ADI AD7756ARS

The AD7756 is a high accuracy electrical power measurement IC with a serial interface and a pulse output. The AD7756 incorporates two second order sigma delta ADCs, reference circuitry, temperature sensor and all the signal processing required to perform active power and energy measurement. The AD7756 contains a sampled waveform register and an Active Energy register capable of holding at least 5 seconds of accumulated power at full load. Data is read from the AD7756 via the serial interface. The AD7756 also provides a pulse output (CF) with a frequency which is proportional to the active power. Besides real power information the AD7756 also provides system calibration features, i.e., channel offset correction, phase calibration and power calibration. The part also incorporates a detection circuit for short duration low voltage variations or sags. The voltage threshold level and the duration (no. of half line cycles) of the variation are user programmable. An open drain logic output (SAG（overline）) goes active low when a sag event occurs. A zero crossing output (ZX) produces an output which is synchronized to the zero crossing point of the line voltage. This output can be used to extract timing or frequency information from the line. The signal is also used internally to the chip in the calibration mode. This permits faster and more accurate calibration of the real power calculation. This signal is also useful for synchronization of relay switching with a voltage zero crossing, thus improving the relay life by reducing the risk of arcing. The interrupt request output is an open drain, active low logic output. The IRQ（overline） output will become active when the accumulated real power register is half full and also when it over flows. A status register will indicate the nature of the interrupt. The AD7756 is available in 20 pin DIP and 20 lead SSOP packages.

• High Accuracy, supports IEC 687/1036
• Less than 0.1% error over a dynamic range of 500 to 1
• An On-Chip user Programmable threshold for line voltage SAG detection and PSU supervisory.
• The AD7756 supplies Sampled Waveform Data and Active Energy (40 Bits).
• Digital Power, Phase & Input Offset Calibration.
• An On-Chip temperature sensor (|±3°C| typical after calibration)
• A SPI compatible Serial Interface.
• A pulse output with programmable frequency.
• An Interrupt Request line (IRQ) and Status register provide early warning of register overflow
• Proprietary ADCs and DSP provide high accuracy over large variations in environmental conditions and time.
• Reference 2.5V±8% (30 ppm/°C typical) with external overdrive capability
• Single 5V Supply, Low power (15mW typical)