Datasheet
11
LTC1544
V.11 (RS422) Interface
A typical V.11 balanced interface is shown in Figure 14. A
V.11 differential generator with outputs A and B with
ground C is connected to a differential receiver with
ground C', inputs A' connected to A, B' connected to B. The
V.11 interface has a differential termination at the receiver
end that has a minimum value of 100Ω. The termination
resistor is optional in the V.11 specification, but for the
high speed clock and data lines, the termination is required
to prevent reflections from corrupting the data. The
receiver inputs must also be compliant with the imped-
ance curve shown in Figure 12.
In V.11 mode, all switches are off except S1 inside the
LTC1344A which connects a 103Ω differential termina-
tion impedance to the cable as shown in Figure 15.
R3
124Ω
R5
20k
LTC1344A
LTC1543
LTC1544
RECEIVER
1544 F15
A
B
A
'
B
'
C
'
R1
51.5Ω
R8
6k
S2
S3
R2
51.5Ω
R6
10k
R7
10k
GND
R4
20k
S1
Figure 15. V.11 Receiver Configuration
AA'
B
C
B'
C'
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION
RECEIVER
100Ω
MIN
1544 F14
V.28 (RS232) Interface
A typical V.28 unbalanced interface is shown in Figure 16.
A V.28 single-ended generator output A with ground C is
connected to a single-ended receiver with input A' con-
nected to A, ground C' connected via the signal return
ground C.
In V.28 mode all switches are off except S3 inside the
LTC1543/LTC1544 which connects a 6k (R8) impedance
to ground in parallel with 20k (R5) plus 10k (R6) for a
combined impedance of 5k as shown in Figure 17. The
noninverting input is disconnected inside the LTC1543/
LTC1544 receiver and connected to a TTL level reference
voltage for a 1.4V receiver trip point.
AA
'
CC
'
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION
RECEIVER
1544 F16
Figure 14. Typical V.11 Interface
R3
124Ω
R5
20k
LTC1344A
LTC1543
LTC1544
RECEIVER
1544 F17
A
B
A
'
B
'
C
'
R1
51.5Ω
R8
6k
S2
S3
R2
51.5Ω
R6
10k
R7
10k
GND
R4
20k
S1
Figure 17. V.28 Receiver Configuration
Figure 16. Typical V.28 Interface
APPLICATIONS INFORMATION
WUU
U