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 The ADE7761B includes a power supply monitoring circuit on Reference 2.5 V 8% (drift 30 ppm/C typical) with external the V supply pin. Internal phase matching circuitry ensures overdrive capability DD that the voltage and current channels are matched. An internal Single 5 V supply, low power no-load threshold ensures that the ADE7761B does not exhibit any creep when there is no load. FUNCTIONAL BLOCK DIAGRAM PGA AGND FAULT V DD 13 8 15 1 POWER SUPPLY MONITOR V 2 1A ADE7761B ADC HPF A > B SIGNAL PROCESSING BLOCK V 4 1N ADC LPF B > A V 3 1B ZERO-CROSSING A B DETECTION MISSING NEUTRAL MISCAL 7 ADC GAIN ADJUST V 6 2P ADC V 5 MISSING NEUTRAL 2N DETECTION 3k 2.5V INTERNAL DIGITAL-TO-FREQUENCY CONVERTER REFERENCE OSCILLATOR 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 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 06797-001ADE7761B TABLE OF CONTENTS Features .............................................................................................. 1 Analog Inputs ............................................................................. 11 General Description ......................................................................... 1 Internal Oscillator ...................................................................... 12 Functional Block Diagram .............................................................. 1 Analog-to-Digital Conversion.................................................. 13 Revision History ............................................................................... 2 Active Power Calculation.......................................................... 14 Specifications..................................................................................... 3 Digital-to-Frequency Conversion............................................ 16 Timing Characteristics ................................................................ 4 Transfer Function....................................................................... 16 Absolute Maximum Ratings............................................................ 5 Fault Detection ........................................................................... 17 Performance Issues That May Affect Billing Accuracy........... 5 Missing Neutral Mode ............................................................... 18 ESD Caution.................................................................................. 5 Applications Information .............................................................. 21 Pin Configuration and Function Descriptions............................. 6 Interfacing to a Microcontroller for Energy Measurement.. 21 Typical Performance Characteristics ............................................. 8 Selecting a Frequency for an Energy Meter Application ...... 21 Test Circuit ........................................................................................ 9 Negative Power Information..................................................... 22 Terminology .................................................................................... 10 Outline Dimensions....................................................................... 23 Theory of Operation ...................................................................... 11 Ordering Guide .......................................................................... 23 Power Supply Monitor ............................................................... 11 REVISION HISTORY 8/07Revision 0: Initial Version Rev. 0 Page 2 of 24