What the AD7755AN is and where it fits
The Analog Devices AD7755AN is a single-phase energy metering IC designed for utility-grade kilowatt-hour meters and submetering applications. It converts the voltage and current inputs from a mains tap and current sensor into a frequency output proportional to real power, with a measurement error of 0.1% over the specified dynamic range. The 390 kOhm input impedance on the voltage channel lets you size the divider directly off the mains without loading the tap. The part runs from a 4.5 V to 5.5 V supply, draws 2 mA typical, and is rated for the industrial temperature range of -40°C to 85°C, so it lives in outdoor meter enclosures without trouble.
Package and mounting — through-hole for serviceability
The AD7755AN comes in a 24-pin PDIP (0.300" body width, 7.62 mm row spacing) with through-hole mounting. That matters if you're repairing a meter board — the DIP socket is easy to swap in the field without hot air, and the scorch mark on the failed IC tells you which part actually died. The supplier device package is 24-PDIP.