ADE7752 Analog Devices, ADE7752 Datasheet - Page 9

• Manufacturer Part Number: ADE7752
• Description: Three Phase Energy Metering IC with Pulse Output
• Manufacturer: Analog Devices

For simplification, we assume that φ
= V
P then becomes:
Where:
As the LPF on each channel eliminates the 2ω
the equation, the Real power measured by the ADE7752 is:
Where:
the ADE7752 after voltage sensing
If full scale AC voltage of ±125 mV peak are applied to the
Voltage channels and Current channels, the expected output
frequency is calculated as follows:
F
VAN = VBN = IA = IB
VCN = IC = 0
V
Table III shows a complete listing of all maximum output
frequencies when using all three channels inputs.
REV. PrB 08/01
P
P
P
P
P
1–5
REF
=
=
V
I
ADE7752 after current sensing
=
A
(
VA
AN
B
V
VAP and VN pins of the ADE7752
V
VBP and VN pins of the ADE7752.
V
and I



+
AN
AN
BN
=V
−



=
+
2
=
+
and V
VC
= 125 mV peak AC = 0.125/
V
V
⋅
2
⋅
= 0.596 Hz, SCF = S0 = S1 = 1
= 2.5 V (nominal reference value).
2
2
C
= V . sin(2π/3) represents the RMS voltage between
= V . sin (π/3) represents the RMS voltage between
V
Freq
I
AN
BN
)
⋅
A
A
B
V
⋅
⋅
×
= V. The equation above becomes:
⋅
V
NOTE: If the on-chip reference is used, actual
output frequencies may vary from device to
device due to reference tolerance of ±8%.
B
V
⋅
cos
⋅
⋅
(
are the voltage RMS at the current input of the
IAP
⋅
I
BN
I
B
cos
⋅
⋅
A
2
=
I
3
( )
I
ω
B
⋅
⋅
A
2
−



are the voltage RMS at the voltage inputs of
l






t
ω
⋅
+
⋅
IAN
sin
sin
×
l
−
sin
t
sin
V
109
+
BN
)
2






2
+
3



π



2
π
3
⋅
3
π
2 .
(
V



3
⋅
2
π
VB



C
3
I
−
π

⋅ 




B
×
+
⋅

⋅ 

−
cos
. 0
⋅
2
+
sin
VC
sin
2
125
⋅



sin
sin
2
V
×
ω
3
PRELIMINARY TECHNICAL DATA
)
C



l
×
t
(
⋅
2
ω



+
×
(
cos



2
ω
IBP
2
ω
l
4
t
. 0
ω
×
l
3
π
t
l



t
+
125
ω
2
l



t
+
−
A

⋅ 

5 .
l
+
t
π
IBN
+
π
3
+
= φ
2
2
)
3
×



π
2
2
2
4
3
3
)
⋅



π
π
. 0
⋅






B
I
cos



volts rms
A

⋅ 

596



⋅
⋅
= φ
cos
cos
2



l
×
ω
( )
⋅
C
ω
component of
I
B
l
l
t
t
( )
= 0 and V
2
⋅
ω
3
cos
+
l
t
=
(10)
2



3
ω
π
. 0
l
t



14
+
(9)
2
3
π



A
– 9 –
SCF
1
0
-
-
-
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 160 times the pulse rate on F1 and F2. The lower the
F
shows how the two frequencies are related, depending on the
states of the logic inputs S0, S1 and SCF. 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 fluctuations—see Signal
Processing Block in Figure 8.
SCF
0
1
0
1
0
1
0
1
Frequency Outputs
Figure 1 shows a timing diagram for the various frequency
outputs. The outputs F1 and F2 are the low frequency
outputs that can be used to directly drive a stepper motor or
electromechanical impulse counter. The F1 and F2 outputs
provide two alternating high going pulses. The pulsewidth
(t
F1 and F2 (t
however the period of F1 and F2 falls below 550 ms (1.81 Hz)
the pulsewidth of F1 and F2 is set to half of their period. The
maximum output frequencies for F1 and F2 are shown in
Table III.
The high frequency CF output is intended to be used for
communications and calibration purposes. CF produces a
90 ms-wide active high pulse (t
to active power. The CF output frequencies are given in
Table IV. As in the case of F1 and F2, if the period of CF
(t
period. For example, if the CF frequency is 20 Hz, the CF
pulsewidth is 25 ms.
1–5
1
5
Table III. Maximum Output Frequency on F1 and F2
) is set at 275 ms and the time between the rising edges of
) falls below 180 ms, the CF pulsewidth is set to half the
frequency selected, the higher the CF scaling. Table IV
Table IV. Maximum Output Frequency on CF
S1
1
1
1
0
0
S1
0
0
0
0
1
1
1
1
S0
1
1
0
1
0
S0 F
0
0
1
1
0
0
1
1
3
) is approximately half the period of F1 (t
Max Frequency
for DC Inputs (Hz)
0.48
62.52
15.6
3.9
0.96
1.19
1.19
4.77
4.77
19.07
19.07
76.29
0.596
1–5
(Hz)
4
CF Max for AC Signals (Hz)
160 x F1, F2 = 78.12
8 x F1, F2 = 3.90
160 x F1, F2 = 312.51
16 x F1, F2 = 31.26
16 x F1, F2 = 130.56
8 x F1, F2 = 62.49
8 x F1, F2 = 250
16 x F1, F2 = 3.90 Hz
) at a frequency proportional
Max Frequency
for AC Inputs (Hz)
0.24
31.26
7.8
1.95
0.48
2
). If