LTC1344A
APPLICATIONS INFORMATION
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION RECEIVER
A
A
'
B
'
C
'
100Ω
MIN
B
C
1344 F06
Figure 6. Typical V.11 Interface
A
51.5Ω
S1
ON
S2
OFF
LTC1344A
Z
124Ω
Z
51.5Ω
B
C
I
Z
3.25mA
–10V
Z
3V
– 3.25mA
–3V
V
Z
10V
1344 F07
V.11
RECEIVER
Figure 7. V.11 Interface Using the LTC1344A
V.28 (RS232) Termination
A typical V.28 unbalanced interface is shown in Figure 8.
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 to C. The V.28 standard requires a 5k terminating
resistor to ground which is included in almost all compli-
ant receivers as shown in Figure 9. Because the termina-
tion is included in the receiver, both switches S1 and S2 in
the LTC1344A are turned off.
U
W
U
U
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION RECEIVER
A
C
A
'
C
'
1344 F08
Figure 8. Typical V.28 Interface
A
51.5Ω
S1
OFF
S2
OFF
LTC1344A
V.28
RECEIVER
124Ω
5k
51.5Ω
B
C
1344 F09
Figure 9. V.28 Interface Using the LTC1344A
V.35 Termination
A typical V.35 balanced interface is shown in Figure 10. A
V.35 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.35 interface requires a T-network termination at the
receiver end and the generator end. In V.35 mode both
switches S1 and S2 in the LTC1344A are turned on as
shown in Figure 11.
The differential impedance measured at the connector
must be 100Ω
±10Ω
and the impedance between shorted
terminals A
'
and B
'
to ground C
'
must be 150Ω
±15Ω.
The
input impedance of the V.35 receiver is connected in
parallel with the T-network inside the LTC1344A, which
could cause the overall impedance to fail the specification
7
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