Low Cost, Low Power,
True RMS-to-DC Converter
AD737
Rev. H
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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
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved.
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
High input impedance: 1012 Ω
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
A general-purpose, buffered voltage output version also
available (AD736)
FUNCTIONAL BLOCK DIAGRAM
CC
VIN
AD737
COM
OUTPUT
FULL-WAVE
RECTIFIER
BIAS
SECTION RMS CORE
INPUT
AMPLIFIER
8kΩ
8kΩ
POWER
DOWN
–VS
+VS
CAV
1
2
3
4
8
7
6
5
00828-001
Figure 1.
GENERAL DESCRIPTION
The AD7371 is a low power, precision, monolithic, true rms-to-dc
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.
Two signal input terminals are provided in the AD737. A high
impedance (1012 Ω) FET input interfaces directly with high R
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. Capable of computing the average rectified value, absolute
value, or true rms value of various input signals.
2. Only one external component, an averaging capacitor, is
required for the AD737 to perform true rms measurement.
3. The low power consumption of 0.72 mW makes the
AD737 suitable for battery-powered applications.
1 Protected under U.S. Patent Number 5,495,245.
AD737
Rev. H | Page 2 of 24
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
Pin Configurations and Function Descriptions ........................... 7
Typical Performance Characteristics ............................................. 8
Theory of Operation ...................................................................... 12
Types of AC Measurement ........................................................ 12
DC Error, Output Ripple, and Averaging Error ..................... 13
AC Measurement Accuracy and Crest Factor ........................ 13
Calculating Settling Time .......................................................... 13
Applications Information .............................................................. 14
RMS Measurement—Choosing an Optimum
Value for CAV ............................................................................... 14
Rapid Settling Times via the Average Responding
Connection .................................................................................. 14
Selecting Practical Values for Capacitors ................................ 14
Scaling Input and Output Voltages .......................................... 14
AD737 Evaluation Board ............................................................... 18
Outline Dimensions ....................................................................... 20
Ordering Guide .......................................................................... 22
REVISION HISTORY
10/08—Rev. G to Rev. H
Added Selectable Average or RMS Conversion Section and
Figure 27 .......................................................................................... 14
Updated Outline Dimensions ....................................................... 20
Changes to Ordering Guide .......................................................... 22
12/06—Rev. F to Rev. G
Changes to Specifications ................................................................ 3
Reorganized Typical Performance Characteristics ...................... 8
Changes to Figure 21 ...................................................................... 11
Reorganized Theory of Operation Section ................................. 12
Reorganized Applications Section ................................................ 14
Added Scaling Input and Output Voltages Section .................... 14
Deleted Application Circuits Heading ......................................... 16
Changes to Figure 28 ...................................................................... 16
Added AD737 Evaluation Board Section .................................... 18
Updated Outline Dimensions ....................................................... 20
Changes to Ordering Guide .......................................................... 21
1/05—Rev. E to Rev. F
Updated Format .................................................................. Universal
Added Functional Block Diagram.................................................. 1
Changes to General Description Section ...................................... 1
Changes to Pin Configurations and Function
Descriptions Section ........................................................................ 6
Changes to Typical Performance Characteristics Section ........... 7
Changes to Table 4 .......................................................................... 11
Change to Figure 24 ....................................................................... 12
Change to Figure 27 ....................................................................... 15
Changes to Ordering Guide .......................................................... 18
6/03—Rev. D to Rev. E
Added AD737JR-5 .............................................................. Universal
Changes to Features .......................................................................... 1
Changes to General Description ..................................................... 1
Changes to Specifications ................................................................. 2
Changes to Absolute Maximum Ratings ........................................ 4
Changes to Ordering Guide ............................................................. 4
Added TPCs 16 through 19 ............................................................. 6
Changes to Figures 1 and 2 .............................................................. 8
Changes to Figure 8 ........................................................................ 11
Updated Outline Dimensions ....................................................... 12
12/02—Rev. C to Rev. D
Changes to Functional Block Diagram ........................................... 1
Changes to Pin Configuration ......................................................... 4
Figure 1 Replaced .............................................................................. 8
Changes to Figure 2 ........................................................................... 8
Figure 5 Replaced ........................................................................... 10
Changes to Application Circuits Figures 4, 6–8 ......................... 10
Outline Dimensions Updated ....................................................... 12
12/99—Rev. B to Rev. C
AD737
Rev. H | Page 3 of 24
SPECIFICATIONS
TA = 25°C, ±VS = ±5 V except as noted, CAV = 33 μF, CC = 10 μF, f = 1 kHz, sine wave input applied to Pin 2, unless otherwise specified.
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 1.
AD737A, AD737J AD737B, AD737K AD737J-5
Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit
ACCURACY
Total Error EIN = 0 to 200 mV rms 0.2/0.3 0.4/0.5 0.2/0.2
0.2/0.3 ±mV/±POR1
±VS = ±2.5 V 0.2/0.3 0.4/0.5 ±mV/±POR1
±VS = ±2.5 V,
input to Pin 1
0.2/0.3
0.4/0.5 ±mV/±POR1
E
IN = 200 mV to 1 V rms −1.2 ±2.0 −1.2
±2.0 POR
Over
Temperature
AQ and BQ EIN = 200 mV rms 0.5/0.7 0.3/0.5 ±POR/°C
JN, JR, KN, KR EIN = 200 mV rms,
±VS = ±2.5 V
0.007 0.007 0.02 ±POR/°C
AN and AR EIN = 200 mV rms,
±VS = ±2.5 V
0.014 0.014 ±POR/°C
Vs. Supply
Voltage
E
IN = 200 mV rms,
±VS = ±2.5 V to ±5 V
0 −0.18 −0.3 0 −0.18 −0.3 0 −0.18 −0.3 %/V
E
IN = 200 mV rms,
±VS = ±5 V to ±16.5 V
0 0.06 0.1 0 0.06 0.1 0 0.06 0.1 %/V
DC Reversal Error DC coupled,
VIN = 600 mV dc
1.3 2.5 1.3 2.5 POR
V
IN = 200 mV dc,
±VS = ±2.5 V
1.7 2.5 POR
Nonlinearity2 E
IN = 0 mV to
200 mV rms,
@ 100 mV rms
0 0.25 0.35 0 0.25 0.35 POR
Input to Pin 13 AC coupled,
EIN = 100 mV rms, after
correction, ±VS = ±2.5 V
0.02 0.1 POR
Total Error,
External Trim
EIN = 0 mV to
200 mV rms
0.1/0.2 0.1/0.2 0.1/0.2 ±mV/±POR
ADDITIONAL
CREST FACTOR
ERROR4
For Crest Factors
from 1 to 3
CAV = CF = 100 μF 0.7 0.7 %
C
AV = 22 μF, CF = 100 μF,
±VS = ±2.5 V, input to
Pin 1
1.7 %
For Crest Factors
from 3 to 5
CAV = CF = 100 μF 2.5 2.5 %
INPUT
CHARACTERISTICS
High-Z Input (Pin 2)
Signal Range
Continuous
RMS Level
±VS = +2.5 V 200 mV rms
±VS = +2.8 V/−3.2 V 200 200 mV rms
±VS = ±5 V to ±16.5 V 1 1 V rms
AD737
Rev. H | Page 4 of 24
AD737A, AD737J AD737B, AD737K AD737J-5
Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit
Peak Transient
Input
±VS = +2.5 V input to
Pin 1
±0.6 V
±VS = +2.8 V/−3.2 V ±0.9
±0.9 V
±VS = ±5 V ±2.7 ±2.7 V
±VS = ±16.5 V ±4.0
±4.0 V
Input Resistance 1012 1012 1012 Ω
Input Bias
Current
±VS = ±5 V 1 25 1 25 1 25 pA
Low-Z Input
(Pin 1) Signal
Range
Continuous
RMS Level
±VS = +2.5 V 300 mV rms
±VS = +2.8 V/−3.2 V 300 300 mV rms
±VS = ±5 V to ±16.5 V 1 1 V rms
Peak Transient
Input
±VS = +2.5 V ±1.7 V
±VS = +2.8 V/−3.2 V ±1.7 ±1.7 V
±VS = ±5 V ±3.8 ±3.8 V
±VS = ±16.5 V ±11 ±11 V
Input Resistance 6.4 8 9.6 6.4 8 9.6 6.4 8 9.6 kΩ
Maximum
Continuous
Nondestructive
Input
All supply voltages ±12 ±12 ±12 V p-p
Input Offset
Voltage5
AC coupled ±3 ±3 ±3 mV
Over the Rated
Operating
Temperature
Range
8 30 8 30 8 30 μV/°C
Vs. Supply VS = ±2.5 V to ±5 V 80 80 80 μV/V
V
S = ±5 V to ±16.5 V 50 150 50 150 μV/V
OUTPUT
CHARACTERISTICS
No load
Output Voltage
Swing
±VS = +2.8 V/−3.2 V −1.6 −1.7 −1.6 −1.7 V
±VS = ±5 V −3.3 −3.4 −3.3 −3.4 V
±VS = ±16.5 V −4 −5 −4 −5 V
±VS = ±2.5 V, input to
Pin 1
−1.1 –0.9 V
Output
Resistance
DC 6.4 8 9.6 6.4 8 9.6 6.4 8 9.6 kΩ
FREQUENCY
RESPONSE
High-Z Input
(Pin 2)
1% Additional
Error
VIN = 1 mV rms 1 1 1 kHz
V
IN = 10 mV rms 6 6 6 kHz
V
IN = 100 mV rms 37 37 37 kHz
V
IN = 200 mV rms 33 33 33 kHz
AD737
Rev. H | Page 5 of 24
AD737A, AD737J AD737B, AD737K AD737J-5
Parameter Conditions Min Typ Max Min Typ Max Min Typ Max Unit
3 dB Bandwidth VIN = 1 mV rms 5 5 5 kHz
V
IN = 10 mV rms 55 55 55 kHz
V
IN = 100 mV rms 170 170 170 kHz
V
IN = 200 mV rms 190 190 190 kHz
Low-Z Input
(Pin 1)
1% Additional
Error
VIN = 1 mV rms 1 1 1 kHz
V
IN = 10 mV rms 6 6 6 kHz
V
IN = 40 mV rms 25 kHz
V
IN = 100 mV rms 90 90 90 kHz
V
IN = 200 mV rms 90 90 90 kHz
3 dB Bandwidth VIN = 1 mV rms 5 5 5 kHz
V
IN = 10 mV rms 55 55 55 kHz
V
IN = 100 mV rms 350 350 350 kHz
V
IN = 200 mV rms 460 460 460 kHz
POWER-DOWN
MODE
Disable Voltage 0 0 V
Input Current,
PD Enabled
VPD = VS 11 11 μA
POWER SUPPLY
Operating
Voltage Range
+2.8/
−3.2
±5 ±16.5 +2.8/
−3.2
±5 ±16.5 ±2.5 ±5 ±16.5 V
Current No input 120
160 120
160 120
160 μA
Rated input 170 210 170 210 170 210 μA
Powered down 25 40 25 40 25 40 μA
1 POR is % of reading.
2 Nonlinearity is defined as the maximum deviation (in percent error) from a straight line connecting the readings at 0 V and at 200 mV rms.
3 After fourth-order error correction using the equation
y = − 0.31009x4 − 0.21692x3 − 0.06939x2 + 0.99756x + 11.1 × 10−6
where y is the corrected result and x is the device output between 0.01 V and 0.3 V.
4 Crest factor error is specified as the additional error resulting from the specific crest factor, using a 200 mV rms signal as a reference. The crest factor is defined as
VPEAK/V rms.
5 DC offset does not limit ac resolution.
AD737
Rev. H | Page 6 of 24
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Supply Voltage ±16.5 V
Internal Power Dissipation 200 mW
Input Voltage ±VS
Output Short-Circuit Duration Indefinite
Differential Input Voltage +VS and −VS
Storage Temperature Range
CERDIP (Q-8) −65°C to +150°C
PDIP (N-8) and SOIC_N (R-8) −65°C to +125°C
Lead Temperature, Soldering (60 sec) 300°C
ESD Rating 500 V
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3. Thermal Resistance
Package Type θJA Unit
8-Lead CERDIP (Q-8) 110 °C/W
8-Lead PDIP (N-8) 165 °C/W
8-Lead SOIC_N (R-8) 155 °C/W
ESD CAUTION
AD737
Rev. H | Page 7 of 24
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
C
C1
V
IN 2
POWER DO WN
3
–V
S4
COM
8
+V
S
7
OUTPUT
6
C
AV
5
AD737
TOP VIEW
(No t t o S cale)
00828-002
1
2
3
4
8
7
6
5
AD737
C
C
V
COM
+V
IN
POWER DO WN
–V
S
S
OUTPUT
C
AV
00828-003
TOP VIEW
(Not to Scal e)
18
2
3
4
7
6
5
AD737
TOP VIEW
(Not to Scale)
C
C
V
IN
POWER DO WN
–V
S
COM
+V
S
OUTPUT
C
AV
00828-004
Figure 2. SOIC_N Pin Configuration (R-8) Figure 3. CERDIP Pin Configuration (Q-8) Figure 4. PDIP Pin Configuration (N-8)
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 CC Coupling Capacitor for Indirect DC Coupling.
2 VIN RMS Input.
3 POWER DOWN Disables the AD737. Low is enabled; high is powered down.
4 –VS Negative Power Supply.
5 CAV Averaging Capacitor.
6 OUTPUT Output.
7 +VS Positive Power Supply.
8 COM Common.
AD737
Rev. H | Page 8 of 24
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, ±VS = ±5 V (except AD737J-5, where ±VS = ±2.5 V), CAV = 33 µF, CC = 10 µF, f = 1 kHz, sine wave input applied to Pin 2,
unless otherwise specified.
V
IN
= 200mV rms
C
AV
= 100µ F
C
F
= 22µ F
–0.5 04286121410 16
ADDIT IONA L E RROR (% o f Readi ng)
00828-005
–0.3
–0.1
0
0.3
0.1
0.5
0.7
SUPPLY VOLTAGE (±V)
Figure 5. Additional Error vs. Supply Voltage
100µV
1mV
10mV
1V
100mV
10
V
004286121410 16
PEAK I NPUT BEF O RE CL I PP I NG (V)
00828-006
2
4
6
8
12
10
14
16
SUPPLY VOLTAGE (±V)
PIN 1
PIN 2
DC COUPLED
Figure 6. Maximum Input Level vs. Supply Voltage
5024681012141618
DUAL SUPPLY VOLTAGE (±V)
00
10
20
15
25
SUPP LY CURRENT (µA)
828-007
Figure 7. Supply Current (Power-Down Mode) vs. Supply Voltage (Dual)
0.1 1 10010 1000
FREQUENC Y (kHz)
INPUT LEVEL (rms)
00828-008
C
AV
= 22µ F, C
F
= 4. 7µF, C
C
= 22µ F
1% ERROR
–3dB
10% ERROR
Figure 8. Frequency Response Driving Pin 1
100µV
1mV
10mV
1V
100mV
10
V
0.1 1 10010 1000
FREQUENCY (kHz)
INPUT LEVEL (rms)
00828-009
C
AV
= 22µF, C
F
= 4. 7µF, C
C
= 22µ F
1% ERROR
10% ERROR
–3dB
Figure 9. Frequency Response Driving Pin 2
C
AV
= 100µ F
C
AV
= 250µ F
0
1
2
3
4
5
6
12345
ADDITIONAL ERROR (% o f Reading )
00828-010
CREST FACTOR (V
PEAK
/V rms)
C
AV
= 10µF
C
AV
= 33µ F
3ms BURST OF 1k Hz =
3 CYCL E S
200mV rms SIG NAL
C
C
= 22µ F
C
F
= 100µ F
Figure 10. Additional Error vs. Crest Factor
AD737
Rev. H | Page 9 of 24
V
IN
= 200mV rms
C
AV
= 100µF
C
F
= 22µF
–0.8
–60 –20–40 200 60 80 100 12040 140
TEMPERATURE (°C)
0082
–0.6
–0.2
–0.4
0
0.4
0.2
0.6
0.8
ADDIT I ONAL ERRO R (% o f Read i ng )
8-011
Figure 11. Additional Error vs. Temperature
–2.5
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0
10mV 100mV 1V 2V
INPUT LEVEL (rms)
ERROR ( % of Reading )
00828-014
C
AV
= 22µF, C
C
= 47µ F,
C
F
= 4. 7µF
1
10
100
10 100 1k
FREQ UE NC Y (Hz)
AVERAG ING CA PACITOR (µF)
00828-015
Figure 14. Error vs. RMS Input Level Using Circuit in Figure 30
0
DC SUPPLY CURRENT (µ A)
00828-012
200
100
400
300
500
0 0.2 0.4 0.6 0.8 1.0
RMS INPUT LEVEL (V)
Figure 12. DC Supply Current vs. RMS Input Level
10µV
100µV
1mV
10m
V
100 1k 10k 100k
–3dB FREQ UE NCY (H z )
00828-013
INPUT LEVEL (rms)
AC CO UP LE D
Figure 13. RMS Input Level vs. –3 dB Frequency
–1%
–0.5%
V
IN
= 200mV rm s
C
C
= 47µF
C
F
= 47µF
Figure 15. Value of Averaging Capacitor vs. Frequency
for Specified Averaging Error
1mV
10mV
100mV
1
V
1 10 100 1k
FREQUENCY (Hz)
0082
INPUT LEVEL (rms)
8-016
–0.5%
–1%
AC COUPLED
C
AV
= 10µF, C
C
= 47µF,
C = 47µ F
F
Figure 16. RMS Input Level vs. Frequency for Specified Averaging Error
AD737
Rev. H | Page 10 of 24
100fA
10n
A
1.0 02468 121410 16
SUPPLY VOLTAGE (±V)
0082
1.5
2.0
2.5
3.0
4.0
3.5
INPUT BI AS CURRENT ( p A)
8-017
Figure 17. Input Bias Current vs. Supply Voltage
1nA
100pA
10pA
1pA
–55 –35 –15 5 25 65 85 10545 125
TEMPERATURE (°C)
