Real-time-clock chip makes low-power oscillator
Yongping Xia, Teldata Inc, Los Angeles, CA -- EDN, November 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 VDD.
