MXL1543 查看數據表（PDF） - Maxim Integrated
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MXL1543 Datasheet PDF : 18 Pages
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+5V Multiprotocol, 3Tx/3Rx, Software-
Selectable Clock/Data Transceivers
Table 1. Mode Selection
MXL1543
MODE NAME
M2
M1
Not Used (Default V.11)
0
0
RS-530A
0
0
RS-530
0
1
X.21
0
1
V.35
1
0
RS-449/V.36
1
0
V.28/RS-232
1
1
No Cable
1
1
Not Used (Default V.11)
0
0
RS-530A
0
0
RS-530
0
1
X.21
0
1
V.35
1
0
RS-449/V.36
1
0
V.28/RS-232
1
1
No Cable
1
1
M0
DCE/
DTE
T1
T2
T3
R1
R2
R3
0
0
V.11
V.11
Z
V.11
V.11
V.11
1
0
V.11
V.11
Z
V.11
V.11
V.11
0
0
V.11
V.11
Z
V.11
V.11
V.11
1
0
V.11
V.11
Z
V.11
V.11
V.11
0
0
V.35
V.35
Z
V.35
V.35
V.35
1
0
V.11
V.11
Z
V.11
V.11
V.11
0
0
V.28
V.28
Z
V.28
V.28
V.28
1
0
Z
Z
Z
Z
Z
Z
0
1
V.11
V.11
V.11
Z
V.11
V.11
1
1
V.11
V.11
V.11
Z
V.11
V.11
0
1
V.11
V.11
V.11
Z
V.11
V.11
1
1
V.11
V.11
V.11
Z
V.11
V.11
0
1
V.35
V.35
V.35
Z
V.35
V.35
1
1
V.11
V.11
V.11
Z
V.11
V.11
0
1
V.28
V.28
V.28
Z
V.28
V.28
1
1
Z
Z
Z
Z
Z
Z
is disabled and receiver R1 is activated. M0, M1, M2,
and DCE/DTE are internally pulled up to VCC to ensure
a logic HIGH if left unconnected.
No-Cable Mode
The MXL1543 will enter no-cable mode when the
mode-select pins are left unconnected or connected
high (M0 = M1 = M2 = 1). In this mode, the multiproto-
col drivers and receivers are disabled and the supply
current drops to 0.5µA. The receivers’ outputs enter a
high-impedance state in no-cable mode, which allow
these output lines to be shared with other receivers’
outputs (the receivers’ outputs have internal pullup
resistors to pull the outputs HIGH if not driven). Also, in
no-cable mode, the transmitter outputs enter a high-
impedance state so that these output lines can be
shared with other devices.
Dual Charge-Pump Voltage Converter
The MXL1543’s internal power supply consists of a reg-
ulated dual charge pump that provides positive and
negative output voltages from a +5V supply. The
charge pump operates in discontinuous mode. If the
output voltage is less than the regulated voltage, the
charge pump is enabled. If the output voltage exceeds
the regulated voltage, the charge pump is disabled.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C5) to generate the VDD
and VEE supplies. Figure 10 shows charge-pump con-
nections.
Fail-Safe Receivers
The MXL1543 guarantees a logic-high receiver output
when the receiver inputs are shorted or open, or when
they are connected to a terminated transmission line
with all the drivers disabled. This is done by setting the
receivers’ threshold between -25mV and -200mV in the
C3
4.7µF
C1
1µF
5V
C4
1µF
MXL1543
VDD
C2+
C1+
C2-
C1-
VEE
VCC
GND
Figure 10. Charge Pump
C2
1µF
C5
4.7µF
10 ______________________________________________________________________________________
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