INPUT BIAS CURRE NT
00828-019
100µV
1mV
10mV
100mV
1
V
1ms 10ms 100ms 1s 10s 100s
SETTLING TIME
INPUT LEVEL (rms)
00828-018
C
C
= 22µ F
C
F
= 0µF
C
AV
= 10µ F
C
AV
= 33µF
C
AV
= 100µ F
Figure 18. RMS Input Level vs. Settling Time for Three Values of CAV
Figure 19. Input Bias Current vs. Temperature
100µV
10mV
1mV
1V
100mV
10
V
0.1 1 10 100 1000
FREQUENC Y (kHz)
INPUT LEVEL (rms)
00828-020
V
S
=±2.5V,
C
AV
= 22µF, C
F
= 4. 7µ F, C
C
= 22µF
Figure 20. Frequency Response Driving Pin 1
AD737
Rev. H | Page 11 of 24
100µV
10mV
1mV
1V
100mV
10
V
0.1 1 10 100 1000
FREQ UE NC Y (kHz)
0082
–2.5
0.5
–0.5
–1.0
–1.5
–2.0
0
1.0
10mV 100mV 1V 2V
INPUT LEVEL (rms)
ERROR (% o f Read i n g )
00828-023
V
S
=±2.5V,
C
AV
= 22µ F, C
F
= 4. 7µ F, C
C
= 22µF
INPUT LEVEL (rms)
8-021
0.5%
–3dB
10%
1% C
AV
= 22µ F, V
S
= ±2.5V
C
C
= 47µF, C
F
= 4. 7µF
Figure 21. Error Contours Driving Pin 1 Figure 23. Error vs. RMS Input Level Driving Pin 1
0
1
2
3
4
5
12345
CREST FACTOR
ADDIT IO N AL ER ROR (% of Rea d in g)
00828-022
C
AV
=
22µF
C
AV
=
10µF
C
AV
=
100µF
C
AV
=
220µF
C
AV
=
33µF
3 CYCL E S OF 1kHz
200mV rms
V
S
= ±2.5V
C
C
= 22µ F
C
F
= 100µ F
Figure 22. Additional Error vs. Crest Factor for Various Values of CAV
AD737
Rev. H | Page 12 of 24
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 Pin 2 or a low impedance, wide dynamic range
input at Pin 1. The high impedance input, with its low input bias
current, is ideal for use with high impedance input attenuators.
The input signal can be either dc-coupled or ac-coupled to the
input amplifier. Unlike other rms converters, the AD737 permits
both direct and indirect ac coupling of the inputs. AC coupling is
provided by placing a series capacitor between the input signal
and Pin 2 (or Pin 1) for direct coupling and between Pin 1 and
ground (while driving Pin 2) for indirect coupling.
RMS
TRANSLINEAR
CORE
8
COM
+V
S
7
6
OUTPUT
5
C
AV
CURRENT
MODE
ABSOLUTE
VALUE
1
2
3
P
O
WER
DOWN
4
C
A
33µF
AC
C
C =
10µF
C
F
10µF
(OPTIONAL
LPF)
V
IN
–V
S
+V
S
V
IN
C
C
–V
S
+
OPTIONAL RETURN PATH
8kΩ
+
+
DC
BIAS
SECTION
FET
OP AMP
1
B
<10pA
8kΩ
00828-024
0.1µF
0.1µF
COMMON
POSITIVE SUPPLY
NEGATI VE SUPPLY
Figure 24. AD737 True RMS Circuit (Test Circuit)
The output of the input amplifier drives a full-wave precision
rectifier which, in turn, drives the rms core. It is the core that
provides the essential rms operations of squaring, averaging,
and square rooting, using an external averaging capacitor, CAV.
Without CAV, the rectified input signal passes through the core
unprocessed, as is done with the average responding connection
(see Figure 26). In the average responding mode, averaging is
carried out by an RC post filter consisting of an 8 kΩ internal
scale factor resistor connected between Pin 6 and Pin 8 and an
external averaging capacitor, CF. In the rms circuit, this addi-
tional filtering stage reduces any output ripple that was not
removed by the averaging capacitor.
Finally, the bias subsection permits a power-down function.
This reduces the idle current of the AD737 from 160 µA to
30 µA. This feature is selected by connecting Pin 3 to Pin 7
(+VS).
TYPES OF AC MEASUREMENT
The AD737 is capable of measuring ac signals by operating as
either an average responding converter or a true rms-to-dc con-
verter. As its name implies, an average responding converter
computes the average absolute value of an ac (or ac and dc)
voltage or current by full-wave rectifying and low-pass filtering
the input signal; this approximates the average. The resulting
output, a dc average level, is then scaled by adding (or reducing)
gain; this scale factor converts the dc average reading to an rms
equivalent value for the waveform being measured. For example,
the average absolute value of a sine wave voltage is 0.636 that of
VPEAK; the corresponding rms value is 0.707 times VPEAK.
Therefore, for sine wave voltages, the required scale factor is
1.11 (0.707 divided by 0.636).
In contrast to measuring the average value, true rms measure-
ment is a universal language among waveforms, allowing the
magnitudes of all types of voltage (or current) waveforms to be
compared to one another and to dc. RMS is a direct measure of
the power or heating value of an ac voltage compared to that of
a dc voltage; an ac signal of 1 V rms produces the same amount
of heat in a resistor as a 1 V dc signal.
