Datasheet ADE7761B (Analog Devices)

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Energy Metering IC with On-Chip Fault and Missing Neutral Detection ADE7761B FEATURES GENERAL DESCRIPTION High accuracy, active energy measurement IC supports
The ADE7761B is a high accuracy, fault-tolerant, electrical energy
IEC 62053-21
measurement IC intended for use with 2-wire distribution systems.
Less than 0.1% error over a dynamic range of 1000 to 1
The part specifications surpass the accuracy requirements as
Supplies active power on the frequency outputs, F1 and F2
quoted in the IEC 62053-21 standard. The only analog circuitry
High frequency output CF is intended for calibration and
used on the ADE7761B is in the ADCs and reference circuit.
supplies instantaneous active power
All other signal processing (such as multiplication and filtering)
Continuous monitoring of the phase and neutral current
is carried out in the digital domain. This approach provides
allows fault detection in 2-wire distribution systems
superior stability and accuracy over extremes in environmental
Current channel input level best suited for shunt and current
conditions and over time. The ADE7761B incorporates a fault
transformer sensors
detection scheme similar to the ADE7751 by continuously
Uses the larger of the two currents (phase or neutral) to bill,
monitoring both phase and neutral currents. A fault is indicated
even during a fault condition
when the currents differ by more than 6.25%.
Continuous monitoring of the voltage and current inputs
The ADE7761B incorporates a missing neutral detection scheme
allows missing neutral detection
by continuously monitoring the input voltage. When a missing
Uses one current input (phase or neutral) to bill when
neutral condition is detected (no voltage input), the ADE7761B
missing neutral is detected
continues billing based on the active current signal (see the
Two logic outputs (FAULT and REVP) can be used to indicate
Missing Neutral Mode section). The missing neutral condition
a potential miswiring, fault, or missing neutral condition
is indicated when the FAULT pin goes high. The ADE7761B
Direct drive for electromechanical counters and 2-phase
supplies average active power information on the low frequency
stepper motors (F1 and F2)
outputs, F1 and F2. The CF logic output gives instantaneous
Proprietary ADCs and DSP provide high accuracy over large
active power information.
variations in environmental conditions and time Reference 2.5 V ± 8% (drift 30 ppm/°C typical) with external
The ADE7761B includes a power supply monitoring circuit on
overdrive capability
the VDD supply pin. Internal phase matching circuitry ensures
Single 5 V supply, low power
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 PGA AGND FAULT VDD 13 8 15 1 POWER SUPPLY MONITOR V 2 1A ADC ADE7761B HPF A > B SIGNAL PROCESSING V 4 1N BLOCK ADC V 3 LPF 1B B > A ZERO-CROSSING A ≠ B DETECTION MISCAL 7 ADC MISSING NEUTRAL GAIN ADJUST V 6 2P ADC V 5 2N MISSING NEUTRAL DETECTION 2.5V 3kΩ INTERNAL REFERENCE OSCILLATOR DIGITAL-TO-FREQUENCY CONVERTER 9 14 17 10 11 12 16 18 19 20
01 0 7-
REF RCLKIN DGND SCF S1 S0 REVP CF F2 F1 IN/OUT
79 06 Figure 1.
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Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING CHARACTERISTICS Timing Diagram ABSOLUTE MAXIMUM RATINGS PERFORMANCE ISSUES THAT MAY AFFECT BILLING ACCURACY Case 1 Case 2 ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TEST CIRCUIT TERMINOLOGY THEORY OF OPERATION POWER SUPPLY MONITOR ANALOG INPUTS Channel V1 (Current Channel) Channel V2 (Voltage Channel) MISCAL Input Typical Connection Diagrams INTERNAL OSCILLATOR ANALOG-TO-DIGITAL CONVERSION Antialias Filter ACTIVE POWER CALCULATION Power Factor Considerations Nonsinusoidal Voltage and Current HPF and Offset Effects DIGITAL-TO-FREQUENCY CONVERSION TRANSFER FUNCTION Frequency Output F1 and Frequency Output F2 Frequency Output CF FAULT DETECTION Fault with Active Input Greater Than Inactive Input Fault with Inactive Input Greater Than Active Input Calibration Concerns MISSING NEUTRAL MODE Important Note for Billing of Active Energy Missing Neutral Detection Missing Neutral Gain Calibration APPLICATIONS INFORMATION INTERFACING TO A MICROCONTROLLER FOR ENERGY MEASUREMENT SELECTING A FREQUENCY FOR AN ENERGY METER APPLICATION Frequency Outputs No-Load Threshold NEGATIVE POWER INFORMATION OUTLINE DIMENSIONS ORDERING GUIDE