AD737AQ Analog Devices Inc, AD737AQ Datasheet

IC AC RMS TO DC CONV 5V 8-CDIP

AD737AQ

Manufacturer Part Number
AD737AQ
Description
IC AC RMS TO DC CONV 5V 8-CDIP
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD737AQ

Rohs Status
RoHS non-compliant
Current - Supply
170mA
Voltage - Supply
±5.0V
Mounting Type
Through Hole
Package / Case
8-CDIP (0.300", 7.62mm)
For Use With
AD737-EVALZ - BOARD EVALUATION FOR AD737

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FEATURES
Computes
Provides
GENERAL DESCRIPTION
The AD737
converter. It is laser trimmed to provide a maximum error of
±0.2 mV ± 0.3% of reading with sine wave inputs. Furthermore, it
maintains high accuracy while measuring a wide range of input
waveforms, including variable duty cycle pulses and triac (phase)
controlled sine waves. The low cost and small physical size of this
converter make it suitable for upgrading the performance of non-
rms precision rectifiers in many applications. Compared to these
circuits, the AD737 offers higher accuracy at equal or lower cost.
The AD737 can compute the rms value of both ac and dc input
voltages. It can also be operated ac-coupled by adding one
external capacitor. In this mode, the AD737 can resolve input
signal levels of 100 μV rms or less, despite variations in tem-
perature or supply voltage. High accuracy is also maintained for
input waveforms with crest factors of 1 to 3. In addition, crest
factors as high as 5 can be measured (while introducing only
2.5% additional error) at the 200 mV full-scale input level.
The AD737 has no output buffer amplifier, thereby significantly
reducing dc offset errors occurring at the output, which makes
the device highly compatible with high input impedance ADCs.
Requiring only 160 μA of power supply current, the AD737 is
optimized for use in portable multimeters and other battery-
powered applications. This converter also provides a power-down
feature that reduces the power-supply standby current to less
than 30 μA.
1
Rev. H
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.
A general-purpose, buffered voltage output version also
Protected under U.S. Patent Number 5,495,245.
available (AD736)
True rms value
Average rectified value
Absolute value
200 mV full-scale input range (larger inputs with
Direct interfacing with 3½ digit CMOS ADCs
High input impedance: 10
Low input bias current: 25 pA maximum
High accuracy: ±0.2 mV ± 0.3% of reading
RMS conversion with signal crest factors up to 5
Wide power supply range: ±2.5 V to ±16.5 V
Low power: 160 μA maximum supply current
No external trims needed for specified accuracy
input attenuator)
1
is a low power, precision, monolithic, true rms-to-dc
12
Ω
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
Two signal input terminals are provided in the AD737. A high
impedance (10
input attenuators, and a low impedance (8 kΩ) input accepts
rms voltages to 0.9 V while operating from the minimum power
supply voltage of ±2.5 V. The two inputs can be used either
single ended or differentially.
The AD737 achieves 1% of reading error bandwidth, exceeding
10 kHz for input amplitudes from 20 mV rms to 200 mV rms,
while consuming only 0.72 mW.
The AD737 is available in four performance grades. The
AD737J and AD737K grades are rated over the commercial
temperature range of 0°C to 70°C. The AD737JR-5 is tested
with supply voltages of ±2.5 V dc. The AD737A and AD737B
grades are rated over the industrial temperature range of
−40°C to +85°C. The AD737 is available in three low cost,
8­lead packages: PDIP, SOIC_N, and CERDIP.
PRODUCT HIGHLIGHTS
1.
2.
3.
Capable of computing the average rectified value, absolute
value, or true rms value of various input signals.
Only one external component, an averaging capacitor, is
required for the AD737 to perform true rms measurement.
The low power consumption of 0.72 mW makes the
AD737 suitable for battery-powered applications.
True RMS-to-DC Converter
POWER
DOWN
–V
V
C
FUNCTIONAL BLOCK DIAGRAM
IN
C
S
1
2
3
4
12
8kΩ
Ω) FET input interfaces directly with high R
Low Cost, Low Power,
SECTION
BIAS
AMPLIFIER
©2008 Analog Devices, Inc. All rights reserved.
INPUT
Figure 1.
FULL-WAVE
RECTIFIER
RMS CORE
AD737
8kΩ
www.analog.com
8
7
6
5
AD737
COM
+V
OUTPUT
C
AV
S

Related parts for AD737AQ

AD737AQ Summary of contents

Page 1

FEATURES Computes True rms value Average rectified value Absolute value Provides 200 mV full-scale input range (larger inputs with input attenuator) Direct interfacing with 3½ digit CMOS ADCs 12 High input impedance: 10 Ω Low input bias current ...

Page 2

AD737 TABLE OF CONTENTS Features .............................................................................................. 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Product Highlights ........................................................................... 1 Revision History ............................................................................... 2 Specifications ..................................................................................... 3 Absolute Maximum Ratings ............................................................ 6 Thermal Resistance ...................................................................... 6 ESD Caution .................................................................................. 6 ...

Page 3

SPECIFICATIONS T = 25°C, ±V = ±5 V except as noted Specifications shown in boldface are tested on all production units at final electrical test. Results from these tests are used to calculate outgoing quality levels. Table ...

Page 4

AD737 Parameter Conditions Peak Transient ±V = +2.5 V input to S Input Pin 1 ±V = +2.8 V/−3 ±V = ± ±V = ±16 Input Resistance Input Bias ±V = ± ...

