High Precision, Wideband RMS-to-DC Converter AD637 Data Sheet FEATURES FUNCTIONAL BLOCK DIAGRAM BUFF IN + BUFF OUT – 25kΩ VIN SQUARER/ DIVIDER ABSOLUTE VALUE RMS OUT – + DEN INPUT 25kΩ – CAV + OUTPUT OFFSET dB OUTPUT BIAS COMMON CS 00788-001 High accuracy 0.02% maximum nonlinearity, 0 V to 2 V rms input 0.1% additional error to crest factor of 3 Wide bandwidth 8 MHz at 2 V rms input 600 kHz at 100 mV rms Computes True rms Square Mean square Absolute value dB output (60 dB range) Chip select/power-down feature allows Analog three-state operation Quiescent current reduction from 2.2 mA to 350 µA Figure 1. GENERAL DESCRIPTION The AD637 is a complete, high accuracy, rms-to-dc converter that computes the true rms value of any complex waveform. It offers performance that is unprecedented in integrated circuit rms-to-dc converters and comparable to discrete and modular techniques in accuracy, bandwidth, and dynamic range. The AD637 computes the true root mean square, mean square, or absolute value of any complex ac (or ac plus dc) input waveform and gives an equivalent dc output voltage. The true rms value of a waveform is more useful than an average rectified signal because it relates directly to the power of the signal. The rms value of a statistical signal relates to the standard deviation of the signal. Superior crest factor compensation permits measurements of signals with crest factors of up to 10 with less than 1% additional error. The wide bandwidth of the AD637 permits the measurement of signals up to 600 kHz with inputs of 200 mV rms and up to 8 MHz when the input levels are above 1 V rms. Direct dB value of the rms output with a range of 60 dB is available on a separate pin. An externally programmed reference current allows the user to select the 0 dB reference voltage to correspond to any level between 0.1 V and 2.0 V rms. A chip select connection on the AD637 permits the user to decrease the supply current from 2.2 mA to 350 µA during periods when the rms function is not in use. This feature Rev. L facilitates the addition of precision rms measurement to remote or handheld applications where minimum power consumption is critical. In addition, when the AD637 is powered down, the output goes to a high impedance state. This allows several AD637s to be tied together to form a wideband true rms multiplexer. The input circuitry of the AD637 is protected from overload voltages in excess of the supply levels. The inputs are not damaged by input signals if the supply voltages are lost. The AD637 is laser wafer trimmed to achieve rated performance without external trimming. The only external component required is a capacitor that sets the averaging period. The value of this capacitor also determines low frequency accuracy, ripple level, and settling time. The on-chip buffer amplifier is used either as an input buffer or in an active filter configuration. The filter can be used to reduce the amount of ac ripple, thereby increasing accuracy. The AD637 is available in accuracy Grade J and Grade K for commercial temperature range (0°C to 70°C) applications, accuracy Grade A and Grade B for industrial range (−40°C to +85°C) applications, and accuracy Grade S rated over the −55°C to +125°C temperature range. All versions are available in hermetically sealed, 14-lead SBDIP, 14-lead CERDIP, and 16-lead SOIC_W packages. Document Feedback 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. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2015 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD637 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Offset Trim .............................................................................. 14 Functional Block Diagram .............................................................. 1 Scale Factor Trim ................................................................... 14 General Description ......................................................................... 1 Choosing the Averaging Time Constant ................................. 14 Revision History ............................................................................... 3 Frequency Response .................................................................. 16 Specifications..................................................................................... 4 AC Measurement Accuracy and Crest Factor ........................ 17 Absolute Maximum Ratings .......................................................... 10 Connection for dB Output ........................................................ 17 ESD Caution ................................................................................ 10 dB Calibration ............................................................................. 18 Pin Configurations and Function Descriptions ......................... 11 Low Frequency Measurements ................................................. 19 Theory of Operation ...................................................................... 12 Vector Summation ..................................................................... 19 Applications Information .............................................................. 13 Evaluation Board ............................................................................ 21 Standard Connection ................................................................. 13 Outline Dimensions ....................................................................... 24 Chip Select ................................................................................... 