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)
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.
1
Protected under U.S. Patent Number 5,495,245.
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.
Low Cost, Low Power,True RMS-to-DC Converter
AD737
FUNCTIONAL BLOCK DIAGRAM
8kΩCAD737C18COMFULL-WAVEVRECTIFIERIN27+VSINPUT8kΩAMPLIFIERPOWER3BIASDOWNSECTIONRMS CORE6OUTPUT–VS45CAV100-82800
Figure 1.
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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved.
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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 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
Rev. H | Page 2 of 24
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AD737
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.
Parameter Conditions ACCURACY Total Error EIN = 0 to 200 mV rms ±VS = ±2.5 V
AD737A, AD737J AD737B, AD737K AD737J-5 in Typ ax in Typ ax in Typ ax Unit 0.2/0.3 ±mV/±POR1 0.4/0.5 0.2/0.2 0.2/0.3 0.2/0.3 0.4/0.5 ±mV/±POR1 0.2/0.3 0.4/0.5 ±mV/±POR1
±VS = ±2.5 V,
input to Pin 1
EIN = 200 mV to 1 V rms −1.2 −1.2 POR ±2.0 ±2.0 Over Temperature AQ and BQ EIN = 200 mV rms ±POR/°C 0.5/0.7 0.3/0.5
0.007 0.007 0.02 ±POR/°C JN, JR, KN, KR EIN = 200 mV rms,
±VS = ±2.5 V
AN and AR EIN = 200 mV rms, 0.014 0.014 ±POR/°C
±VS = ±2.5 V
Vs. Supply Voltage EIN = 200 mV rms, −0.18 %/V 0 −0.3 0 −0.18 −0.3 0 −0.18 −0.3
±VS = ±2.5 V to ±5 V
EIN = 200 mV rms, 0.06 %/V 0 0.1 0 0.06 0.1 0 0.06 0.1
±VS = ±5 V to ±16.5 V
DC Reversal Error DC coupled, 1.3 2.5 1.3 2.5 POR
VIN = 600 mV dc
M M M M 1.7 2.5 M VIN = 200 mV dc, M POR
±VS = ±2.5 V
Nonlinearity2 EIN = 0 mV to 0.25 POR 0 0.35 0 0.25 0.35
200 mV rms, @ 100 mV rms 3
Input to Pin 1 AC coupled, 0.02 0.1 POR
EIN = 100 mV rms, after correction, ±VS = ±2.5 V
Total Error, EIN = 0 mV to 0.1/0.2 0.1/0.2 0.1/0.2 ±mV/±POR External Trim 200 mV rms ADDITIONAL CREST FACTOR ERROR4
For Crest Factors CAV = CF = 100 μF 0.7 0.7 % from 1 to 3 CAV = 22 μF, CF = 100 μF, 1.7 %
±VS = ±2.5 V, input to Pin 1
For Crest Factors CAV = CF = 100 μF 2.5 2.5 % from 3 to 5 INPUT CHARACTERISTICS High-Z Input (Pin 2) Signal Range Continuous ±VS = +2.5 V mV rms 200 RMS Level
±VS = +2.8 V/−3.2 V mV rms 200 200 ±VS = ±5 V to ±16.5 V V rms 1 1
Rev. H | Page 3 of 24
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AD737
AD737A, AD737J AD737B, AD737K AD737J-5 Parameter Conditions in Typ ax in Typ ax in Typ ax Unit Peak Transient ±VS = +2.5 V input to V ±0.6 Input Pin 1
±VS = +2.8 V/−3.2 V V ±0.9 ±0.9 ±VS = ±5 V ±2.7 ±2.7 V ±VS = ±16.5 V V ±4.0 ±4.0 Input Resistance 1012 1012 1012 Ω Input Bias ±VS = ±5 V 1 25 1 25 1 25 pA Current Low-Z Input (Pin 1) Signal Range
Continuous ±VS = +2.5 V 300 mV rms RMS Level
±VS = +2.8 V/−3.2 V 300 300 mV rms ±VS = ±5 V to ±16.5 V 1 1 V rms Peak Transient ±VS = +2.5 V ±1.7 V Input
±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
