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AD737JN 参数 Datasheet PDF下载

AD737JN图片预览
型号: AD737JN
PDF下载: 下载PDF文件 查看货源
内容描述: 低成本,低功耗,真RMS至DC转换器 [Low Cost, Low Power, True RMS-to-DC Converter]
分类和应用: 转换器
文件页数/大小: 8 页 / 152 K
品牌: AD [ ANALOG DEVICES ]
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a
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 3 1/2 Digit
CMOS A/D Converters
High Input Impedance of 10
12
Low Input Bias Current: 25 pA max
High Accuracy: 0.2 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: 160 A max Supply Current
No External Trims Needed for Specified Accuracy
AD736—A General Purpose, Buffered Voltage
Output Version Also Available
PRODUCT DESCRIPTION
Low Cost, Low Power,
True RMS-to-DC Converter
AD737*
FUNCTIONAL BLOCK DIAGRAM
8k
C
C
1
FULL
WAVE
RECTIFIER
INPUT
AMPLIFIER
BIAS
SECTION
RMS CORE
AD737
8
COM
V
IN
2
8k
7 +V
S
POWER
DOWN
3
6 OUTPUT
–V
S
4
5 C
AV
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 this converter make it suitable for upgrading the per-
formance 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 ex-
ternal capacitor. In this mode, the AD737 can resolve input sig-
nal 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 AD737 has no output buffer amplifier, thereby significantly
reducing dc offset errors occuring at the output. This allows the
device to be highly compatible with high input impedance A/D
converters.
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 which reduces the power supply standby current
to less than 30
µA.
*Protected
under U.S. Patent Number 5,495,245.
The AD737 allows the choice of two signal input terminals: a
high impedance (10
12
Ω)
FET input which will directly interface
with high Z input attenuators and a low impedance (8 kΩ) input
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 AD737 achieves a 1% of reading error bandwidth exceed-
ing 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 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, 8-lead packages: plas-
tic DIP, plastic SO and hermetic cerdip.
PRODUCT HIGHLIGHTS
1. The AD737 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 AD737 to perform true rms measurement.
3. The low power consumption of 0.72 mW makes the AD737
suitable for many battery powered applications.
REV. C
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: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999