13 Ordering Guide .......................................................................... 25 Optional Trims for High Accuracy .......................................... 13 Rev. L | Page 2 of 25 Data Sheet AD637 REVISION HISTORY 4/15—Rev. K to Rev. L 10/06—Rev. H to Rev. I Changes to Features Section, Figure 1, and General Description Section ................................................................................................ 1 Changes to Table 1 ............................................................................ 4 Added Table 2; Renumbered Sequentially ..................................... 6 Added Table 3 .................................................................................... 8 Changed Pin NC to Pin NIC (Throughout) ................................11 Changes to Theory of Operation Section and Figure 4 .............12 Changes to Figure 5.........................................................................13 Changes to Optional Trims for High Accuracy Section and Figure 8; Added Offset Trim Section and Scale Factor Trim Section...............................................................................................14 Changes to Choosing the Averaging Time Constant and Figure 11 ...........................................................................................15 Changes to Figure 20 ......................................................................19 Changes to Figure 21 ......................................................................20 Changes to Ordering Guide ...........................................................26 Changes to Table 1 ............................................................................ 3 Changes to Figure 4 .......................................................................... 7 Changes to Figure 7 .......................................................................... 9 Changes to Figure 16, Figure 18, and Figure 19 .......................... 12 Changes to Figure 20 ...................................................................... 13 12/05—Rev. G to Rev. H Updated Format ................................................................. Universal Changes to Figure 1 .......................................................................... 1 Changes to Figure 11 ...................................................................... 10 Updated Outline Dimensions........................................................ 16 Changes to Ordering Guide ........................................................... 17 4/05—Rev. F to Rev. G Changes to Figure 15 ......................................................................11 Changes to Figure 16 ......................................................................12 Changes to Evaluation Board Section and Figure 23 .................16 Added Figure 24; Renumbered Sequentially ...............................17 Changes to Figure 25 Through Figure 29 ....................................17 Changes to Figure 30 ......................................................................18 Added Figure 31 ..............................................................................18 Deleted Table 6; Renumbered Sequentially .................................18 Changes to Ordering Guide ...........................................................20 Updated Format ................................................................. Universal Changes to Figure 1 .......................................................................... 1 Changes to General Description ..................................................... 1 Deleted Product Highlights ............................................................. 1 Moved Figure 4 to Page .................................................................... 8 Changes to Figure 5 .......................................................................... 9 Changes to Figure 8 ........................................................................ 10 Changes to Figure 11, Figure 12, Figure 13, and Figure 14 ....... 11 Changes to Figure 19 ...................................................................... 14 Changes to Figure 20 ...................................................................... 14 Changes to Figure 21 ...................................................................... 16 Updated Outline Dimensions........................................................ 17 Changes to Ordering Guide ........................................................... 18 4/07—Rev. I to Rev. J 3/02—Rev. E to Rev. F Added Evaluation Board Section ..................................................16 Updated Outline Dimensions ........................................................20 Edits to Ordering Guide ................................................................... 