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| 型号： | AD737JRZ-5-R7 |
| 厂商： | Analog Devices Inc |
| 文件页数： | 12/24页 |
| 文件大小： | 0K |
| 描述： | IC TRUE RMS/DC CONV LP 8-SOIC |
| 产品培训模块： | Introduction to Analog RMS-to-DC Technology: Converters and Applications |
| 标准包装： | 1,000 |
| 电流 - 电源： | 170µA |
| 电源电压： | ±2.5 V ~ 16.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SO |
| 包装： | 带卷 (TR) |
| 配用： | AD737-EVALZ-ND - BOARD EVALUATION FOR AD737 |
AD737
THEORY OF OPERATION
As shown in Figure 23, the AD737 has four functional subsec-
tions: an input amplifier, a full-wave rectifier, an rms core, and a
bias section. The FET input amplifier allows a high impedance,
buffered input at Pin 2 or a low impedance, wide dynamic range
input at Pin 1. The high impedance input, with its low input bias
current, is ideal for use with high impedance input attenuators.
The input signal can be either dc-coupled or ac-coupled to the
input amplifier. Unlike other rms converters, the AD737 permits
both direct and indirect ac coupling of the inputs. AC coupling is
provided by placing a series capacitor between the input signal
and Pin 2 (or Pin 1) for direct coupling and between Pin 1 and
ground (while driving Pin 2) for indirect coupling.
AC
C C = 10μF
+
DC
OPTIONAL RETURN PATH
CURRENT
MODE
ABSOLUTE
VALUE
Data Sheet
external averaging capacitor, C F . In the rms circuit, this addi-
tional filtering stage reduces any output ripple that was not
removed by the averaging capacitor.
Finally, the bias subsection permits a power-down function.
This reduces the idle current of the AD737 from 160 μA to
30 μA. This feature is selected by connecting Pin 3 to Pin 7 (+V S ).
TYPES OF AC MEASUREMENT
The AD737iscapableofmeasuringacsignalsbyoperatingas
either an average responding converter or a true rms-to-dc con-
verter. As its name implies, an average responding converter
computes the average absolute value of an ac (or ac and dc)
voltage or current by full-wave rectifying and low-pass filtering
the input signal; this approximates the average. The resulting
output, a dc average level, is then scaled by adding (or reducing)
gain; this scale factor converts the dc average reading to an rms
equivalent value for the waveform being measured. For example,
the average absolute value of a sine wave voltage is 0.636 that
of V PEAK ; the corresponding rms value is 0.707 times V PEAK .
Therefore, for sine wave voltages, the required scale factor is
C C
1
8k?
8
COM
1.11 (0.707 divided by 0.636).
In contrast to measuring the average value, true rms measure-
V IN
V IN
2
8k?
7
+
+V S
C F
10μF
(OPTIONAL
LPF)
ment is a universal language among waveforms, allowing the
magnitudes of all types of voltage (or current) waveforms to be
compared to one another and to dc. RMS is a direct measure of
FET
OP AMP
I B < 10pA
the power or heating value of an ac voltage compared to that of
a dc voltage; an ac signal of 1 V rms produces the same amount
of heat in a resistor as a 1 V dc signal.
POWER 3
DOWN
BIAS
SECTION
RMS
TRANSLINEAR
6
OUTPUT
Mathematically, the rms value of a voltage is defined (using a
simplified equation) as
Avg ( V 2 )
V rms =
–V S
4
CORE
5
C AV
This involves squaring the signal, taking the average, and then
C A
33μF
+
obtaining the square root. True rms converters are smart recti-
fiers; they provide an accurate rms reading regardless of the
type of waveform being measured. However, average responding
POSITIVE SUPPLY
COMMON
0.1μF
+V S
converters can exhibit very high errors when their input signals
deviate from their precalibrated waveform; the magnitude of
0.1μF
NEGATIVE SUPPLY –V S
Figure 23. AD737 True RMS Circuit (Test Circuit)
The output of the input amplifier drives a full-wave precision
rectifier, which, in turn, drives the rms core. It is the core that
provides the essential rms operations of squaring, averaging,
and square rooting, using an external averaging capacitor, C AV .
the error depends on the type of waveform being measured. As
an example, if an average responding converter is calibrated to
measure the rms value of sine wave voltages and then is used
to measure either symmetrical square waves or dc voltages,
the converter has a computational error 11% (of reading)
The transfer function for the AD737 is
Without C AV , the rectified input signal passes through the core
unprocessed, as is done with the average responding connection
(see Figure 25). In the average responding mode, averaging is
carried out by an RC post filter consisting of an 8 k? internal
scale factor resistor connected between Pin 6 and Pin 8 and an
Rev. I | Page 12 of 24
V OUT =
Avg ( V IN 2 )
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD737JRZ-5-RL | 功能描述:IC TRUE RMS/DC CONV LP 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD737JRZ-R7 | 功能描述:IC TRUE RMS/DC CONV LP 8-SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD737JRZ-RL | 功能描述:IC CONV TRUE RMS-DC LP 8SOIC RoHS:是 类别:集成电路 (IC) >> PMIC - RMS 至 DC 转换器 系列:- 标准包装:46 系列:- 电流 - 电源:1.2mA 电源电压:±18 V，36 V 安装类型:表面贴装 封装/外壳:16-SOIC（0.295"，7.50mm 宽） 供应商设备封装:16-SOIC W 包装:管件 |
| AD737KN | 制造商:Rochester Electronics LLC 功能描述:RMS-DC CONVERTER IC - Bulk |
| AD737KR | 制造商:AD 制造商全称:Analog Devices 功能描述:Low Cost, Low Power, True RMS-to-DC Converter |
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