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Enable smarter power monitoring using Microchip's 16bit MCUs

Posted: 29 May 2015 ?? ?Print Version ?Bookmark and Share

Keywords:Gartner Research? power monitoring? MCU? power supplies? Microchip Technology?

The problem chip vendors have had in addressing this broad set of power measurement market applications is how to provide the basic measurement capabilities across a wide enough spectrum of applications to keep the cost of deployment low, but at the same allow developers to implement them with a minimum of additional software or hardware development costs.

In past years, IC vendors, including Microchip, have attempted to address these needs with multichip solutions, usually a chip with the analogue building blocks and an MCU that the developer would program with the algorithms and operations appropriate to the power measurement task. Alternatively, they have used a combination of dedicated control logic and analogue functions targeted at specific power monitoring needs.

But many of these market segments, particularly targeting the home, are becoming highly competitive and cost-sensitive. Companies are rushing to compete in these markets, but not all of them have both the necessary programming skills and domain expertise in power-monitoring applications. And all of them want to keep costs down.

To address this broad spectrum of power monitoring needs, the MCP39F511 includes two 24bit delta-sigma ADCs with 94.5 decibels of signal-to-noise and distortion ratio (SINAD) performance, a low-drift voltage reference, and an internal oscillator. In addition, it has a number of on chip enhancements that make it possible to do accurate power measurements with no more than 0.1 per cent error across a wide 4000:1 dynamic range, allowing it to meet most power meter application accuracy requirements, especially where small shunt sensors are used. The MCP39F511 incorporates zero crossing detection (ZCD) capabilities that can be used for synchronisation to minimise voltage spikes and electrical noise if switching occurs at the point where the voltage is momentarily zero.

MCP39F511 demo board

The MCP39F511 demo board allows access to software that developer can use to configure the power monitoring IC to a wide range of applications.

What makes the MCP39F511 more than just another dedicated power monitoring chip is the inclusion of a PIC-based 16bit calculation engine at the core of the device. Rather than designing the chip to be programmed in the traditional sense by a developer, the calculation engine has been pre-programmed by Microchip engineers to provide access to a set of power management algorithms.

Via a menu accessible from a desktop PC, a developer can select the functions needed and the calculation engine quickly configures the on-chip analogue building blocks to fit the specific set of power monitoring and power factor correction needs. The MCP39F511also includes 512 bytes of user programmable EEPROM that a developer can access through page read/write commands to log critical events relating to operating conditions or to do troubleshooting.

According to Jefferay Lawton, senior product marketing engineer in Microchip's analogue & interface products division, the aim of this design is to provide the means to configure the MCP39F511 quickly to particular needs without the overhead of additional programming, which would increase both cost and time to market.

A power monitor demonstration board is supplied with the MCP39F511. It connects to a desktop PC via a USB link where power monitor utility software developed by Microchip can be used to programme a fully functional single-phase power and energy monitoring system. The software also provides developers with an automated control mode. This will allow experimentation with all system configuration settings such as PWM output frequencies, zero crossing detection options and event configurations. The software can also be used to create custom calibration set-ups as well as access an automated calibration process that can be used to quickly calibrate energy meters.

- Bernard Cole
??EE Times Europe

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