3 2/11—Rev. J to Rev. K Rev. L | Page 3 of 25 AD637 Data Sheet SPECIFICATIONS At 25°C, test frequency = 1 kHz, VIN units are VRMS, VS = ±15 V dc, unless otherwise noted. Table 1. Parameter TRANSFER FUNCTION CONVERSION ACCURACY Total Error, Internal Trim TMIN to TMAX vs. Supply DC Reversal Nonlinearity Total Error ERROR VS. CREST FACTOR (CF) AVERAGING TIME CONSTANT INPUT CHARACTERISTICS Signal Range Input Resistance Input Offset Voltage FREQUENCY RESPONSE Bandwidth for 1% (0.09 dB) Additional Error Test Conditions/Comments Min AD637J/AD637A Typ Max VOUT = avg (VIN ) See Figure 5 VIN = 300 mV VIN = −300 mV −2 V < VIN < +2 V 2 V full scale 7 V full scale External trim Additional, at 1 V rms For CF = 1 to 2 For CF = 3 For CF = 10 30 100 ±1 ± 0.5 ±3.0 ± 0.6 150 300 0.25 0.04 0.05 ±0.5 ± 0.1 Specified accuracy ±0.1 ±1.0 25 VS = ±15 V Continuous Transient VS = ±5 V Continuous Transient 0 to 7 8 mV rms ±% of reading mV ± % of reading μV/V μV/V % of reading % of FSR % of FSR mV ± % of reading CF, % % of reading % of reading ms/μF CAV ±15 V rms V p-p ±6 9.6 ±0.5 V rms V p-p kΩ mV 0 to 4 6.4 Unit 2 VIN = 20 mV VIN = 200 mV VIN = 2 V 11 66 200 kHz kHz kHz VIN = 20 mV VIN = 200 mV VIN = 2 V 150 1 8 kHz MHz MHz vs. temperature ±0.05 13.5 2.2 ±3 dB OUTPUT CHARACTERISTICS Offset Voltage Voltage Swing, 2 kΩ load 0 to 12.0 0 to 2 6 VS = ±3 V Output Current Short-Circuit Current Resistance Resistance 20 0.5 100 CS high CS low Rev. L | Page 4 of 25 ±1 ±0.089 mV mV/°C V V mA mA Ω kΩ Data Sheet Parameter dB OUTPUT Error Scale Factor Scale Factor Tempco IREF for 0 dB = 1 V rms IREF Range BUFFER AMPLIFIER Input Output Voltage Range Input Offset Voltage Input Current Input Resistance Output Current Short-Circuit Current Small Signal Bandwidth Slew Rate DENOMINATOR INPUT Input Range Input Resistance Offset Voltage CHIP SELECT (CS) RMS On Level RMS Off Level IOUT of Chip Select AD637 Test Conditions/Comments Min VIN = 7 mV to 7 V rms, 0 dBV 5 1 2 kΩ load, to −VS AD637J/AD637A Typ Max ±0.5 −3 +0.33 −0.033 20 80 100 −VS to (+VS − 2.5) ±0.8 ±2 ±2 ±10 108 −0.13 +5 20 1 5 20 0 to 10 25 ±0.2 30 ±0.5 Open or 2.4 < VC < +VS VC < 0.2 VC < 0.2 CS low CS high 10 0 10 + ((25 kΩ) × CAV) 10 + ((25 kΩ) × CAV) On Time Constant Off Time Constant POWER SUPPLY Operating Voltage Range Quiescent Current Standby Current ±3.0 2.2 350 Rev. L | Page 5 of 25 ±18 3 450 Unit dBV mV/dB % of reading/°C dB/°C µA µA V mV nA Ω mA mA MHz V/µs V kΩ mV V V µA µA µs µs V mA µA AD637 Data Sheet Table 2. Parameter TRANSFER FUNCTION CONVERSION ACCURACY Total Error, Internal Trim TMIN to TMAX vs. Supply DC Reversal Nonlinearity Total Error ERROR VS. CREST FACTOR (CF) AVERAGING TIME CONSTANT INPUT CHARACTERISTICS Signal Range Input Resistance Input Offset Voltage FREQUENCY RESPONSE Bandwidth for 1% (0.09 dB) Additional Error Test Conditions/Comments Min AD637K/AD637B Typ Max VOUT = avg (VIN ) See Figure 5 VIN = 300 mV VIN = −300 mV −2 V < VIN < +2 V 2 V full scale 7 V full scale External trim Additional, at 1 V rms For CF = 1 to 2 For CF = 3 For CF = 10 30 100 ±0.5 ± 0.2 ±2.0 ± 0.3 150 300 0.1 0.02 0.05 ±0.25 ± 0.05 Specified accuracy ±0.1 ±1.0 25 VS = ±15 V Continuous Transient VS = ±5 V Continuous Transient 0 to 7 8 mV rms ±% of reading mV ± % of reading μV/V μV/V % of reading % of FSR % of FSR mV ± % of reading CF, % % of reading % of reading ms/μF CAV ±15 V rms V p-p ±6 9.6 ±0.2 V rms V p-p kΩ mV 0 to 4 6.4 Unit 2 VIN = 20 mV VIN = 200 mV VIN = 2 V 11 66 200 kHz kHz kHz VIN = 20 mV VIN = 200 mV VIN = 2 V 150 1 8 kHz MHz MHz vs. temperature ±0.04 13.5 2.2 ±3 dB OUTPUT CHARACTERISTICS Offset Voltage Voltage Swing, 2 kΩ load 0 to 12.0 0 to 2 6 VS = ±3 V Output Current Short-Circuit Current Resistance Resistance dB OUTPUT Error Scale Factor Scale Factor Tempco ±0.5 ±0.056 20 0.5 100 CS high CS low VIN = 7 mV to 7 V rms, 0 dBV IREF for 0 dB = 1 V rms IREF Range 5 1 Rev. L | Page 6 of 25 ±0.3 −3 +0.33 −0.033 20 80 100 mV mV/°C V V mA mA Ω kΩ dBV mV/dB % of reading/°C dB/°C μA μA Data Sheet Parameter BUFFER AMPLIFIER Input Output Voltage Range Input Offset Voltage Input Current Input Resistance Output Current Short-Circuit Current Small Signal Bandwidth Slew Rate DENOMINATOR INPUT Input Range Input Resistance Offset Voltage CHIP SELECT (CS) RMS On Level RMS Off Level IOUT of Chip Select AD637 Test Conditions/Comments Min −0.13 2 kΩ load, to −VS 20 AD637K/AD637B Typ Max Unit −VS to (+VS − 2.5) ±0.5 ±1 ±2 ±5 108 +5 20 1 5 V mV nA Ω mA mA MHz V/μs 0 to 10 25 ±0.2 30 ±0.5 Open or 2.4 < VC < +VS VC < 0.2 CS low CS high 10 0 10 + ((25 kΩ) × CAV) 10 + ((25 kΩ) × CAV) On Time Constant Off Time Constant POWER SUPPLY Operating Voltage Range Quiescent Current Standby Current ±3.0 2.2 350 Rev. L | Page 7 of 25 ±18 3 450 V kΩ mV V V μA μA μs μs V mA μA AD637 Data Sheet Table 3. Parameter TRANSFER FUNCTION CONVERSION ACCURACY Total Error, Internal Trim TMIN to TMAX vs. Supply DC Reversal Nonlinearity Total Error ERROR VS. CREST FACTOR (CF) AVERAGING TIME CONSTANT INPUT CHARACTERISTICS Signal Range Input Resistance Input Offset Voltage FREQUENCY RESPONSE Bandwidth for 1% (0.09 dB) Additional Error Test Conditions/Comments AD637S Typ Min Max VOUT = avg (VIN ) See Figure 5 VIN = 300 mV VIN = −300 mV −2 V < VIN < +2 V 2 V full scale 7 V full scale External trim Additional, at 1 V rms For CF = 1 to 2 For CF = 3 For CF = 10 30 100 ±1 ± 0.5 ±6 ± 0.7 150 300 0.25 0.04 0.05 ±0.5 ± 0.1 Specified accuracy ±0.1 ±1.0 25 VS = ±15 V Continuous Transient VS = ±5 V Continuous Transient 0 to 7 8 mV rms ±% of reading mV ± % of reading μV/V μV/V % of reading % of FSR % of FSR mV ± % of reading CF, % % of reading % of reading ms/μF CAV ±15 V rms V p-p ±6 9.6 ±0.5 V rms V p-p kΩ mV 0 to 4 6.4 Unit 2 VIN = 20 mV VIN = 200 mV VIN = 2 V 11 66 200 kHz kHz kHz VIN = 20 mV VIN = 200 mV VIN = 2 V 150 1 8 kHz MHz MHz vs. temperature ±0.04 13.5 2.2 ±3 dB OUTPUT CHARACTERISTICS Offset Voltage Voltage Swing, 2 kΩ load 0 to 12.0 0 to 2 6 VS = ±3 V Output Current Short-Circuit Current Resistance Resistance dB OUTPUT Error Scale Factor Scale Factor Tempco ±1 ±0.07 20 0.5 100 CS high CS low VIN = 7 mV to 7 V rms, 0 dBV IREF for 0 dB = 1 V rms IREF Range 5 1 Rev. L | Page 8 of 25 ±0.5 −3 +0.33 −0.033 20 80 100 mV mV/°C V V mA mA Ω kΩ dBV mV/dB % of reading/°C dB/°C μA μA Data Sheet Parameter BUFFER AMPLIFIER Input Output Voltage Range Input Offset Voltage Input Current