All supply voltages ±12 ±12 ±12 V p-p Maximum
Continuous Nondestructive Input
AC coupled mV Input Offset ±3 ±3 ±3
Voltage5
8 30 8 30 8 30 μV/°C Over the Rated
Operating Temperature Range Vs. Supply VS = ±2.5 V to ±5 V 80 80 80 μV/V VS = ±5 V to ±16.5 V 50 150 50 150 μV/V OUTPUT No load CHARACTERISTICS MMMMMMOutput Voltage ±VS = +2.8 V/−3.2 V −1.6 −1.7 −1.6 −1.7 V Swing
±VS = ±5 V −3.3 −3.4 −3.3 −3.4 V ±VS = ±16.5 V V −4 −5 −4 −5 ±VS = ±2.5 V, input to −1.1 –0.9 V
Pin 1
Output DC 6.4 8 9.6 6.4 8 9.6 6.4 8 9.6 kΩ Resistance FREQUENCY RESPONSE High-Z Input (Pin 2)
1% Additional VIN = 1 mV rms 1 1 1 kHz Error VIN = 10 mV rms 6 6 6 kHz VIN = 100 mV rms 37 37 37 kHz VIN = 200 mV rms 33 33 33 kHz
Rev. H | Page 4 of 24
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AD737
AD737A, AD737J AD737B, AD737K AD737J-5 Parameter Conditions in Typ ax in Typ ax in Typ ax Unit 3 dB Bandwidth VIN = 1 mV rms 5 5 5 kHz VIN = 10 mV rms 55 55 55 kHz VIN = 100 mV rms 170 170 170 kHz VIN = 200 mV rms 190 190 190 kHz Low-Z Input (Pin 1)
1% Additional VIN = 1 mV rms 1 1 1 kHz Error VIN = 10 mV rms 6 6 6 kHz VIN = 40 mV rms 25 kHz VIN = 100 mV rms 90 90 90 kHz VIN = 200 mV rms 90 90 90 kHz 3 dB Bandwidth VIN = 1 mV rms 5 5 5 kHz VIN = 10 mV rms 55 55 55 kHz VIN = 100 mV rms 350 350 350 kHz VIN = 200 mV rms 460 460 460 kHz POWER-DOWN MODE
Disable Voltage 0 0 V Input Current, VPD = VS 11 11 μA PD Enabled POWER SUPPLY Operating +2.8/ ±5 ±16.5 +2.8/ ±5 ±16.5 ±2.5 ±5 ±16.5 V Voltage Range −3.2 −3.2 Current No input 120 120 120 μA 160 160 160 Rated input 170 210 170 210 170 210 μA Powered down 25 40 25 40 25 40 μA POR is % of reading.
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
MMMMMMVPEAK/V rms.
5
DC offset does not limit ac resolution.
12
Rev. H | Page 5 of 24
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AD737
ABSOLUTE MAXIMUM RATINGS
Table 2.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device Parameter Rating soldered in a circuit board for surface-mount packages. Supply Voltage ±16.5 V
Internal Power Dissipation 200 mW
Table 3. Thermal Resistance
Input Voltage ±VS
Package Type θJA Unit Output Short-Circuit Duration Indefinite
8-Lead CERDIP (Q-8) 110 °C/W Differential Input Voltage +VS and −VS
8-Lead PDIP (N-8) 165 °C/W Storage Temperature Range
8-Lead SOIC_N (R-8) 155 °C/W 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 CAUTION
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.
Rev. H | Page 6 of 24
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AD737
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
CC1VIN2POWER DOWN38COM+VS00828-002CC1VIN2POWER DOWN38AD7377AD737COM+VS7CC1VIN200828-0038COM+VSCAV00828-0046OUTPUTTOP VIEW(Not to Scale)–VS45CAV
TOP VIEW6OUTPUT(Not to Scale)5CAV–VS4AD737TOP VIEW(Not to Scale)765POWER DOWN3–VS4OUTPUTFigure 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.
