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Real-time-clock chip makes low-power oscillator

Yongping Xia, Teldata Inc, Los Angeles, CA -- EDN, 11/23/2000

Many systems use watch-crystal-based, 32.768-kHz oscillators. In battery-powered designs, the 32-kHz oscillator may consume a fairly high percentage of the total power budget. Reduced power consumption equates to longer battery life, smaller batteries, and smaller products. Ricoh (www.ricoh.com) manufactures more than 10 types of real-time-clock chips, including the RS5C372B (Figure 1). This device is an eight-pin IC with a built-in oscillator, programmable periodic interrupts, and an I²C interface to a µC. The only function the device in Figure 1 uses is the 32-kHz oscillator. Using only the IC and the crystal, the circuit consumes low current over its 1.5 to 6V power-supply range, as the table in Figure 1 shows. The CMOS-based output delivers a waveform with an amplitude of 0V to V_DD.

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