MAX3170 Ver la hoja de datos (PDF) - Maxim Integrated
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MAX3170 Datasheet PDF : 16 Pages
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+3.3V, Multiprotocol, 3 Tx/3 Rx, Software-
Selectable Clock/Data Transceiver
Table 1. Mode Selection
PROTOCOL
M2
V.11
0
RS-530A
0
RS-530
0
X.21
0
V.35
1
RS-449/V.36
1
V.28/RS-232
1
No cable
1
V.11
0
RS-530A
0
RS-530
0
X.21
0
V.35
1
RS-449/V.36
1
V.28/RS-232
1
No cable
1
Z = High impedance
LOGIC INPUTS
M1 M0
DCE/DTE
0
0
0
0
1
0
1
0
0
1
1
0
0
0
0
0
1
0
1
0
0
1
1
0
0
0
1
0
1
1
1
0
1
1
1
1
0
0
1
0
1
1
1
0
1
1
1
1
TRANSMITTERS
T1
T2
T3
V.11
V.11
Z
V.11
V.11
Z
V.11
V.11
Z
V.11
V.11
Z
V.35
V.35
Z
V.11
V.11
Z
V.28
V.28
Z
Z
Z
Z
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.35
V.35
V.35
V.11
V.11
V.11
V.28
V.28
V.28
Z
Z
Z
RECEIVERS
R1
R2
R3
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.11
V.35
V.35
V.35
V.11
V.11
V.11
V.28
V.28
V.28
Z
Z
Z
Z
V.11
V.11
Z
V.11
V.11
Z
V.11
V.11
Z
V.11
V.11
Z
V.35
V.35
Z
V.11
V.11
Z
V.28
V.28
Z
Z
Z
Mode Selection
The state of the mode select pins M0, M1, and M2
determines which serial interface protocol is selected
(Table 1). The state of the DCE/DTE input determines
whether the transceiver will be configured as a DTE or
a DCE serial port. When the DCE/DTE input is logic
HIGH, driver T3 is activated and receiver R1 is dis-
abled. When the DCE/DTE input is logic LOW, driver T3
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.
The MAX3170’s mode can be selected through soft-
ware control of the M0, M1, M2, and DCE/DTE inputs.
Alternatively, the mode can be selected by shorting the
appropriate combination of mode control inputs to
GND. The inputs left floating will be internally pulled up
to VCC (logic HIGH). If the M0, M1, and M2 mode
inputs are all unconnected, the MAX3170 will enter no-
cable mode and the supply current will drop to 1mA.
No-Cable Mode
The MAX3170 will enter no-cable mode when the mode
select pins are left unconnected or tied high (M0 = M1
= M2 = 1). In this mode, the multiprotocol drivers and
receivers are disabled and the supply current drops to
1mA. The receiver outputs enter a high-impedance
state in no-cable mode, which allows these output lines
to be shared with other receivers (the receiver outputs
have an internal pull-up resistor to pull the outputs
HIGH if not driven). Also, in no-cable mode, the trans-
mitter outputs enter a high-impedance state so that
these output lines can be shared with other devices.
Dual Charge-Pump Voltage Converter
The MAX3170’s internal power supply consists of a reg-
ulated dual charge pump that provides positive and
negative output voltages from a +3.3V 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, C4) to generate the V+
and V- supplies. See Figure 6 for charge-pump con-
nections.
Fail-Safe Receivers
The MAX3170 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 drivers disabled. This is done by setting the
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