Input Resistance Output Current Short-Circuit Current Small Signal Bandwidth Slew Rate DENOMINATOR INPUT Input Range Input Resistance Offset Voltage CHIP SELECT (CS) RMS On Level RMS Off Level IOUT of Chip Select AD637 AD637S Typ Test Conditions/Comments Min Max Unit 2 kΩ load, to −VS −VS to (+VS − 2.5) ±0.8 ±2 ±2 ±10 108 −0.13 +5 20 1 5 V mV nA Ω mA mA MHz V/μs 20 0 to 10 25 ±0.2 30 ±0.5 Open or 2.4 < VC < +VS CS low CS high 10 0 10 + ((25 kΩ) × CAV) 10 + ((25 kΩ) × CAV) On Time Constant Off Time Constant POWER SUPPLY Operating Voltage Range Quiescent Current Standby Current ±3.0 2.2 350 Rev. L | Page 9 of 25 ±18 3 450 V kΩ mV V V μA μA μs μs V mA μA AD637 Data Sheet ABSOLUTE MAXIMUM RATINGS Table 4. Parameter ESD Rating Supply Voltage Internal Quiescent Power Dissipation Output Short-Circuit Duration Storage Temperature Range Lead Temperature (Soldering 10 sec) Rated Operating Temperature Range AD637J, AD637K AD637A, AD637B AD637S, 5962-8963701CA Rating 500 V ±18 V dc 108 mW Indefinite −65°C to +150°C 300°C Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. ESD CAUTION 0°C to 70°C −40°C to +85°C −55°C to +125°C Rev. L | Page 10 of 25 Data Sheet AD637 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS 14 BUFF OUT NIC 2 13 VIN BUFF IN 1 16 BUFF OUT NIC 2 15 VIN 14 NIC 12 NIC COMMON 3 TOP VIEW 11 +VS (Not to Scale) 10 –VS CS 5 OUTPUT OFFSET 4 COMMON 3 AD637 OUTPUT OFFSET 4 9 RMS OUT dB OUTPUT 7 8 CAV NIC = NO INTERNAL CONNECTION CS 5 DEN INPUT 6 00788-002 DEN INPUT 6 AD637 13 +VS TOP VIEW (Not to Scale) 12 –VS 11 RMS OUT dB OUTPUT 7 10 CAV NIC 8 9 NIC NIC = NO INTERNAL CONNECTION Figure 2. 14-Lead SBDIP/CERDIP Pin Configuration 00788-003 BUFF IN 1 Figure 3. 16-Lead SOIC_W Pin Configuration Table 5. 14-Lead SBDIP/CERDIP Pin Function Descriptions Table 6. 16-Lead SOIC_W Pin Function Descriptions Pin No. 1 2, 12 3 4 5 6 7 8 9 10 11 13 14 Pin No. 1 2, 8, 9, 14 3 4 5 6 7 10 11 12 13 15 16 Mnemonic BUFF IN NIC COMMON OUTPUT OFFSET CS DEN INPUT dB OUTPUT CAV RMS OUT −VS +VS VIN BUFF OUT Description Buffer Input No Internal Connection Analog Common Output Offset Chip Select Denominator Input dB Output Averaging Capacitor Connection RMS Output Negative Supply Rail Positive Supply Rail Signal Input Buffer Output Rev. L | Page 11 of 25 Mnemonic BUFF IN NIC COMMON OUTPUT OFFSET CS DEN INPUT dB OUTPUT CAV RMS OUT −VS +VS VIN BUFF OUT Description Buffer Input No Internal Connection Analog Common Output Offset Chip Select Denominator Input dB Output Averaging Capacitor Connection RMS Output Negative Supply Rail Positive Supply Rail Signal Input Buffer Output AD637 Data Sheet THEORY OF OPERATION FILTER/AMPLIFIER BUFF OUT BUFF IN ONE QUADRANT SQUARER/DIVIDER 14 1 8 CAV 11 +VS 24kΩ BUFFER AMPLIFIER A5 A4 I4 I1 24kΩ Q4 RMS OUT 7 dB OUTPUT 3 COMMON Q1 ABSOLUTE VALUE VOLTAGE TO CURRENT CONVERTER 6kΩ 9 BIAS Q5 Q2 6kΩ Q3 I3 A3 5 CS 6 DEN INPUT 4 OUTPUT OFFSET 10 – VS 24kΩ A2 VIN 13 125Ω 12kΩ AD637 00788-004 A1 Figure 4. Simplified Schematic The AD637 embodies an implicit solution of the rms equation that overcomes the inherent limitations of straightforward rms computation. The actual computation performed by the AD637 follows the equation: V 2 V rms Avg IN V rms Figure 4 is a simplified schematic of the AD637, subdivided into four major sections: absolute value circuit (active rectifier), squarer/divider, filter circuit, and buffer amplifier. The input voltage (VIN), which can be ac or dc, is converted to a unipolar current (I1) by the A1 and A2 absolute value circuit. I1 drives one input of the squarer/divider, which has the transfer function: 2 I4 I1 I3 The output current of the squarer/divider, I4, drives A4, forming a low-pass filter with the external averaging capacitor. If the RC time constant of the filter is much greater than the longest period of the input signal, then the A4 output is proportional to the average of I4. The output of this filter amplifier is used by A3 to provide the denominator current I3, which equals Avg I4 and is returned to the squarer/divider to complete the implicit rms computation I 2 I 4 Avg 1 I4 I 1 rms and VOUT = VIN rms To compute the absolute value of the input signal, the averaging capacitor is omitted. However, a small capacitance value at the averaging capacitor pin is recommended to maintain stability; 5 pF is sufficient for this purpose. The circuit operates identically to that of the rms configuration, except that I3 is now equal to I4, giving 2 I4 I1 I4 I4 = |I1| The denominator current can also be supplied externally by providing a reference voltage (VREF) to Pin 6. The circuit operates identically to the rms case, except that I3 is now proportional to VREF. Therefore, 2 I 4 Avg I1 I3 and VOUT VIN 2 VDEN This is the mean square of the input signal. Rev. L | Page 12 of 25 Data Sheet AD637 APPLICATIONS INFORMATION 20 3 COMMON OUTPUT 4 OFFSET 4.7kΩ +VS 5 CS –VS 7 dB OUTPUT + 10 RMS OUT 9 – + 11 +VS –VS VOUT = VIN2 + CAV 25kΩ ±15 ±5 ±10 SUPPLY VOLTAGE – DUAL SUPPLY (V) ±18 The AD637 includes a chip select feature that allows the user to decrease the quiescent current of the device from 2.2 mA to 350 µA. This is done by driving CS, Pin 5, to below 0.2 V dc. Under these conditions, the output goes into a high impedance state. In addition to reducing the power consumption, the outputs of multiple devices can be connected in parallel to form a wide bandwidth rms multiplexer. Tie Pin 5 high to disable the chip select. (OPTIONAL) BIAS ±3 CHIP SELECT VIN NIC 12 – 0 Figure 6. Maximum VOUT vs. Supply Voltage VIN 13 SQUARER/ DIVIDER DEN 6 INPUT 25kΩ 0 CAV 8 NIC = NO INTERNAL