AD637-EVALZ Analog Devices Inc, AD637-EVALZ Datasheet

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AD637-EVALZ

Manufacturer Part Number
AD637-EVALZ
Description
BOARD EVALUATION FOR AD637
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD637-EVALZ

Main Purpose
Interface, RMS to DC Converters
Utilized Ic / Part
AD637
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Secondary Attributes
-
Embedded
-
Primary Attributes
-
FEATURES
High accuracy
Wide bandwidth
Computes
dB output (60 dB range)
Chip select/power-down feature allows
14-lead SBDIP, 14-lead low cost CERDIP, and 16-lead SOIC_W
GENERAL DESCRIPTION
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.
Rev. K
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
rights of third parties that may result from its use. Specifications subject to change without notice. No
license 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.
0.02% maximum nonlinearity, 0 V to 2 V rms input
0.10% additional error to crest factor of 3
8 MHz at 2 V rms input
600 kHz at 100 mV rms
True rms
Square
Mean square
Absolute value
Analog three-state operation
Quiescent current reduction from 2.2 mA to 350 μA
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
DEN INPUT
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) appli-
cations, 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.
COMMON
OUTPUT
BUFF IN
OFFSET
V
CS
IN
High Precision, Wideband
FUNCTIONAL BLOCK DIAGRAM
25kΩ
ABSOLUTE
VALUE
RMS-to-DC Converter
©2011 Analog Devices, Inc. All rights reserved.
SQUARER/
DIVIDER
BIAS
Figure 1.
25kΩ
AD637
www.analog.com
AD637
BUFF
OUT
RMS OUT
C
dB OUTPUT
AV

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AD637-EVALZ Summary of contents

Page 1

... 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) appli- cations, and accuracy Grade S rated over the − ...

Page 2

... AD637 TABLE OF CONTENTS Features .............................................................................................. 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Functional Description .................................................................... 7 Standard Connection ................................................................... 8 Chip Select..................................................................................... 8 Optional Trims for High Accuracy ............................................ 8 REVISION HISTORY 2/11—Rev Rev. K Changes to Figure 15...................................................................... 11 Changes to Figure 16 ...

Page 3

... Specified accuracy ±0.1 ±1 ±15 ± ±6 ±6 ±15 ±15 9.6 6.4 8 9.6 ±0.2 ±0 200 150 1 8 AD637 Unit mV ±% of reading mV ± reading μV/V μV reading % of FSR % of FSR mV ± reading % of reading % of reading ms/μ rms V p-p V rms V p-p V p-p kΩ ...

Page 4

... All minimum and maximum specifications are guaranteed, although only those shown in boldface are tested on all production units. 2 Accuracy specified 0 V rms rms dc with AD637 connected, as shown in 3 Nonlinearity is defined as the maximum deviation from the straight line connecting the readings and 2 V. ...

Page 5

... Storage Temperature Range Lead Temperature (Soldering 10 sec) Rated Operating Temperature Range AD637J, AD637K AD637A, AD637B AD637S, 5962-8963701CA Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress Rating rating only; functional operation of the device at these or any ...

Page 6

... RMS OUT Table 4. 16-Lead SOIC_W Pin Function Descriptions Pin No Rev Page BUFF IN BUFF OUT COMMON AD637 OUTPUT OFFSET + TOP VIEW S (Not to Scale) CS – DEN INPUT RMS OUT OUTPUT CONNECT Figure 3. 16-Lead SOIC_W Pin Configuration Mnemonic Description BUFF IN Buffer Input NC No Connection ...

Page 7

... BUFF IN 24kΩ ABSOLUTE VALUE VOLTAGE TO CURRENT CONVERTER 6kΩ 12kΩ The AD637 embodies an implicit solution of the rms equation that overcomes the inherent limitations of straightforward rms computation. The actual computation performed by the AD637 follows the equation ⎡ ⎤ ⎢ ⎥ IN ...

Page 8

... Figure 6. The output signal can be used buffered or nonbuffered, depending on the characteristics of the load buffer is needed, tie the buffer input (Pin 1) to common. The output of the AD637 is capable of driving 5 mA into a 2 kΩ load without degrading the accuracy of the device. BUFF ...

