OPTICAL ISOLATION for RS485/RS422 NEC Optocouplers for Isolated RS485/RS422 Serial Communications Interfaces NEC OPTOCOUPLERS POWER The RS485 serial communications standard is commonly used in data acquisition applications. The standard supports 32 drivers and receivers in a 2- or 4-wire dif- PWM ferential configuration with cable lengths LMS1487 ISOLATION TRANSCEIVER up to 4000 feet. Galvanic isolation becomes critical in the prevention of ground loops, electrical noise and power spikes in these widely NEC OPTOCOUPLERS distributed systems. KEY REQUIREMENTS Key requirements for optocouplers used for isolation in these applications DATA include: • Wide range of data transfer rates • High Common Mode Rejection (CMR) • Compact size • Repeatability • Reliability RECOMMENDED OPTOCOUPLERS See specifications on next page DIFFERENTIAL BUS TRANSCEIVER IC National Semiconductor’s LMS1487 is a 1 Mbps Analog Devices low power differential bus/line transceiver PS8101 3750 Vr.m.s breakdown voltage, high CMR, 35V VCC, miniature 5 pin SOP package PS8802-1, -2 anced transmission lines, it combines a 2500 Vr.m.s breakdown voltage, high CMR, 35V VCC, one or two channel, miniature S08 package TRI-STATE TM differential line driver and PS8821-1, -2 2500 Vr.m.s breakdown voltage, high CMR, 7V VCC, one or two channel, miniature S08 packages designed for high speed bidirectional data communication on multipoint bus transmission lines. Designed for bal- differential input receiver, both of which operate from a single 5.0 V power supply. The LMS1487 is available in an 8 pin SOIC or 8 pin DIP package. APPLICATION NOTE AVAILABLE An application Note: 2.5 Mbps Isolated RS485 Communications Interface with up to 500 mW Supplementary Power is available at www.cel.com. 10 Mbps Digital Devices PS9117A 3750 Vr.m.s. breakdown voltage, high CMR, single channel, open collector output, 5 pin SOP package PS9121 3750 Vr.m.s. breakdown voltage, high CMR, 3.3 V VCC, single channel, 5 pin SOP package PS9821-1, -2 2500 Vr.m.s breakdown voltage, high CMR, 3.3 V VCC, one or two channel, miniature S08 packages Data sheets and Application Notes are available at: www.cel.com CL578A 10.22.07 NEC OPTOCOUPLERS SPECIFIC ATIONS Data Sheets for these devices can be found at www.cel.com NEC 1 Mbps Analog Optocouplers Part Number Description VCC (V) I C (mA) tPHL (ns) tPLH (ns) CTR (%) Safety Certification High CMR, high breakdown voltage, miniature 5 pin SOP package 3750 35 8 0.5 0.6 N = 15 to 35 UL, VDE High CMR, high voltage, one and two channel, 8 pin SOP package 2500 35 8 0.3 0.6 N = 15 to 35 UL, VDE Low power consumption, one and two channel, 8 pin SOP package 2500 7 8 0.3 0.5 N = 20 to 40 UL, VDE PS8821-1, -2 Absolute Maximum Ratings BV (Vr.m.s.) PS8101 PS8802-1, -2 OPTICAL ISOLATION for RS485/RS422 NEC 1 0 Mbps Digital Optocouplers Part Number Description High CMR, open collector output, miniature 5 pin SOP package PS9117A PS9121 PS9821-1, -2 Typical Perfomance VCC (V) IFHL (mA) tPHL (ns) tPLH (ns) BV (Vr.m.s.) Safety Certification 7 2 40 45 3750 UL, VDE 2.5 40 45 3750 UL, VDE 2.5 45 50 2500 UL, VDE High CMR, low pulse width distortion, 5 pin SOP package 2.7 – 5.5 High CMR, one or two channel, 8-pin SOP package 2.7 – 5.5 #ALIFORNIA%ASTERN,ABORATORI #ALIFORNIA%ASTERN,ABORATORIES California Eastern Laboratories 4590 Patrick Henry Drive Santa Clara, CA 95054 408.919.2500 [email protected] www.cel.com ÊÕÃiÃÃÊ*>ÀÌiÀÊvÊ ÊiVÌÀVÃÊ À«À>Ì° .%#ISATRADEMARKOF.%##ORPORATION ÊÕÃiÃÃÊ*>ÀÌiÀÊvÊ ÊiVÌÀVÃÊ À«À>Ì° .%#ISATRADEMARKOF.%##ORPORATION