+3.3V Multiprotocol Software-Selectable
Cable Terminators and Transceivers
*NODE C IS PROVIDED IN NETWORKS 1,2,3.
A
A
A
R1
52Ω
S1 ON
C*
R3
127Ω
S2 OFF
R2
52Ω
B
B
R1
52Ω
S1 ON
S2 ON
C*
R3
127Ω
R2
52Ω
B
R1
52Ω
S1 OFF
S2 OFF
C*
R3
127Ω
R2
52Ω
V.11 MODE
V.35 MODE
Figure 5. MAX3172/MAX3174 Termination Network Configurations
HIGH-Z MODE
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION RECEIVER
A
A′
100Ω
MIN
B
B′
C
C′
Figure 6. Typical V.11 Interface
configured for V.10 or V.28 operation as a driver or
receiver (Table 3). This mode-selection table is compati-
ble for use with the MAX3170 (clock/data transceiver)
and the MAX3171/MAX3173 (control transceiver). For
example, if X.21 mode is selected in DCE mode (M2 = 0,
M1 = 1, M0 = 1, and DCE/DTE = 1), the MAX3170,
MAX3171/MAX3173, and MAX3172/MAX3174 trans-
ceivers will all be placed in X.21 DCE mode.
Fail-Safe
The MAX3172/MAX3174 guarantee a logic HIGH
receiver output when the receiver input is shorted to
GND or when it is connected to a terminated transmis-
sion line with the driver disabled. The V.10 receiver
threshold is between +25mV and +250mV. If the V.10
receiver input voltage is less than +25mV, R4OUT is
logic HIGH. If the V.10 receiver input is greater than
+250mV, R4OUT is logic LOW.
The V.28 receiver threshold is between +0.8V and
+2.0V. If the V.28 receiver input voltage is less than
+0.8V, R4OUT is logic HIGH. If the receiver input is
greater than +2.0V, R4OUT is logic LOW. If the driving
transmitter is disabled or disconnected, the receiver’s
input voltage is pulled to zero by its internal termination.
With the receiver thresholds of the MAX3172/MAX3174,
this results in a logic HIGH.
Applications Information
Older multiprotocol cable termination implementations
have been constructed using expensive relays with dis-
crete resistors, custom cables with built-in termination,
or complex circuit board configurations to route signals
to the correct termination. The MAX3172/MAX3174 pro-
vide a simple solution to this termination problem. All
required termination configurations are software selec-
table using four mode-control input pins (M2, M1, M0,
and DCE/DTE).
V.11 Termination
For high-speed data transmission, the V.11 specifica-
tion recommends terminating the cable at the receiver
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