MXL1344A
the V.35 receiver. Internal to the MXL1344A, S1 and S2
are closed to connect the T-network resistors to the cir-
cuit.
The V.35 specification allows for ±4V of ground difference
between the V.35 generator and V.35 load, with data
rates as high as 10Mbps. The MXL1344A maintains cor-
rect termination impedance over these conditions.
V.35 EMI reduction
For applications where EMI reduction is especially
important, the MXL1344A 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
MXL1543) do not require external termination because
the receiver includes an internal 5kΩ termination resis-
tor. When the MXL1344A is placed in V.28 mode, all six
of the termination networks are placed in a high-Z
mode. In high-Z mode, the MXL1344A termination net-
works will not interfere with the MXL1543's internal 5kΩ
termination.
In Figure 10, the MXL1344A and MXL1543 are placed
in V.28 mode. Switches S1 and S2 are opened on the
MXL1344A to place the network in high-Z mode. Switch
S3 is closed on the MXL1543 to enable the 5kΩ termi-
nating resistor.
A Complete X.21 Interface
A complete DTE-to-DCE interface operating in X.21
mode is shown in Figure 11. The MXL1344A terminates
the V.11 clock and data signals. The MXL1543 carries
the clock and data signals, and the MXL1544/MAX3175
carries the control signals. The control signals generally
do not require external termination.
Compliance Testing
A European Standard EN 45001 test report for the
MXL1543, MXL1544/MAX3175, and MXL1344A chipset
will be available from Maxim upon completion of test-
ing. Contact Maxim Quality Assurance for a copy of the
report.
Chip Information
TRANSISTOR COUNT: 1,054
PROCESS TECHNOLOGY: BiCMOS
+5V Multiprotocol, Software-Selectable
Cable Terminator
10 ______________________________________________________________________________________
