MAX13174E Datasheet, PDF (9/13 Pages) Maxim Integrated Products – +5V Multiprotocol, Pin-Selectable Cable Terminator

+5V Multiprotocol, Pin-Selectable
Cable Terminator
GENERATOR
BALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION RECEIVER
A
A′
100Ω
MIN
B
B′
C
C′
Figure 6. Typical V.11 Interface
In Figure 7, the MAX13174E is used to terminate the
V.11 receiver on the MAX13170E. Internal to the
MAX13174E, S1 is closed and S2 is open to present a
104Ω typical differential resistance and high-Z com-
mon-mode impedance. The MAX13170E's internal V.28
termination is disabled by opening S3.
The V.11 specification allows for signals with common-
mode variations of ±7V and differential signal ampli-
tudes from 2V to 6V. The MAX13174E maintains
termination impedance between 100Ω and 110Ω over
these conditions.
V.35 Termination
Figure 8 shows a standard V.35 interface. The generator
and the load must both present a 100Ω ±10Ω differential
impedance and a 150Ω ±15Ω common-mode imped-
ance. The V.35 driver generates a current output
(±11mA, typ) that develops an output voltage between
440mV and 660mV across the load termination networks.
In Figure 9, the MAX13174E is used to implement the
resistive T-network that is needed to properly terminate
the V.35 receiver. Internal to the MAX13174E, S1 and S2
are closed to connect the T-network resistors to the circuit.
The V.35 specification allows for ±4V of ground difference
between the V.35 generator and V.35 load. The
MAX13174E maintains correct termination impedance
over these conditions.
V.35 EMI reduction
For applications where EMI reduction is especially
important, the MAX13174E termination networks provide
a pin for shunting common-mode driver currents to
GND. Mismatches between the driver A and B output
propagation delays can create a common-mode distur-
bance on the cable. This common-mode energy can be
shunted to GND by placing a 100pF capacitor to GND
from the center tap of the T-network termination (R1C,
R2C, and R3C as shown in Figure 5).
V.28 Termination
Most industry-standard V.28 receivers (including the
MAX13170E and MAX13172E) do not require external
termination because the receiver includes an internal
5kΩ termination resistor. When the MAX13174E is
A′
A
R1
MAX13174E
52Ω
R5
55kΩ
R8
5kΩ
R6
11kΩ
MAX13170E
RECEIVER
S1
R3
S2 _124Ω
R2
52Ω
B′
C′
S3
+-
1.4V
R7
11kΩ
R4
B
55kΩ
S1
S2
GND
Figure 7. V.11 Termination and Internal Resistance Networks
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