Datenblatt-pdf.com


AD737 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD737
Beschreibung True RMS-to-DC Converter
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 24 Seiten
AD737 Datasheet, Funktion
Data Sheet
FEATURES
Computes
True rms value
Average rectified value
Absolute value
Provides
200 mV full-scale input range (larger inputs with input
scaling)
Direct interfacing with 3½ digit CMOS analog-to-digital
converters (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: 25 μA (typical) standby current
No external trims needed for specified accuracy
The AD737 output is negative going; the AD736 is a positive
output-going version of the same basic device
GENERAL DESCRIPTION
The AD737 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 the AD737 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 computes the rms value of both ac and dc input
voltages, and is ac-coupled by adding an input capacitor. In this
mode, the AD737 resolves input signal levels of 100 μV rms or
less, despite variations in temperature or supply voltage. High
accuracy is maintained for input waveforms with crest factors of
1 to 3 and crest factors at 2.5% or less with respect to full-scale
input level.
The AD737 has no output buffer amplifier, thereby significantly
reducing dc offset errors occurring at the output and making
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. In power-down mode, the standby supply
current in is typically 25 μA.
Rev. J
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
Low Cost, Low Power,
True RMS-to-DC Converter
AD737
FUNCTIONAL BLOCK DIAGRAM
CC 8k
8kCOM
CF
VIN
ABSOLUTE
VALUE
CIRCUIT
SQUARER
DIVIDER
OUTPUT
+VS
POWER
DOWN
BIAS
SECTION
Figure 1.
CAV
–VS
CAV
The AD737 has both high (1012 Ω) and low impedance input
options. The high-Z FET input connects high source impedance
input attenuators, and a low impedance (8 kΩ) input accepts
rms voltages of up 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 two performance grades. The AD737J
and AD737K grades operate 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 grade operates over the
industrial temperature range of −40°C to +85°C. The AD737 is
available in two low cost, 8­lead packages: PDIP and SOIC_N.
PRODUCT HIGHLIGHTS
1. Computes the average rectified, absolute, or true rms value
of a signal regardless of waveform.
2. Only one external component, an averaging capacitor, is
required for the AD737 to perform true rms measurement.
3. The standby power consumption of 125 μW 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 ©1988–2015 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com






AD737 Datasheet, Funktion
AD737
Data Sheet
Parameter
POWER-DOWN MODE
Disable Voltage
Input Current,
PD Enabled
POWER SUPPLY
Operating Voltage
Range
Current
Test Conditions/
Comments
VPD = VS
No input
Rated input
Powered down
AD737A, AD737J
Min Typ
Max
0
11
+2.8/
−3.2
±5
120
170
25
±16.5
160
210
40
AD737K
Min Typ
Max
0
11
+2.8/
−3.2
±5
120
170
25
±16.5
160
210
40
AD737J-5
Min Typ
Max
Unit
V
μA
±2.5 ±5
120
170
25
±16.5
160
210
40
V
μA
μA
μA
1 POR is % of reading.
2 Nonlinearity is defined as the maximum deviation (in percent error) from a straight line connecting the readings at 0 V and at 200 mV rms.
3 After fourth-order error correction using the equation
y = −0.31009x4 − 0.21692x3 − 0.06939x2 + 0.99756x + 11.1 × 10−6
where y is the corrected result and x is the device output between 0.01 V and 0.3 V.
4 Crest factor error is specified as the additional error resulting from the specific crest factor, using a 200 mV rms signal as a reference. The crest factor is defined as
VPEAK/V rms.
5 DC offset does not limit ac resolution.
6 Value is measured with respect to COM.
Rev. J | Page 6 of 24

6 Page









AD737 pdf, datenblatt
AD737
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
CAV = 22µF, VS = ±2.5V
CC = 47µF, CF = 4.7µF
–2.5
10mV
100mV
INPUT LEVEL (rms)
1V
Figure 22. Error vs. RMS Input Level Driving Pin 1
2V
Data Sheet
Rev. J | Page 12 of 24

12 Page





SeitenGesamt 24 Seiten
PDF Download[ AD737 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
AD73022.7 V to 5.5 V/ Parallel Input Dual Voltage Output 8-Bit DACAnalog Devices
Analog Devices
AD7303+2.7 V to +5.5 V/ Serial Input/ Dual Voltage Output 8-Bit DACAnalog Devices
Analog Devices
AD7304+3 V/+5 V/ Rail-to-Rail Quad/ 8-Bit DACAnalog Devices
Analog Devices
AD7305+3 V/+5 V/ Rail-to-Rail Quad/ 8-Bit DACAnalog Devices
Analog Devices
AD7306+5 V Powered RS-232/RS-422 TransceiverAnalog Devices
Analog Devices

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche