Dual DC-DC Regulator for Electronic Organizer

The MC33680 is a dual DC-DC regulator designed for electronic organizer applications. Both regulators apply Pulse-Frequency-Modulation (PFM). The main step-up regulator output can be externally adjusted from 2.7V to 5V. An internal synchronous rectifier is used to ensure high efficiency (achieve 87%). The auxiliary regulator with a built-in power transistor can be configured to produce a wide range of positive voltage (can be used for LCD contrast voltage). This voltage can be adjusted from +5V to +25V by an external potentiometer.

The MC33680 has been designed for battery powered hand-held products. With the low start-up voltage from 1V and the low quiescent current (typical 35 µA); the MC33680 is best suited to operate from 1 to 2 AA/ AAA cell. Moreover, supervisory functions such as low battery detection, CPU Power-Good signal, and back-up battery control, for lithium battery or supercap are also included in the chip.