High Precision, Wideband
RMS-to-DC Converter
AD637
FEATURES
High accuracy
FUNCTIONAL BLOCK DIAGRAM
BUFFER
IN
0.02% max nonlinearity, 0 V to 2 V rms input
0.10% additional error to crest factor of 3
Wide bandwidth
8 MHz at 2 V rms input
600 kHz at 100 mV rms
BUFFER
OUT
25kΩ
RMS OUT
ABSOLUTE
VALUE
SQUARER/
DIVIDER
V
IN
Computes
True rms
Square
Mean square
25kΩ
DENOMINATOR
IN
C
AV
Absolute value
OUTPUT
OFFSET
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
14-lead SBDIP, 14-lead low cost CERDIP, and 16-lead SOIC_W
BIAS
COM
CS
Figure 1. SBDIP (D-14) and CERDIP (Q-14) Packages
GENERAL DESCRIPTION
The input circuitry of the AD637 is protected from overload
voltages that are in excess of the supply levels. The inputs are
not damaged by input signals if the supply voltages are lost.
The AD637 is a complete high accuracy, monolithic 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. A crest factor compensation scheme in the
AD637 permits measurements of signals with crest factors of up
to 10 with less than 1% additional error. The circuit’s wide
bandwidth 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.
The AD637 is available in Accuracy Grades J and K for
commercial temperature range (0°C to 70°C) applications;
Accuracy Grades A and 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 packages.
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 since it relates directly to the power of the signal.
The rms value of a statistical signal is also related to the
standard deviation of the signal.
As with previous monolithic rms converters from ADI, the
AD637 has an auxiliary dB output available to the user. The
logarithm of the rms output signal is brought out to a separate
pin, allowing direct dB measurement with a useful range of 60
dB. 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.
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 time
period. The value of this capacitor also determines low
frequency accuracy, ripple level, and settling time.
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 facilitates the
addition of precision rms measurement to remote or hand-held
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 on-chip buffer amplifier can be 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.
Rev. G
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
Fax: 781.461.3113
www.analog.com
©2005 Analog Devices, Inc. All rights reserved.
5秒后页面跳转
AO3401场效应管参数、引脚图、应用原理图
BT131可控硅参数及引脚图、工作原理详解
74LS32芯片参数、引脚图及功能真值表
全球首块英伟达H200交付 黄仁勋“送货上门”
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
技术参数
数据手册
如果您发现信息不准确，
