ADE7755ARSZRL Analog Devices Inc, ADE7755ARSZRL Datasheet - Page 18

Energy Metering IC With Pulse Output

ADE7755ARSZRL

Manufacturer Part Number
ADE7755ARSZRL
Description
Energy Metering IC With Pulse Output
Manufacturer
Analog Devices Inc
Datasheet

Specifications of ADE7755ARSZRL

Input Impedance
390 KOhm
Measurement Error
0.1%
Voltage - I/o High
2.4V
Voltage - I/o Low
0.8V
Current - Supply
3mA
Voltage - Supply
4.75 V ~ 5.25 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
24-SSOP (0.200", 5.30mm Width)
Meter Type
Single Phase
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
For Use With
EVAL-ADE7755ZEB - BOARD EVALUATION FOR AD7755
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

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ADE7755
Table 8. Maximum Output Frequency on CF
SCF
1
0
1
0
1
0
1
0
SELECTING A FREQUENCY FOR AN ENERGY
METER APPLICATION
As shown in Table 6, the user can select one of four frequencies.
This frequency selection determines the maximum frequency
on F1 and F2. These outputs are intended to be used to drive
the energy register (electromechanical or other). Because only
four different output frequencies can be selected, the available
frequency selection has been optimized for a meter constant of
100 imp/kWh with a maximum current between 10 A and 120 A.
Table 9 shows the output frequency for several maximum currents
(I
constant is 100 imp/kWh.
Table 9. F1 and F2 Frequency at 100 imp/kWh
I
12.5
25
40
60
80
120
The f
this range of output frequencies on F1 and F2. When designing
an energy meter, the nominal design voltage on Channel 2 (voltage)
should be set to half scale to allow for calibration of the meter
constant. The current channel should also be no more than half
scale when the meter sees maximum load. This allows overcurrent
signals and signals with high crest factors to be accommodated.
Table 10 shows the output frequency on F1 and F2 when both
analog inputs are half scale. The frequencies listed in Table 10
align well with those listed in Table 9 for maximum load.
Table 10. F1 and F2 Frequency with Half-Scale AC Inputs
S1
0
0
1
1
MAX
MAX
(A)
) with a line voltage of 220 V. In all cases, the meter
i
S0
0
1
0
1
frequencies (i = 1, 2, 3, or 4) allow complete coverage of
f
f
f
f
f
1
1
2
3
4
, f
= 1.7
= 3.4
= 6.8
= 13.6
0
0
0
0
1
1
1
1
S1
2
, f
3
, and f
4
F1 and F2 (Hz)
0.076
0.153
0.244
0.367
0.489
0.733
(Hz)
S0
0
0
1
1
0
0
1
1
F1 and F2 Frequency on CH1 and
CH2 Half-Scale AC Inputs (Hz)
0.085
0.17
0.34
0.68
f
f
f
f
f
f
f
f
f
1
1
2
2
3
3
4
4
1
, f
= 1.7
= 1.7
= 3.4
= 3.4
= 6.8
= 6.8
= 13.6
= 13.6
2
, f
3
, and f
4
(Hz)
Rev. A | Page 18 of 20
CF Maximum for AC Signals
128 × F1, F2 = 43.52 Hz
64 × F1, F2 = 21.76 Hz
64 × F1, F2 = 43.52 Hz
32 × F1, F2 = 21.76 Hz
32 × F1, F2 = 43.52 Hz
16 × F1, F2 = 21.76 Hz
16 × F1, F2 = 43.52 Hz
2048 × F1, F2 = 5.57 kHz
When selecting a suitable f
meter design, the frequency output at I
with a meter constant of 100 imp/kWh should be compared with
Column 4 of Table 10. The frequency that is closest in Table 10
determines the best choice of f
example, if a meter with a maximum current of 25 A is being
designed, the output frequency on F1 and F2 with a meter constant
of 100 imp/kWh is 0.153 Hz at 25 A and 220 V (from Table 9).
Table 10, the closest frequency to 0.153 Hz in Column 4, is 0.17 Hz.
Therefore, f
FREQUENCY OUTPUTS
Figure 2 shows a timing diagram for the various frequency
outputs. The F1 and F2 outputs are the low frequency outputs
that can be used to directly drive a stepper motor or electro-
mechanical impulse counter. The F1 and F2 outputs provide
two alternating low going pulses. The pulse width (t
275 ms, and the time between the falling edges of F1 and F2 (t
is approximately half the period of F1 (t
F1 and F2 falls below 550 ms (1.81 Hz), the pulse width of F1 and
F2 is set to half of their period. The maximum output frequencies
for F1 and F2 are shown in Table 7.
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 listed in Table 8.
As in the case of F1 and F2, if the period of CF (t
180 ms, the CF pulse width is set to half the period. For example,
if the CF frequency is 20 Hz, the CF pulse width is 25 ms.
When the high frequency mode is selected (that is, SCF = 0,
S1 = S0 = 1), the CF pulse width is fixed at 18 μs. Therefore, t
is always 18 μs, regardless of the output frequency on CF.
2
(3.4 Hz, see Table 6) is selected for this design.
i
frequency (i = 1, 2, 3, or 4) for a
i
frequency (i = 1, 2, 3, or 4). For
4
) at a frequency proportional
2
). If, however, the period of
MAX
(maximum load)
5
) falls below
1
) is set at
4
3
)

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