Page 5

Parameter Conditions 3 dB Bandwidth rms rms 100 mV rms 200 mV rms IN Low-Z Input (Pin 1) 1% Additional rms ...

Page 6

AD737 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltage Internal Power Dissipation Input Voltage Output Short-Circuit Duration Differential Input Voltage Storage Temperature Range CERDIP (Q-8) PDIP (N-8) and SOIC_N (R-8) Lead Temperature, Soldering (60 sec) ESD Rating Stresses above those ...

Page 7

PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS C COM AD737 POWER DOWN OUTPUT 3 TOP VIEW 6 (Not to Scale) – Figure 2. SOIC_N Pin Configuration (R-8) Table ...

Page 8

AD737 TYPICAL PERFORMANCE CHARACTERISTICS T = 25°C, ±V = ±5 V (except AD737J-5, where ± unless otherwise specified. 0 200mV rms 100µ 22µF F 0.3 0.1 0 –0.1 –0.3 ...

Page 9

V = 200mV rms 100µ 22µF F 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –60 –40 – TEMPERATURE (°C) Figure 11. Additional Error vs. Temperature 500 400 ...

Page 10

AD737 4.0 3.5 3.0 2.5 2.0 1.5 1 SUPPLY VOLTAGE (±V) Figure 17. Input Bias Current vs. Supply Voltage 1V 100mV C = 10µF AV 10mV C = 33µF AV 1mV 100µV 1ms 10ms 100ms ...

Page 11

V = ±2.5V 22µ 4.7µ 22µ 100mV 0.5% 10mV 10% 1mV –3dB 1% 100µV 0 FREQUENCY (kHz) Figure 21. Error Contours Driving Pin ...

Page 12

AD737 THEORY OF OPERATION As shown in Figure 24, the AD737 has four functional subsec- tions: an input amplifier, a full-wave rectifier, an rms core, and a bias section. The FET input amplifier allows a high impedance, buffered input at ...

Page 13

DC ERROR, OUTPUT RIPPLE, AND AVERAGING ERROR Figure 25 shows the typical output waveform of the AD737 with a sine wave input voltage applied. As with all real-world devices, the ideal output never exactly achieved; ...

Page 14

AD737 APPLICATIONS INFORMATION RMS MEASUREMENT—CHOOSING AN OPTIMUM VALUE FOR C AV Because the external averaging capacitor, C tified input signal during rms computation, its value directly affects the accuracy of the rms measurement, especially at low frequencies. Furthermore, because the ...

Page 15

Battery Operation All the level-shifting for battery operation is provided by the 3½ digit converter, shown in Figure 28. Alternatively, an external op amp adds flexibility by accommodating nonzero common-mode voltages and providing output scaling and offset to zero. When ...

Page 16

AD737 SWITCH CLOSED ACTIVATES POWER-DOWN MODE. AD737 DRAWS JUST 40µA IN THIS MODE 1PRV 0.01µF V 200mV IN 1N4148 9MΩ 2V 900kΩ 47kΩ 20V 1W 1N4148 90kΩ 200V POWER 10kΩ 1µF + INPUT SCALE FACTOR ADJ 69.8kΩ ...

Page 17

C C 10µ AD737 8kΩ COM FULL-WAVE RECTIFIER 8kΩ INPUT AMPLIFIER POWER BIAS 3 DOWN SECTION –V S RMS 4 CORE + R1** CAL CONNECT *Q1, ...

Page 18

AD737 AD737 EVALUATION BOARD An evaluation board, AD737-EVALZ, is available for experi- ments or for becoming familiar with rms-to-dc converters. Figure photograph of the board; Figure 35 to Figure 38 show the signal and power plane copper ...

Page 19

Table 7. AD737 Evaluation Board Bill of Materials Qty Name Description 1 Test loop Red 1 Test loop Green 2 Capacitor Tantalum 10 μ Capacitor 0.1 μ 0603, X7R 1 Capacitor Tantalum ...

Page 20

AD737 OUTLINE DIMENSIONS COPLANARITY 5.00 (0.1968) 4.80 (0.1890 6.20 (0.2441) 4.00 (0.1574) 1 5.80 (0.2284) 3.80 (0.1497) 4 1.27 (0.0500) BSC 1.75 (0.0688) 1.35 (0.0532) 0.25 (0.0098) 8° 0.10 (0.0040) 0° 0.51 (0.0201) 0.10 0.31 (0.0122) 0.25 (0.0098) ...

Page 21

BSC 0.210 (5.33) MAX 0.015 0.150 (3.81) (0.38) 0.015 (0.38) MIN 0.130 (3.30) 0.115 (2.92) SEATING PLANE 0.022 (0.56) 0.005 (0.13) 0.018 ...

Page 22

... AD737 ORDERING GUIDE Model Temperature Range AD737AN −40°C to +85°C 1 AD737ANZ −40°C to +85°C AD737AQ −40°C to +85°C AD737AR −40°C to +85°C 1 AD737ARZ −40°C to +85°C AD737BQ −40°C to +85°C AD737JN 0°C to 70°C 1 AD737JNZ 0° ...

Page 23

NOTES Rev Page AD737 ...

Page 24

AD737 NOTES ©2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00828-0-10/08(H) Rev Page ...

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