Rev. H | Page 7 of 24
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AD737
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.
0.7VIN = 200mV rmsCAV = 100µFCF = 22µF10VCAV = 22µF, CF = 4.7µF, CC = 22µF1VADDITIONAL ERROR (% of Reading)0.50.3INPUT LEVEL (rms)100mV1% ERROR10mV0.10–0.1–3dB–0.300828-0051mV00828-00810% ERROR100µV0.1–0.50246810SUPPLY VOLTAGE (±V)121416110FREQUENCY (kHz)1001000Figure 5. Additional Error vs. Supply Voltage
16DC COUPLEDPEAK INPUT BEFORE CLIPPING (V)Figure 8. Frequency Response Driving Pin 1
10VCAV = 22µF, CF = 4.7µF, CC = 22µF1V141210PIN 18PIN 21mV00828-006INPUT LEVEL (rms)100mV1% ERROR10mV10% ERROR–3dB100µV0.100246810SUPPLY VOLTAGE (±V)121416110FREQUENCY (kHz)1001000Figure 6. Maximum Input Level vs. Supply Voltage
256Figure 9. Frequency Response Driving Pin 2
3ms BURST OF 1kHz =3 CYCLES200mV rms SIGNALCC = 22µFCF = 100µFADDITIONAL ERROR (% of Reading)5CAV = 10µFSUPPLY CURRENT (µA)204CAV = 33µF15321000828-0071CAV = 250µF01234CRESTFACTOR (VPEAK/V rms)502468101214DUAL SUPPLY VOLTAGE (±V)16185
Figure 7. Supply Current (Power-Down Mode) vs. Supply Voltage (Dual) Figure 10. Additional Error vs. Crest Factor
Rev. H | Page 8 of 24
00828-010CAV = 100µF00828-0092元器件交易网www.cecb2b.com
0.80.60.40.20–0.2–0.400828-011AD737
1.0ADDITIONAL ERROR (% of Reading)VIN = 200mV rmsCAV = 100µFCF = 22µFERROR (% of Reading)0.50–0.5–1.0–1.5–2.0–0.8–60–40–20020406080TEMPERATURE (°C)100120140–2.510mV100mVINPUT LEVEL (rms)1V2VFigure 11. Additional Error vs. Temperature
500Figure 14. Error vs. RMS Input Level Using Circuit in Figure 30
100VIN = 200mV rmsCC = 47µFCF = 47µF300AVERAGING CAPACITOR (µF)400DC SUPPLY CURRENT (µA)10–0.5%20010000828-012–1%00828-015000.20.40.6RMS INPUT LEVEL (V)0.81.0110100FREQUENCY (Hz)1kFigure 12. DC Supply Current vs. RMS Input Level
Figure 15. Value of Averaging Capacitor vs. Frequency
for Specified Averaging Error
1V10mVAC COUPLED–1%–0.5%INPUT LEVEL (rms)INPUT LEVEL (rms)1mV100mV100µV10mV00828-01310µV1001k10k–3dB FREQUENCY (Hz)100k1mV110FREQUENCY (Hz)1001kFigure 13. RMS Input Level vs. –3 dB Frequency Figure 16. RMS Input Level vs. Frequency for Specified Averaging Error
Rev. H | Page 9 of 24
00828-016AC COUPLEDCAV = 10µF, CC = 47µF,CF = 47µF00828-014–0.6CAV = 22µF, CC = 47µF,CF = 4.7µF元器件交易网www.cecb2b.com
AD737
4.010nA3.51nAINPUT BIAS CURRENT00828-017INPUT BIAS CURRENT (pA)3.0100pA2.510pA2.01.51pA00828-0191.00246810SUPPLY VOLTAGE (±V)121416100fA–55–35–155254565TEMPERATURE (°C)85105125Figure 17. Input Bias Current vs. Supply Voltage
1VCC = 22µFCF = 0µF1V100mVINPUT LEVEL (rms)INPUT LEVEL (rms)Figure 19. Input Bias Current vs. Temperature
10VVS=±2.5V,CAV = 22µF, CF = 4.7µF, CC = 22µFCAV = 10µF10mVCAV = 33µFCAV = 100µF100mV10mV1mV1mV00828-01800828-020100µV1ms10ms100ms1sSETTLING TIME10s100s100µV0.1110FREQUENCY (kHz)1001000Figure 18. RMS Input Level vs. Settling Time for Three Values of CAV Figure 20. Frequency Response Driving Pin 1
