LT1785 Linear Technology, LT1785 Datasheet - Page 7

• Manufacturer Part Number: LT1785
• Description: 60V Fault Protected RS485/RS422 Transceivers
• Manufacturer: Linear Technology

FU CTIO TABLES
SWITCHI G TI E WAVEFOR S
TEST CIRCUITS
LT1785 Receiving
LT1785 Transmitting
* 0mV for LT1785A
DI
U
RE
RE
0
0
1
1
1
0
0
0
1
5V
Figure 3. Driver/Receiver Timing Test Circuit
DE
DI
INPUTS
–V
A
B
DE
5V
0V
V
0V
DE
U
1
1
0
1
1
0
0
0
0
B
A
O
O
U
INPUTS
R
DIFF
DI
DI
W
0
1
X
0
1
X
X
X
X
C
C
V
L1
L2
Hi-Z
O
A
0
1
0
1
– 200mV
200mV*
Open
1/2 V
A-B
X
A
B
O
10%
t
OUTPUTS
r
Hi-Z
1.5V
B
1
0
1
0
Figure 5. Driver Propagation Delays
RE
90%
t
W
t
OUTPUT
PLH
SKEW
f = 125kHz, t
Hi-Z
RO
Hi-Z
Hi-Z
Hi-Z
0
1
1
RO
0
1
1785/91 F03
15pF
RO
V
r
DIFF
10ns, t
= V(A) – V(B)
LT1791
* 0mV for LT1791A
RE
f
0
0
0
0
0
0
0
0
0
1
1
1
10ns
UNDER TEST
OUTPUT
DE
0
0
0
1
1
1
1
1
1
0
1
1
t
PHL
INPUTS
Figure 4. Driver Timing Test Load
t
f
DI
X
X
X
0
0
0
1
1
1
X
0
1
1.5V
C
90%
500
L
10%
t
SKEW
– 200mV
200mV*
– 200mV
200mV*
– 200mV
200mV*
Open
Open
Open
A-B
X
X
X
LT1785/LT1785A
LT1791/LT1791A
1/2 V
O
S1
S2
Hi-Z
Hi-Z
Hi-Z
Hi-Z
Y
0
0
0
1
1
1
0
1
1785/91 F05
OUTPUTS
Hi-Z
Hi-Z
Hi-Z
Hi-Z
1785/91 F04
Z
1
1
1
0
0
0
1
0
V
CC
Hi-Z
Hi-Z
Hi-Z
RO
0
1
1
0
1
1
0
1
1
7