Real-Time Analog Computational Unit (ACU) AD538 FEATURES FUNCTIONAL BLOCK DIAGRAM m V = V (V /V ) transfer function O Y Z X I D X 25k Wide dynamic range (denominator) 1000:1 100 V X Simultaneous multiplication and division Resistor-programmable powers and roots LOG B RATIO No external trims required 25k Low input offsets <100 V V A Z 100 Low error 0.25% of reading (100:1 range) I Z Monolithic construction +10V INTERNAL Real-time analog multiplication, division and VOLTAGE +2V REFERENCE exponentiation V Y High accuracy analog division with a wide input dynamic range 25k I Y On board +2 V or +10 V scaling reference AD538 LOG Voltage and current (summing) input modes C ANTILOG Monolithic construction with lower cost and higher reliability than hybrid and modular circuits I OUTPUT V O APPLICATIONS One- or two-quadrant multiply/divide Figure 1. Log ratio computation Squaring/square rooting Trigonometric function approximations Linearization via curve fitting Precision AGC Power functions GENERAL DESCRIPTION The AD538 is a monolithic real-time computational circuit multiplication and division can be set using the on-chip +2 V or that provides precision analog multiplication, division, and +10 V references, or controlled externally to provide simultaneous exponentiation. The combination of low input and output offset multiplication and division. Exponentiation with an m value voltages and excellent linearity results in accurate computation from 0.2 to 5 can be implemented with the addition of one or over an unusually wide input dynamic range. Laser wafer two external resistors. trimming makes multiplication and division with errors as low Direct log ratio computation is possible by using only the log as 0.25% of reading possible, while typical output offsets of ratio and output sections of the chip. Access to the multiple 100 V or less add to the overall off-the-shelf performance level. summing junctions adds further to the flexibility of the AD538. Real-time analog signal processing is further enhanced by the Finally, a wide power supply range of 4.5 V to 18 V allows 400 kHz bandwidth of the device. operation from standard 5 V, 12 V and 15 V supplies. m The overall transfer function of the AD538 is VO = VY(VZ/VX) . The AD538 is available in two accuracy grades (A and B) over Programming a particular function is via pin strapping. No the industrial (25C to +85C) temperature range and one external components are required for one-quadrant (positive grade (S) over the military (55C to +125C) temperature input) multiplication and division. Two-quadrant (bipolar range. The device is packaged in an 18-lead TO-118 hermetic numerator) division is possible with the use of external level side-brazed ceramic DIP. A-grade chips are also available. shifting and scaling resistors. The desired scale factor for both Rev. E 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 2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 00959-001AD538 TABLE OF CONTENTS Features .............................................................................................. 1 Stability Precautions ................................................................... 10 Applications ....................................................................................... 1 Using The Voltage References .................................................. 10 Functional Block Diagram .............................................................. 1 One-Quadrant Multiplication/Division .................................. 11 General Description ......................................................................... 1 Two-Quadrant Division ............................................................ 12 Revision History ............................................................................... 2 Log Ratio Operation .................................................................. 12 Specifications ..................................................................................... 3 Analog Computation Of Powers And Roots .......................... 13 Absolute Maximum Ratings ............................................................ 5 Square Root Operation .............................................................. 13 ESD Caution .................................................................................. 5 Applications Information .............................................................. 15 Pin Configuration and Function Descriptions ............................. 6 Transducer Linearization .......................................................... 15 Typical Performance Characteristics ............................................. 7 ARC-Tangent Approximation .................................................. 15 Theory of Operation ........................................................................ 9 Outline Dimensions ....................................................................... 16 Re-Examination of Multiplier/Divider Accuracy .................... 9 Ordering Guide .......................................................................... 16 Functional Description .............................................................. 10 REVISION HISTORY 6/11Rev. D to Rev. E Updated Format .................................................................. Universal Added Table 3 .................................................................................... 6 Changes to Ordering Guide .......................................................... 11 5/10Rev. C to Rev. D Updated Outline Dimensions ....................................................... 11 Changes to Ordering Guide .......................................................... 11 Rev. E Page 2 of 16