MXL1543B Datasheet, PDF (14/18 Pages) Maxim Integrated Products – +5V Multiprotocol, 3Tx/3Rx, Software- Selectable Clock/Data Transceivers

+5V Multiprotocol, 3Tx/3Rx, Software-
Selectable Clock/Data Transceivers
GENERATOR
UNBALANCED
INTERCONNECTING
CABLE
LOAD
CABLE
TERMINATION
A
A′
RECEIVER
Figure 17. Typical V.28 Interface
C
GND
C′
GND
A′
A
R1
MXL1344A
52Ω
R5
12kΩ
R8
5kΩ
R6
12kΩ
S1
S3
S2
R3
124Ω
MXL1543B
RECEIVER
R2
52Ω
B′
R7
12kΩ
R4
B
12kΩ
C′
GND
Figure 18. V.28 Termination and Internal Resistance Networks
nals developed across the cable (referenced from C to
C’) of up to ±4V, allowing for error-free reception in
noisy environments.
In Figure 16, the MXL1344A is used to implement the
resistive T network that is needed to properly terminate
the V.35 driver and receiver. Internal to the MXL1344A,
S1 and S2 are closed to connect the T-network resis-
tors to the circuit. The V.28 termination resistor (internal
to the MXL1543B) is disabled by opening S3 to avoid
interference with the T-network impedance.
V.28 Interface
The V.28 interface is an unbalanced single-ended inter-
face (Figure 17). The V.28 driver generates a minimum
of ±5V across a 3kΩ load impedance between A’ and
C’. The V.28 receiver has a single-ended input. To aid
in rejecting system noise, the MXL1543B’s V.28 receiv-
er has a typical hysteresis of 0.05V.
Figure 18 shows the MXL1344A’s termination network
disabled by opening S1 and S2. The MXL1543B’s inter-
nal 5kΩ V.28 termination is enabled by closing S3.
DTE vs. DCE Operation
Figure 19 shows a DCE or DTE controller-selectable
interface. DCE/DTE (pin 14) switches the port’s mode
of operation. See Table 1.
This application requires only one DB-25 connector,
but separate cables for DCE or DTE signal routing. See
Figure 19 for complete signal routing in DCE and DTE
modes.
Complete Multiprotocol X.21 Interface
A complete DTE-to-DCE interface operating in X.21
mode is shown in Figure 20. The MXL1543B is used to
generate the clock and data signals, and the
MXL1544/MAX3175 generate the control signals and
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