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Details, datasheet, quote on part number:AD736JR
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FEATURES COMPUTES True RMS Value Average Rectified Value Absolute Value PROVIDES 200 mV Full-Scale Input Range (Larger Inputs with Input Attenuator) L High Input Impedance of 1012 ow Input Bias Current: 25 pA max High Accuracy: 0.3 mV 0.3% of Reading RMS Conversion with Signal Crest Factors Up to 5 Wide Power Supply Range: +2.8 V, 3.2 V to 16.5 V Low Power: 200 A max Supply Current Buffered Voltage Output No External Trims Needed for Specified Accuracy AD737--An Unbuffered Voltage Output Version with Chip Power Down Is Also Available PRODUCT DESCRIPTION
Low Cost, Low Power, True RMS-to-DC Converter AD736
FUNCTIONAL BLOCK DIAGRAM
which allows the measurement of 300 mV input levels, while operating from the minimum power supply voltage of +2.8 V, 3.2 V. The two inputs may be used either singly or differentially. The AD736 achieves a 1% of reading error bandwidth exceeding 10 kHz for input amplitudes from 20 mV rms to 200 mV rms while consuming only 1 mW. The AD736 is available in four performance grades. The AD736J and AD736K grades are rated over the commercial temperature range of 0°C to +70°C. The AD736A and AD736B grades are rated over the industrial temperature range of 40°C to +85°C. The AD736 is available in three low-cost, 8-pin packages: plastic mini-DIP, plastic SO and hermetic cerdip.
PRODUCT HIGHLIGHTS
The AD736 is a low power, precision, monolithic true rms-to-dc converter. It is laser trimmed to provide a maximum error of ± 0.3 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 AD736 offers higher accuracy at equal or lower cost. The AD736 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 AD736 can resolve input signal levels of 100 µV rms or less, despite variations in temperature 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 AD736 has its own output buffer amplifier, thereby providing a great deal of design flexibility. Requiring only 200 µA of power supply current, the AD736 is optimized for use in portable multimeters and other battery powered applications. The AD736 allows the choice of two signal input terminals: a high impedance (1012 ) FET input which will directly interface with high Z input attenuators and a low impedance (8 k) input
1. The AD736 is 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 AD736 to perform true rms measurement. 3. The low power consumption of 1 mW makes the AD736 suitable for many battery powered applications. 4. A high input impedance of 1012 eliminates the need for an external buffer when interfacing with input attenuators. 5. A low impedance input is available for those applications requiring up to 300 mV rms input signal operating from low power supply voltages.
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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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703
AD736SPECIFICATIONS otherwise noted.)
Model Conditions Min
(@ +25 C
5 V supplies, ac coupled with 1 kHz sine-wave input applied unless
AD736K/B Typ
V OUT =
2
AD736J/A Typ
Max
2
Min
Max
Units
TRANSFER FUNCTION CONVERSION ACCURACY Total Error, Internal Trim1 All Grades 1 kHz Sine Wave ac Coupled Using CC 0200 mV rms 200 mV1 V rms
V OUT =
Avg .(V IN )
Avg .(V IN )
0.3/0.3 1.2 0.007 0 0 0 +0.06 0.18 1.3 +0.25 0.1/0.5 0.7 2.5
0.5/0.5 2.0 0.7/0.7
0.2/0.2 1.2 0.007
0.3/0.3 2.0 0.5/0.5
± mV/± % of Reading % of Reading ± mV/± % of Reading ± % of Reading/°C %/V %/V % of Reading % of Reading ± mV/± % of Reading % Additional Error % Additional Error
