1-chip, 0.1%-accurate AC power monitoring with mΩ shunts

January 29, 2014 // By Graham Prophet
Microchip’s MCP39F501 is a power-monitoring IC that embeds high-accuracy signal acquisition and power calculations, with digital data output.

The chip carries out real-time measurement of AC power with 0.1% error across a 4000:1 dynamic range, with integrated power calculations and programmable event notifications; use it in consumer, commercial and industrial products.

The chip has the expected architecture of a voltage input channel and a current channel that senses voltage across a series shunt resistor in the load current path. Each has a 24-bit delta-sigma ADCs, that feed a 16-bit calculation engine, EEPROM and a flexible two-wire interface. An integrated low-drift voltage reference in addition to 94.5 dB of SINAD performance on each measurement channel yields the 0.1% error and 4000:1 dynamic range figure. Inputs are scaled to be in the ±1V range, and the typical-application data sheet shows shunt resistors in the 0.5 – 4 mOhm range.

As it is directly connected to the load lines, isolation is needed, that you can provide by opto-couplers in the digital path to (and from) a microcontroller. The chip has an operating temperature range of -40°C to +125°C that allows it to be used in more extreme environments: it comes in a 28-lead QFN 5 x 5 mm package. It is supported by the MCP39F501 Demonstration Board (ARD00455) priced at $89.99.

Microchip; www.microchip.com/get/G8CX