GENERAL DESCRIPTION

The ML4851 is a low power boost regulator designed for DC to DC conversion in 1 to 3 cell battery powered systems. The maximum switching frequency can exceed 100kHz, allowing the use of small, low cost inductors.

The combination of BiCMOS process technology, internal synchronous rectification, variable frequency operation, and low supply current make the ML4851 ideal for 1 cell applications. The ML4851 is capable of start-up with input voltages as low as 1V and is available in 5V and 3.3V output versions with output voltage accuracy of ±3.

An integrated synchronous rectifier 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 ML4851 requires only one inductor and two capacitors to build a very small regulator circuit capable of achieving conversion efficiencies in excess of 90.

The circuit also contains a RESET output which goes low when the IC can no longer function due to low input voltage, or when the DETECT input drops below 200mV.

FEATURES

■ Guaranteed full load start-up and operation at 1V input

■ Maximum switching frequency > 100kHz

■ Pulse Frequency Modulation (PFM) and internal

synchronous rectification for high efficiency

■ Minimum external components

■ Low ON resistance internal switching FETs

■ Micropower operation

■ 5V and 3.3V output versions