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AD637:  High Precision, Wideband RMS-to-DC Converter

Product Details


The AD637 is a complete, high accuracy, monolithic rms-to-dc converter that computes the true rms value of any complex waveform. It offers performance that is unprecedented in integrated circuit rms-to-dc converters and comparable to discrete and modular techniques in accuracy, bandwidth, and dynamic range. A crest factor compensation scheme in the AD637 permits measurements of signals with crest factors of up to 10 with less than 1% additional error. The wide band-width of the AD637 permits the measurement of signals up to 600 kHz with inputs of 200 mV rms and up to 8 MHz when the input levels are above 1 V rms.

As with previous monolithic rms converters from Analog Devices, Inc., the AD637 has an auxiliary dB output available to users. The logarithm of the rms output signal is brought out to a separate pin, allowing direct dB measurement with a useful range of 60 dB. An externally programmed reference current allows the user to select the 0 dB reference voltage to correspond to any level between 0.1 V and 2.0 V rms.

A chip select connection on the AD637 permits the user to decrease the supply current from 2.2 mA to 350 μA during periods when the rms function is not in use. This feature facilitates the addition of precision rms measurement to remote or handheld applications where minimum power consumption is critical. In addition, when the AD637 is powered down, the output goes to a high impedance state. This allows several AD637s to be tied together to form a wideband true rms multiplexer.

The input circuitry of the AD637 is protected from overload voltages in excess of the supply levels. The inputs are not damaged by input signals if the supply voltages are lost.

The AD637 is available in accuracy Grade J and Grade K for commercial temperature range (0°C to 70°C) applications, accuracy Grade A and Grade B for industrial range (−40°C to +85°C) applications, and accuracy Grade S rated over the −55°C to +125°C temperature range. All versions are available in hermetically sealed, 14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages. The AD637 computes the true root mean square, mean square, or absolute value of any complex ac (or ac plus dc) input waveform and gives an equivalent dc output voltage. The true rms value of a waveform is more useful than an average rectified signal because it relates directly to the power of the signal. The rms value of a statistical signal is also related to the standard deviation of the signal.

The AD637 is laser wafer trimmed to achieve rated performance without external trimming. The only external component required is a capacitor that sets the averaging time period. The value of this capacitor also determines low frequency accuracy, ripple level, and settling time.

The on-chip buffer amplifier can be used either as an input buffer or in an active filter configuration. The filter can be used to reduce the amount of ac ripple, thereby increasing accuracy.

Data Sheet, Rev. J, 4/07

FEATURES and BENEFITS

  • High accuracy
    0.02% maximum nonlinearity, 0 V to 2 V rms input
    0.10% additional error to crest factor of 3
  • Computes
    True rms
    Square
    Mean square
    Absolute value
  • dB output (60 dB range)
  • Wide bandwidth
    8 MHz at 2 V rms input
    600 kHz at 100 mV rms
  • Chip select/power-down feature allows
    Analog three-state operation
    Quiescent current reduction from 2.2 mA to 350 μA
  • 14-lead SBDIP, 14-lead low cost CERDIP, and 16-lead SOIC_W

Functional Block Diagram for AD637

Documentation

Title Content Type File Type
AD637: High Precision, Wideband RMS-to-DC Converter Data Sheet (Rev K, 02/2011) (pdf, 942 kB) Data Sheets PDF
AD637: Military Data Sheet  (Rev A, 06/2001) (pdf) Data Sheets PDF
AN-653: Improving Temperature, Stability, and Linearity of High Dynamic Range RMS RF Power Detectors  (pdf, 415 kB) Application Notes PDF
AN-268: RMS-to-DC Converters Ease Measurement Tasks  (pdf, 638 kB)
RMS-to-DC Converters compute the true RMS value of a signal without regard to waveform shape.
Application Notes PDF
RMS-to-DC Application Guide Second Edition Design Handbooks HTML
Introduction to Analog RMS-to-DC Technology: Converters and Applications Online Training Modules HTML
ADI Warns Against Misuse of COTS Integrated Circuits  (pdf, 13 kB)
(Revised 1/03)
Invites Customer Participation in Creative Mil/Aero System Solutions
Recommended Reading PDF
Space Qualified Parts List  (pdf, 93 kB)
This document lists 67 (240+) space level products that are available from Analog Devices. Many of the products listed are state-of-the-art data conversion and signal processing products that were previously only available as commercial or military Class B products. Through our Space Products Group and MIL-PRF-38535 certified Level V (Class S) facility, we are pleased to offer these products to the space marketplace.
Aerospace Information PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Design Tools,Models,Drivers & Software