Rev. H | Page 10 of 24
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10VVS=±2.5V,CAV = 22µF, CF = 4.7µF, CC = 22µF1.00.5AD737
1VERROR (% of Reading)10%–3dB00828-021INPUT LEVEL (rms)0–0.5–1.0–1.5–2.0100mV0.5%10mV1mV1%100µV0.1110FREQUENCY (kHz)1001000–2.510mV100mVINPUT LEVEL (rms)1V2VFigure 21. Error Contours Driving Pin 1
53 CYCLES OF 1kHz200mV rmsVS = ±2.5VCC = 22µFCF = 100µFCAV =10µFFigure 23. Error vs. RMS Input Level Driving Pin 1
ADDITIONAL ERROR (% of Reading)4CAV =22µFCAV =100µF3CAV =33µF2CAV =220µF00828-02210123CRESTFACTOR45Figure 22. Additional Error vs. Crest Factor for Various Values of CAV
Rev. H | Page 11 of 24
00828-023CAV = 22µF, VS = ±2.5VCC = 47µF, CF = 4.7µF元器件交易网www.cecb2b.com
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 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.
ACCC =10µF +DCOPTIONAL RETURNPATHCURRENTMODEABSOLUTEVALUECC18external 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
8kΩVINVINCOM+28kΩFETOPAMP1B<10pA7+VSCF10µF(OPTIONALLPF)POWERDOWN3BIASSECTION6OUTPUTRMSTRANSLINEARCORE–VS45CAVV rms = Avg(V2)
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
VOUT = Avg(VIN)
CA33µF+POSITIVE SUPPLYCOMMON0.1µFNEGATIVE SUPPLY0.1µF+VS00828-024–VS
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
Rev. H | Page 12 of 24
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AD737
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.
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.
EOIDEALEODC ERROR = EO – EO (IDEAL)AVERAGE EO = EO00828-026DOUBLE-FREQUENCYRIPPLETIME
Figure 25. Output Waveform for Sine Wave Input Voltage
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.
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.
Table 5. Error Introduced by an Average Responding Circuit When Measuring Common Waveforms
True RMSReading of an Average Responding Circuit Calibrated to Type of Waveform Crest Factor
Value (V) an RMS Sine Wave Value (V) 1 V Peak Amplitude (VPEAK/V rms)
Undistorted Sine Wave 1.414 0.707 0.707 Symmetrical Square Wave 1.00 1.00 1.11 Undistorted Triangle Wave 1.73 0.577 0.555 Gaussian Noise (98% of
3 0.333 0.295 Peaks <1 V)
Rectangular 2 0.5 0.278 Pulse Train 10 0.1 0.011 SCR Waveforms 50% Duty Cycle 2 0.495 0.354 25% Duty Cycle 4.7 0.212 0.150
Error (%)
0 11.0 −3.8
−11.4 −44 − −28 −30
Rev. H | Page 13 of 24
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AD737
APPLICATIONS INFORMATION
RMS MEASUREMENT—CHOOSING AN OPTIMUM VALUE FOR CAV
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.
VINRMS1MΩ1CCCOM8+2.5VVOUTDC72VAD737+VSIN34–VSOUTCAV6533µFrmsAVG–2.5V33µFNTR4501NT1ASSUMED TOBE A LOGICSOURCE00828-039
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
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.
8kΩ1FL=
1
(1)
2π×8000×CC(inFarads)CCAD737FULL-WAVERECTIFIERINPUTAMPLIFIER8kΩ8COMVIN7+VSNote 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.
