AD637ARZ

AD637ARZ FEATURES

High accuracy0.02% maximum nonlinearity, 0 V to 2 V rms input0.1% additional error to crest factor of 3Wide bandwidth8 MHz at 2 V rms input600 kHz at 100 mV rmsComputesTrue rmsSquareMean squareAbsolute valuedB output (60 dB range)Chip select/power-down feature allowsAnalog three-state operationQuiescent current reduction from 2.2 mA to 350 µA

AD637ARZ GENERAL DESCRIPTION

The AD637 is a complete, high accuracy, rms-to-dc converterthat computes the true rms value of any complex waveform. Itoffers performance that is unprecedented in integrated circuitrms-to-dc converters and comparable to discrete and modulartechniques in accuracy, bandwidth, and dynamic range. TheAD637 computes the true root mean square, mean square, orabsolute value of any complex ac (or ac plus dc) input waveformand gives an equivalent dc output voltage. The true rms value ofa waveform is more useful than an average rectified signalbecause it relates directly to the power of the signal. The rmsvalue of a statistical signal relates to the standard deviation ofthe signal.Superior crest factor compensation permits measurementsof signals with crest factors of up to 10 with less than 1%additional error. The wide bandwidth of the AD637 permits themeasurement of signals up to 600 kHz with inputs of 200 mV rmsand up to 8 MHz when the input levels are above 1 V rms.Direct dB value of the rms output with a range of 60 dB isavailable on a separate pin. An externally programmedreference current allows the user to select the 0 dB referencevoltage to correspond to any level between 0.1 V and 2.0 V rms.A chip select connection on the AD637 permits the user todecrease the supply current from 2.2 mA to 350 µA duringperiods when the rms function is not in use. This featurefacilitates the addition of precision rms measurement to remoteor handheld applications where minimum power consumptionis critical. In addition, when the AD637 is powered down, theoutput goes to a high impedance state. This allows severalAD637s to be tied together to form a wideband true rmsmultiplexer.The input circuitry of the AD637 is protected from overloadvoltages in excess of the supply levels. The inputs are notdamaged by input signals if the supply voltages are lost.The AD637 is laser wafer trimmed to achieve rated performancewithout external trimming. The only external componentrequired is a capacitor that sets the averaging period. The valueof this capacitor also determines low frequency accuracy, ripplelevel, and settling time.The on-chip buffer amplifier is used either as an input buffer orin an active filter configuration. The filter can be used to reducethe amount of ac ripple, thereby increasing accuracy.The AD637 is available in accuracy Grade J and Grade K forcommercial temperature range (0°C to 70°C) applications, accuracyGrade A and Grade B for industrial range (−40°C to +85°C) appli-cations, and accuracy Grade S rated over the −55°C to +125°Ctemperature range. All versions are available in hermetically sealed,14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages.Rev. LDocument FeedbackInformation furnished by Analog Devices is believed to be accurate and reliable. However, noresponsibility is assumed by Analog Devices for its use, nor for any infringements of patents or otherrights of third parties that may result from its use. Specifications subject to change without notice. Nolicense is granted by implication or otherwise under any patent or patent rights of Analog Devices.Trademarks and registered trademarks are the property of their respective owners.One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.Tel: 781.329.4700©2015 Analog Devices, Inc. All rights reserved.Technical Supportwww.analog.com