AD637KD Analog Devices Inc, AD637KD Datasheet

RMS TO DC CONVERTER IC

AD637KD

Manufacturer Part Number
AD637KD
Description
RMS TO DC CONVERTER IC
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD637KD

Rohs Status
RoHS non-compliant
Current - Supply
2.2mA
Voltage - Supply
±3.0V ~ 18V
Mounting Type
Through Hole
Package / Case
14-CDIP (0.300", 7.62mm)
Bandwidth
8MHz
Supply Current
2.2mA
Power Dissipation Pd
108mW
Supply Voltage Range
± 3V To ± 18V
Digital Ic Case Style
DIP
No. Of Pins
14
Operating Temperature Range
0°C To +70°C
For Use With
AD637-EVALZ - BOARD EVALUATION FOR AD637
Lead Free Status / RoHS Status

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
AD637KD
Manufacturer:
ADI
Quantity:
485
Part Number:
AD637KDZ
Manufacturer:
ADI
Quantity:
485
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

Related parts for AD637KD

AD637KD Summary of contents

Page 1

FEATURES High accuracy 0.02% maximum nonlinearity rms input 0.10% additional error to crest factor of 3 Wide bandwidth 8 MHz rms input 600 kHz at 100 mV rms Computes True rms Square ...

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 ...

Page 3

SPECIFICATIONS At 25°C and ±15 V dc, unless otherwise noted. Table 1. AD637J/AD637A Parameter Min Typ TRANSFER FUNCTION V = OUT CONVERSION ACCURACY 2 Total Error, Internal Trim Figure MIN MAX vs. Supply 30 ...

Page 4

AD637 AD637J/AD637A Parameter Min Typ OUTPUT CHARACTERISTICS Offset Voltage vs. Temperature ±0.05 Voltage Swing, 13 12.0 ±15 V Supply, 2 kΩ Load Voltage Swing, 2 ±3 V Supply, 2 kΩ Load Output Current 6 Short-Circuit ...

Page 5

ABSOLUTE MAXIMUM RATINGS Table 2. Parameter ESD Rating Supply Voltage Internal Quiescent Power Dissipation Output Short-Circuit Duration Storage Temperature Range Lead Temperature (Soldering 10 sec) Rated Operating Temperature Range AD637J, AD637K AD637A, AD637B AD637S, 5962-8963701CA Stresses above those listed under ...

Page 6

AD637 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS BUFF AD637 COMMON 3 OUTPUT OFFSET TOP VIEW 4 (Not to Scale DEN INPUT 6 dB OUTPUT CONNECT Figure 2. 14-Lead SBDIP/CERDIP Pin Configuration ...

Page 7

FUNCTIONAL DESCRIPTION BUFF OUT 14 1 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. ...

Page 8

AD637 STANDARD CONNECTION The AD637 is simple to connect for a majority of rms measurements. In the standard rms connection shown in Figure 5, only a single external capacitor is required to set the averaging time constant. In this configuration, ...

Page 9

AD637K MAX 2.5 0 EXTERNAL TRIM –2.5 AD637K: 0.5mV ± 0.2% 0.25mV ± 0.05% EXTERNAL –5.0 0 0.5 1.0 INPUT LEVEL (V) Figure 7. Maximum Total Error vs. Input Level AD637K Internal and External Trims AD637 1 BUFF IN ...

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 ...

Page 11

Table 5. Practical Values of C and C2 for Various Input Waveforms AV Absolute Value Input Waveform Circuit Waveform and Period and Period T 1/ Symmetrical Sine Wave Sine Wave with dc Offset T ...

Page 12

AD637 AC MEASUREMENT ACCURACY AND CREST FACTOR Crest factor is often overlooked in determining the accuracy measurement. Crest factor is defined as the ratio of the peak signal amplitude to the rms value of the signal (CF ...

Page 13

CALIBRATION Refer to Figure 20: • Set 1.00 V rms IN • Adjust R1 for 0 dB out = 0.00 V • Set 0.10 V rms IN ...

Page 14

AD637 OUTPUT 1MΩ 4 OFFSET 50kΩ ADJUST + –V S 4.7kΩ NOTES 1. VALUES CHOSEN TO GIVE 0.1% AVERAGING ERROR @ 1Hz CONNECT. LOW FREQUENCY MEASUREMENTS If ...

Page 15

EXPANDABLE BUFFER AD637 IC1 BUFF IN 1 ABSOLUTE 2 NC VALUE 3 COMMON BIAS OUTPUT SECTION 4 OFFSET SQUARER/DIVIDER + 4.7kΩ 25kΩ 6 DEN INPUT FILTER 7 dB OUTPUT BUFFER AD637 IC2 BUFF ...

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. ...

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 ...

Page 18

AD637 GND1 GND2 GND3 GND4 + 50kΩ +V – CF2 47µF 25V POWER SUPPLY – 10µF 10µF 25V 25V + – FILTER BUF_IN 4 OUT 1 2 ...

Page 19

OUTLINE DIMENSIONS 0.005 (0.13) MIN 0.080 (2.03) MAX 14 8 0.310 (7.87) 0.220 (5.59 PIN 1 0.100 (2.54) BSC 0.765 (19.43) MAX 0.060 (1.52) 0.200 (5.08) MAX 0.015 (0.38) 0.150 (3.81) 0.200 (5.08) MIN 0.125 (3.18) SEATING 0.070 ...

Page 20

... AD637BR AD637BRZ AD637JD AD637JDZ AD637JQ AD637JR AD637JR-REEL 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. ...

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