dsp/mcuZONE Products for the week of April 11, 2011Texas Instruments Says…
MSP430 microcontroller portfolio expands to offer industry’s first programmable metrology devices for low-cost analog front end solutions
Series allows increased functionality, flexibility and high-precision measurement in metering applications
Focusing on metering and Smart Grid applications, Texas Instruments Incorporated has announced the MSP430AFE2xx series of metrology analog front end (AFE) ultra-low-power 16-bit microcontrollers. Part of TI's leading embedded processing portfolio, the low-cost MSP430AFE series offers the industry’s first programmable single-phase metrology devices supported with multiple communication interfaces. The microcontrollers enable system partitioning in metering applications, such as electricity meters, home automation, sub-metering and energy saving systems, which allows flexible, stand-alone, high-quality measurement. The MSP430AFE series is based on a 16-bit RISC architecture with a system frequency of 12MHz, offering 3X the system speed over competing parts to drive increased functionality. The microcontroller achieves less than 0.1 percent error in energy accuracy over a wide dynamic range of 2400:1, enabled by three independent 24-bit sigma-delta converters supporting anti-tamper.
The MSP430AFE2xx series is also supported by multiple tools, demos and EVMs to provide several options for developers to begin evaluation and move quickly to production. Allowing users to manage energy usage and begin saving money, the RF-capable MSP430 Energy Watchdog demo displays the electricity consumption of any plug-in appliance on an LCD display. The programmable MSP430AFE EVM can be used to test the new MSP430AFE2xx as a calibrated electricity meter. Additionally, the MSP-TS430PW24 target board and MSP-FET430U24 flash emulation tool can be used to program and debug the MSP430AFE devices.
Key features and benefits of the MSP430AFE2xx Series:
- Single-phase metrology analog front end supporting class 0.1percent accuracy over a 2400:1 dynamic range
- Three 24-bit sigma-delta analog-to-digital converters (ADCs) with simultaneous sampling for single-phase measurement and anti-tampering, and a small 24-pin TSSOP package for optimal space saving
- Programmable MSP430AFE devices offer flexibility in system design and performance
- Comprehensive TI libraries for measuring energy, power, voltage, current and several other key metering criteria provide quick and robust single-phase metrology implementation
- Up to 16KB Flash and 512B RAM provides design flexibility with programmable memory via SPI and UART interfaces
- Integrated peripherals, including 16-bit timer, watchdog and hardware multiplier allow for customer controlled tasks and math intensive computations in ultra-low power modes
TI’s latest addition to their versatile MSP430 MCU family is another example of their talent for producing application-specific solutions that have both the functionality and pricing to help designers quickly address emerging market opportunities. In this case, they have added an extremely precise analog front end to a Flash memory-equipped version their basic MCU platform. This combination of programmability and high accuracy makes it a natural for smart meter/smart grid applications as well as the first generation of energy-aware consumer goods that TI expects to emerge over the next few years.
Although the TMS320 RISC core probably has enough processing horsepower to support many of the other functions associated with Smart meters, TI has positioned these MCU-driven devices as so-called dumb metrology front ends that are paired with another MSP430 that serves as a management processor which takes care of the housekeeping an display drive functions as well as serve as an interface to the Smart Meter’s host processor. Besides ensuring that conflicting software demands do not compromise the precision of its measurements, a segmented approach allows the MSP430AFE2xx series to be used as part of a cost-effective 2-chip solution that can be tweaked to comply with various national meter design regulations. China, for example, ensures the accuracy of its meters by requiring that all products be built according to a standardized smart meter architecture with a stand-alone metrology chip.
The MSP430AFE2xx series combines a Flash-programmable 430 RISC core with a sophisticated analog front-end that consists of three independent 24-bit sigma-delta ADCs (running at 1048 Msample/s) sitting behind a set of precision PGAs. This is a big step up from the 16-bit converters offered on previous 430 variants, a step which may live up to TI’s claims that it is an industry-first in this market segment (I cannot recall another sub-$1 MCU that offered a true 24-bit ADC capability). Instead of the multiplexed scheme used in many 12- and 16-bit products, TI eliminated the associated noise and non-linearities they can introduce by providing separate ADCs for amplitude and current measurements.
If TI is actually making proper use of those extra 8 bits, it should indeed allow them to deliver a sub-0.1% error in energy accuracy rate across a very wide dynamic range. While some 16-bit parts are able to deliver nearly this level of accuracy across a narrow sweet spot, they cannot touch TI’s claimed range of 2400:1 that allows it to deliver accurate phase data even at extremely high and low current levels. A range of 0.1% is roughly double of competing parts. Software developers will appreciate the synchronized ADC sampling logic that lets the MCU (or its associated timers) simultaneously trigger all three converters at the same time, enabling perfectly-synched snapshots of line current and voltage with no software compensation required. The extremely accurate phase measurements this part is capable of producing will become increasingly important in smart power systems which, among other things, will allow utilities to remotely monitor line conditions: which provide important clues on the health and status of their distribution network.
The AFE’s third ADC can be used for other measurements, including tamper-detect functions which monitor the neutral line for the spikes that occur when a would-be power thief messes with the hot or ground leads. Although anti-tamper features are most popular in India and Asia these days I expect they will begin to appear in the next-generation of North American and European markets. Each of the ADCs also has a selectable temperature sense function. Normally, the converters use an on-chip thermistor but TI says there are provisions for using an external sense element. When used in a smart meter, these capabilities may come in handy as a way to allow a utility to remotely monitor the meter’s actual operating conditions and the ambient temperature at each customer location.
Besides its place in the obvious smart meter products, TI expects the MSP430AFE2xx series to find applications in so-called sub-metering functions in which allow consumer electronics, appliances, PV arrays, and other energy-intensive products to monitor and report their own power consumption. The accuracy these MCUs provide will likely also find a warm welcome in higher-powered 3-phase meters and multi-phase industrial power monitoring applications. At the moment, these designs will require multiple chips to implement but TI has quietly hinted that we can expect to see a similar part with more ADC channels at some point during the next year or so.
Whatever product you choose to develop, your task will be made easier by the collection of application-oriented development platforms and the library of software tools and smart meter-oriented application code that TI has rolled out along with these MCUs. For details, check out our review of the development resources for this MCU in greenpowerZONE.