Integrated Circuit True RMS-to-DC Converter Data Sheet AD536A FEATURES FUNCTIONAL BLOCK DIAGRAM AD536A True rms-to-dc conversion Laser trimmed to high accuracy ABSOLUTE V IN VALUE 0.2% maximum error (AD536AK) 0.5% maximum error (AD536AJ) Wide response capability dB SQUARER/ COM Computes rms of ac and dc signals DIVIDER 450 kHz bandwidth: V rms > 100 mV + +V S C 2 MHz bandwidth: V rms > 1 V AV Signal crest factor of 7 for 1% error CURRENT MIRROR dB output with 60 dB range 25k Low power: 1.2 mA quiescent current R L Single- or dual-supply operation I OUT Monolithic integrated circuit +V S BUFFER IN 55C to +125C operation (AD536AS) BUF 25k BUFFER GENERAL DESCRIPTION OUT 80k The AD536A is a complete monolithic integrated circuit that V S performs true rms-to-dc conversion. It offers performance Figure 1. comparable or superior to that of hybrid or modular units costing much more. The AD536A directly computes the true rms value of The AD536A is available in two accuracy grades (J and K) for any complex input waveform containing ac and dc components. commercial temperature range (0C to 70C) applications, and A crest factor compensation scheme allows measurements with 1% one grade (S) rated for the 55C to +125C extended range. error at crest factors up to 7. The wide bandwidth of the device The AD536AK offers a maximum total error of 2 mV 0.2% extends the measurement capability to 300 kHz with less than 3 dB of reading, while the AD536AJ and AD536AS have maximum errors for signal levels greater than 100 mV. errors of 5 mV 0.5% of reading. All three versions are available in a hermetically sealed 14-lead DIP or a 10-pin TO-100 metal An important feature of the AD536A, not previously available header package. The AD536AS is also available in a 20-terminal in rms converters, is an auxiliary dB output pin. The logarithm leadless hermetically sealed ceramic chip carrier. of the rms output signal is brought out to a separate pin to allow the dB conversion, with a useful dynamic range of 60 dB. Using The AD536A computes the true root-mean-square level of a an externally supplied reference current, the 0 dB level can be complex ac (or ac plus dc) input signal and provides an equiva- conveniently set to correspond to any input level from 0.1 V to lent dc output level. The true rms value of a waveform is a more 2 V rms. useful quantity than the average rectified value because it relates The AD536A is laser trimmed to minimize input and output offset directly to the power of the signal. The rms value of a statistical voltage, to optimize positive and negative waveform symmetry signal also relates to its standard deviation. (dc reversal error), and to provide full-scale accuracy at 7 V rms. An external capacitor is required to perform measurements to the As a result, no external trims are required to achieve the rated fully specified accuracy. The value of this capacitor determines the unit accuracy. low frequency ac accuracy, ripple amplitude, and settling time. The input and output pins are fully protected. The input circuitry The AD536A operates equally well from split supplies or a can take overload voltages well beyond the supply levels. Loss of single supply with total supply levels from 5 V to 36 V. With supply voltage with the input connected to external circuitry does 1 mA quiescent supply current, the device is well suited for a not cause the device to fail. The output is short-circuit protected. wide variety of remote controllers and battery-powered instruments. Rev. G 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 19762019 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. 00504-001AD536A Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Frequency Response .....................................................................9 General Description ......................................................................... 1 AC Measurement Accuracy and Crest Factor ...........................9 Functional Block Diagram .............................................................. 1 Applications Information .............................................................. 11 Revision History ............................................................................... 2 Typical Connections .................................................................. 11 Specif icat ions ..................................................................................... 3 Optional External Trims For High Accuracy ......................... 11 Absolute Maximum Ratings ............................................................ 5 Single-Supply Operation ........................................................... 12 ESD Caution .................................................................................. 5 Choosing the Averaging Time Constant ................................. 12 Pin Configurations and Function Descriptions ........................... 6 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 15 Theory of Operation ........................................................................ 8 Connections for dB Operation ................................................... 8 REVISION HISTORY Change to Figure 2 ............................................................................ 5 3/2019Rev. F to Rev. G Changes to Figure 5 and Table 5 ..................................................... 7 Changes to Figure 15 ...................................................................... 10 Change to Figure 16 ....................................................................... 12 Changes to Connections for dB Operation Section .................. 11 Changes to Ordering Guide .......................................................... 15 Changes to Figure 17 ...................................................................... 12 Changes to Frequency Response Section .................................... 12 11/2014Rev. E to Rev. F Updated Outline Dimensions ....................................................... 14 Change to Figure 1 ........................................................................... 1 Changes to Ordering Guide .......................................................... 15 Changes to Table 1 ............................................................................ 3 Change to Figure 16 ....................................................................... 12 3/2006Rev. B to Rev. C Changes to Ordering Guide .......................................................... 15 Updated Format .................................................................. Universal Changed Product Description to General Description ................ 1 7/2012Rev. D to Rev. E Changes to General Description ..................................................... 1 Reorganized Layout ............................................................ Universal Changes to Table 1 ............................................................................. 3 Changes to Figure 1 .......................................................................... 1 Changes to Table 2 ............................................................................. 5 Changes to Figure 6 .......................................................................... 8 Added Pin Configurations and Function Descriptions ............... 6 Changed Standard Connection to Typical Connections ............. 8 Changes to Figure 7 .......................................................................... 9 Changes to Figure 13, Figure 14, and Figure 15 ......................... 11 Changed Single Supply Connection to Single Supply Changes to Figure 16, Figure 17, and Single-Supply Operation O p erat ion ............................................................................................ 9 Section .............................................................................................. 12 Changes to Connections for dB Operation................................. 11 Changes to Figure 21 ...................................................................... 13 Changes to Figure 17 ...................................................................... 12 Updated Outline Dimensions ....................................................... 14 Updated Outline Dimensions ....................................................... 14 Changes to Ordering Guide .......................................................... 15 8/2008Rev. C to Rev. D 6/1999Rev. A to Rev. B Changes to Features Section............................................................ 1 Changes to General Description Section ...................................... 1 Changes to Figure 1 .......................................................................... 1 1/1976Revision 0: Initial Version Changes to Table 2 ............................................................................ 5 Rev. G Page 2 of 15