TMINTMAX A&B Grades @ 200 mV rms J&K Grades @ 200 mV rms vs. Supply Voltage @ 200 mV rms Input VS = ± 5 V to ± 16.5 V @ 200 mV rms Input VS = ± 5 V to ± 3 V dc Reversal Error, dc Coupled @ 600 mV dc Nonlinearity2, 0 mV200 mV @ 100 mV rms Total Error, External Trim 0200 mV rms ERROR vs. CREST FACTOR3 Crest Factor 1 to 3 CAV, CF = 100 µF Crest Factor = 5 CAV, CF = 100 µF INPUT CHARACTERISTICS High Impedance Input (Pin 2) Signal Range Continuous rms Level VS = +2.8 V, 3.2 V Continuous rms Level VS = ± 5 V to ± 16.5 V Peak Transient Input VS = +2.8 V, 3.2 V Peak Transient Input VS = ± 5 V Peak Transient Input VS = ± 1 6 . 5 V Input Resistance Input Bias Current VS = ± 3 V to ± 16.5 V Low Impedance Input (Pin 1) Signal Range Continuous rms Level VS = +2.8 V, 3.2 V Continuous rms Level VS = ± 5 V to ± 16.5 V Peak Transient Input VS = +2.8 V, 3.2 V Peak Transient Input VS = ± 5 V Peak Transient Input VS = ± 1 6 . 5 V Input Resistance Maximum Continuous Nondestructive Input All Supply Voltages Input Offset Voltage4 ac Coupled J&K Grades A&B Grades vs. Temperature vs. Supply VS = ± 5 V to ± 16.5 V vs. Supply VS = ± 5 V to ± 3 V OUTPUT CHARACTERISTICS Output Offset Voltage J&K Grades A&B Grades vs.Temperature vs. Supply VS = ± 5 V to ± 16.5 V VS = ± 5 V to ± 3 V Output Voltage Swing 2 k Load VS = +2.8 V, 3.2 V 2 k Load VS = ± 5 V 2 k Load VS = ± 1 6 . 5 V No Load VS = ± 1 6 . 5 V Output Current Short-Circuit Current Output Resistance @ dc FREQUENCY RESPONSE High Impedance Input (Pin 2) For 1% Additional Error Sine-Wave Input VIN = 1 mV rms VIN = 10 mV rms VIN = 100 mV rms VIN = 200 mV rms
+0.1 0.3 2.5 +0.35
0 0 0
+0.06 0.18 1.3 +0.25 0.1/0.3 0.7 2.5
+0.1 0.3 2.5 +0.35
0.9 4.0
200 1 ± 2.7 10 12 1 25
0.9 4.0
200 1 ± 2.7 1 012 1 25
mV rms V rms V V V pA
6.4
± 1.7 ± 3.8 ± 11 8
300 l
9.6 ± 12 3 3 30 150
6.4
± 1.7 ± 3.8 ± 11 8
300 l
9.6 ± 12 3 3 30 150
mV rms V rms V V V k V p-p mV mV µV/°C µV/V µV/V
8 50 80 ± 0.1 1 50 50 0 to +1.6 0 to +3.6 0 to +4 0 to +4 2 +1.7 +3.8 +5 +12 3 0.2
8 50 80 ± 0.1 1 50 50 0 to +1.6 0 to +3.6 0 to +4 0 to +4 2 +1.7 +3.8 +5 +12 3 0.2
0.5 0.5 20 130
0.3 0.3 20 130
mV mV µV/°C µV/V µV/V V V V V mA mA
1 6 37 33
1 6 37 33
kHz kHz kHz kHz
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AD736
Model Conditions Min AD736J/A Typ Max Min AD736K/B Typ Max Units
± 3 dB Bandwidth VIN = 1 mV rms VIN = 10 mV rms VIN = 100 mV rms VIN = 200 mV rms
Sine-Wave Input 5 55 170 190 5 55 170 190 kHz kHz kHz kHz
FREQUENCY RESPONSE Low Impedance Input (Pin 1) For 1% Additional Error Sine-Wave Input VIN = 1 mV rms VIN = 10 mV rms VIN = 100 mV rms VIN = 200 mV rms ± 3 dB Bandwidth Sine-Wave Input VIN = l mV rms VIN = 10 mV rms VIN = 100 mV rms VIN = 200 mV rms POWER SUPPLY OperatingVoltageRange Quiescent Current 200 mV rms, No Load TEMPERATURE RANGE Operating, Rated Performance Commercial (0°C to +70°C) Industrial (40°C to +85°C)
1 6 90 90 5 55 350 460 +2.8, 3.2 ± 5 160 230 ± 16.5 200 270
1 6 90 90 5 55 350 460 +2.8, 3.2 ± 5 160 230 ± 16.5 200 270
kHz kHz kHz kHz kHz kHz kHz kHz Volts µA µA
Zero Signal Sine-Wave Input
AD736J AD736A
AD736K AD736B
NOTES l Accuracy is specified with the AD736 connected as shown in Figure 16 with capacitor C C. 2 Nonlinearity is defined as the maximum deviation (in percent error) from a straight line connecting the readings at 0 and 200 mV rms. Output offset voltage is adjusted to zero. 3 Error vs. Crest Factor is specified as additional error for a 200 mV rms signal. C.F. = V PEAK/V rms. 4 DC offset does not limit ac resolution. Specifications are subject to change without notice. Specifications shown in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels.
