Energy Metering IC with On-Chip
Fault and Missing Neutral Detection
ADE7761
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
AGND
8
FAULT
15
V
DD
1
POWER
SUPPLY MONITOR
V
1A 2
V
1N 4
ADC
V
1B 3
MISCAL
7
V
2P 6
V
2N 5
4kΩ
2.5V
REFERENCE
INTERNAL
OSCILLATOR
ADC
B>A
A<>B
ZERO CROSSING
DETECTION
MISSING NEUTRAL
GAIN ADJUST
ADC
A>B
HPF
ADE7761
SIGNAL PROCESSING
BLOCK
LPF
ADC
MISSING NEUTRAL
DETECTION
DIGITAL-TO-FREQUENCY CONVERTER
04407-0-001
9
14
17
10
11
12
16
18
19
20
REF
IN/OUT
RCLKIN
DGND
SCF
S1
S0 REVP CF
F2
F1
Figure 1.
Rev. A
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infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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registered trademarks are the property of their respective owners.
.
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© 2004 Analog Devices, Inc. All rights reserved.
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