参数资料
| 型号： | AD737-EVALZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 13/24页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR AD737 |
| 标准包装： | 1 |
| 主要目的： | 接口，RMS 到 DC 转换器 |
| 已用 IC / 零件： | AD737 |
| 已供物品： | 板 |
| 相关产品： | AD737JRZ-RL-ND - IC CONV TRUE RMS-DC LP 8SOIC AD737ARZ-ND - IC TRUE RMS/DC CONV LP 8SOIC AD737ANZ-ND - IC TRUE RMS/DC CONV LP 8-DIP AD737JRZ-5-ND - IC TRUE RMS/DC CONV LP 8-SOIC AD737JRZ-R7-ND - IC TRUE RMS/DC CONV LP 8-SOIC AD737JRZ-5-R7-ND - IC TRUE RMS/DC CONV LP 8-SOIC AD737JRZ-5-RL-ND - IC TRUE RMS/DC CONV LP 8-SOIC AD737JRZ-ND - IC TRUE RMS/DC CONV LP 8-SOIC AD737JNZ-ND - IC TRUE RMS/DC CONV LP 8-DIP AD737KR-REEL7-ND - IC AC RMS TO DC CONV 5V 8-SOIC 更多... |
Data Sheet
DC ERROR, OUTPUT RIPPLE, AND
AVERAGING ERROR
a sine wave input voltage 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.
E O
IDEAL
E O
DC ERROR = E O – E O (IDEAL)
AD737
AC MEASUREMENT ACCURACY AND
CREST FACTOR
The 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
amplitude (crest factor = 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. These
types of waveforms require a long averaging time constant to
DOUBLE-FREQUENCY
RIPPLE
AVERAGE E O = E O
TIME
shows the additional error vs. the crest factor of the AD737 for
various values of C AV .
CALCULATING SETTLING TIME
Figure 24. Output Waveform for Sine Wave Input Voltage
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. The dc
error component is, therefore, set solely by the value of the
averaging capacitor used—no amount of post filtering (using a
very large postfiltering capacitor, C F ) allows the output voltage
to equal its ideal value. The ac error component, an output
ripple, can be easily removed using a large enough C F .
In most cases, the combined magnitudes of the dc and ac error
components must be considered when selecting appropriate
values for C AV and C F capacitors. This combined error, repre-
senting 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 decrease rapidly. If the input frequency
doubles, the dc error and ripple reduce to one-quarter and
one-half of their original values, respectively, and rapidly
become insignificant.
for the AD737 to settle when its input level is reduced in ampli-
tude. The net time required for the rms converter to settle is
the difference between two times extracted from the graph:
the initial time minus the final settling time. As an example,
consider the following conditions: a 33 μF averaging capacitor,
an initial rms input level of 100 mV, and a final (reduced) input
level of 1 mV. From Figure 17, the initial settling time (where
the 100 mV line intersects the 33 μF line) is approximately
80 ms. The settling time corresponding to the new or final
input level of 1 mV is approximately 8 seconds. Therefore, the
net time for the circuit to settle to its new value is 8 seconds
minus 80 ms, which is 7.92 seconds.
Note that, because of the inherent smoothness of the decay
characteristic of a capacitor/diode combination, this is the
total settling time to the final value (not the settling time to 1%,
0.1%, and so on, of the final value). Also, this graph provides
the worst-case settling time because the AD737 settles very
quickly with increasing input levels.
Table 5. Error Introduced by an Average Responding Circuit When Measuring Common Waveforms
Type of Waveform
Crest Factor
True RMS
Reading of an Average Responding Circuit
1 V Peak Amplitude
Undistorted Sine Wave
Symmetrical Square Wave
Undistorted Triangle Wave
Gaussian Noise (98% of Peaks <1 V)
Rectangular
Pulse Train
(V PEAK /V rms)
1.414
1.00
1.73
3
2
10
Value (V)
0.707
1.00
0.577
0.333
0.5
0.1
Calibrated to an RMS Sine Wave Value (V)
0.707
1.11
0.555
0.295
0.278
0.011
Error (%)
0
11.0
?3.8
?11.4
?44
?89
SCR Waveforms
50% Duty Cycle
25% Duty Cycle
2
4.7
0.495
0.212
0.354
0.150
?28
?30
Rev. I | Page 13 of 24
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| AD737JN | 制造商:Analog Devices 功能描述:IC RMS TO DC CONVERTER DIP8 737 |
| AD737JNZ | 功能描述:IC TRUE RMS/DC CONV LP 8-DIP 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 |
| AD737JR | 制造商:Analog Devices 功能描述:RMS-to-DC Converter 8-Pin SOIC N 制造商:Rochester Electronics LLC 功能描述:RMS-DC CONVERTER IC - Bulk 制造商:Analog Devices 功能描述:Special Function IC Package/Case:8-SOIC |
| AD737JR-5 | 制造商:Analog Devices 功能描述:RMS-to-DC Converter 8-Pin SOIC |
| AD737JR-5-REEL | 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 |
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