The MC34280 is a power supply integrated circuit which provides two boost regulated outputs and some power management supervisory functions. Both regulators apply PulseFrequencyModulation (PFM). The main stepup 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 builtin 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; or by a microprocessor, digitally through a 6bit internal DAC. The MC34280 has been designed for battery powered handheld products. With the low startup voltage from 1V and the low quiescent current (typical 35 A); the MC34280 is best suited to operate from 1 to 2 AA/ AAA cell. Moreover, supervisory functions such as low battery detection, CPU poweron reset, and backup battery control, are also included in the chip. It makes the MC34280 the best onechip power management solution for applications such as electronic organizers and PDAs.