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MAX3157

MAX3157

High CMRR RS-485 Transceiver with ±50V Isolation

Low-Cost ±50V Isolated RS-485/RS-422 Transceiver Available in a Surface Mount Package

Data Sheet
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Overview

Description

The MAX3157 is a high CMRR RS-485/RS-422 data-communications 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 limited and protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs 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 disabled. 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.
MAX3157: Typical Operating Circuit MAX3157: Typical Operating Circuit Enlarge+

Key Features

  • ±50V Isolated Data Interface
  • +5V Single Supply
  • Low-Cost Replacement for Opto-Isolated Transceivers
  • True Fail-Safe Receiver While Maintaining EIA/TIA-485 Compliance
  • Pin-Selectable Full/Half-Duplex Operation
  • Phase Controls to Correct for Twisted-Pair Reversal
  • 25µA Low-Power Shutdown Mode
  • Thermal Shutdown for Driver Overload Protection
  • 28-Pin SSOP Package
  • Slew Rate Limited Reduced EMI

Applications/Uses

  • Automated Test Equipment (ATE)
  • Building Energy Management (HVAC)
  • Building Security/Remote Cameras
  • High-Speed Access (Telecom)
  • Industrial Sensor Transmitters/Transducers
  • Motor and Motion Control
  • POS Terminals
  • Programmable Logic Controllers
  • Remote Cameras
  • Telecom Switches
  • Test and Measurement Equipment
  • X-Ray and Ultrasound Diagnostics

Key Specs

Part Number Tx/Rx Duplex VSUPPLY
(V)		 Galvanic Isolation
(±V)		 ICC
(mA)		 Data Rate
(kbps)		 Tx EN Rx EN ICC (Shutdn.)
(µA)		 Rx/Tx on Bus Rx Failsafe w/ Inputs Slew Rate Limiting Oper. Temp.
(°C)		 Package/Pins Budgetary
Price
typ min typ See Notes
MAX3157  1Tx + 1Rx Half/Full 5 50 25 250 Yes Yes 25 32 Open or Shorted No
-40 to +85
0 to +70
PDIP(W)/28
SSOP/28
 $4.93 @1k
See All RS-485/RS-422 Line Driver/Receivers (193)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Design Resources

Technical Documents

Tutorial 2045 Understanding Common-Mode Signals
App Note 1137 Using the MAX3157 High-CMR RS-485 Transceivers
Tutorial 763 Guidelines for Proper Wiring of an RS-485 (TIA/EIA-485-A) Network
Tutorial 736 RS-485 (EIA/TIA-485) Differential Data Transmission System Basics

Quality and Environmental Data

Product Reliability Reports: MAX3157.pdf 
Lead-Free Package Tin (Sn) Whisker Reports

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Technical Docs