The SP6644/6645 devices are high-efficiency, low-power step-up DC-DC converters ideal for single or dual alkaline cell applications such as pagers, remote controls, pointing devices, medical monitors, and other low-power portable end products. Designers can control the SP6644 device with an active LOW shutdown input. The SP6644 device features an active low output for batteries below +1.0V. The SP6645 device features an active low output for batteries below +2.0V. Both devices contain a 0.8 synchronous rectifier, a 0.5 N-channel MOSFET power switch, an internal voltage reference, circuitry for pulsefrequency-modulation, and an under voltage comparator. The output voltage for the SP6644/6645 devices is preset to +3.3V + 4% or can be adjusted from +2V to +5.5V by manipulating two external resistors TYPICAL APPLICATION CIRCUIT