- 您现在的位置：买卖IC网 > PDF目录373897 > AD736KR (ANALOG DEVICES INC) Low Cost, Low Power, True RMS-to-DC Converter PDF资料下载
参数资料
| 型号： | AD736KR |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 模拟专用变换器 |
| 英文描述： | Low Cost, Low Power, True RMS-to-DC Converter |
| 中文描述： | RMS TO DC CONVERTER, 0.005 MHz, PDSO8 |
| 封装： | MS-012AA, SOIC-8 |
| 文件页数： | 7/8页 |
| 文件大小： | 218K |
| 代理商： | AD736KR |
AD736
REV. C
–7–
As shown, the dc error is the difference between the average of
the output signal (when all the ripple in the output has been
removed by external filtering) and the ideal dc output. T he dc
error component is therefore set solely by the value of averaging
capacitor used-no amount of post filtering (i.e., using a very
large C
F
) will allow the output voltage to equal its ideal value.
T he ac error component, an output ripple, may be easily re-
moved by using a large enough post filtering capacitor, C
F
.
In most cases, the combined magnitudes of both the dc and ac
error components need to be considered when selecting appro-
priate values for capacitors C
AV
and C
F
. T his combined error,
representing the maximum uncertainty of the measurement is
termed the “averaging error” and is equal to the peak value of
the output ripple plus the dc error.
As the input frequency increases, both error components de-
crease rapidly: if the input frequency doubles, the dc error and
ripple reduce to 1/4 and 1/2 their original values, respectively,
and rapidly become insignificant.
AC ME ASURE ME NT ACCURACY AND CRE ST FACT OR
T he crest factor of the input waveform is often overlooked when
determining the accuracy of an ac measurement. Crest factor is
defined as the ratio of the peak signal amplitude to the rms am-
plitude (C.F. = V
PEAK
/V rms). Many common waveforms, such
as sine and triangle waves, have relatively low crest factors (
≤
2).
Other waveforms, such as low duty cycle pulse trains and SCR
waveforms, have high crest factors. T hese types of waveforms
require a long averaging time constant (to average out the long
time periods between pulses). Figure 6 shows the additional
error vs. crest factor of the AD736 for various values of C
AV
.
SE LE CT ING PRACT ICAL VALUE S FOR INPUT
COUPLING (C
C
), AVE RAGING (C
AV
) AND FILT E RING
(C
F
) CAPACIT ORS
T able II provides practical values of C
AV
and C
F
for several
common applications.
T able II. AD737 Capacitor Selection Chart
Application
rms
Input
Level
Low
Frequency Crest
Cutoff
(–3dB)
Max
C
AV
C
F
Settling
T ime*
to 1%
Factor
General Purpose
rms Computation
0–1 V
20 Hz
200 Hz
5
5
5
5
150
μ
F 10
μ
F 360 ms
15
μ
F
1
μ
F
33
μ
F
10
μ
F 360 ms
3.3
μ
F
1
μ
F
None
33
μ
F 1.2 sec
None
3.3
μ
F 120 ms
36 ms
0–200 mV 20 Hz
200 Hz
36 ms
General Purpose
Average
Responding
0–1 V
20 Hz
200 Hz
0–200 mV 20 Hz
None
None
100
μ
F 33
μ
F 1.2 sec
82
μ
F
27
μ
F 1.0 sec
33
μ
F 1.2 sec
3.3
μ
F 120 ms
200 Hz
SCR Waveform
Measurement
0–200 mV 50 Hz
5
5
60 Hz
0–100 mV 50 Hz
5
5
50
μ
F
47
μ
F
33
μ
F 1.2 sec
27
μ
F 1.0 sec
60 Hz
Audio
Applications
Speech
0–200 mV 300 Hz
3
1.5
μ
F
100
μ
F 68
μ
F 2.4 sec
0.5
μ
F 18 ms
Music
0–100 mV 20 Hz
10
*Settling time is specified over the stated rms input level with the input signal increasing
from zero. Settling times will be greater for decreasing amplitude input signals.
RMS ME ASURE ME NT – CHOOSING T HE OPT IMUM
VALUE FOR C
AV
Since the external averaging capacitor, C
AV
, “holds” the recti-
fied input signal during rms computation, its value directly af-
fects the accuracy of the rms measurement, especially at low
frequencies. Furthermore, because the averaging capacitor ap-
pears across a diode in the rms core, the averaging time constant
will increase exponentially as the input signal is reduced. T his
means that as the input level decreases, errors due to nonideal
averaging will
reduce
while the time it takes for the circuit to
settle to the new rms level will
increase
. T herefore, lower input
levels allow the circuit to perform better (due to increased aver-
aging) but increase the waiting time between measurements.
Obviously, when selecting C
AV
, a trade-off between computa-
tional accuracy and settling time is required.
Figure 17. AD736 Average Responding Circuit
RAPID SE T T LING T IME S VIA T HE AVE RAGE
RE SPONDING CONNE CT ION (FIGURE 17)
Because the average responding connection does not use the
C
AV
averaging capacitor, its settling time does not vary with in-
put signal level; it is determined solely by the RC time constant
of C
F
and the internal 8 k
resistor in the output amplifier’s
feedback path.
DC E RROR, OUT PUT RIPPLE , AND AVE RAGING
E RROR
Figure 18 shows the typical output waveform of the AD736 with
a sine-wave input applied. As with all real-world devices, the
ideal output of V
OUT
= V
IN
is never exactly achieved; instead,
the output contains both a dc and an ac error component.
Figure 18. Output Waveform for Sine-Wave Input Voltage
相关PDF资料 |
PDF描述 |
|---|---|
| AD736KR-REEL | Low Cost, Low Power, True RMS-to-DC Converter |
| AD7376AN10 | +-15 V Operation Digital Potentiometer |
| AD7376AN100 | +-15 V Operation Digital Potentiometer |
| AD7376AR10 | +-15 V Operation Digital Potentiometer |
| AD7376ARU50 | Software RoHS Compliant: Yes |
相关代理商/技术参数 |
参数描述 |
|---|---|
| AD736KR-REEL | 功能描述:IC TRUE RMS TO DC CONV 5V 8SOIC RoHS:否 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 |
| AD736KR-REEL7 | 功能描述:IC AC RMS TO DC CONV 5V 8-SOIC RoHS:否 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 |
| AD736KR-REEL-7 | 制造商:AD 制造商全称:Analog Devices 功能描述:Low Cost, Low Power, True RMS-to-DC Converter |
| AD736KRZ | 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 |
| AD736KRZ-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 |
发布紧急采购，3分钟左右您将得到回复。