Datasheet
13
LTC2847
sn2847 2847fs
Figure 22. Typical V.11 Interface
Figure 21. V.10 Receiver Configuration
Figure 24. Typical V.28 Interface
Figure 25. V.28 Receiver Configuration
Figure 23. V.11 Receiver Configuration
1
Actually, there is no switch S1 in receivers R2 and R3. However, for simplicity, all termination
networks on the LTC2847 can be treated identically if it is assumed that an S1 switch exists and is
always closed on the R2 and R3 receivers.
APPLICATIO S I FOR ATIO
WUUU
The cable termination is then the 30k input impedance to
ground of the LTC2845 V.10 receiver.
V.11 (RS422) Interface
A typical V.11 balanced interface is shown in Figure 22. A
V.11 differential generator with outputs A and B and
ground C is connected to a differential receiver with input
A' connected to A, input B' connected to B, and ground C'
connected via the signal return to ground C. 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 essen-
tial to prevent reflections from corrupting the data. The
receiver inputs must also be compliant with the imped-
ance curve shown in Figure 20.
In V.11 mode, all switches are off except S1 of the
LTC2847’s receivers which connects a 103Ω differential
termination impedance to the cable as shown in Figure
23
1
. The LTC2845 only handles control signals, so no
termination other than its V.11 receivers’ 30k input imped-
ance is necessary.
V.28 (RS232) Interface
A typical V.28 unbalanced interface is shown in Figure 24.
A V.28 single-ended generator with output A and ground
C is connected to a single-ended receiver with input A'
connected to A and ground C' connected via the signal
return to ground C.
R5
20k
LTC2845
RECEIVER
2847 F21
A
B
A
'
B'
C'
R8
6k
S3
R6
10k
R7
10k
GND
R4
20k
AA'
B
C
B'
C'
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION
RECEIVER
100Ω
MIN
2847 F22
R3
124Ω
R5
20k
LTC2847
RECEIVER
2847 F23
A
'
B
'
C
'
R1
51.5Ω
R8
6k
S2
S3
R2
51.5Ω
R6
10k
R7
10k
GND
R4
20k
S1
AA
'
CC
'
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION
RECEIVER
2847 F24
R3
124Ω
R5
20k
LTC2847
RECEIVER
2847 F25
A
'
B
'
C
'
R1
51.5Ω
R8
6k
S2
S3
R2
51.5Ω
R6
10k
R7
10k
GND
R4
20k
S1