Microcontroller has precision temperature-compensated real-time clock

Samples have been shipping of the S7C17M11, a low power 16bit microcontroller with on-chip Flash memory, a crystal unit, and accurate real-time clock (RTC) with a temperature compensation function. Epson says that it has integrated a crystal unit into the microcontroller package for timekeeping in microcontroller-equipped devices such as electricity meters. It says the S7C17M11 allows users to develop accurate timekeeping efficiently even under harsh environmental conditions, such as in outdoor meters.

An ordinary RTC consists of a timekeeping IC that is connected to an external crystal unit. Time is measured based on the frequency of the crystal unit. However, the stability of the crystal unit’s oscillation frequency varies by product. Temperature can effect frequency stability, and therefore accuracy, and fluctuations in oscillation frequency have to be taken into account. To meet this challenge, the company integrated one of its own high-stability crystal units into the S7C17M11 microcontroller package and developed technology for detecting and correcting frequency deviations caused by temperature changes. The S7C17M11 is accurate to within 10s/month at temperatures between 0 and 50 degree C, 13.2s/month between -30 and 70 degree C, and 26.4s/month between -40 and 85 degree C.

The integrated device is also claimed to eliminate the need for adjustments, to reduce development time and reduce the number of discrete components.
Integrated peripheral circuits include Flash memory, a 12bit ADC, and an LCD driver with a built-in liquid crystal power supply for a 240-segment display. Power consumption in RTC mode is 2.25microA (typical).



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