Energy Metering IC with On-Chip Fault and
Missing Neutral Detection
ADE7761A
FEATURES
GENERAL DESCRIPTION
High accuracy, active energy measurement IC supports
IEC 62053-21
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 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
The ADE7761A 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 ADE7761A 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 ADE7761A 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 ADE7761A incorporates a missing neutral detection
scheme by continuously monitoring the input voltage. When a
missing neutral condition is detected—no voltage input—the
ADE7761A 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
ADE7761A supplies average active power information on the
low frequency outputs, F1 and F2. The CF logic output gives
instantaneous active power information.
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
The ADE7761A includes a power-supply monitoring circuit on
the VDD supply pin. Internal phase matching circuitry ensures
that the voltage and current channels are matched. An internal
no-load threshold ensures that the ADE7761A does not exhibit
any creep when there is no load.
FUNCTIONAL BLOCK DIAGRAM
V
PGA AGND
FAULT
15
DD
1
13
8
POWER
SUPPLY MONITOR
V
V
V
2
4
1A
ADE7761A
SIGNAL PROCESSING
BLOCK
ADC
ADC
ADC
ADC
HPF
A>B
1N
LPF
B>A
A<>B
3
7
ZERO CROSSING
DETECTION
1B
MISSING NEUTRAL
GAIN ADJUST
MISCAL
6
5
V
V
2P
MISSING NEUTRAL
DETECTION
2N
3kΩ
2.5V
REFERENCE
INTERNAL
OSCILLATOR
DIGITAL-TO-FREQUENCY CONVERTER
9
14
17
10
11
12
16
18
19
20
REF
RCLKIN
DGND
SCF S1 S0 REVP CF F2 F1
IN/OUT
Figure 1.
Rev. 0
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responsibility is assumed by Analog Devices for its use, nor for any 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 or otherwise under any patent or patent rights of Analog Devices.
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