Title Content Type File Type
AD637 SPICE Macro Model SPICE Models HTML

Evaluation Kits & Symbols & Footprints

Evaluation Boards & KitsView the Evaluation Boards and Kits page for documentation and purchasing

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

SampleSample & Buy

Price, packaging, availability

AD637 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
5962-8963701CA Status: Production 14 ld CerDIP 14 Mil Tube, 25 $87.62 $79.21 N  Material Info PCN Purchase
AD637AQ Status: Production 14 ld CerDIP 14 Ind Tube, 25 $26.25 $23.74 N  Material Info PCN Purchase
AD637AR Status: Last Time Buy 16 ld SOIC - Wide 16 Ind Tube, 47 $26.60 $24.03 N  Material Info PCN/PDN Purchase
AD637ARZ Status: Production 16 ld SOIC - Wide 16 Ind Tube, 47 $22.36 $20.21 Y  Material Info PCN Purchase
AD637BR Status: Last Time Buy 16 ld SOIC - Wide 16 Ind Tube, 47 $31.52 $31.52 N  Material Info PCN/PDN Purchase
AD637BRZ Status: Production 16 ld SOIC - Wide 16 Ind Tube, 47 $26.51 $26.51 Y  Material Info PCN Purchase
AD637JD Status: Production 14 ld Bottom-Brazed CerDIP 14 Comm. Tube, 25 $38.70 $34.98 N  Material Info PCN/PDN Purchase
AD637JDZ Status: Production 14 ld Bottom-Brazed CerDIP 14 Comm. Tube, 25 $34.10 $30.82 Y  Material Info PCN Purchase
AD637JQ Status: Production 14 ld CerDIP 14 Comm. Tube, 25 $14.60 $13.20 N  Material Info PCN Purchase
AD637JRZ Status: Production 16 ld SOIC - Wide 16 Comm. Tube, 47 $12.41 $11.23 Y  Material Info PCN Purchase
AD637JRZ-R7 Status: Production 16 ld SOIC - Wide 16 Comm. Reel, 250 $12.41 $11.23 Y  Material Info PCN Purchase
AD637JRZ-RL Status: Production 16 ld SOIC - Wide 16 Comm. Reel, 1000 - $11.23 Y  Material Info PCN Purchase
AD637KDZ Status: Production 14 ld Bottom-Brazed CerDIP 14 Comm. Tube, 25 $56.33 $50.93 Y  Material Info PCN Purchase
AD637KQ Status: Production 14 ld CerDIP 14 Comm. Tube, 25 $24.94 $22.53 N  Material Info PCN Purchase
AD637KRZ Status: Production 16 ld SOIC - Wide 16 Comm. Tube, 47 $21.37 $19.31 Y  Material Info PCN Purchase
AD637SD Status: Production 14 ld Bottom-Brazed CerDIP 14 Mil Tube, 25 $86.35 $78.05 N  Material Info PCN Purchase
AD637SD/883B Status: Production 14 ld Bottom-Brazed CerDIP 14 Mil Tube, 25 $95.37 $86.22 N  Material Info PCN Purchase
AD637SQ/883B Status: Production 14 ld CerDIP 14 Mil Tube, 25 $79.84 $72.18 N  Material Info PCN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

AD637 Evaluation Board
Model Description Price RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD637-EVALZ Status: Production Evaluation Board $100.90 Yes -

Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.

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