CONNECTION Figure 5. Standard RMS Connection The performance of the AD637 is tolerant of minor variations in the power supply voltages; however, if the supplies used exhibit a considerable amount of high frequency ripple, it is advisable to bypass both supplies to ground through a 0.1 µF ceramic disc capacitor placed as close to the device as possible. OPTIONAL TRIMS FOR HIGH ACCURACY The AD637 includes provisions for trimming out output offset and scale factor errors resulting in significant reduction in the maximum total error, as shown in Figure 7. The residual error is due to a fixed input offset in the absolute value circuit and the residual nonlinearity of the device. The output signal range of the AD637 is a function of the supply voltages, as shown in Figure 6. Use the output voltage buffered or nonbuffered, depending on the characteristics of the load. Connect the buffer input (Pin 1) to common if buffering is not required. The output of the AD637 is capable of driving 5 mA into a 2 kΩ load without degrading the accuracy of the device. 5.0 AD637K MAX 2.5 ERROR (mV) ABSOLUTE VALUE +VS 5 BUFF OUT 14 NC – 2 NIC 10 INTERNAL TRIM AD637K EXTERNAL TRIM 0 –2.5 AD637K: 0.5mV ± 0.2% 0.25mV ± 0.05% EXTERNAL –5.0 0 0.5 1.0 INPUT LEVEL (V) 1.5 Figure 7. Maximum Total Error vs. Input Level AD637K Internal and External Trims Rev. L | Page 13 of 25 2.0 00788-007 AD637 + 00788-005 1 BUFF IN 15 00788-006 The AD637 is simple to connect for a majority of rms measurements. In the standard rms connection shown in Figure 5, only a single external capacitor is required to set the averaging time constant. In this configuration, the AD637 computes the true rms of any input signal. An averaging error, the magnitude of which is dependent on the value of the averaging capacitor, is present at low frequencies. For example, if the filter capacitor, CAV, is 4 µF, the error is 0.1% at 10 Hz and increases to 1% at 3 Hz. To measure ac signals, the AD637 can be ac-coupled by adding a nonpolar capacitor in series with the input, as shown in Figure 5. MAX VOUT (Volts 2kΩ Load) STANDARD CONNECTION AD637 Data Sheet Offset Trim Ground the input signal (VIN) and adjust R1 until the output voltage at Pin 9 measures 0 V. Alternatively, apply the least expected value of VIN.at the input VIN and adjust R1 until the dc output voltage at Pin 9 measures the same value as the rms input. The value of CAV and the 25 kΩ feedback resistor establish the averaging time constant, and solely determines the magnitude of the rms-to-dc conversion error. Furthermore, any postconversion filtering does not improve the dc component composite result. Equation 1 defines the approximate peak value of the ac ripple component of the composite output. 50 in % of reading where (τ > 1 / f ) 6.3 τf Scale Factor Trim Insert Resistor R4 in series with the input to decrease the range of the scale factor. Connect a precision source to Pin 13 and adjust the output for the desired full-scale input to VIN, using either a calibrated dc or 1 kHz ac voltage, and adjust Resistor R3 to give the correct output at Pin 9 (that is, 1 V rms at the input results in a dc output voltage of 1.000 V dc). A 2 V p-p sine wave input yields 0.707 V dc at the output. Remaining errors are due to the nonlinearity. (1) EO IDEAL EO DC ERROR = AVERAGE OF OUTPUT – IDEAL AVERAGE ERROR DOUBLE-FREQUENCY RIPPLE 00788-009 Referring to Figure 8 for optional external gain and offset trim schematic. The following sections describe trimming for greater accuracy in detail. TIME Figure 9. Enlarged Composite Conversion Result for a Sinusoidal Input 1 BUFF IN AD637 + – 2 NIC 3 COMMON R2 1MΩ R1 50kΩ –VS +VS OUTPUT 4 OFFSET Increasing the value of the averaging capacitor or adding a postrms filter network reduces the ripple error. VIN NIC 12 BIAS SQUARER/ DIVIDER 4.7kΩ 5 CS +VS 11 –VS 10 DEN 6 INPUT 25kΩ 7 R4 VIN 13 147Ω – – + dB OUTPUT +VS 1 in % of reading 0.16 + 6.4 τ 2 f 2 –VS RMS OUT 9 + 25kΩ The dc error appears as a frequency dependent offset at the output of the AD637 and follows the relationship RMSOUT + CAV 100 CAV 8 R3 1kΩ NIC = NO INTERNAL CONNECTION 00788-008 SCALE FACTOR TRIM Figure 8. Optional External Gain and Offset Trims CHOOSING THE AVERAGING TIME CONSTANT The AD637 computes the true rms value of both dc and ac input signals. For dc inputs, the output tracks the absolute value of the input exactly. However, when the voltage is ac, the converted dc output voltage asymptotically approaches the theoretical rms value of the input. The deviation from the ideal rms value is due to the implicit denominator inherent to averaging over an infinite time span. Because the error diminishes as the averaging period increases, it quickly becomes negligible. The remaining error components are the ac ripple and dc offset voltage, if any. The ac and averaging error components are both functions of the input-frequency (f) and the averaging time constant τ (τ: 25 ms/µF of averaging capacitance). Figure 9 shows the output errors, which are enlarged for clarity. The frequency of the ac component (ripple) is twice the frequency of the input, the dc error is the RSS sum of the average rectified error and any fixed value dc offset. 