ADE7761ARS-REF Analog Devices Inc, ADE7761ARS-REF Datasheet - Page 24

• Manufacturer Part Number: ADE7761ARS-REF
• Description: IC ENERGY METERING 20-SSOP
• Manufacturer: Analog Devices Inc

Specifications of ADE7761ARS-REF

• Rohs Status: RoHS non-compliant

ADE7761
Table 9. F1 and F2 Frequency with Half-Scale AC Inputs
S0
0
0
1
1
When selecting a suitable F
frequency output at I
of 100 impulses/kWh should be compared with Column 4 of
Table 9. The frequency that is closest in Table 9 determines the
best choice of frequency (F
maximum current of 40 A is being designed, the output
frequency on F1 and F2 with a meter constant of
100 impulses/kWh is 0.266 Hz at 40 A and 240 V (from
Table 8). Looking at Table 9, the closest frequency to 0.266 Hz
in Column 4 is 0.17 Hz. Therefore, F2 (3.4 Hz; see Table 5) is
selected for this design.
Frequency Outputs
Figure 2 shows a timing diagram for the various frequency
outputs. 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
tional to active power. The CF output frequencies are given in
Table 7. As in the case of F1 and F2, if the period of CF (t
below 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.
S1
0
1
0
1
F
1.72
3.44
6.86
13.5
1–4
MAX
(maximum load) with a meter constant
Frequency on F1 and F2,
Ch 1 and Ch 2,
Half-Scale AC Inputs (Hz)
0.085
0.17
0.34
0.68
1-4
1–4
). For example, if a meter with a
frequency for a meter design, the
4
) at a frequency that is propor-
5
) falls
Rev. A | Page 24 of 28
No-Load Threshold
The ADE7761 includes a no-load threshold and startup current
feature that eliminates creep effects in the meter. The ADE7761
is designed to issue a minimum output frequency. Any load
generating a frequency lower than this minimum frequency
does not cause a pulse to be issued on F1, F2, or CF. The mini-
mum output frequency is given as 0.0045% of the full-scale
output frequency. (See Table 7 for maximum output frequencies
for ac signals).
For example, an energy meter with a meter constant of
100 impulses/kWh on F1, F2 using SCF = 1, S1 = 0, and S0 = 1,
the maximum output frequency at F1 or F2 is 0.68 Hz and 43.52
Hz on CF. The minimum output frequency at F1 or F2 is
0.0045% of 0.68 Hz or 3.06 × 10
CF (64 × F1 Hz).
In this example, the no-load threshold is equivalent to 1.1 W of
load or a startup current of 4.6 mA at 240 V. Compare this value
to the IEC61036 specification, which states that the meter must
start up with a load equal to or less than 0.4% I
meter, 0.4% of I
Note that the no-load threshold is not enabled when using the
high CF frequency mode: SCF = 0, S1 = S0 = 1.
NEGATIVE POWER INFORMATION
The ADE7761 detects when the current and voltage channels
have a phase shift greater than 90 ° . This mechanism can detect
wrong connection of the meter or generation of negative power.
The REVP pin output goes active high when negative power is
detected, and active low when positive power is detected. The
REVP pin output changes state as a pulse is issued on CF.
B
is equivalent to 20 mA.
–5
Hz. This is 1.96 × 10
B
. For a 5 A (I
–3
Hz at
B
)