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| 型号： | AD636JHZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 12/17页 |
| 文件大小： | 670K |
| 描述： | IC CONV RMS-DC LOW LVL TO100-10 |
| 产品培训模块： | Introduction to Analog RMS-to-DC Technology: Converters and Applications |
| 标准包装： | 1 |
| 电流 - 电源： | 800µA |
| 电源电压： | ±2.5 V ~ 16 V |
| 安装类型： | 通孔 |
| 封装/外壳： | TO-100-10 金属罐 |
| 供应商设备封装： | TO-100-10 |
| 包装： | 散装 |
| 产品目录页面： | 786 (CN2011-ZH PDF) |
Data Sheet
AD636
Rev. E | Page 11 of 16
slightly more restricted than in the dual supply connection. The
load resistor, RL, is necessary to provide current sinking capability.
C2
3.3礔
AD636
ABSOLUTE
VALUE
SQUARER
DIVIDER
10k&
10k&
CURRENT
MIRROR
C
AV
BUF
+
20k&
NONPOLARIZED
39k&
0.1礔
0.1礔
+V
S
V
OUT
R
L
k&TO 10k&
IN
1
2
3
4
5
6
7
14
13
12
11
10
9
8
V
IN
NC
V
S
C
AV
dB
BUF OUT
BUF IN
NC
NC
NC
COM
R
L
I
OUT
N =N NNE T
+
Figure 11. Single-Supply Connection (See Text)
CHOOSING THE AVERAGING TIME CONSTANT
The AD636 computes the rms of both ac and dc signals. If the
input is a slowly varying dc voltage, the output of the AD636
tracks the input exactly. At higher frequencies, the average
output of the AD636 approaches the rms value of the input
signal. The actual output of the AD636 differs from the ideal
output by a dc (or average) error and some amount of ripple, as
demonstrated in Figure 12.
TIME
IDEAL
E
O
DCERROR=E
O
E
O
(IDEAL)
AVERAGEE
O
=E
O
DOUBLE-FREQUENCY
RIPPLE
O
Figure 12. Typical Output Waveform for Sinusoidal Input
The dc error is dependent on the input signal frequency and the
value of C
AV
. Figure 13 can be used to determine the minimum
value of C
AV,
which yields a given % dc error above a given
frequency using the standard rms connection.
The ac component of the output signal is the ripple. There are
two ways to reduce the ripple. The first method involves using a
large value of CAV. Because the ripple is inversely proportional
to C
AV
, a tenfold increase in this capacitance effects a tenfold
reduction in ripple. When measuring waveforms with high crest
factors (such as low duty cycle pulse trains), the averaging time
constant should be at least ten times the signal period. For example,
a 100 Hz pulse rate requires a 100 ms time constant, which
corresponds to a 4 糉 capacitor (time constant = 25 ms per 糉).
INPUT FREQUENCY Hz
100
0.01
1
10
0.1
1
10
100
0.1
0.01
0
.
0
1
%
E
R
R
O
R
0
.
1
%
E
R
R
O
R
*% dc ERROR + % RIPPLE (PEAK)
1
%
E
R
R
O
R
1
10
100
1k
10k
100k
VALUES FOR C
AV
AND
1% SETTLING TIME FOR
STATED % OF READING
AVERAGING ERROR*
ACCURACY ?0% DUE TO
COMPONENT TOLERANCE
1
0
%
E
R
R
O
R
Figure 13. Error/Settling Time Graph for Use with the Standard RMS
Connection
The primary disadvantage in using a large CAV to remove ripple
is that the settling time for a step change in input level is
increased proportionately. Figure 13 shows the relationship
between C
AV
and 1% settling time is 115 ms for each microfarad
of C
AV
. The settling time is twice as great for decreasing signals
as for increasing signals (the values in Figure 13 are for decreasing
signals). Settling time also increases for low signal levels, as
shown in Figure 14.
rms INPUTLEVEL
10.0
7.5
0
10mV
100mV
1.0
5.0
2.5
1V
1mV
Figure 14. Settling Time vs. Input Level
A better method for reducing output ripple is the use of a post-
filter. Figure 15 shows a suggested circuit. If a single-pole filter
is used (C3 removed, R
X
shorted), and C2 is approximately
5 times the value of CAV, the ripple is reduced, as shown in
Figure 16, and the settling time is increased. For example, with
CAV = 1 礔 and C2 = 4.7 糉, the ripple for a 60 Hz input is
reduced from 10% of reading to approximately 0.3% of reading.
The settling time, however, is increased by approximately a
factor of 3. The values of C
AV
and C2 can therefore be reduced
to permit faster settling times while still providing substantial
ripple reduction.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD636JHZ | 制造商:Analog Devices 功能描述:IC, RMS-DC CONV, 1%, 1.5MHZ, TO-100-10 |
| AD636JN | 制造商:未知厂家 制造商全称:未知厂家 功能描述:RMS-to-DC Converter |
| AD636JQ | 制造商:未知厂家 制造商全称:未知厂家 功能描述:RMS-to-DC Converter |
| AD636K | 制造商:AD 制造商全称:Analog Devices 功能描述:Low Level, True RMS-to-DC Converter |
| AD636KCWE | 制造商:Maxim Integrated Products 功能描述: |
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