Mathematically, the rms value of a voltage is defined (using a
simplified equation) as
)( 2
VAvgV rms =
This involves squaring the signal, taking the average, and then
obtaining the square root. True rms converters are smart recti-
fiers; they provide an accurate rms reading regardless of the
type of waveform being measured. However, average responding
converters can exhibit very high errors when their input signals
deviate from their precalibrated waveform; the magnitude of
the error depends on the type of waveform being measured. As
an example, if an average responding converter is calibrated to
measure the rms value of sine wave voltages and then is used to
measure either symmetrical square waves or dc voltages, the
converter has a computational error 11% (of reading) higher
than the true rms value (see Table 5).
The transfer function for the AD737 is
)( 2
INOUT VAvgV =
AD737
Rev. H | Page 13 of 24
AVERAGE EO = EO
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 of VOUT = VIN is never exactly achieved; instead,
the output contains both a dc and an ac error component.
DC ERROR = EO – EO (IDEAL)
EO
IDEAL
EO
DOUBLE-FREQUENCY
RIPPLE
TIME
00828-026
Figure 25. Output Waveform for Sine Wave Input Voltage
As shown, the dc error is the difference between the average of
the output signal (when all the ripple in the output has been
removed by external filtering) and the ideal dc output. The dc
error component is, therefore, set solely by the value of the
averaging capacitor used—no amount of post filtering (using a
very large postfiltering capacitor, CF) allows the output voltage
to equal its ideal value. The ac error component, an output
ripple, can be easily removed using a large enough CF.
In most cases, the combined magnitudes of the dc and ac error
components must be considered when selecting appropriate
values for CAV and CF capacitors. This combined error, repre-
senting the maximum uncertainty of the measurement, is
termed the averaging error and is equal to the peak value of the
output ripple plus the dc error. As the input frequency increases,
both error components decrease rapidly. If the input frequency
doubles, the dc error and ripple reduce to one-quarter and
one-half of their original values, respectively, and rapidly
become insignificant.
AC MEASUREMENT ACCURACY AND
CREST FACTOR
The crest factor of the input waveform is often overlooked when
determining the accuracy of an ac measurement. Crest factor is
defined as the ratio of the peak signal amplitude to the rms
amplitude (crest factor = VPEAK/V rms). Many common
waveforms, such as sine and triangle waves, have relatively low
crest factors (≥2). Other waveforms, such as low duty cycle
pulse trains and SCR waveforms, have high crest factors. These
types of waveforms require a long averaging time constant to
average out the long time periods between pulses. Figure 10
shows the additional error vs. the crest factor of the AD737 for
various values of CAV.
CALCULATING SETTLING TIME
Figure 18 can be used to closely approximate the time required
for the AD737 to settle when its input level is reduced in
amplitude. The net time required for the rms converter to settle
is the difference between two times extracted from the graph:
the initial time minus the final settling time. As an example,
consider the following conditions: a 33 µF averaging capacitor,
an initial rms input level of 100 mV, and a final (reduced) input
level of 1 mV. From Figure 18, the initial settling time (where
the 100 mV line intersects the 33 µF line) is approximately
80 ms. The settling time corresponding to the new or final input
level of 1 mV is approximately 8 seconds. Therefore, the net
time for the circuit to settle to its new value is 8 seconds minus
80 ms, which is 7.92 seconds.
Note that, because of the inherent smoothness of the decay
characteristic of a capacitor/diode combination, this is the total
settling time to the final value (not the settling time to 1%,
0.1%, and so on, of the final value). Also, this graph provides
the worst-case settling time because the AD737 settles very
quickly with increasing input levels.
Table 5. Error Introduced by an Average Responding Circuit When Measuring Common Waveforms
Type of Waveform
1 V Peak Amplitude
Crest Factor
(VPEAK/V rms)
True RMS
Value (V)
Reading of an Average Responding Circuit Calibrated to
an RMS Sine Wave Value (V) Error (%)
Undistorted Sine Wave 1.414 0.707 0.707 0
Symmetrical Square Wave 1.00 1.00 1.11 11.0
Undistorted Triangle Wave 1.73 0.577 0.555 −3.8
Gaussian Noise (98% of
Peaks <1 V) 3 0.333 0.295 −11.4
Rectangular 2 0.5 0.278 −44
Pulse Train 10 0.1 0.011 −89
SCR Waveforms
50% Duty Cycle 2 0.495 0.354 −28
25% Duty Cycle 4.7 0.212 0.150 −30
AD737
Rev. H | Page 14 of 24
APPLICATIONS INFORMATION
RMS MEASUREMENT—CHOOSING AN OPTIMUM
VALUE FOR CAV
VINRMS
–2.5V
18
7
6
5
4
3
2
CC
VIN
COM
+V
S
OUT
C
AV
–V
S
33µF 33µF
AD737
VOUT
DC
+2.5V
1MΩ
Because the external averaging capacitor, CAV, holds the rec-
tified input signal during rms computation, its value directly
affects the accuracy of the rms measurement, especially at low
frequencies. Furthermore, because the averaging capacitor is
connected across a diode in the rms core, the averaging time
constant (τAV) increases exponentially as the input signal
decreases. It follows that decreasing the input signal decreases
errors due to nonideal averaging but increases the settling time
approaching the decreased rms-computed dc value. Thus,
diminishing input values allow the circuit to perform better
(due to increased averaging) while increasing the waiting time
between measurements. A trade-off must be made between
computational accuracy and settling time when selecting CAV .
RAPID SETTLING TIMES VIA THE AVERAGE
RESPONDING CONNECTION
Because the average responding connection shown in Figure 26
does not use an averaging capacitor, its settling time does not vary
with input signal level; it is determined solely by the RC time
constant of CF and the internal 8 kΩ output scaling resistor.
