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參數(shù)資料
| 型號： | AD7751 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Energy Metering IC with On-Chip Fault Detection(高精度容錯(cuò)電子能量測量芯片) |
| 中文描述： | 電能計(jì)量IC片故障檢測（高精度容錯(cuò)電子能量測量芯片） |
| 文件頁數(shù)： | 12/16頁 |
| 文件大小： | 287K |
| 代理商： | AD7751 |
AD7751
12
PRELIM B1 1098
AD7751 TRANSFER FUNCTION
Frequency Outputs F1 and F2
The AD7751 calculates the product of two voltage signals (on
Channel 1 and Channel 2) and then low pass filters this
product to extract real power information. This real power
information is then converted to a frequency. The frequency
information is output on F1 and F2 in the form of active low
pulses. The pulse rate at these outputs is relatively low, e.g.
0.17Hz maximun for ac signals with S0 = S1 = 0
—see Table III. This means that the frequency at these outputs
is generated from real power information accumulated over a
relatively long period of time. The result is an output frequency
which is proportional to the averge real power. The averaging
of the real power signal is implicit to the digital to frequency
conversion. The output frequency or pulse rate is related to the
input voltage signals by the following equation.
Freq
5.7
V1 V2 Gain
V
REF
F
1 - 4
2
=
×
×
where,
Freq
V1
=
=
Output frequency on F1 and F2 (Hz)
Differential RMS voltage signal on Channel 1
(volts)
Differential RMS voltage signal on Channel 2
(volts)
1, 2, 8 or 16 depending on the PGA gain selection
made using logic inputs G0 and G1
The reference voltage (2.5V ± 8%) (volts)
One of four possible frequencies selected by using
the logic inputs S0 and S1—see Table II
V2
=
Gain
=
V
REF
F
1-4
=
=
TABLE II
S1
S0
F
1-4
(Hz)
XTAL/CLKIN*
0
0
1
1
0
1
0
1
0.85
1.7
3.41
6.83
3.579MHz / 2
22
3.579MHz / 2
21
3.579MHz / 2
20
3.579MHz / 2
19
*NOTE F1-4 are a binary fraction of the master clock and therefore will vary
if the specified CLKIN frequency is altered.
Example 1
Thus if full scale differential dc voltages of +660mV and
-660mV are applied to V1 and V2 respectively ( 660mV is the
maximum differential voltage which can be connected to
channel 1 and channel 2) the expected output frequency is
calculated as follows.
Gain
F
1-4
V1
V2
=
=
=
=
1, G0 = G1 = 0
0.85Hz, S0 = S1 = 0
+660mV dc = 0.66 volts (RMS of dc = dc)
-660mV dc = 0.66 volts (RMS of dc = |dc|)
V
REF
=
2.5V (nominal reference value).
NOTE: If the on chip reference is used actual
output frequencies may vary from device to device
due to reference tolerence of ±8%.
Freq
5.7 0.66 0.66 1 0.85
2.5
2
=
=
034
.
Example 2
In this example ac voltages of ±660mV peak applied to V1 and
V2 then the expected output frequency is calculated as follows.
Gain
=
1, G0 = G1 = 0
F
1-4
=
0.85Hz, S0 = S1 = 0
V1
=
RMS of 660mV peak ac =
0.66 /
2
volts
V2
=
RMS of 660mV peak ac =
0.66 /
2
volts
V
REF
=
2.5V (nominal reference value).
NOTE: If the on chip reference is used actual
output frequencies may vary from device to device
due to reference tolerence of ±8%.
Freq
5.7 0.66 0.66 1 0.85
×
2
2 2.5
2
=
=
017
.
As can be seen from these two example calculations the
maximum output frequency for ac inputs is alway half of that
for dc input signals. Table II shows a complete listing of all
maximum output frequencies.
TABLE III
Max Frequency
for dc inputs (Hz)
Max Frequency
for ac inputs (Hz)
S1
S0
0
0
1
1
0
1
0
1
0.34
0.68
1.36
2.72
0.17
0.34
0.68
1.36
Frequency Output CF
The pulse output CF (Calibration Frequency) is intended for
use during calibration. The output pulse rate on CF can be up
to 128 times the pulse rate on F1 and F2. The lower the F1-4
frequency selected the higher the CF scaling. Table IV shows
how the two frequencies are related depending on the states of
the logic inputs S0, S1 and SFC. Because of its relatively high
pulse rate, the frequency at this logic output is proportional to
the instantaneous real power. As is the case with F1 and F2 the
frequency is derived from the output of the low pass filter after
multiplication. However because the output frequency is high,
this real power information is accumulated over a much shorter
time. Hence less averaging is carried out in the digital to
frequency conversion. With much less averaging of the real
power signal, the CF output is much more responsive to power
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7751AAN | 制造商:Analog Devices 功能描述: 制造商:Rochester Electronics LLC 功能描述:PRODUCT TO FREQUENCY CONV - Bulk |
| AD7751AAN-REF | 制造商:Analog Devices 功能描述: |
| AD7751AARS | 制造商:Rochester Electronics LLC 功能描述:PRODUCT TO FREQUENCY CONV - Bulk |
| AD7751ABRS | 制造商:AD 制造商全稱:Analog Devices 功能描述:Energy Metering IC With On-Chip Fault Detection |
| AD7751AN | 制造商:Rochester Electronics LLC 功能描述:PRODUCT TO FREQUENCY CONV - Bulk |
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