2+CF33µFPOWER3DOWNBIASSECTION6VOUTOUTPUTRMSCORE5CAVSCALING 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.
00828-025–VS4POSITIVE SUPPLY0.1µFCOMMON0.1µFNEGATIVE SUPPLY+VSExtending or Scaling the Input Range
–VSFigure 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.
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.
Rev. H | Page 14 of 24
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AD737
Next, using the IOUTMAG value from Equation 2, calculate the feedback resistor required for 6 V output using
RFB=
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.
6 V
=48.1 kΩ (3)
125 μA
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.
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
IINMAG=
10 V
=125 μA=IOUTMAG (2)
69.8 kΩ +2.5 kΩ +8 kΩ
Table 6. AD737 Capacitor Selection
Application
General-Purpose RMS Computation
General-Purpose Average Responding
SCR Waveform Measurement
Audio Applications Speech Music
1
RMS Input Level 0 V to 1 V
0 mV to 200 mV
0 V to 1 V
0 mV to 200 mV
0 mV to 200 mV
0 mV to 100 mV
0 mV to 200 mV 0 mV to 100 mV
Low Frequency Cutoff (−3 dB) 20 Hz 200 Hz 20 Hz 200 Hz 20 Hz 200 Hz 20 Hz 200 Hz 50 Hz 60 Hz 50 Hz 60 Hz
300 Hz 20 Hz
Maximum Crest Factor 5 5 5 5 5 5 5 5 3 10
CAV (μF) 150 15 33 3.3 None None None None 100 82 50 47 1.5 100
CF (μF) 10 1 10 1 33 3.3 33 3.3 33 27 33 27 0.5 68
Settling Time1 to 1% 360 ms 36 ms 360 ms 36 ms 1.2 sec 120 ms 1.2 sec 120 ms 1.2 sec 1.0 sec 1.2 sec 1.0 sec
18 ms 2.4 sec
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.
Rev. H | Page 15 of 24
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AD737
SWITCH CLOSEDACTIVATESPOWER-DOWNMODE.AD737 DRAWSJUST 40µA IN THIS MODE1PRV0.01µFVIN9MΩ2V900kΩ20V90kΩ200V10kΩ47kΩ1W1N41483CC10µF++1µF20kΩ+VSAD5CC8kΩ1200mV1N4148AD737FULL-WAVERECTIFIERINPUTAMPLIFIER8kΩCOM81.23V200kΩ31/2 DIGIT ICL7136TYPE CONVERTERREF HIGHREF LOWCOMMON50kΩVIN2+VS7+VPOWERDOWN–VS4BIASSECTIONOUTPUT61MΩ0.1µFLOWANALOGHIGH+9VCAVRMSCORE51µF00828-027++33µF–VS
Figure 28. 3½ Digit DVM Circuit
INPUT SCALEFACTORADJR1R2C169.8kΩ5kΩ0.47µF1%1INPUTCCCOM8NC5VR378.7kΩR45kΩCF0.47µFR580.6kΩ5VOUTPUT ZEROADJUST22VIN+VS7C20.01µF3AD737POWERDOWNOUTPUT60.01µF17AD8541AR3546OUTPUT4–VSCAV5C30.01µF+CAV33µF5VC42.2µFR7100kΩ2.5V00828-028C5+1µFNC = NO CONNECTR8100kΩ
Figure 29. Battery-Powered Operation for 200 mV Maximum RMS Full-Scale Input
CC10µF+100ΩSCALEFACTORADJUSTCOM8CC8kΩ1AD737FULL-WAVERECTIFIERINPUTAMPLIFIER8kΩ200Ω+VIN27+VSCF10µFPOWER3DOWN–VS4OUTPUT6BIASSECTIONVOUTRMSCORECAV5CAV33µF00828-029+
Figure 30. External Scale Factor Trim
Rev. H | Page 16 of 24
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13Q114CC10µFCC+12*8NCAD737