POSITI VE SUPPLY +VS
0.1µF
COMMON
–VS
0.1µF
NEGATI VE SUPPLY
VOUT
CC
VIN CF
33µF
00828-025
COM
OUTPUT
AD737
BIAS
SECTION
INPUT
AMPLIFIER
8kΩ
8kΩ
POWER
DOWN
–VS
+VS+
CAV
1
2
3
4
8
7
6
5
FULL-WAVE
RECTIFIER
RMS
CORE
Figure 26. AD737 Average Responding Circuit
Selectable Average or RMS Conversion
For some applications, it is desirable to be able to select between
rms-value-to-dc conversion and average-value-to-dc conversion.
If CAV is disconnected from the root-mean core, the AD737 full-
wave rectifier is a highly accurate absolute value circuit. A CMOS
switch whose gate is controlled by a logic level selects between
average and rms values.
00828-039
rms
AVG
NTR4501NT1 ASSUMED TO
BE A LOGIC
SOURCE
Figure 27. CMOS Switch Is Used to Select RMS or Average Responding Modes
SELECTING PRACTICAL VALUES FOR CAPACITORS
Table 6 provides practical values of CAV and CF for several
common applications.
The input coupling capacitor, CC, in conjunction with the 8 kΩ
internal input scaling resistor, determines the −3 dB low frequency
roll-off. This frequency, FL, is equal to
()
FaradsinC
F
C
L××π
=80002
1 (1)
Note that, at FL, the amplitude error is approximately −30%
(−3 dB) of reading. To reduce this error to 0.5% of reading,
choose a value of CC that sets FL at one-tenth of the lowest
frequency to be measured.
In addition, if the input voltage has more than 100 mV of dc
offset, the ac coupling network at Pin 2 is required in addition
to Capacitor CC.
SCALING INPUT AND OUTPUT VOLTAGES
The AD737 is an extremely flexible device. With minimal
external circuitry, it can be powered with single- or dual-
polarity power supplies, and input and output voltages are
independently scalable to accommodate nonmatching I/O
devices. This section describes a few such applications.
Extending or Scaling the Input Range
For low supply voltage applications, the maximum peak voltage
to the device is extended by simply applying the input voltage to
Pin 1 across the internal 8 kΩ input resistor. The AD737 input
circuit functions quasi-differentially, with a high impedance
FET input at Pin 2 (noninverting) and a low impedance input at
Pin 1 (inverting, see Figure 26). The internal 8 kΩ resistor behaves
as a voltage-to-current converter connected to the summing
node of a feedback loop around the input amplifier. Because the
feedback loop acts to servo the summing node voltage to match
the voltage at Pin 2, the maximum peak input voltage increases
until the internal circuit runs out of headroom, approximately
double for a symmetrical dual supply.
AD737
Rev. H | Page 15 of 24
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 an external operational amplifier is used,
the output polarity is positive going.
Figure 29 shows an op amp used in a single-supply application.
Note that the combined input resistor value (R1 + R2 + 8 kΩ)
matches that of the R5 feedback resistor. In this instance, the
magnitudes of the output dc voltage and the rms of the ac input
are equal. R3 and R4 provide current to offset the output to 0 V.
Scaling the Output Voltage
The output voltage can be scaled to the input rms voltage. For
example, assume that the AD737 is retrofitted to an existing
application using an averaging responding circuit (full-wave
rectifier). The power supply is 12 V, the input voltage is 10 V ac,
and the desired output is 6 V dc.
For convenience, use the same combined input resistance as
shown in Figure 29. Calculate the rms input current as
OUTMAG
INMAG II =μ=
++
=A 125
k 8 k 2.5 k 69.8
V 10 (2)
Next, using the IOUTMAG value from Equation 2, calculate the
feedback resistor required for 6 V output using
k 48.1
A 125
V 6 =
μ
=
FB
R (3)
Select the closest-value standard 1% resistor, 47.5 kΩ.
Because the supply is 12 V, the common-mode voltage at the
R7/R8 divider is 6 V, and the combined resistor value
(R3 + R4) is equal to the feedback resistor, or 47.5 kΩ.
R2 is used to calibrate the transfer function (gain), and R4 sets
the output voltage to zero with no input voltage.
Perform calibration as follows:
1. With no ac input applied, adjust R4 for 0 V.
2. Apply a known input to the input.
3. Adjust the R2 trimmer until the input and output match.
The op amp selected for any single-supply application must bea
rail-to-rail type, for example an AD8541, as shown in Figure 29.
For higher voltages, a higher voltage part, such as an OP196,
can be used. When calibrating to 0 V, the specified voltage
above ground for the operational amplifier must be taken into
account. Adjust R4 slightly higher as appropriate.
Table 6. AD737 Capacitor Selection
Application RMS Input Level
Low Frequency
Cutoff (−3 dB)
Maximum
Crest Factor CAV (μF) CF (μF) Settling Time1 to 1%
General-Purpose RMS
Computation
0 V to 1 V 20 Hz 5 150 10 360 ms
200 Hz 5 15 1 36 ms
0 mV to 200 mV 20 Hz 5 33 10 360 ms
200 Hz 5 3.3 1 36 ms
General-Purpose Average
Responding
0 V to 1 V 20 Hz None 33 1.2 sec
200 Hz None 3.3 120 ms
0 mV to 200 mV 20 Hz None 33 1.2 sec
200 Hz None 3.3 120 ms
SCR Waveform
Measurement
0 mV to 200 mV 50 Hz 5 100 33 1.2 sec
60 Hz 5 82 27 1.0 sec
0 mV to 100 mV 50 Hz 5 50 33 1.2 sec
60 Hz 5 47 27 1.0 sec
Audio Applications
Speech 0 mV to 200 mV 300 Hz 3 1.5 0.5 18 ms
Music 0 mV to 100 mV 20 Hz 10 100 68 2.4 sec
1 Settling time is specified over the stated rms input level with the input signal increasing from zero. Settling times are greater for decreasing amplitude input signals.
