Overview: MC34280 Power Supply & Management IC for Handheld Electronic Products
The MC34280 is a power supply integrated circuit which provides two boost regulated outputs and some power management supervisory functions. 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; or by a microprocessor, digitally through a 6–bit internal DAC. The MC34280 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 MC34280 is best suited to operate from 1 to 2 AA/ AAA cell. Moreover, supervisory functions such as low battery detection, CPU power–on reset, and back–up battery control, are also included in the chip. It makes the MC34280 the best one–chip power management solution for applications such as electronic organizers and PDAs.
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