Regulated 3.3V Charge Pump

The MAX679 step-up, regulated charge pump generates a 3.3V ±4% output voltage from a 1.8V to 3.6V input voltage (two alkaline, NiCd, or NiMH; or one Lithium-Ion battery). Output current is 20mA (min) from a 2.0V input. Only three external capacitors are needed to build a complete DC-DC converter.

The MAX679's switching frequency is pin selectable at 330kHz or 1MHz to allow trade-offs between lowest supply current and smallest-size capacitors. The logic shutdown function reduces the supply current to 5µA (max) and disconnects the load from the input. Special soft-start circuitry prevents excessive current from being drawn from the battery during start-up. This DC-DC converter requires no inductors and has low EMI. It is available in the ultra-small µMAX® package, which is only 1.11mm high and half the area of an 8-pin SO.

Applications

* Backup Battery Boost Converters * Battery-Powered Applications * Miniature Equipment * Translators * Two-Way Paging

* Regulated 3.3V ±4% Output

* Ultra-Small: 1.1mm-High, 8-Pin µMAX Package

* No Inductors Required

* Up to 1MHz Operation (small external components)

* Fits into 0.05 in.²

* Up to 85% Efficiency

* 1.8V to 3.6V Input Voltage Range

* 50µA Quiescent Supply Current

* 1µA Shutdown Current

* Only three small capacitors required