Page 9

... AV Figure 10. Comparison of Percent DC Error to the Percent Peak Ripple over Frequency Using the AD637 in the Standard RMS Connection with a 1 × μF C The ac ripple component of averaging error is greatly reduced by increasing the value of the averaging capacitor. There are two major disadvantages to this: the value of the averaging capacitor ...

Page 10

... AD637 AD637 1 BUFF ABSOLUTE VALUE 3 COMMON SQUARER/ OUTPUT DIVIDER 4 OFFSET BIAS +V 4.7kΩ 25kΩ DEN 25kΩ 6 INPUT 7 dB OUTPUT RX 24kΩ Figure 11. 2-Pole Sallen-Key Filter Figure 12 shows values of C and the corresponding averaging AV error as a function of sine wave frequency for the standard rms connection ...

Page 11

... To ensure that the input signal is accurately presented to the converter, the input buffer must have a −3 dB bandwidth that is wider than that of the AD637. Note the importance of slew rate in this application. For example, the minimum slew rate required for rms, 5 MHz, sine wave input signal is 44 V/μs. The user is ...

Page 12

... PULSE WIDTH (µs) Figure 17. AD637 Error vs. Pulse Width Rectangular Pulse Figure curve of additional reading error for the AD637 for rms input signal with crest factors from 1 to 11. A rectangular pulse train (pulse width 100 μs) is used for this test because it is the worst-case waveform for rms measurement (all the energy is contained in the peaks) ...

Page 13

... AD637 BUFF OUT ABSOLUTE VALUE NC 12 BIAS SECTION SQUARER/DIVIDER 25kΩ 10 –V S 25kΩ FILTER CONNECT +V S AD508J Figure 20. dB Connection Rev Page SCALE FACTOR 33.2kΩ ADJUST 5kΩ 1kΩ 60.4Ω AD707JN 6 COMPENSATED OUTPUT + 100mV/dB – – OUT 1µF AD637 ...

Page 14

... The output of the circuit AV1 This concept can be expanded to include additional terms by feeding the signal from Pin 9 of each additional AD637 through a 10 kΩ resistor to the summing junction of the AD711 and tying all of the denominator inputs (Pin 6) together ...

Page 15

... INPUT 6 dB OUTPUT FILTER 7 Figure 22. Vector Sum Configuration Rev Page BUFF OUT 25kΩ 10 –V – OUT 9 100pF 5pF 10kΩ 10kΩ BUFF OUT AD711K Y 13 10kΩ 20kΩ 25kΩ 10 –V – OUT 9 100pF OUT X Y AD637 ...

Page 16

... AD637 EVALUATION BOARD Figure 23 shows a digital image of the AD637-EVALZ, an evaluation board specially designed for the AD637 available at www.analog.com and is fully tested and ready for bench testing after connecting power and signal I/O. The circuit is configured for dual power supplies, and standard BNC connectors serve as the signal input and output ports ...

Page 17

... Figure 24. AD637-EVALZ Assembly Figure 25. Component Side Silkscreen Figure 26. Evaluation Board—Component Side Copper Figure 27. Evaluation Board—Secondary Side Copper Figure 28. Evaluation Board—Internal Power Plane Figure 29. Evaluation Board—Internal Ground Plane Rev Page AD637 ...

Page 18

... CS – DEN INPUT RMS OUT OUTPUT C AV DB_OUT 24.3kΩ Figure 30. Evaluation Board Schematic Figure 31. AD637-EVALZ Typical Bench Configuration Rev Page BUF_OUT RMS_IN RMS_IN CIN 22µF 16V + 0.1µF –V DC_OUT S C4 0.1µF DC_OUT + C AV 22µF 16V + CF1 R5 47µ ...

Page 19

... REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 33. 14-Lead Ceramic Dual In-Line Package [CERDIP] (Q-14) Dimensions shown in inches and (millimeters) Rev Page 0.320 (8.13) 0.290 (7.37) 0.015 (0.38) 0.008 (0.20) 0.320 (8.13) 0.290 (7.37) 0.015 (0.38) 15° 0.008 (0.20) 0° AD637 ...

Page 20

... AD637JR-REEL7 AD637JRZ AD637JRZ-RL AD637JRZ-R7 AD637KD AD637KDZ AD637KQ AD637KRZ AD637SD AD637SD/883B AD637SQ/883B AD637-EVALZ RoHS Compliant Part standard microcircuit drawing is available. ©2007–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 10.50 (0.4134) 10.10 (0.3976 ...

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