AD737
Rev. H | Page 16 of 24
COM
+V
AD589
1.23V
C
AV
C
C
POWER
DOWN 0.1µF
C
C
10µF
SW ITCH CL OSE D
ACTIVATES
POWER-DOWN
MODE. A D737 DRAWS
JUST 40µA IN THIS MODE
2V
20V
200V
9MΩ
900kΩ
90kΩ
10kΩ
V
IN
200mV
V
IN
–V
S
+
+
+V
S
+
1µF
OUTPUT 1MΩ
+V
S
1N4148
1N4148
–V
S
47kΩ
1W
1µF
+
COMMON
33µF
REF LO W
REF HIG H
3
1
/
2
DIG IT I CL 7136
TYP E CONVERTER
LOW
HIGH
ANALOG 9V
200kΩ
20kΩ
50kΩ
+
1PRV
0.01µF
RMS
CORE
AD737
BIAS
SECTION
INPUT
AMPLIFIER
8kΩ
8kΩ
1
2
3
4
8
7
6
5
FULL-WAVE
RECTIFIER
00828-027
Figure 28. 3½ Digit DVM Circuit
INPUT SCAL E FACTOR ADJ
COM
INPU
C
AV
C
AV
33µF
C
F
0.47µF
C1
0.47µF
C5
C4
2.2µF R7
100kΩ
R4
5kΩ
R2
5kΩ
R3
78.7kΩR5
80.6kΩ
R1
69.8kΩ
1%
R8
C3
0.01µF
0.01µF
C2
0.01µF
C
C
POWER
DOWN
T
1µF 100kΩ
V
IN
–V
S
OUTPUT
+V
S
+
OUTPUT
AD737
+
5V
5V
2.5V
AD8541AR
5V
NC
NC = NO CO NNE CT
1 8
OUTPUT ZERO
ADJUST
2
3
4
7
1
627
54
5
3
6
00828-028
Figure 29. Battery-Powered Operation for 200 mV Maximum RMS Full-Scale Input
V
OUT
RMS
CORE
C
C
V
IN
C
F
10µF
00828-029
COM
OUTPUT
AD737
BIAS
SECTION
INPUT
AMPLIFIER
SCALE FACTOR
ADJUST
8kΩ
8kΩ
POWER
DOWN
–V
S
+V
S
+
C
AV
1
2
3
4
8
7
6
5
100Ω
200Ω
C
AV
33µF
C
C
10µF
+
FULL-WAVE
RECTIFIER
+
Figure 30. External Scale Factor Trim
AD737
Rev. H | Page 17 of 24
+
R
CAL
** R1** I
REF
10 *11
9
Q2
**R1 + R
CAL
IN Ω = 10,000 × 4.3V
0dB INPUT LEVEL IN V
AD711
1kΩ
3500PPM/°C
60.4Ω
13 Q1
12
14
*PRECISION
RESISTOR
CORP
TYPE PT/ST
2kΩ
31.6kΩ
SCALE
FACTOR
TRIM
dB OUTPU
T
100mV/dB
RMS
CORE
AD737
BIAS
SECTION
INPUT
AMPLIFIER
8kΩ
8kΩ
1
2
3
4
8
7
6
5
3
6
2
V
IN
POWER
DOWN
–V
S
C
C
COM
OUTPUT
+V
S
NC
C
AV
C
AV
+
00828-030
C
C
10µF
NC = NO CONNECT
*Q1, Q2 PART OF RCA CA3046 OR SIMIL AR NP N TRANSI STOR ARRAY.
FULL-WAVE
RECTIFIER
Figure 31. dB Output Connection
COM
1
2
3
8
7
6
V
OUT
+V
S
–V
S
+V
S
C
C
V
IN
POWER
DOWN
AD737
INPUT
AMPLIFIER
OFFSET
A
DJUST
500kΩ
8kΩ
SCALE
FACTOR
ADJUST
1kΩ
1MΩ
1kΩ
499Ω
00828-031
FULL-WAVE
RECTIFIER
Figure 32. DC-Coupled Offset Voltage and Scale Factor Trims
AD737
Rev. H | Page 18 of
AD737 EVALUATION BOARD
An evaluation board, AD737-EVALZ, is available for experi-
ments or for becoming familiar with rms-to-dc converters.
Figure 33 is a photograph of the board; Figure 35 to Figure 38
show the signal and power plane copper patterns. The board is
designed for multipurpose applications and can be used for the
AD736 as well. Although not shipped with the board, an optional
socket that accepts the 8lead surface mount package is
available from Enplas Corp.
00828-033
Figure 35. AD737 Evaluation Board—Component-Side Copper
00828-038
Figure 33. AD737 Evaluation Board
00828-034
Figure 36. AD737 Evaluation Board—Secondary-Side Copper
00828-032
Figure 34. AD737 Evaluation Board—Component-Side Silkscreen
As described in the Applications Information section, the AD737
can be connected in a variety of ways. As shipped, the board is
configured for dual supplies with the high impedance input
connected and the power-down feature disabled. Jumpers are
provided for connecting the input to the low impedance input
(Pin 1) and for dc connections to either input. The schematic with
movable jumpers is shown in Figure 39. The jumper positions in
black are default connections; the dotted-outline jumpers are
optional connections. The board is tested prior to shipment and
requires only a power supply connection and a precision meter to
perform measurements. Table 7 provides a bill of materials for the
AD737 evaluation board.
