MAX3157 Datasheet, PDF (1/13 Pages) Maxim Integrated Products – High CMRR RS-485 Transceiver with ±50V Isolation

19-1778; Rev 3; 11/01
High CMRR RS-485 Transceiver
with ±50V Isolation
General Description
The MAX3157 is a high CMRR RS-485/RS-422 data-com-
munications interface providing ±50V isolation in a
hybrid microcircuit. A single +5V supply on the logic side
powers both sides of the interface, with external ±50V
capacitors transferring power from the logic side to the
isolated side. Each MAX3157 contains one transmitter
and one receiver and is guaranteed to operate at data
rates up to 250kbps. Drivers are short-circuit current lim-
ited and protected against excessive power dissipation
by thermal shutdown circuitry that places the driver out-
puts into a high-impedance state. The receiver input has
a fail-safe feature that guarantees a logic high receiver
output if the inputs are open, shorted, or connected to a
terminated transmission line with all drivers disabled.
The MAX3157 typically draws 25mA of supply current
when unloaded or when fully loaded with the driver dis-
abled. Supply current drops to 25µA when the device is
placed in shutdown mode. The device is pin selectable
between half- and full-duplex mode and also features
independently programmable receiver and transmitter
output phase through separate pins. The MAX3157 is a
low-cost replacement for opto-isolated transceivers. For
fully isolated RS-485/RS-422 transceivers, refer to the
MAX1480 family data sheet.
________________________Applications
Industrial Controls
Level Translators
Telecommunications
Local Area Networks
V_CC
0.1µF
MICRO
V_CC
H/F
TXP
RXP
DE
MAX3157
DI
RE
RO
GND
ISOV_CC
A
B
Y
Z
YR
ZR
AR
BR
C1LO C1HI C2LO C2HI ISOCOM
Features
o ±50V Isolated Data Interface
o +5V Single Supply
o Low-Cost Replacement for Opto-Isolated
Transceivers
o True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compliance
o Pin-Selectable Full/Half-Duplex Operation
o Phase Controls to Correct for Twisted-Pair
Reversal
o 25µA Low-Power Shutdown Mode
o Thermal Shutdown for Driver Overload Protection
o 28-Pin SSOP Package
o Slew Rate Limited Reduced EMI
Ordering Information
PART
MAX3157CAI
MAX3157EAI
MAX3157CPI
MAX3157EPI
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
28 PDIP
28 PDIP
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
C3
1µF
RT = 100Ω
RS-485
NODE
RG
±50V
C1
C2
C4
0.047µF 0.047µF
10nF
GND OFFSET
REMOTE GND
________________________________________________________________ Maxim Integrated Products 1
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