ade7761.pdf ADE7761A.pdf

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. 
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.