1kΩ3500PPM/°C60.4ΩSCALEFACTORTRIMPRECISIONRESISTORCORPTYPE PT/ST2kΩ31.6kΩ28kΩ1AD737COMFULL-WAVERECTIFIERINPUTAMPLIFIER8kΩVIN27+VSPOWER3DOWNOUTPUT6BIASSECTIONAD7116dB OUTPUT100mV/dB–VSCAV34RMSCORE5+10Q2*11CAVRCAL**R1**IREF9NC = NO CONNECT*Q1, Q2PART OF RCA CA3046 OR SIMILAR NPN TRANSISTORARRAY.**R1 + R INΩ = 10,000 ×4.3VCAL0dB INPUT LEVEL IN VFigure 31. dB Output Connection
OFFSETADJUST
500kΩ+VS–VS1MΩ1kΩCC8kΩCOM499Ω1AD73781kΩFULL-WAVESCALEFACTORVIN2RECTIFIER7+VADJUSTINPUTSAMPLIFIERPOWER1336VOUT0DOWN-82800 Figure 32. DC-Coupled Offset Voltage and Scale Factor Trims
Rev. H | Page 17 of 24
030-82800
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AD737
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
00828-03400828-032
Figure 36. AD737 Evaluation Board—Secondary-Side Copper
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
Rev. H | Page 18 of 24
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AD737
GND1GND2GND3GND4C1+10µF25V
W1DCCOUP–VS+VSW3AC COUP+–VS+VS+C210µF25VW4LO-Z INLO-ZR30ΩCCVINJ1CIN0.1µFP2HI-Z SELINHI-ZAD7371CC2VINCOM+VS87DUTR40ΩVOUTJ2CF1H
GNDR11MΩW23POWERDOWNOUTPUT6+VS+VSC60.1µFCAV4–VS–VSCAV33µF16V+CAV5J3PDFILTNORMSELPIN300828-037C40.1µFCF2
Figure 39. AD737 Evaluation Board Schematic
Table 7. AD737 Evaluation Board Bill of Materials
Qty Name 1 Test loop 1 Test loop 2 Capacitor 3 Capacitor 1 Capacitor 5 Test loop 1 Integrated circuit 4 Test loop 2 Connector 1 Header
1 eader 1 Resistor 2 Resistor 4 Header
Description
Red Green
Tantalum 10 μF, 25 V 0.1 μF, 16 V, 0603, X7R
Tantalum 33 μF, 16V, 20%, 6032 Purple
RMS-to-DC converter Black
BNC, right angle 6 pins, 2 × 3 3 pins
1 MΩ, 1/10 W, 1%, 0603 0 Ω, 5%, 0603 2 Pins, 0.1\" center
Reference Designator Manufacturer Mfg. Part Number +VS Components Corp. TP-104-01-02 −VS Components Corp. TP-104-01-05 C1, C2 Nichicon F931E106MCC C4, C6, CIN KEMET C0603C104K4RACTU CAV Nichicon F931C336MCC CAV, HI-Z, LO-Z, VIN, VOUTComponents Corp. TP-104-01-07 DUT Analog Devices, Inc. AD737JRZ GND1, GND2, GND3, GND4 Components Corp. TP-104-01-00 J1, J2 AMP 227161-1 J3 3M 929836-09-03 P2 Molex 22-10-2031 R1 Panasonic ERJ3EKF1004V R3, R4 Panasonic ERJ3GEY0R00V W1, W2, W3, W4 Molex 22-10-2021
Rev. H | Page 19 of 24
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AD737
OUTLINE DIMENSIONS
5.00(0.1968)4.80(0.10)4.00 (0.1574)3.80 (0.1497)81546.20 (0.2441)5.80 (0.2284)1.27 (0.0500)BSC1.75 (0.0688)0.50 (0.0196)45°0.25 (0.0099)0.25 (0.0098)1.35 (0.0532)0.10 (0.0040)8°0°COPLANARITY0.51 (0.0201)0.10SEATING0.31 (0.0122)0.25 (0.0098)1.27 (0.0500)PLANE0.17 (0.0067)0.40 (0.0157)COMPLIANTTO JEDEC STANDARDS MS-012-AACONTROLLING DIMENSIONSARE IN MILLIMETERS; INCH DIMENSIONS(INPARENTHESES)ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FORREFERENCE ONLYANDARE NOTAPPROPRIATE FOR USE IN DESIGN.Figure 40. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
