3.3 V, Full-Duplex, 840 A, 20 Mbps, EIA RS-485 Transceiver Data Sheet ADM3491-1 FEATURES FUNCTIONAL BLOCK DIAGRAM Operates with 3.3 V supply ADM3491-1 EIA RS-422 and RS-485 compliant over full CM range 19 k input impedance A Up to 50 transceivers on bus RO R B 20 Mbps data rate RE Short-circuit protection Specified over full temperature range DE Thermal shutdown Interoperable with 5 V logic Z DI D 840 A supply current Y 2 nA shutdown current Available in PDIP, SOIC, and TSSOP Meets IEC1000-4-4 (>1 kV) Figure 1. 8 ns skew Upgrade for MAX3491, SN75ALS180 APPLICATIONS Telecommunications DTEDCE interface Packet switching Local area networks Data concentration Data multiplexers Integrated services digital network (ISDN) AppleTalk Industrial controls GENERAL DESCRIPTION The ADM3491-1 is a low power, differential line transceiver The input impedance is 19 k, allowing up to 50 transceivers to designed to operate using a single 3.3 V power supply. Low be connected on the bus. A thermal shutdown circuit prevents power consumption, coupled with a shutdown mode, makes it excessive power dissipation caused by bus contention or by ideal for power-sensitive applications. It is suitable for commu- output shorting. This feature forces the driver output into a high nication on multipoint bus transmission lines. impedance state if a significant temperature increase is detected in the internal driver circuitry during fault conditions. The ADM3491-1 is intended for balanced data transmission and complies with both Electronic Industries Association (EIA) If the inputs are unconnected (floating), the receiver contains a Standards RS-485 and RS-422. It contains a differential line fail-safe feature that results in a logic high output state. driver and a differential line receiver, making it suitable for full- The ADM3491-1 is fabricated on BiCMOS, an advanced mixed duplex data transfer. technology process combining low power CMOS with fast switching bipolar technology. Rev. C Document Feedback 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 19982014 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 05234-001ADM3491-1 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Typical Performance Characteristics ..............................................7 Applications ....................................................................................... 1 Test Circuits ........................................................................................9 General Description ......................................................................... 1 Switching Characteristics .............................................................. 10 Functional Block Diagram .............................................................. 1 Theory of Operation ...................................................................... 11 Revision History ............................................................................... 2 Differential Data Transmission ................................................ 11 Specif icat ions ..................................................................................... 3 Cable and Data Rate ................................................................... 11 Timing Specifications .................................................................. 4 Receiver Open-Circuit Fail-Safe Feature ................................ 11 Absolute Maximum Ratings ............................................................ 5 Outline Dimensions ....................................................................... 12 ESD Caution .................................................................................. 5 Ordering Guide .......................................................................... 13 Pin Configurations and Function Descriptions ........................... 6 REVISION HISTORY 6/14Rev. B to Rev. C 11/04Rev. 0 to Rev. A Changes to Ordering Guide .......................................................... 13 Format Updated .................................................................. Universal Changes to Specifications Section ................................................... 3 10/06Rev. A to Rev. B Changes to Ordering Guide .......................................................... 13 Changes to Part Number ................................................... Universal Updated Format .................................................................. Universal 1/98Revision 0: Initial Version Changes to Features .......................................................................... 1 Changes to General Description .................................................... 1 Changes to Table 2 ............................................................................ 4 Changes to Table 3 ............................................................................ 4 Changes to Figure 24 and Figure 25 ............................................. 10 Changes to Table 8 .......................................................................... 11 Updated Outline Dimensions ....................................................... 12 Changes to Ordering Guide .......................................................... 13 Rev. C Page 2 of 16