10 PEAK RIPPLE 1.0 DC ERROR 0.1 10 100 1k SINE WAVE INPUT FREQUENCY (Hz) 10k 00788-010 +VS ABSOLUTE VALUE DC ERROR OR RIPPLE (% of Reading) OUTPUT OFFSET TRIM BUFF OUT 14 NC Figure 10. Comparison of Percent DC Error to the Percent Peak Ripple over Frequency Using the AD637 in the Standard RMS Connection with a 1 × µF CAV The ac ripple component of averaging error is greatly reduced by increasing the value of the averaging capacitor. However, the value of the averaging capacitor increases exponentially while the settling time increases directly proportion to the value of the averaging capacitor (TS = 115 ms/µF of averaging capacitance). Rev. L | Page 14 of 25 Data Sheet AD637 –VS 10k REQUIRED CAV (µF) FOR 1% SETTLING TIME IN SECONDS MULTIPLY READING BY 0.115 0.01 100k 00788-012 100 1k INPUT FREQUENCY (Hz) 1 5% Figure 12 shows values of CAV and the corresponding averaging error as a function of sine wave frequency for the standard rms connection. The 1% settling time is shown on the right side of Figure 12. 1 1% Figure 11. 2-Pole Sallen-Key Filter 10 0.1 0.1 0.01 1 10k 0.01 100k Figure 13. Values of CAV, C2, and 1% Settling Time for Stated % of Reading for 1-Pole Post Filter; Averaging Error (% DC Error + % Ripple (Peak) Accuracy ±20% Due to Component Tolerance) 100 100 10 10 R O R R ER O % R 01 ER OR 0. R R ER RO ER 1 1 1% 0. 5% The symmetry of the input signal also has an effect on the magnitude of the averaging error. Table 7 gives the practical component values for various types of 60 Hz input signals. These capacitor values can be directly scaled for frequencies other than 60 Hz—that is, for 30 Hz, these values are doubled, and for 120 Hz they are halved. 1k 100 INPUT FREQUENCY (Hz) 1% Figure 13 shows the relationship between the averaging error, signal frequency settling time, and averaging capacitor value. Figure 13 is drawn for filter capacitor values of 3.3× the averaging capacitor value. This ratio sets the magnitude of the ac and dc errors equal at 50 Hz. As an example, by using a 1 µF averaging capacitor and a 3.3 µF filter capacitor, the ripple for a 60 Hz input signal is reduced from 5.3% of the reading using the averaging capacitor alone to 0.15% using the 1-pole filter. This gives a factor of 30 reduction in ripple, and yet the settling time only increases by a factor of 3. The values of Filter Capacitor CAV and Filter Capacitor C2 can be calculated for the desired value of averaging error and settling time by using Figure 13. 10 FOR 1% SETTLING TIME IN SECONDS MULTIPLY READING BY 0.400 NIC = NO INTERNAL CONNECTION 10 R O R R ER O R % 01 R ER 0. O R R 1% 0. ER RO ER FOR A 1 POLE FILTER SHORT RX AND REMOVE C3 100 00788-013 24kΩ 100 REQUIRED CAV (AND C2) C2 = 3.3 × CAV CAV 8 C2 10 Figure 12. Values for CAV and 1% Settling Time for Stated % of Reading; Averaging Error (% DC Error + % Ripple (Peak)); Accuracy Includes ±20% Component Tolerance + CAV 25kΩ RX 24kΩ + 1 0.1 0.01 1 10 100 1k INPUT FREQUENCY (Hz) 0.1 10k 0.01 100k FOR 1% SETTLING TIME IN SECONDS MULTIPLY READING BY 0.365 + 0.01 +VS REQUIRED CAV (AND C2 + C3) C2 = C3 = 2.2 × CAV 7 dB OUTPUT – 0.1 C3 RMS OUT 9 – + 0.1 + 00788-011 DEN 6 INPUT 25kΩ 10 1.0 00788-014 –VS R 4.7kΩ 5 CS 11 R +VS O R ER BIAS % 01 0. +VS VIN NIC 12 SQUARER/ DIVIDER R OUTPUT 4 OFFSET O R ER 3 COMMON O R ER VIN 13 ABSOLUTE VALUE 1.0 R – 2 NIC 1% 0. BUFF OUT 14 10 O R ER AD637 + 10 % 10 1 BUFF IN 100 100 1% A preferable ripple reduction method is to use a post conversion one or two-pole low-pass filter, as shown in Figure 11. Usually a single-pole filter gives the best overall compromise between ripple and settling time. Use the two-pole Sallen-Key for more ripple attenuation. Figure 14. Values of CAV, C2, and C3 and 1% Settling Time for Stated % of Reading for 2-Pole Sallen-Key Filter; Averaging Error (% DC Error + %Ripple (Peak) Accuracy ±20% Due to Component Tolerance) Use Figure 14 to determine the required value of CAV, C2, and C3 for the desired level of ripple and settling time. Rev. L | Page 15 of 25 AD637 Data Sheet Table 7. Practical Values of CAV and C2 for Various Input Waveforms Absolute Value Circuit Waveform and Period Input Waveform and Period 1/2T T A Minimum R × CAV Time Constant 1/2T Recommended Standard Values for CAV and C2 for 1% Averaging Error @ 60 Hz with T = 16.6 ms CAV (μF) C2 (μF) 0.47 1.5 1% Settling Time 181 ms T 0.82 2.7 325 ms 10 (T − T2) 6.8 22 2.67 sec 10 (T − 2T2) 5.6 18 2.17 sec 0V Symmetrical Sine Wave T T B 0V Sine Wave with dc Offset T C T T2 T2 0V Pulse Train Waveform T T D T2 0V T2 FREQUENCY RESPONSE 10 Rev. L | Page 16 of 25 1V RMS INPUT 1 1% 0.01 10% ±3dB 100mV RMS INPUT 10mV RMS INPUT 1k 10k 100k INPUT FREQUENCY (Hz) 1M Figure 15. Frequency Response 10M 00788-015 0.1 To take full advantage of the wide bandwidth of the AD637, use care in the selection of the input buffer amplifier. To ensure that the input signal is accurately presented to the converter, the input buffer must have a −3 dB bandwidth that is wider than that of the AD637. Note the importance of slew rate in this application. For example, the minimum slew rate required for a 1 V rms, 5 MHz, sine wave input signal is 44 V/μs. The user is cautioned that this is the minimum rising or falling slew rate and that care must be exercised in the selection of the buffer amplifier, because some amplifiers exhibit a two-to-one difference between rising and falling slew rates. The AD845 is recommended as a precision input buffer. 