GENERAL DESCRIPTION

The ML4775 is a boost regulator designed for DC to DC conversion in 1 to 3 cell battery powered systems. The combination of BiCMOS process technology, internal synchronous rectification, variable frequency operation, and low supply current make the ML4775 ideal for 1 cell applications. The ML4775 is capable of start-up with input voltages as low as 1V, and the output voltage can be set anywhere between 2.5V and 5.5V by an external resistor divider connected to the SENSE pin.

Unlike regulators using external Schottky diodes, the ML4775 isolates the load from the battery when the SHDN pin is high. This is accomplished by an integrated synchronous rectifier which eliminates the need for an external Schottky diode and provides a lower forward voltage drop, resulting in higher conversion efficiency. In addition, low quiescent battery current and variable frequency operation result in high efficiency even at light loads. The ML4775 requires a minimum number of external components to build a very small regulator circuit capable of achieving conversion efficiencies in excess of 90.

FEATURES

■ Guaranteed start-up and operation at 1V input

■ Pulse Frequency Modulation and Internal Synchronous

Rectification for high efficiency

■ Isolates the load from the input during shutdown

■ Minimum external components

■ Low ON resistance internal switching FETs

■ Micropower operation

■ Adjustable output voltage (2.5V to 5.5V)