ADE7761A: Energy Metering IC with On-Chip Fault and Missing Neutral Detection

The ADE7761A is a high accuracy, fault-tolerant, electricalenergy measurement IC intended for use with 2-wiredistribution systems. The part specifications surpass theaccuracy requirements as quoted in the IEC 62053-21 standard.The only analog circuitry used on the ADE7761A is in theADCs and reference circuit. All other signal processing (such asmultiplication and filtering) is carried out in the digital domain. This approach provides superior stability and accuracy over extremes in environmental conditions and over time. TheADE7761A incorporates a fault detection scheme similar to theADE7751 by continuously monitoring both phase and neutralcurrents. A fault is indicated when the currents differ by morethan 6.25%.

The ADE7761A incorporates a missing neutral detectionscheme by continuously monitoring the input voltage. When amissing neutral condition is detected—no voltage input—theADE7761A continues billing based on the active current signal(see the Missing Neutral Mode section). The missing neutralcondition is indicated when the FAULT pin goes high. TheADE7761A supplies average active power information on thelow frequency outputs, F1 and F2. The CF logic output givesinstantaneous active power information.

The ADE7761A includes a power-supply monitoring circuit onthe V_DD 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.

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