7V RMS INPUT 2V RMS INPUT VOUT (V) The frequency response of the AD637 at various signal levels is shown in Figure 15. The dashed lines show the upper frequency limits for 1%, 10%, and ±3 dB of additional error. For example, note that for 1% additional error with a 2 V rms input, the highest frequency allowable is 200 kHz. A 200 mV signal can be measured with 1% error at signal frequencies up to 100 kHz. Data Sheet AD637 1.5 AC MEASUREMENT ACCURACY AND CREST FACTOR INCREASE IN ERROR (%) 1.0 Crest factor is often overlooked in determining the accuracy of an ac measurement. Crest factor is defined as the ratio of the peak signal amplitude to the rms value of the signal (CF = VP/V rms). Most common waveforms, such as sine and triangle waves, have relatively low crest factors (≤2). Waveforms that resemble low duty cycle pulse trains, such as those occurring in switching power supplies and SCR circuits, have high crest factors. For example, a rectangular pulse train with a 1% duty cycle has 0.5 0 –0.5 POSITIVE INPUT PULSE CAV = 22µF –1.0 –1.5 Vp 100µs e0 eIN(RMS) = 1 V RMS 1 MAGNITUDE OF ERROR (% of RMS Level) INCREASE IN ERROR (%) CAV = 22µF 1 CF = 10 0.1 5 6 7 CREST FACTOR 8 9 10 11 1.8 1.6 1.4 1.2 00788-017 1000 CF = 10 1.0 0.8 CF = 7 0.6 0.4 0.2 0 CF = 3 100 10 PULSE WIDTH (µs) 4 2.0 10 1 3 Figure 18. Additional Error vs. Crest Factor Figure 16. Duty Cycle Timing 0.01 2 CF = 3 0 0.5 1.0 VIN (V RMS) 1.5 2.0 00788-019 0 100µs η = DUTY CYCLE = T CF = 1/ η 00788-016 T 00788-018 a crest factor of 10 (CF = 1 ). Figure 19. Error vs. RMS Input Level for Three Common Crest Factors CONNECTION FOR dB OUTPUT Figure 17. AD637 Error vs. Pulse Width Rectangular Pulse Figure 18 is a curve of additional reading error for the AD637 for a 1 V rms input signal with crest factors from 1 to 11. A rectangular pulse train (pulse width 100 μs) is used for this test because it is the worst-case waveform for rms measurement (all the energy is contained in the peaks). The duty cycle and peak amplitude were varied to produce crest factors from l to 10 while maintaining a constant 1 V rms input amplitude. Another feature of the AD637 is the logarithmic, or decibel, output. The internal circuit that computes dB works well over a 60 dB range. Figure 20 shows the dB measurement connection. The user selects the 0 dB level by setting R1 for the proper 0 dB reference current, which is set to cancel the log output current from the squarer/divider circuit at the desired 0 dB point. The external op amp is used to provide a more convenient scale and to allow compensation of the 0.33%/°C temperature drift of the dB circuit. The temperature resistor, R3, as shown in Figure 20, is available from Precision Resistor Co., Inc., in Largo, Fla. (Model PT146). Rev. L | Page 17 of 25 AD637 Data Sheet dB CALIBRATION Refer to Figure 20: • • • • Set VIN = 1.00 V dc or 1.00 V rms Adjust R1 for 0 dB output = 0.00 V Set VIN = 0.1 V dc or 0.10 V rms Adjust R2 for dB output = −2.00 V Any other dB reference can be used by setting VIN and R1 accordingly. R2 33.2kΩ SIGNAL INPUT 5kΩ BUFFER AD637 1 BUFF IN 2 NIC ABSOLUTE VALUE 3 COMMON OUTPUT 4 OFFSET +VS dB SCALE FACTOR ADJUST 4.7kΩ +VS SQUARER/DIVIDER 2 +VS –VS 7 AD707JN 3 NIC 12 BIAS SECTION 60.4Ω VIN 13 5 CS DEN 6 INPUT R3 1kΩ* BUFF OUT 14 4 6 COMPENSATED dB OUTPUT +100mV/dB –VS 11 +VS 10 –VS RMS OUT 9 25kΩ 25kΩ FILTER 7 dB OUTPUT + 1µF CAV 8 10kΩ +VS R1 500kΩ +2.5V AD508J 0dB ADJUST 00788-020 *1kΩ + 3500ppm SEE TEXT NIC = NO INTERNAL CONNECTION Figure 20. dB Connection Rev. L | Page 18 of 25 Data Sheet AD637 V+ 1µF 3.3MΩ 3.3MΩ BUFFER 2 NIC +VS OUTPUT OFFSET 50kΩ ADJUST 1MΩ 4 VIN 13 BIAS SECTION SQUARER/ DIVIDER +VS 5 CS 11 –VS 10 4.7kΩ DEN 6 INPUT 25kΩ 4 6 FILTERED V RMS OUTPUT V– SIGNAL INPUT 6.8MΩ 1000pF +VS –VS RMS OUT 9 + 7 AD548JN 2 NIC 12 3 COMMON +VS –VS ABSOLUTE VALUE OUTPUT OFFSET 1µF BUFF OUT 14 AD637 1 BUFF IN 7 3 25kΩ dB OUTPUT VIN2 V RMS 100µF CAV 8 499kΩ 1% R 00788-021 CAV1 3.3µF NOTES 1. VALUES CHOSEN TO GIVE 0.1% AVERAGING ERROR AT 1Hz. 2. NIC = NO INTERNAL CONNECTION. Figure 21. AD637 as a Low Frequency RMS Converter LOW FREQUENCY MEASUREMENTS VECTOR SUMMATION If the frequencies of the signals to be measured are below 10 Hz, the value of the averaging capacitor required to deliver even 1% averaging error in the standard rms connection becomes extremely large. Figure 21 shows an alternative method of obtaining low frequency rms measurements. Determine the averaging time constant by the product of R and CAV1, in this circuit, 0.5 sec/µF of CAV. This circuit permits a 20:1 reduction in the value of the averaging capacitor, permitting the use of high quality tantalum capacitors. It is suggested that the 2-pole, Sallen-Key filter shown in Figure 21 be used to obtain a low ripple level and minimize the value of the averaging capacitor. Use two AD637s for vector summation as shown in Figure 22. Here, the averaging capacitors are omitted (nominal 100 pF capacitors are used to ensure stability of the filter amplifier), and the outputs are summed as shown. The output of the circuit is If the frequency of interest is below 1 Hz, or if the value of the averaging capacitor is still too large, increase the 20:1 ratio. This is accomplished by increasing the value of R. If this is done, it is suggested that a low input current, low offset voltage amplifier, such as the AD548, be used instead of the internal buffer amplifier. This is necessary to minimize the offset error introduced by the combination of amplifier input currents and the larger resistance. VOUT = VX 2 + VY 2 This concept can be expanded to include additional terms by feeding the signal from Pin 9 of each additional AD637 through a 10 kΩ resistor to the summing junction of the AD711 and tying all of the denominator inputs (Pin 6) together. If CAV is added to IC1 in this configuration, then the output is VX 2 + VY 2 If the averaging capacitor is included on both IC1 and IC2, the output is VX 2 + VY 2 This circuit has a dynamic range of 10 V to 10 mV and is limited only by the 0.5 mV offset voltage of the AD637. The useful bandwidth is 