MAX3172 Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Fabricante
MAX3172 Datasheet PDF : 19 Pages
| |||
+3.3V Multiprotocol Software-Selectable
Cable Terminators and Transceivers
Table 1. Termination Mode Selection
MODE
V.10/RS-423
RS-530A
RS-530
X.21
V.35
M2
M1
M0
DCE/DTE INVERT
R1
R2
R3
R4
R5
0
0
0
0
X
Z
Z
Z
Z
Z
0
0
1
0
X
Z
Z
V.11
V.11
V.11
0
1
0
0
X
Z
Z
V.11
V.11
V.11
0
1
1
0
X
Z
Z
V.11
V.11
V.11
1
0
0
0
X
V.35
V.35
V.35
V.35
V.35
RS-449/V.36
1
0
1
0
X
Z
Z
V.11
V.11
V.11
V.28/RS-232
1
1
0
0
X
Z
Z
Z
Z
Z
No Cable
1
1
1
0
X
V.11
V.11
V.11
V.11
V.11
V.10/RS-423
0
0
0
1
X
Z
Z
Z
Z
Z
RS-530A
0
0
1
1
X
Z
Z
Z
V.11
V.11
RS-530
0
1
0
1
X
Z
Z
Z
V.11
V.11
X.21
0
1
1
1
X
Z
Z
Z
V.11
V.11
V.35
1
0
0
1
X
V.35
V.35
V.35
V.35
V.35
RS-449/V.36
1
0
1
1
X
Z
Z
Z
V.11
V.11
V.28/RS-232
1
1
0
1
X
Z
Z
Z
Z
Z
No Cable
1
1
1
1
X
V.11
V.11
V.11
V.11
V.11
Detailed Description
The MAX3172/MAX3174 contain five software-selectable
multiprotocol cable termination networks. Each network is
capable of terminating V.11 transceivers (RS-422, RS-
530, RS-530A, RS-449, V.36, and X.21) with a 100Ω dif-
ferential load, V.35 transceivers with a T-network load, or
V.28 (RS-232) and V.10 transceivers (RS-423) with an
open circuit load. The MAX3172/MAX3174, along with the
MAX3170 and MAX3171/MAX3173, form a complete
+3.3V software-selectable DTE or DCE interface port sup-
porting V.11/RS-422, RS-530, RS-530A, V.36/RS-449,
V.35, V.28/RS-232, V.10/RS-423, and X.21 serial inter-
faces.
The MAX3172/MAX3174 also contain a multiprotocol
transceiver that is software-selectable between V.10 and
V.28 operation modes. This transceiver is intended as the
handshake signal I/O in a DCE/DTE port application, and
is designed to use V+ and V- levels generated by the
MAX3171/MAX3173 charge pump. The MAX3172 fea-
tures 10µs deglitching on the V.10/V.28 receiver input to
allow unterminated operation. The MAX3174 is used in
applications that do not require deglitching on the serial
handshake signals.
No-Cable Mode
The MAX3172/MAX3174 enter no-cable mode when the
mode-select inputs are all HIGH (M0 = M1 = M2 = 1). In
this mode, the driver, receiver, and bias circuitry are dis-
abled, and the supply current drops to less than 200µA.
Table 2. Switch Configuration by Mode
MODE
SW1
SW2
V.35
V.11
ON
ON
ON
OFF
V.28/V.10 (Z)
OFF
OFF
In no-cable mode, all five termination networks are
placed in the V.11 mode of operation (shorting pins R_A
and R_B with a 100Ω resistor). The receiver output enters
a high-impedance state in no-cable mode, allowing this
output line to be shared with other receivers (the receiver
output has an internal pullup resistor to pull the output
HIGH if not driven). Also, in no-cable mode, the transmit-
ter output enters a high-impedance state so that this out-
put can be shared with other devices.
Cable Termination
The MAX3172/MAX3174 software-selectable resistor net-
works are intended for use with the MAX3170 clock/data
transceiver chip. The termination network is used for the
V.11, V.35, and V.28 transmitters. The MAX3172/
MAX3174 provide the advantage of not having to build
expensive termination networks from resistors and relays,
manually changing termination modules, or building ter-
mination networks into custom cables.
Each termination network can be in one of three modes:
V.35, V.11, or high impedance (high-Z) as shown in
Figure 5 (see Table 2). For example, in V.35 mode, all five
_______________________________________________________________________________________ 9
Share Link: 