High Speed, Isolated RS-485 Transceiver with Integrated Transformer Driver ADM2485 FEATURES FUNCTIONAL BLOCK DIAGRAM V D1 D2 V DD2 DD1 Half-duplex, isolated RS-485 transceiver Integrated oscillator driver for external transformer OSC PROFIBUS compliant ADM2485 Complies with ANSI/TIA/EIA RS-485-A-98 and RTS DE OUT ISO 8482:1987(E) Data rate: 16 Mbps 5 V or 3.3 V operation (V ) DD1 TxD 50 nodes on bus High common-mode transient immunity: >25 kV/s A RxD Isolated DE OUT status output B Thermal shutdown protection RE Safety and regulatory approvals UL recognition: 2500 V rms for 1 minute per UL 1577 GND GND 1 2 VDE Certificate of Conformity Figure 1. DIN V VDE V 0884-10 (VDE V 0884-10):2006-12 Reinforced insulation, V = 560 V peak IORM Operating temperature range: 40C to +85C Wide-body, 16-lead SOIC package APPLICATIONS Isolated RS-485/RS-422 interfaces PROFIBUS networks Industrial field networks Multipoint data transmission systems GENERAL DESCRIPTION The ADM2485 differential bus transceiver is an integrated, The ADM2485 driver has an active high enable. The driver galvanically isolated component designed for bidirectional data differential outputs and the receiver differential inputs are communication on multipoint bus transmission lines. It is connected internally to form a differential input/output port designed for balanced transmission lines and complies with that imposes minimal loading on the bus when the driver is ANSI/TIA/EIA RS-485-A-98 and ISO 8482:1987(E). disabled or when V or V = 0 V. Also provided is an active DD1 DD2 high receiver disable that causes the receive output to enter a The device employs Analog Devices, Inc., iCoupler technology high impedance state. to combine a 3-channel isolator, a three-state differential line driver, and a differential input receiver into a single package. An The device has current-limiting and thermal shutdown features on-chip oscillator outputs a pair of square waveforms that drive to protect against output short circuits and situations where bus an external transformer to provide isolated power with an external contention might cause excessive power dissipation. The part is transformer. The logic side of the device can be powered with fully specified over the industrial temperature range and is available either a 5 V or a 3.3 V supply, and the bus side is powered with in a 16-lead, wide-body SOIC package. an isolated 5 V supply. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. GALVANIC ISOLATION 06021-001ADM2485 TABLE OF CONTENTS Features .............................................................................................. 1 Typical Performance Characteristics ........................................... 10 Applications....................................................................................... 1 Test Circuits..................................................................................... 13 Functional Block Diagram .............................................................. 1 Circuit Description......................................................................... 14 General Description ......................................................................... 1 Electrical Isolation...................................................................... 14 Revision History ............................................................................... 2 Truth Tables................................................................................. 14 Specifications..................................................................................... 3 Thermal Shutdown .................................................................... 14 Timing Specifications .................................................................. 5 Receiver Fail-Safe Inputs ........................................................... 14 Package Characteristics ............................................................... 6 Magnetic Field Immunity.......................................................... 15 Regulatory Information............................................................... 6 Applications Information .............................................................. 16 Insulation and Safety-Related Specifications............................ 6 PCB Layout ................................................................................. 16 VDE 0884-2 Insulation Characteristics..................................... 7 Transformer Suppliers ............................................................... 16 Absolute Maximum Ratings............................................................ 8 Applications Diagram................................................................ 16 ESD Caution.................................................................................. 8 Outline Dimensions ....................................................................... 17 Pin Configuration and Function Descriptions............................. 9 Ordering Guide .......................................................................... 17 REVISION HISTORY 12/07Rev. 0 to Rev. A Updated Format..................................................................Universal Changes to Features Section............................................................ 1 Changes to Table 4............................................................................ 6 Changes to VDE 0884-2 Insulation Characteristics Section ...... 7 Changes to PCB Section and Figure 34 ....................................... 16 Updated Outline Dimensions ....................................................... 17 1/07Revision 0: Initial Version Rev. A Page 2 of 20