19-1778; Rev 3; 11/01
High CMRR RS-485 Transceiver
with 鹵50V Isolation
General Description
The MAX3157 is a high CMRR RS-485/RS-422 data-com-
munications interface providing 鹵50V isolation in a
hybrid microcircuit. A single +5V supply on the logic side
powers both sides of the interface, with external 鹵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 25碌A(chǔ) 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.
o
鹵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
25碌A(chǔ) Low-Power Shutdown Mode
o
Thermal Shutdown for Driver Overload Protection
o
28-Pin SSOP Package
o
Slew Rate Limited Reduced EMI
Features
MAX3157
Ordering Information
PART
MAX3157CAI
MAX3157EAI
MAX3157CPI
MAX3157EPI
TEMP. RANGE
0擄C to +70擄C
-40擄C to +85擄C
0擄C to +70擄C
-40擄C to +85擄C
PIN-PACKAGE
28 SSOP
28 SSOP
28 PDIP
28 PDIP
________________________Applications
Industrial Controls
Level Translators
Telecommunications
Local Area Networks
V
CC
0.1碌F
V
CC
H/F
TXP
RXP
MICRO
DE
DI
RE
RO
GND
ISOV
CC
A
B
Y
Z
YR
ZR
AR
BR
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
MAX3157
RT = 100鈩?/div>
RS-485
NODE
RG
C1LO C1HI C2LO C2HI ISOCOM
鹵50V
C1
0.047碌F
C2
0.047碌F
C4
10nF
GND OFFSET
REMOTE GND
________________________________________________________________
Maxim Integrated Products
REMOTE MICRO
C3
1碌F
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim鈥檚 website at www.maxim-ic.com.
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