00828-035
Figure 37. AD737 Evaluation Board—Internal Power Plane
00828-036
Figure 38. AD737 Evaluation Board—Internal Ground Plane
24
AD737
Rev. H | Page 19 of 24
J1
C1
10µF
25V
C2
10µF
25V
–VS
18
7
6
5
4
3
2CC
POWER
DOWN
COM
+VS
–VS
OUTPUT
CAV
+
VS
CIN
0.1µF
CAV
33
µ
F
16V
+
W1
DC
COUP
DUT
AD737
P2
HI-Z SEL
GND
IN HI-Z
W4
LO-Z IN
SEL
PIN3
FILT
PD
NORM
+
C4
0.1µF
J2
VOUT
+
C6
0.1µF
CC
+
R3
0Ω
CF2
R4
0Ω
W2
R1
1MΩ
–V
S+
V
VIN
S
–VS+VS
GND1 GND3GND2 GND4
CF1
W3
AC COUP
CAV
LO-Z
VIN +VS
00828-037
J3
Figure 39. AD737 Evaluation Board Schematic
Table 7. AD737 Evaluation Board Bill of Materials
Qty Name Description Reference Designator Manufacturer Mfg. Part Number
1 Test loop Red +VS Components Corp. TP-104-01-02
1 Test loop Green −VS Components Corp. TP-104-01-05
2 Capacitor Tantalum 10 μF, 25 V C1, C2 Nichicon F931E106MCC
3 Capacitor 0.1 μF, 16 V, 0603, X7R C4, C6, CIN KEMET C0603C104K4RACTU
1 Capacitor Tantalum 33 μF, 16V, 20%, 6032 CAV Nichicon F931C336MCC
5 Test loop Purple CAV, HI-Z, LO-Z, VIN, VOUT Components Corp. TP-104-01-07
1 Integrated circuit RMS-to-DC converter DUT Analog Devices, Inc. AD737JRZ
4 Test loop Black GND1, GND2, GND3, GND4 Components Corp. TP-104-01-00
2 Connector BNC, right angle J1, J2 AMP 227161-1
1 Header 6 pins, 2 × 3 J3 3M 929836-09-03
1 Header 3 pins P2 Molex 22-10-2031
1 Resistor 1 MΩ, 1/10 W, 1%, 0603 R1 Panasonic ERJ3EKF1004V
2 Resistor 0 Ω, 5%, 0603 R3, R4 Panasonic ERJ3GEY0R00V
4 Header 2 Pins, 0.1" center W1, W2, W3, W4 Molex 22-10-2021
AD737
Rev. H | Page 20 of 24
(I N PARENT HE S E S ) ARE RO UN DE D-OFF M ILLIMETER EQUIVALENTS FO R
REF E RENCE ON LY AND ARE NOT AP P R O PRIATE FOR US E IN DES IG N.
012407-
OUTLINE DIMENSIONS
CONTROLLI N G DI M E NS IO NS ARE I N M ILLI METERS ; INCH DIME NS IO NS
COM P LIANT TO JE DE C S TANDARDS MS- 012-AA
A
0.25 (0.0098)
0.17 (0.0067)
1.27 (0. 0500)
0.40 (0. 0157)
0.50 (0. 0196)
0.25 (0. 0099) 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.2 5 ( 0.009 8)
0.1 0 ( 0.004 0)
4
1
85
5.00 (0.1968)
4.80 (0.1890)
4.00 ( 0.157 4)
3.80 ( 0.149 7)
1.27 (0.0500)
BSC
6.20 (0. 2441)
5.80 (0. 2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
Figure 40. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
0.310 (7.87)
0.220 (5.59)
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
0.005 (0.13)
MIN 0.055 (1.40)
MAX
0.100 (2.54) BSC
15°
0°
0.320 (8.13)
0.290 (7.37)
0.015 (0.38)
0.008 (0.20)
SEATING
PLANE
0.200 (5.08)
MAX
0.405 (10.29) MAX
0.150 (3.81)
MIN
0.200 (5.08)
0.125 (3.18)
0.023 (0.58)
0.014 (0.36) 0.070 (1.78)
0.030 (0.76)
0.060 (1.52)
0.015 (0.38)
14
58
Figure 41. 8-Lead Ceramic Dual In-Line Package [CERDIP]
(Q-8)
Dimensions shown in inches and (millimeters)
AD737
Rev. H | Page 21 of 24
COM PLI ANT TO JEDEC S TANDARDS MS-001
CONT ROLLING DIM E NS IONS ARE I N INCHES; M ILLIMET ER DIMENSIONS
(IN PARENTHESES ) ARE ROUNDE D-OF F I NCH EQUI VALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIAT E F OR USE IN DES IGN.
CORNER LE ADS MAY BE CONFIG URED AS WHO L E O R HALF L EADS .
070606-A
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
SEATING
PLANE
0.015
(0.38)
MIN
0.210 (5.33)
MAX
0.150 ( 3.81)
0.130 ( 3.30)
0.115 (2. 92)
0.070 ( 1.78)
0.060 ( 1.52)
0.045 ( 1.14)
8
14
5
0.280 ( 7.11)
0.250 ( 6.35)
0.240 ( 6.10)
0.100 (2.54)
BSC
0.400 ( 10 .16)
0.365 ( 9.27)
0.355 ( 9.02)
0.060 ( 1 .52)
MAX
0.430 (10.92)
MAX
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
0.325 ( 8.26)
0.310 ( 7.87)
0.300 ( 7.62)
0.195 ( 4.95)
0.130 ( 3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
PLANE
0.005 (0.13)
MIN
Figure 42. 8-Lead Plastic Dual-In-Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
AD737
Rev. H | Page 22 of 24
ORDERING GUIDE
Model Temperature Range Package Description Package Option
AD737AN −40°C to +85°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737ANZ1
−40°C to +85°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737AQ −40°C to +85°C 8-Lead Ceramic Dual In-Line Package [CERDIP] Q-8
AD737AR −40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737ARZ1
−40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737BQ −40°C to +85°C 8-Lead Ceramic Dual In-Line Package [CERDIP] Q-8
AD737JN 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737JNZ1
0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737JR 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JR-REEL 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JR-REEL7 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JR-5 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JR-5-REEL 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JR-5-REEL7 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ1
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ-R71
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ-RL1
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ-51
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ-5-R71
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737JRZ-5-RL1
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KN 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737KNZ1
0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] N-8
AD737KR 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KR-REEL 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KR-REEL7 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KRZ1
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KRZ-RL1
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737KRZ-R71
0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] R-8
AD737-EVALZ1
Evaluation Board
1 Z = RoHS Compliant Part.
AD737
Rev. H | Page 23 of 24
NOTES
AD737
Rev. H | Page 24 of 24
NOTES
©2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00828-0-10/08(H)
