Complementary Output States
V
IH
Input High Voltage DI, DE, RE ● 2V
V
IL
Input Low Voltage DI, DE, RE ● 0.8 V
I
IN1
Input Current DI, DE, RE ● 5 µA
I
IN2
Input Current (A, B); (LT1791 or LT1785 with V
IN
= 12V ● 0.15 0.3 mA
DE = 0V) V
IN
= –7V ● –0.15 –0.08 mA
–60V ≤ V
IN
≤ 60V ● –6 6 mA
V
TH
Differential Input Threshold Voltage for Receiver LT1785/LT1791: –7V ≤ V
CM
≤ 12V ● –0.2 0.2 V
LT1785A/LT1791A: –7V ≤ V
CM
≤ 12V ● –0.2 0 V
∆V
TH
Receiver Input Hysteresis –7V < V
CM
< 12V 20 mV
V
OH
Receiver Output High Voltage I
O
= –400µA, V
ID
= 200mV ● 3.5 4 V
V
OL
Receiver Output Low Voltage I
O
= 1.6mA, V
ID
= –200mV ● 0.3 0.5 V
Three-State (High Impedance) Output Current RE > 2V or Power Off ● –1 1 µA
at Receiver 0V < V
OUT
< 6V
R
IN
Receiver Input Resistance (LT1791) –7V ≤ V
CM
≤ 12V ● 85 125 kΩ
– 60V ≤ V
CM
≤ 60V 125 kΩ
LT1785 –7V ≤ V
CM
≤ 12V ● 50 90 kΩ
RS485 Unit Load 0.25
I
SC
Driver Short-Circuit Current V
OUT
= HIGH, Force V
O
= –7V ● 35 250 mA
V
OUT
= LOW, Force V
O
= 12V ● 35 250 mA
Driver Output Fault Current V
O
= 60V ● 6mA
V
O
= –60V ● –6 mA
Receiver Short-Circuit Current 0V ≤ V
O
≤ V
CC
● ±35 mA
Driver Three-State Output Current –7V ≤ V
O
≤ 12V ● –0.2 0.3 mA
–60V ≤ V
O
≤ 60V ● –6 6 mA
I
CC
Supply Current No Load, RE = 0V, DE = 5V ● 5.5 9 mA
No Load, RE = 5V, DE = 5V
● 5.5 9 mA
No Load, RE = 0V, DE = 0V
● 4.5 8 mA
No Load, RE = 5V, DE = 0V
● 0.2 0.3 mA
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C, V
CC
= 5V.