Texas Instruments has introduced what it calls the industry's first system-on-chip microcontroller unit for electronic energy meters. With its programmable communication capabilities, the MSP430FE42x family of application-specific MCUs has been designed for manufacturers developing electronic energy meters with features such as automated meter reading, smart card prepayment, and multiple rate billing.
The device family features a low-power flash MCU coupled with an integrated, high-performance analog front-end on a single-chip, cutting the total system chip count by 80%, which is said to improve performance and reliability and reduce cost and time to market. Systems using the MSP430FE42x family don't require multiple crystals, an EEPROM, LCD driver, external real time clock, or 5V power supplies.
To improve performance and simplify system design, the device integrates an embedded signal processor (ESP) for single phase e-meters, and features to perform the energy metrology functions, such as: three independent 16-bit sigma-delta analog-to-digital converters operating at an over-sampled rate of 1MHz; three programmable gain amplifiers; and a temperature sensor and precision voltage reference.
The converted line voltage and current signals are digitally processed, providing:
- energy and line period measurement;
- negative power flow indication;
- peak voltage and current;
- phase and line-to-neutral current comparisons for tamper detection.
With phase matching between current and voltage channels, the ESP performs the calculations to supply accurate active energy, apparent energy, RMS voltage, current and waveform samples. The ESP provides a claimed 0.1 percent accurate energy measurement over a dynamic current range of 1000 to 1.
A flexible clock system with five low-power modes enables low-power performance and operation using one 32-kHz watch crystal. The MSP430FE42x operates at 3V with the CPU and ESP active at 2.5mA.
The MSP430FE42x family is compatible with the existing $99 MSP-FET430P410 JTAG emulation toolkit. The tool supports real-time in-system application development, accessing the flash device's embedded emulation capability. The tool comes with a JTAG interface, target board and an integrated development environment that includes a debugger, assembler/linker, and 4kB C-Compiler.
The MSP430FE42x family offers 8kB, 16kB or 32kB on-chip Flash memory options and 256B to 1kB RAM. It is available for pre-production and engineering evaluation now with full production planned for late 2003. The 8kB MSP430FE423 is priced at $2.95 per unit in 100,000-piece quantities.
Texas Instruments Inc.