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參數(shù)資料
| 型號： | ADE7759ARSRL |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 模擬信號調(diào)理 |
| 英文描述： | Active Energy Metering IC with di/dt Sensor Interface |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, PDSO20 |
| 封裝： | SSOP-20 |
| 文件頁數(shù)： | 23/32頁 |
| 文件大?。?/td> | 530K |
| 代理商： | ADE7759ARSRL |
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REV. 0
ADE7759
–23–
isolated interface to external calibration equipment. Figure 38
illustrates the Energy-to-Frequency conversion in the ADE7759.
The Energy-to-Frequency conversion is accomplished by accumu-
lating the Active power signal in a 24-bit register. An output
pulse
is generated when there is a zero to one transition on the MSB
(most significant bit) of the register. Under steady load conditions
the output frequency is proportional to the Active Power. The output
frequency at CF, with full-scale ac signals on Channel 1 and Chan-
nel 2 and CFDEN = 000h, CFNUM = 000h, and APGAIN = 000h,
is approximately 5.593 kHz. This can be calculated as follows:
With the Active Power Gain register set to 000h, the average
value of the instantaneous power signal (output of LPF2) is
CCCDh or 52,429 decimal. An output frequency is generated
on CF when the MSB in the energy to frequency register (24 bits)
toggles, i.e., when the register accumulates 2
23
. This means the
register is updated 2
23
/CCCDh times (or 159.999 times). Since
the update rate is 4/CLKIN or 1.1175
μ
s, the time between
MSB toggles (CF pulses) is given as:
159 999
1 1175
.
1 78799 10
.
5592 86
(
s
4
.
.
)
–
×
=
μ
s
Hz
Equation 8 gives an expression for the output frequency at the
Energy-to-Frequency (ETF) output with the contents of CFDEN
and CFNUM registers are both zero.
Average LPF Output
(
)
=
ETF Output Hz
CLKIN
×
2
2
25
(8)
This output frequency is easily scaled by a pair of Calibration
Frequency Divider registers (CFDEN[11:0] and CFNUM[11:0]).
These frequency scaling registers are 12-bit registers that can
scale the output frequency by 1 to 2
12
. The output frequency is
given by the expression below.
CF Hz
(
ETF Output Hz
CFNUM
CFDEN
)
(
)
[
[
=
×
+
+
1: ]
1: ]
1
1
(9)
For example, if the
CF
output frequency is 5.59286 kHz while
the contents of
CFNUM
and
CFDEN
are zero, the CF output
frequency can be set to 25Hz by writing 8BDh (2237 in decimal) to
the CFDEN register and 00Ah (10 in decimal) to the CFNUM
register. Note that the CFNUM and CFDEN registers are meant
only to scale down the frequency from the ETF output. Therefore,
the content of CFDEN should always be set no less than that of
the CFNUM register, i.e., the maximum output frequency from
CF pin will never exceed that of the ETF output. The power-up
default value for CFDEN is 3Fh and CFNUM is 0h.
The output frequency will have a slight ripple at a frequency equal
to twice the line frequency. This is due to imperfect filtering of
the instantaneous power signal to generate the Active Power
signal—see Active Power Calculation section. Equation 3 gives
an expression for the instantaneous power signal. This is filtered
by LPF2, which has a magnitude response given by Equation 10.
H( )
f
Hz
/8 9
=
+
1
1
(10)
The Active Power signal (output of LPF2) can be rewritten as
p t
( )
VI
VI
/8 9
f
Hz
f t
l
l
cos
=
(
)
1 2
4
π
(11)
where
fl
is the line frequency (e.g., 60 Hz)
From Equation 6
E t
VIt
VI
f
f
Hz
f t
l
l
l
( )
/8 9
sin
=
(
)
(
)
4
1 2
4
π
π
(12)
From Equation 12 it can be seen that there is a small ripple in the
energy calculation due to a sin(2
ω
t) component. This is shown
graphically in Figure 39. The Active Energy calculation is shown
by the dashed straight line and is equal to V
×
I
×
t. The sinusoidal
ripple in the Active Energy calculation is also shown. Since the
average value of a sinusoid is zero, this ripple will not contribute
to the energy calculation over time. However, the ripple can be
observed in the frequency output, especially at higher output
frequencies. The ripple will get larger as a percentage of the fre-
quency at larger loads and higher output frequencies. The reason
is that at higher output frequencies the integration or averaging
time in the Energy-to-Frequency conversion process is shorter.
As a consequence, some of the sinusoidal ripple is observable in
the frequency output. Choosing a lower output frequency at CF
for calibration can significantly reduce the ripple. Also averaging
the output frequency by using a longer gate time for the counter
will achieve the same results.
SIGN 2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
–
1
2
–
2
2
–
3
2
–
4
2
–
5
2
–
6
2
–
7
2
–
8
15
0
APOS [15:0]
LPF2
20
+
+
+
+
WAVEFORM [23:0]
ENERGY-TO-FREQUENCY
23
0
23
0
MSB
TRANSITION
CF
ACTIVE POWER OFFSET
CALIBRATION
11
0
CFDEN [11:0]
11
0
CFNUM [11:0]
ACTIVE POWER
SIGNAL
–
P
Figure 38. Energy-to-Frequency Conversion
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ADE7759ARSZ | 功能描述:IC ENERGY METERING 1PHASE 20SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 能量測量 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:* |
| ADE7759ARSZRL | 功能描述:IC ENERGY METERING 1PHASE 20SSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 能量測量 系列:- 產(chǎn)品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:* |
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