Energy Metering IC with On-Chip Fault and
Missing Neutral Detection
ADE7761B
Rev. 0
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FEATURES
High accuracy, active energy measurement IC supports
IEC 62053-21
Less than 0.1% error over a dynamic range of 1000 to 1
Supplies active power on the frequency outputs, F1 and F2
High frequency output CF is intended for calibration and
supplies instantaneous active power
Continuous monitoring of the phase and neutral current
allows fault detection in 2-wire distribution systems
Current channel input level best suited for shunt and current
transformer sensors
Uses the larger of the two currents (phase or neutral) to bill,
even during a fault condition
Continuous monitoring of the voltage and current inputs
allows missing neutral detection
Uses one current input (phase or neutral) to bill when
missing neutral is detected
Two logic outputs (FAULT and REVP) can be used to indicate
a potential miswiring, fault, or missing neutral condition
Direct drive for electromechanical counters and 2-phase
stepper motors (F1 and F2)
Proprietary ADCs and DSP provide high accuracy over large
variations in environmental conditions and time
Reference 2.5 V ± 8% (drift 30 ppm/°C typical) with external
overdrive capability
Single 5 V supply, low power
GENERAL DESCRIPTION
The ADE7761B is a high accuracy, fault-tolerant, electrical energy
measurement IC intended for use with 2-wire distribution systems.
The part specifications surpass the accuracy requirements as
quoted in the IEC 62053-21 standard. The only analog circuitry
used on the ADE7761B is in the ADCs and reference circuit.
All other signal processing (such as multiplication and filtering)
is carried out in the digital domain. This approach provides
superior stability and accuracy over extremes in environmental
conditions and over time. The ADE7761B incorporates a fault
detection scheme similar to the
ADE7751 by continuously
monitoring both phase and neutral currents. A fault is indicated
when the currents differ by more than 6.25%.
The ADE7761B incorporates a missing neutral detection scheme
by continuously monitoring the input voltage. When a missing
neutral condition is detected (no voltage input), the ADE7761B
continues billing based on the active current signal (see the
Missing Neutral Mode section). The missing neutral condition
is indicated when the FAULT pin goes high. The ADE7761B
supplies average active power information on the low frequency
outputs, F1 and F2. The CF logic output gives instantaneous
active power information.
The ADE7761B includes a power supply monitoring circuit on
the V
DD
supply pin. Internal phase matching circuitry ensures
that the voltage and current channels are matched. An internal
no-load threshold ensures that the ADE7761B does not exhibit
any creep when there is no load.
FUNCTIONAL BLOCK DIAGRAM
MISCAL
ADC
6
5
V
2P
V
2N
ADC
ADC
4
3
7
V
1B
ADC
2
V
1A
AGND FAULT
DD
V
1N
2.5V
REFERENCE
INTERNAL
OSCILLATOR
MISSING NEUTRAL
GAIN ADJUST
MISSING NEUTRAL
DETECTION
9 14 17 10 11 12
B > A
A ≠ B
A > B
ZERO-CROSSING
DETECTION
ADE7761B
SIGNAL PROCESSING
BLOCK
15 18
POWER
SUPPLY MONITOR
DIGITAL-TO-FREQUENCY CONVERTER
16 18 19 20
F1F2CFREVPS0S1SCFDGNDRCLKINREF
IN/OUT
HPF
LPF
3kΩ
PG
13
06797-001
Figure 1.
