ICs Make Meter Designs Easier, Energy Theft Harder

Oct 1, 2007 12:00 PM
By David Morrison, Editor, Power Electronics Technology

In May, Texas Instruments announced sampling of its 16-MHz MSP430F47x4 ultralow-power microcontrollers (MCUs) for single- and multiphase meters. By integrating up to four individual 16-bit sigma-delta ADCs, a 32-bit x 32-bit hardware multiplier, a 160-segment LCD driver with contrast control, up to 60 kbytes of flash memory and a real-time clock, the F47x4 devices enable a 5:1 reduction in system components, according to the vendor.

Fig. 5. With its numerous on-chip peripherals, the MSP430F47x4 16-MHz microcontrollers from Texas Instruments can be used to implement single- and multiphase meter designs, while limiting standby power consumption to just 1.5 µA. (click image to see full-sized figure)

With standby power consumption as low as 1.5 µA, a meter based on these devices allows utilities to reduce overall system power consumption. The F47x4 series MCUs feature several low-power modes, allowing the meter to sleep with almost no power drain between readings. An extremely fast wake-up brings the device to full clock speed within 6 µs. Together with a fast shutdown, this “instant-on” wake-up minimizes time spent in active mode.

The MSP430F47x4 series of MCUs are available for sampling. Unit pricing starts at $7.50 each in quantities of 1000.

Maxim Integrated Products also has introduced a 16-bit MCU targeting electricity metering and other industrial, medical or consumer applications that require a real-time clock and an LCD controller. Announced in July, the MAXQ3100 16-bit RISC microcontroller features an integrated temperature sensor and battery-backed, digitally trimmable real-time clock. The latter feature enables very accurate time keeping, which is critical for applications based on time-of-use events such as electricity tariffs.

An addition to the MAXQ microcontroller product line, the MAXQ3100 includes an LCD interface that supports up to 160 segments, a frequency-locked loop, two analog comparators and a digital temperature sensor. The MAXQ3100 has 16 kbytes of EEPROM program memory, 1 kbyte of data SRAM, a watchdog timer, two serial ports (USARTs) and three timers.

Fig. 6. The MAXQ3100 16-bit RISC microcontroller features an LCD display driver and a real-time clock with a dedicated battery backup pin. (click image to see full-sized figure)

The dedicated RTC battery-backup pin lets a battery keep the RTC running when the controller's main power supply is absent. The built-in power-management circuit automatically detects and switches the RTC supply back to the main controller power supply whenever it is available. This intelligent power-management approach maximizes the RTC's battery life.

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© 2007 Penton Media, Inc.