Energy Metering IC with On-Chip
Fault and Missing Neutral Detection

ADE7761


Rev. A
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FEATURES
High accuracy active energy measurement IC, supports
IEC 687/61036
Less than 0.1% error over a dynamic range of 500 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 channels input level best suited for 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 ADE7761 is a high accuracy, fault tolerant, electrical energy
measurement IC intended for use with 2-wire distribution
systems. The part specifications surpass the accuracy require-
ments as quoted in the IEC61036 standard.
The only analog circuitry used on the ADE7761 is in the ADCs
and reference circuit. All other signal processing (such as multi-
plication 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 ADE7761 incorporates a fault detection scheme similar to
the ADE7751 by continuously monitoring both the phase and
neutral currents. A fault is indicated when these currents differ
by more than 6.25%.
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FUNCTIONAL BLOCK DIAGRAM
MISCAL
ADC
6
5
V
2P
V
2N
ADC
ADC
4
3
7
V
1B
ADC
2V
1A
AGND FAULT V
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
ADE7761
SIGNAL PROCESSING
BLOCK
15 18
POWER
SUPPLY MONITOR
DIGITAL-TO-FREQUENCY CONVERTER
16 18 19 20
F1F2CFREVPS0S1SCFDGNDRCLKINREF
IN/OUT
HPF
LPF
4kΩ
04407-0-001

Figure 1.