ADE7760ARSRL Analog Devices Inc, ADE7760ARSRL Datasheet - Page 17

• Manufacturer Part Number: ADE7760ARSRL
• Description: IC ENERGY METER W/OCFD 20SSOP TR
• Manufacturer: Analog Devices Inc

Specifications of ADE7760ARSRL

• Rohs Status: RoHS non-compliant
• Input Impedance: 400 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 4mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.200", 5.30mm Width)
• Meter Type: Single Phase
• Lead Free Status / Rohs Status: Not Compliant

Note that if the on-chip reference is used, actual output
frequencies may vary from device to device due to reference
tolerance of ±8%.
As can be seen from these two example calculations, the
maximum output frequency for ac inputs is always half of that
for dc input signals. Table 7 shows a complete listing of all
maximum output frequencies for ac signals.
Table 7. Maximum Output Frequency on CF, F1, and F2 for
AC Inputs
SCF
1
0
1
0
1
0
1
0
FAULT DETECTION
The ADE7760 incorporates a novel fault detection scheme that
warns of fault conditions and allows the ADE7760 to continue
accurate billing during a fault event. The ADE7760 does this by
continuously monitoring both the phase and neutral (return)
currents. A fault is indicated when these currents differ by more
than 6.25%. However, even during a fault, the output pulse rate
on F1 and F2 is generated using the larger of the two currents.
Because the ADE7760 looks for a difference between the voltage
signals on V
transducers be closely matched.
On power-up, the output pulse rate of the ADE7760 is pro-
portional to the product of the voltage signals on V
Channel 2. If there is a difference of greater than 6.25% between
V
active after about 1 s. In addition, if V
ADE7760 selects V
automatically disabled when the voltage signal on Channel 1 is
less than 0.3% of the full-scale input range. This eliminates false
detection of a fault due to noise at light loads.
Fault with Active Input Greater than Inactive Input
If V
billing), and the voltage signal on V
93.75% of V
inputs are filtered and averaged to prevent false triggering of
this logic output.
CF
F
1
1A
−
Frequency
1A
and V
F
2
is the active current input (that is, is being used for
S1
0
0
0
0
1
1
1
1
Frequency
1B
on power-up, the fault indicator (FAULT) becomes
1A
S0
0
0
1
1
0
0
1
1
1A
, the fault indicator becomes active. Both analog
and V
=
F
F1, F2 Maximum
Frequency
(Hz)
0.34
0.34
0.68
0.68
1.36
1.36
2.72
2.72
1
=
1B
−
1B
. 5
as the input. The fault detection is
F
, it is important that both current
2
70
×
×
64
. 0
66
2
=
×
22
×
0 .
. 0
2
1B
×
66
Hz
CF Maximum
Frequency
(Hz)
43.52
21.76
43.52
21.76
43.52
21.76
43.52
5570
1B
(inactive input) falls below
2
5 .
is greater than V
×
2
. 1
72
Hz
=
1A
. 0
and
34
1A
CF to
F1
Ratio
128
64
64
32
32
16
16
2048
Hz
, the
Rev. 0 | Page 17 of 24
As a consequence of the filtering, there is a time delay of
approximately 3 s on the logic output FAULT after the fault
event. The FAULT logic output is independent of any activity on
outputs F1 or F2. Figure 23 shows one condition under which
FAULT becomes active. Because V
still greater than V
swap to the V
Fault with Inactive Input Greater than Active Input
Figure 24 illustrates another fault condition. If the difference
between V
for billing), becomes greater than 6.25% of V
indicator goes active, and there is also a swap over to the V
input. The analog input V
there is a time constant of about 3 s associated with this swap.
V
greater than V
order—becomes greater than 6.25% of V
indicator, however, becomes inactive as soon as V
6.25% of V
between V
0V
0V
1A
Figure 23. Fault Conditions for Active Input Greater than Inactive Input
Figure 24. Fault Conditions for Inactive Input Greater than Active Input
does not swap back to being the active channel until V
V
V
<0
FAULT
1B
1A
FAULT + SWAP
<0
6.25% OF ACTIVE INPUT
6.25% OF INACTIVE INPUT
< 93.75% OF V
< 93.75% OF V
V
V
V
V
1A
1A
1B
1B
1B
1A
1B
, the inactive input, and V
. This threshold eliminates potential chatter
and V
1B
1B
AGND
AGND
input occurs. V
and the difference between V
1B
1B
1A
1B
, billing is maintained on V
.
>0
V
V
V
V
1A
1B
1A
1B
1B
>0
V
V
V
becomes the active input. Again,
V
V
V
1A
1N
1B
1A
1N
1B
ACTIVE POINT – INACTIVE INPUT
1A
ACTIVE POINT – INACTIVE INPUT
remains the active input.
1A
is the active input and it is
1A
, the active input (used
A
B
A
B
1A
. The FAULT
COMPARE
COMPARE
FILTER
FILTER
1B
AND
AND
1A
, the FAULT
1A
and V
, that is, no
1A
ADE7760
is within
FAULT
TO
MULTIPLIER
FAULT
TO
MULTIPLIER
1B
—in this
1A
1B
is