MAX3157 19-1778 Rev 3 11/01 High CMRR RS-485 Transceiver with 50V Isolation General Description Features The MAX3157 is a high CMRR RS-485/RS-422 data-com- 50V Isolated Data Interface munications interface providing 50V isolation in a +5V Single Supply hybrid microcircuit. A single +5V supply on the logic side powers both sides of the interface, with external 50V Low-Cost Replacement for Opto-Isolated capacitors transferring power from the logic side to the Transceivers isolated side. Each MAX3157 contains one transmitter True Fail-Safe Receiver While Maintaining and one receiver and is guaranteed to operate at data rates up to 250kbps. Drivers are short-circuit current lim- EIA/TIA-485 Compliance ited and protected against excessive power dissipation Pin-Selectable Full/Half-Duplex Operation by thermal shutdown circuitry that places the driver out- Phase Controls to Correct for Twisted-Pair puts into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic high receiver Reversal output if the inputs are open, shorted, or connected to a 25A Low-Power Shutdown Mode terminated transmission line with all drivers disabled. Thermal Shutdown for Driver Overload Protection The MAX3157 typically draws 25mA of supply current when unloaded or when fully loaded with the driver dis- 28-Pin SSOP Package abled. Supply current drops to 25A when the device is Slew Rate Limited Reduced EMI 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 Ordering Information fully isolated RS-485/RS-422 transceivers, refer to the PART TEMP. RANGE PIN-PACKAGE MAX1480 family data sheet. MAX3157CAI 0C to +70C 28 SSOP Applications MAX3157EAI -40C to +85C 28 SSOP Industrial Controls MAX3157CPI 0C to +70C 28 PDIP Level Translators MAX3157EPI -40 C to +85C 28 PDIP Telecommunications Pin Configurations appear at end of data sheet. Local Area Networks Typical Operating Circuit V CC 0.1 F V ISOV CC CC H/F C3 TXP A 1 F RXP B Y RS-485 RT = 100 MICRO NODE DE Z MAX3157 DI YR RE ZR RO AR BR RG GND C1LO C1HI C2LO C2HI ISOCOM 50V C4 C1 C2 10nF GND OFFSET 0.047 F 0.047 F REMOTE GND Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. REMOTE MICROHigh CMRR RS-485 Transceiver with 50V Isolation ABSOLUTE MAXIMUM RATINGS All voltages referenced to GND unless otherwise noted. Supply Voltage (V ).............................................................+7V Charge-Pump Capacitance Low CC Cable Ground (ISOCOM) ....................................................75V (C1LO, C2LO) .......................................-0.3V to (V + 0.3V) CC Isolated Supply ISOVCC Relative to Cable Ground Charge-Pump Capacitance High (C1HI, C2HI) Relative (ISOCOM) ............................................................................+7V to Cable Ground (ISOCOM) ...........-0.3V to (ISOVCC + 0.3V) Digital Input, Output Voltage Continuous Power Dissipation (DI, DE, RE, TXP, RXP, RO)......................-0.3V to (V + 0.3V) 28-Pin SSOP (derate 10.8mW/C above +70C) ........860mW CC Digital Inputs (H/F) Relative to Cable Ground 28-Pin PDIP (derate 14.3mW/C above +70C)........1143mW (ISOCOM) ..........................................-0.3V to (ISOVCC + 0.3V) Operating Temperature Ranges Driver Output Voltage (Y, Z), Relative to Cable Ground MAX3157C I .....................................................0C to +70C (ISOCOM).............................................................-8V to +12.5V MAX3157E I ..................................................-40C to +85C Receiver Input Voltage (A, B), Relative to Cable Ground Junction Temperature......................................................+150C (ISOCOM).............................................................-8V to +12.5V Storage Temperature Range ............................-65C to +160C Termination Connections (YR, ZR, AR, BR) Relative to Cable Lead Temperature (soldering, 10s) ................................+300C Ground (ISOCOM)................................................-8V to +12.5V Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +5V 5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047F, C3 = C4 = 1F, T = T to T , unless otherwise noted. CC A MIN MAX Typical values are at V = +5V and T = +25C.) (Note 1) CC A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS DRIVER Differential Driver Output, V Figure 1, R = 10M 6V OD1 No Load Figure 1, R = 50 (RS-422) 2.0 Differential Driver Output, V V OD2 Loaded Figure 1, R = 27 (RS-485) 1.5 Change in Magnitude of Differential Output Voltage V Figure 1, R = 50 or R = 27 0.2 V OD (Note 2) Figure 1, R = 50 or R = 27 , Driver Common-Mode Voltage V 3.5 V OC V relative to ISOCOM OC Change in Magnitude of Common-Mode Voltage V Figure 1, R = 50 or R = 27 0.2 V OC (Note 2) DE, DI, RE, TXP, RXP, relative to GND, Input High Voltage V 2.0 V IH H/F relative to ISOCOM DE, DI, RE, TXP, RXP, relative to GND, Input Low Voltage V 0.8 V IL H/F relative to ISOCOM DI Input Hysteresis V 100 mV HYS I DE, DI, RE 2 IN1 Input Current A I H/F, TXP, RXP internal pulldown 10 40 IN2 DE = GND, V = GND or 5.25V, -7V (V - CC IN -5.0 8.0 V ) 12V, AR = BR = ISOCOM ISOCOM Input Current (A and B) I mA IN3 DE = GND, V = GND or 5.25V, -7V (V - CC IN -0.58 1.0 V ) 12V, AR open, BR open ISOCOM 2 MAX3157