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 16.5 V Internal Power Dissipation2 . . . . . . . . . . . . . . . . . . . . . 200 mW Input Voltage . . . . . . . . . . . . . . . . . . . . . . . ± VS Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Differential Input Voltage . . . . . . . . . . . . . . . . . . +VS and VS Storage Temperature Range (Q) . . . . . . 65°C to +150°C Storage Temperature Range (N, R) . . . . . 65°C to +125°C Operating Temperature Range AD736J/K . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C AD736A/B . . . . . . . . . . . . . . . . . . . . . . . . . . 40°C to +85°C
ORDERING GUIDE Temperature Range 0°C to +70°C 0°C to +70°C 0°C to +70°C 0°C to +70°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 Package Description Plastic Mini-DIP Plastic Mini-DIP Plastic SOIC Plastic SOIC Cerdip Cerdip Plastic SOIC Plastic SOIC Plastic SOIC Plastic SOIC Package Option N-8 N-8 SO-8 SO-8 Q-8 Q-8 SO-8 SO-8 SO-8 SO-8
ABSOLUTE MAXIMUM RATINGS 1
Lead Temperature Range (Soldering 60 sec) . . . . . . . . +300°C ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 V
NOTES 1 Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and 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 . 2 8-Pin Plastic Package: JA = 165°C/W 8-Pin Cerdip Package: JA = 110°C/W 8-Pin Small Outline Package: JA = 155°C/W
PIN CONFIGURATION 8-Pin Mini-DIP (N-8), 8-Pin SOIC (R-8), 8-Pin Cerdip (Q-8)
Model AD736JN AD736KN AD736JR AD736KR AD736AQ AD736BQ AD736JR-REEL AD736JR-R EEL-7 AD736KR-R EEL AD736KR-R EEL-7
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AD736 Typical Characteristics
Figure 1. Additional Error vs. Supply Voltage
Figure 2. Maximum Input Level vs. SupplyVoltage
Figure 3. Peak Buffer Output vs. Supply Voltage
Figure 4. Frequency Response Driving Pin 1
Figure 5. Frequency Response Driving Pin 2
Figure 6. Additional Error vs. Crest Factor vs. CAV
Figure 7. Additional Error vs. Temperature
Figure 8. DC Supply Current vs. RMS lnput Level
Figure 9. 3 dB Frequency vs. RMS Input Level (Pin2)
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Typical Characteristics AD736
Figure 10. Error vs. RMS Input Voltage (Pin 2), Output Buffer Offset Is Adjusted To Zero
Figure 11. CAV vs. Frequency for Specified Averaging Error
Figure 12. RMS Input Level vs. Frequency for Specified Averaging Error
Figure 13. Pin 2 Input Bias Current vs. Supply Voltage
Figure 14. Settling Time vs. RMS Input Level for Various Values of CAV
Figure 15. Pin 2 Input Bias Current vs. Temperature
CALCULATING SETTLING TIME USING FIGURE 14
The graph of Figure 14 may be used to closely approximate the time required for the AD736 to settle when its input level is reduced in amplitude. The net time required for the rms converter to settle will be 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 14, the initial settling time (where the 100 mV line intersects the 33 µF line) is around 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 will be 8 seconds minus 80 ms which is 7.92 seconds. Note that, because of the smooth decay characteristic inherent with a capacitor/diode combination, this is the total settling time to the final value (i.e., not the settling time to 1%, 0.1%, etc., of final value). Also, this graph provides the worst case settling time, since the AD736 will settle very quickly with increasing input levels.
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