100 kHz. Rev. L | Page 19 of 25 AD637 Data Sheet EXPANDABLE BUFFER 1 IC1 BUFF IN AD637 BUFF OUT VXIN 13 ABSOLUTE VALUE 2 NIC 3 COMMON NIC 12 BIAS SECTION OUTPUT 4 OFFSET +VS DEN 6 INPUT 11 SQUARER/DIVIDER +VS 25kΩ 5 CS 4.7kΩ –VS +VS 10 –VS RMS OUT 9 25kΩ 100pF FILTER 7 14 dB OUTPUT 8 BUFFER 2 NIC IC2 AD637 BUFF OUT ABSOLUTE VALUE 3 COMMON +VS DEN 6 INPUT SQUARER/DIVIDER 25kΩ 5 CS 4.7kΩ 14 VYIN AD711K 13 10kΩ NIC 12 BIAS SECTION OUTPUT 4 OFFSET +VS –VS CAV 10kΩ 10kΩ 1 BUFF IN 5pF 11 10 +VS 20kΩ –VS RMS OUT 9 25kΩ 100pF FILTER dB OUTPUT VOUT = NIC = NO INTERNAL CONNECTION Figure 22. Vector Sum Configuration Rev. L | Page 20 of 25 VX2 + VY2 00788-022 7 8 Data Sheet AD637 EVALUATION BOARD amp, and is configured on the AD637-EVALZ as a low-pass Sallen-Key filter whose fC < 0.5 Hz. Users can connect to the buffer by moving the FILTER switch to the on position. DC_OUT is still the output of the AD637, and the test loop, BUF_OUT, is the output of the buffer. The R2 trimmer adjusts the output offset voltage. Referring to the schematic in Figure 30, the input connector RMS_IN is capacitively coupled to Pin 15 (VIN of SOIC package) of the AD637. The DC_OUT connector is connected to Pin 11, RMS OUT, with provisions for connections to the output buffer between Pin 1 and Pin 16. The buffer is an uncommitted op The LPF frequency is changed by changing the component values of CF1, CF2, R4, and R5. See Figure 24 and Figure 30 to locate these components. Note that a wide range of capacitor and resistor values can be used with the AD637 buffer amplifier. 00788-123 Figure 23 shows a digital image of the AD637-EVALZ, an evaluation board specially designed for the AD637. It is available at www.analog.com and is fully tested and ready for bench testing after connecting power and signal I/O. The circuit is configured for dual power supplies, and standard BNC connectors serve as the signal input and output ports. Figure 23. AD637-EVALZ Rev. L | Page 21 of 25 Data Sheet 00788-124 00788-127 AD637 Figure 27. Evaluation Board—Secondary Side Copper 00788-128 00788-125 Figure 24. AD637-EVALZ Assembly Figure 28. Evaluation Board—Internal Power Plane 00788-126 00788-129 Figure 25. Component Side Silkscreen Figure 29. Evaluation Board—Internal Ground Plane Figure 26. Evaluation Board—Component Side Copper Rev. L | Page 22 of 25 AD637 Data Sheet –VS GND1 GND2 GND3 GND4 C1 10µF 25V +VS + + –VS +VS FILTER BUF_IN 4 1 2 OUT 5 3 6 1 C2 10µF 25V IN BUFF OUT BUFF IN 16 BUF_OUT 2 3 +VS R1 1MΩ R2 50kΩ +VS 4 R3 4.7kΩ 5 –VS 6 7 NIC Z1 AD637 COMMON NIC OUTPUT OFFSET +VS CS –VS RMS OUT DEN INPUT dB OUTPUT CAV NIC NIC DB_OUT 8 VIN R4 24.3kΩ 14 CIN 22µF 16V RMS_IN 13 C3 0.1µF 12 C4 0.1µF 11 + 10 +VS –VS DC_OUT DC_OUT CAV 22µF 16V 9 + R5 24.3kΩ CF1 47µF 25V CF2 47µF 25V 00788-130 + 15 + RMS_IN NIC = NO INTERNAL CONNECTION Figure 30. Evaluation Board Schematic AC OR DC INPUT SIGNAL SOURCE FROM PRECISION CALIBRATOR OR FUNCTION GENERATOR PRECISION DMM TO MONITOR VOUT Figure 31. AD637-EVALZ Typical Bench Configuration Rev. L | Page 23 of 25 00788-131 POWER SUPPLY AD637 Data Sheet OUTLINE DIMENSIONS 0.005 (0.13) MIN 0.080 (2.03) MAX 8 14 1 PIN 1 0.310 (7.87) 0.220 (5.59) 7 0.100 (2.54) BSC 0.765 (19.43) MAX 0.200 (5.08) MAX 0.200 (5.08) 0.125 (3.18) 0.023 (0.58) 0.014 (0.36) 0.060 (1.52) 0.015 (0.38) 0.320 (8.13) 0.290 (7.37) 0.150 (3.81) MIN SEATING PLANE 0.070 (1.78) 0.030 (0.76) 0.015 (0.38) 0.008 (0.20) CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN Figure 32. 14-Lead Side-Brazed Ceramic Dual In-Line Package [SBDIP] (D-14) Dimensions shown in inches and (millimeters) 0.005 (0.13) MIN 14 1 PIN 1 0.098 (2.49) MAX 8 0.310 (7.87) 0.220 (5.59) 7 0.100 (2.54) BSC 0.785 (19.94) MAX 0.200 (5.08) MAX 0.200 (5.08) 0.125 (3.18) 0.023 (0.58) 0.014 (0.36) 0.320 (8.13) 0.290 (7.37) 0.060 (1.52) 0.015 (0.38) 0.150 (3.81) MIN SEATING 0.070 (1.78) PLANE 0.030 (0.76) 15° 0° 0.015 (0.38) 0.008 (0.20) CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 33. 14-Lead Ceramic Dual In-Line Package [CERDIP] (Q-14) Dimensions shown in inches and (millimeters) Rev. L | Page 24 of 25 Data Sheet AD637 10.50 (0.4134) 10.10 (0.3976) 9 16 7.60 (0.2992) 7.40 (0.2913) 8 1.27 (0.0500) BSC 0.30 (0.0118) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122) 10.65 (0.4193) 10.00 (0.3937) 0.75 (0.0295) 45° 0.25 (0.0098) 2.65 (0.1043) 2.35 (0.0925) SEATING PLANE 8° 0° 0.33 (0.0130) 0.20 (0.0079) COMPLIANT TO JEDEC STANDARDS MS-013-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. 1.27 (0.0500) 0.40 (0.0157) 03-27-2007-B 1 Figure 34. 16-Lead Standard Small Outline Package [SOIC_W] Wide Body (RW-16) Dimensions shown in millimeters and (inches) ORDERING GUIDE Model1 5962-8963701CA AD637AQ AD637ARZ AD637BRZ AD637JD AD637JDZ AD637JQ AD637JRZ AD637JRZ-RL AD637JRZ-R7 AD637KDZ AD637KQ AD637KRZ AD637SD AD637SD/883B AD637SQ/883B AD637-EVALZ 1 2 Notes 2 Temperature Range −55°C to +125°C −40°C to +85°C −40°C to +85°C −40°C to +85°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C 0°C to 70°C −55°C to +125°C −55°C to +125°C −55°C to +125°C Package Description 14-Lead CERDIP 14-Lead CERDIP 16-Lead SOIC_W 16-Lead SOIC_W 14-Lead SBDIP 14-Lead SBDIP 14-Lead CERDIP 16-Lead SOIC_W 16-Lead SOIC_W 16-Lead SOIC_W 14-Lead SBDIP 14-Lead CERDIP 16-Lead SOIC_W 14-Lead SBDIP 14-Lead SBDIP 14-Lead CERDIP Evaluation Board Z = RoHS Compliant Part. A standard microcircuit drawing is available. ©2015 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00788-0-4/15(L) Rev. L | Page 25 of 25 Package Option Q-14 Q-14 RW-16 RW-16 D-14 D-14 Q-14 RW-16 RW-16 RW-16 D-14 Q-14 RW-16 D-14 D-14 Q-14