Isolated, Loop-Powered Voltage-to-Current Converter 1B21 FEATURES FUNCTIONAL BLOCK DIAGRAM Wide input range: 0 V to 1 V up to 0 V to 10 V OUT 1 18 SIGNAL FB HIGH ISOLATION High CMV isolation: 1500 V rms 17 INPUT Programmable output ranges: 4mA to 20mA MODULATOR DEMODULATOR 0 to 20 mA T1 REF POWER 19 REF OUT Load resistance range: 0 to 1.35 k maximum OUT 38 TIMING TIMING ISOLATION LOW 20 +15V High accuracy 22 15V OSCILLATOR RECTIFIER Low offset tempco: 300 nA/C COM 21 1B21 T2 Low gain tempco: 50 ppm/C Low nonlinearity: 0.02% Figure 1. High CMR: 90 dB minimum Small package: 0.7 2.1 0.35 Meets IEEE Standard 472: transient protection (SWC) APPLICATIONS Multichannel process control DACcurrent loop interface Analog transmitters and controllers Remote data acquisition systems GENERAL DESCRIPTION The 1B21 is an isolated voltage-to-current converter that provides a loop supply compliance of 27V, which is sufficient to incorporates a unique circuit design utilizing transformer-based drive a 1.35 k load resistance. isolation and automated surface-mount manufacturing technology. The 1B21 is fully specified over 25C to +85C and operates It provides an unbeatable combination of versatility and perfor- over the industrial (40C to +85C) temperature range. mance in a compact plastic package. Designed for industrial DESIGN FEATURES AND USER BENEFITS applications, it is especially suited for harsh environments with extremely high common-mode interference. High CMV Isolation. The 1B21 features high input to output galvanic isolation to eliminate ground loops and offer protection Functionally, the V/I converter consists of four basic sections: against damage from transients and fault voltages. The isolation input conditioning, modulator, demodulator and current source barrier will withstand continuous CMV of 1500V rms and (see Figure 1). The input is a resistor-programmable gain stage meets the IEEE Standard for Transient Voltage Protection that accepts a 0 V to 1 V up to 0 V to 10 V voltage input. This (Std. 472-SWC). maps into a 0 mA to 20 mA output or can be offset by 20% using the internal reference for 4 mA to 20 mA operation. The Small Size. The 1B21 package size (0.7 2.1 DIP) makes it an high level signal is modulated and passed across the barrier excellent choice in multichannel systems for maximum channel which provides complete input to output galvanic isolation of density. The 0.35 height also facilitates applications with 1500 V rms continuous by the use of transformer-coupling limited board clearance. techniques. Nonlinearity is an excellent 0.05% maximum. Ease of Use. Complete isolated voltage-to-current conversion Designed for multichannel applications, the 1B21 requires an with minimum external parts required to get a conditioned external loop supply and can accept up to 30 V maximum. This current signal. No external buffers or drivers are required. Rev. C 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. 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Trademarks and registered trademarks are the property of their respective owners. 08530-0011B21 TABLE OF CONTENTS Features .............................................................................................. 1 Inside the 1B21 ..................................................................................5 Applications ....................................................................................... 1 Using the 1B21 ...............................................................................5 Functional Block Diagram .............................................................. 1 Applications Information .................................................................7 General Description ......................................................................... 1 Output Protection .........................................................................7 Design Features and User Benefits ................................................. 1 Low Drift Input Network .............................................................7 Revision History ............................................................................... 2 Multiloop Isoaltion .......................................................................7 Specif icat ions ..................................................................................... 3 Outline Dimensions ..........................................................................8 Pin Configuration ............................................................................. 4 Ordering Guide .............................................................................8 REVISION HISTORY 12/09Rev. B to Rev. C Updated Format .................................................................. Universal Changes to Figure 1 .......................................................................... 1 Changes to Table 1 ............................................................................ 3 Changes to Inside the 1B21 Section, Figure 4, Using the 1B21 Section, and Table 2 ................................................................ 5 Changes to TC Considerations of External Resistors Section .... 6 Changes to Figure 8 .......................................................................... 7 Added Ordering Guide Section ...................................................... 8 6/91Rev. A to Rev. B Rev. C Page 2 of 8