MSP430AFE2xx architecture
Be it smart meters or smoke detectors, accurate sensing is key to successful products. Texas Instruments's (TI) low power, 16-bit MSP430 microcontrollers have been utilized for these applications for quite awhile. The latest incarnation, the MSP430AFE2xx (Fig. 1), targets metrology applications like those mentioned using a new analog front end (AFE). It challenges many ROM-based solutions with a low power flash-based platform.
The 16-bit micro includes from 4 to 8 Kbytes of flash and up to 256 bytes of RAM. It has a 6-bit multiplier, 16-bit timers and a USART that can handle an SPI interface. The AFE include one to three 24-bit Sigma-Delta ADCs. These may be used in single phase metering applications in which case the extra channels could be used for anti-tampering or temperature sensing. The ADCs have a 0.1% accuracy with a dynamic range of 2400:1.
The chips are available in 24-pin TSOP packages. This supports up to 11 GPIOs.
The software development tools include the MSP430 Code Composer IDE and TI's Energy Library. There are a number of demo and eval platforms available as well. The MSP430AFE EVM is a single phase eletric meter device that includes support for RF and infrared communication. The metrology software that comes with the application note includes calibration using and external GUI. The Energy Watchdog demo module has an LCD display with a pass through plug. It monitors the power passing through the device using a pair of MSP430 chips. The other provides LCD and USB support.