Dallas - A line of microcontrollers from Texas Instruments Inc. combines TI's MSP430 flash MCU core and an analog front end for manufacturers developing electronic energy meters with sophisticated features such as automated meter reading, smart-card prepayment and multiple-rate billing.
Systems using the MSP430FE42x line do not require multiple crystals, an E2PROM, LCD driver, external real-time clock or expensive 5-volt power supplies, said Mark Buccini, MSP430 product line marketing manager. In addition, the single-chip MCU eliminates the need for expensive long-lead-time custom multichip analog front ends.
To perform energy metrology functions the device integrates an embedded signal processor, three independent 16-bit sigma-delta A/D converters operating at an oversampled rate of 1 MHz, three programmable-gain amplifiers, a temperature sensor and a precision voltage reference.
With precise phase matching between current and voltage channels, the embedded signal processor performs the necessary calculations to supply accurate active-energy, apparent-energy, rms voltage, current and waveform samples. The embedded signal processor provides a 0.1 percent accurate energy measurement over a dynamic current range of 1,000 to 1, greatly surpassing the 1 percent accuracy common in typical mechanical meters, TI said.
Having the embedded signal processor completely manage critical energy calculations lets the designer use the freed-up central processing unit functions for differentiated meter features such as display and automated reading.
A clock system with five low-power modes enables ultralow-power performance and complete operation using only a single 32-kHz watch crystal. The low-frequency watch crystal, in combination with the integrated user-programmable, digitally controlled oscillator, precisely meets system power and performance requirements. The microcontrollers operate at 3 V with the CPU and embedded signal processor active at only 2.5 milliamps. In a power outage the device can run in standby mode at typical current consumption of 1.1 microamps with a real-time-clock function active.
The line also includes MSP430 peripherals such as an enhanced watchdog timer, integrated LCD driver, brownout protection, supply voltage supervisor, three-channel pulse-width-modulation timer, serial communication interface (asynchronous UART or synchronous SPI) and serial on-board programming, which requires no external programming voltage.
The line is fully compatible with the existing $99 MSP-FET430P410 JTAG emulation tool kit. The tool supports real-time in-system application development, accessing the flash device's embedded emulation capability. The tool comes complete with a JTAG interface, target board and an integrated development environment that includes a debugger, assembler/linker and 4-kbyte C compiler.
The line offers 8, 16 or 32 kbytes of on-chip flash memory and 256 bytes to 1 kbyte of RAM. The MCU is housed in a 64-pin quad flat pack and is available for preproduction and engineering evaluation now, with full production planned for late in the year. The 8-kbyte MSP430FE423 is priced at $4.85 per unit in 1,000-piece quantities.
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