Energy Metering IC a with On-Chip Fault Detection * ADE7751 FEATURES The only analog circuitry used in the ADE7751 is in the ADCs High Accuracy, Surpasses 50 Hz/60 Hz IEC 687/1036 and reference circuit. All other signal processing (e.g., multipli- Less than 0.1% Error over a Dynamic Range of 500 to 1 cation and filtering) is carried out in the digital domain. This Supplies Average Real Power on the Frequency approach provides superior stability and accuracy over extremes Outputs F1 and F2 in environmental conditions and over time. High-Frequency Output CF Is Intended for Calibration The ADE7751 incorporates a novel fault detection scheme that and Supplies Instantaneous Real Power warns of fault conditions and allows the ADE7751 to continue Continuous Monitoring of the Phase and Neutral accurate billing during a fault event. The ADE7751 does this Current Allows Fault Detection in 2-Wire by continuously monitoring both the phase and neutral (return) Distribution Systems currents. A fault is indicated when these currents differ by more ADE7751 Uses the Larger of the Two Currents (Phase than 12.5%. Billing is continued using the larger of the two currents. or Neutral) to BillEven During a Fault Condition The ADE7751 supplies average real power information on the Two Logic Outputs (FAULT and REVP) Can Be Used to low-frequency outputs F1 and F2. These logic outputs may be Indicate a Potential Miswiring or Fault Condition used to directly drive an electromechanical counter or interface Direct Drive for Electromechanical Counters and to an MCU. The CF logic output gives instantaneous real power 2-Phase Stepper Motors (F1 and F2) information. This output is intended to be used for calibration purposes. A PGA in the Current Channel Allows the Use of Small Values of Shunt and Burden Resistance The ADE7751 includes a power supply monitoring circuit on the Proprietary ADCs and DSP Provide High Accuracy over AV supply pin. The ADE7751 will remain in a reset condition DD Large Variations in Environmental Conditions and Time until the supply voltage on AV reaches 4 V. If the supply falls DD On-Chip Power Supply Monitoring below 4 V, the ADE7751 will also be reset and no pulses will be On-Chip Creep Protection (No Load Threshold) issued on F1, F2, and CF. On-Chip Reference 2.5 V 8% (30 ppm/ C Typical) Internal phase matching circuitry ensures that the voltage and with External Overdrive Capability current channels are matched whether the HPF in Channel 1 is Single 5 V Supply, Low Power (15 mW Typical) on or off. The ADE7751 also has anticreep protection. Low-Cost CMOS Process The ADE7751 is available in 24-lead DIP and SSOP packages. GENERAL DESCRIPTION The ADE7751 is a high-accuracy, fault-tolerant electrical energy measurement IC that is intended for use with 2-wire distribution systems. The part specifications surpass the accuracy require- ments as quoted in the IEC1036 standard. FUNCTIONAL BLOCK DIAGRAM G0 G1 AV AGND FAULT AC/DC DV DGND DD DD ADE7751 POWER SIGNAL SUPPLY MONITOR PROCESSING A<>B BLOCK V1A ...110101... A ADC HPF A>B PGA V1N 1, 2, 8, 16 ...110101... B PHASE ADC CORRECTION MULTIPLIER V1B B>A PGA 1, 2, 8, 16 LPF V2P ...11011001... ADC V2N DIGITAL-TO-FREQUENCY CONVERTER 4k 2.5V REFERENCE F1 REF CLKIN CLKOUT SCF S0 S1 REVP CF F2RESET IN/OUT *US Patent 5,745,323 5,760,617 5,862,069 5,872,469. REV. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties that Tel: 781/329-4700 www.analog.com may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781/326-8703 Analog Devices, Inc., 2002(AV = DV = 5 V 5%, AGND = DGND = 0 V, On-Chip Reference, DD DD 1, 2 CLKIN = 3.58 MHz, T to T = 40 C to +85 C.) MIN MAX ADE7751SPECIFICATIONS Parameter Value Unit Test Conditions/Comments 3 ACCURACY 1 Measurement Error on Channels 1 and 2 One Channel with Full-Scale Signal (660 mV) Gain = 1 0.1 % Reading typ Over a Dynamic Range 500 to 1 Gain = 2 0.1 % Reading typ Over a Dynamic Range 500 to 1 Gain = 8 0.1 % Reading typ Over a Dynamic Range 500 to 1 Gain = 16 0.1 % Reading typ Over a Dynamic Range 500 to 1 1 Phase Error between Channels Line Frequency = 45 Hz to 55 Hz V1 Phase Lead 37 (PF = 0.8 Capacitive) 0.1 Degrees() max AC/DC = 0 and AC/DC = 1 V1 Phase Lag 60 (PF = 0.5 Inductive) 0.1 Degrees() max AC/DC = 0 and AC/DC = 1 1 AC Power Supply Rejection AC/DC = 1, S0 = S1 = 1, G0 = G1 = 0 Output Frequency Variation (CF) 0.2 % Reading typ V1 = 100 mV rms, V2 = 100 mV rms 50 Hz Ripple on AV of 200 mV rms 100 Hz DD 1 DC Power Supply Rejection AC/DC = 1, S0 = S1 = 1, G0 = G1 = 0 Output Frequency Variation (CF) 0.3 % Reading typ V1 = 100 mV rms, V2 = 100 mV rms, AV = DV = 5 V 250 mV DD DD 1, 4 FAULT DETECTION See Fault Detection Section Fault Detection Threshold Inactive i/p <> Active i/p 12.5 % typ (V1A or V1B Active) Input Swap Threshold Inactive i/p > Active i/p 14 % of Active typ (V1A or V1B Active) Accuracy Fault Mode Operation V1A Active, V1B = AGND 0.1 % Reading typ Over a Dynamic Range 500 to 1 V1B Active, V1A = AGND 0.1 % Reading typ Over a Dynamic Range 500 to 1 Fault Detection Delay 3 Second typ Swap Delay 3 Second typ ANALOG INPUTS See Analog Inputs Section Maximum Signal Levels 1V max V1A, V1B, V1N, V2N, and V2P to AGND Input Impedance (DC) 390 k min CLKIN = 3.58 MHz Bandwidth 14 kHz typ CLKIN/256, CLKIN = 3.58 MHz 1 ADC Offset Error 25 mV max See Terminology and Typical Performance Characteristics 1 Gain Error 10 % Ideal typ External 2.5 V Reference, Gain = 1, V1 = V2 = 660 mV dc 1 Gain Error Match 0.4 % Ideal typ External 2.5 V Reference REFERENCE INPUT REF Input Voltage Range 2.7 V max 2.5 V + 8% IN/OUT 2.3 V min 2.5 V 8% Input Impedance 3.2 k min Input Capacitance 10 pF max ON-CHIP REFERENCE Nominal 2.5 V Reference Error 200 mV max Temperature Coefficient 30 ppm/C typ CLKIN Note All Specifications for CLKIN of 3.58 MHz Input Clock Frequency 4 MHz max 1 MHz min 4 LOGIC INPUTS SCF, S0, S1, AC/DC, RESET, G0, and G1 Input High Voltage, V 2.4 V min DV = 5 V 5% INH DD Input Low Voltage, V 0.8 V max DV = 5 V 5% INL DD 3 A max Typically 10 nA, V = 0 V to DV Input Current, I IN IN DD Input Capacitance, C 10 pF max IN 2 REV. 0