0.005 (0.13)MIN0.055 (1.40)MAX850.310 (7.87)0.220 (5.59)140.100 (2.54) BSC0.405 (10.29) MAX0.320 (8.13)0.290 (7.37)0.200 (5.08)0.060 (1.52)MAX0.015 (0.38)0.200 (5.08)0.150 (3.81)0.125 (3.18)MIN0.023 (0.58)SEATING0.015 (0.38)0.014 (0.36)0.070 (1.78)PLANE15°0.030 (0.76) 0°0.008 (0.20)CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FORREFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 41. 8-Lead Ceramic Dual In-Line Package [CERDIP]
(Q-8)
Dimensions shown in inches and (millimeters)
Rev. H | Page 20 of 24
-A704210
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0.400 (10.16)0.365 (9.27)0.355 (9.02)815AD737
40.280 (7.11)0.250 (6.35)0.240 (6.10)0.100 (2.54)0.325 (8.26)0.310 (7.87)0.300 (7.62)BSC0.060 (1.52)0.210 (5.33)MAX0.195 (4.95)MAX0.130 (3.30)0.150 (3.81)0.0150.115 (2.92)(0.38)0.015 (0.38)0.130 (3.30)MINGAUGE0.115 (2.92)SEATINGPLANE0.014 (0.36)PLANE0.010 (0.25)0.022 (0.56)0.018 (0.46)0.005 (0.13)0.430 (10.92)0.008 (0.20)MAX0.014 (0.36)MIN0.070 (1.78)0.060 (1.52)0.045 (1.14)COMPLIANTTO JEDEC STANDARDS MS-001CONTROLLING DIMENSIONSARE IN INCHES; MILLIMETER DIMENSIONS(INPARENTHESES)ARE ROUNDED-OFF INCH EQUIVALENTS FORREFERENCE ONLYANDARE NOTAPPROPRIATE FOR USE IN DESIGN.CORNER LEADS MAY BE CONFIGUREDAS WHOLE OR HALF LEADS.Figure 42. 8-Lead Plastic Dual-In-Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
Rev. H | Page 21 of 24
A-606070
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AD737
ORDERING GUIDE
Model AD737AN AD737ANZ1AD737AQ AD737AR AD737ARZ1AD737BQ AD737JN AD737JNZ1AD737JR
AD737JR-REEL AD737JR-REEL7 AD737JR-5
AD737JR-5-REEL AD737JR-5-REEL7 AD737JRZ1
AD737JRZ-R71AD737JRZ-RL1AD737JRZ-51
AD737JRZ-5-R71AD737JRZ-5-RL1AD737KN AD737KNZ1AD737KR
AD737KR-REEL AD737KR-REEL7 AD737KRZ1
AD737KRZ-RL1AD737KRZ-R71AD737-EVALZ1
Temperature Range Package Description −40°C to +85°C 8-Lead Plastic Dual In-Line Package [PDIP] −40°C to +85°C 8-Lead Plastic Dual In-Line Package [PDIP] −40°C to +85°C 8-Lead Ceramic Dual In-Line Package [CERDIP] −40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] −40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] −40°C to +85°C 8-Lead Ceramic Dual In-Line Package [CERDIP] 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] 0°C to 70°C 8-Lead Plastic Dual In-Line Package [PDIP] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] 0°C to 70°C 8-Lead Standard Small Outline Package [SOIC_N] Evaluation Board Package Option
N-8 N-8 Q-8 R-8 R-8 Q-8 N-8 N-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 R-8 N-8 N-8 R-8 R-8 R-8 R-8 R-8 R-8
1
Z = RoHS Compliant Part.
Rev. H | Page 22 of 24
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AD737
NOTES
Rev. H | Page 23 of 24
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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. H | Page 24 of 24
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