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  • MCP39F521 Power Monitor

  • Created: Jul 27, 2016

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The MCP39F521 is an all-in-one electronic device specifically designed for single-phase power monitoring. It can be used in measuring input power for AC/DC power supplies or loads used in consumer and industrial applications. The device includes dual-channel delta-sigma ADCs, a 16-bit calculation engine, EEPROM and a flexible two-wire I2C interface. An integrated low-drift voltage reference with 10 ppm/°C in addition to 94.5 dB of signal-to-noise and distortion ratio (SINAD) performance on each measurement channel allows for better than 0.1% accurate designs across a 4000:1 dynamic range.

This reference design features a circuit that uses the MCP39F521 device to monitor the power consumed by a load. The MCP39F521 measures the power consumed by the load from a 90-230V AC source. The AC source is inserted in the male power entry receptacle (J1) while the load connects to the female power receptacle (J2). The MCP39F521 measures the voltage from the AC source through its V1- pin. A 0.002Ω current sense resistor is placed between the Neutral terminals of J1 and J2 wherein the MCP39F521 measures the current consumed by the load. In this design, a temperature sensor is also included to measure the temperature around the board. The event pin (EVENT) that can be configured to act as an output flag based on various internal raise conditions and the zero crossing detection pin (ZCD) are also provided and can be used through J6 and J8 headers, respectively.

The MCP39F521 and other devices used in this circuit can be powered by the AC source in J1 through the LNK304 converter or by a 9V power supply inserted at J3. The two sources can be switched through JP2. The MCP1754S/3.3V device regulates the input voltage from either of the sources to 3.3V that supplies the MCP39F521. After the MCP39F521 calculated the active power, reactive power, RMS current, RMS voltage, active energy (both import and export), reactive energy and other typical power quantities, it sends the data to the MCP2221 device through the ISO1541 digital isolator. The MCP2221 sends the data to a computer through the female mini-B USB connector (J10). To display the reading, the user needs to use the MCP39F521 Power Monitor Utility software provided by Microchip.



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