ML4770

July 2000 PRELIMINARY ML4770* 2 Cell, Adjustable Output, High Current Boost Regulator with Load Disconnect GENERAL DESCRIPTION The ML4770 is a continuous conduction mode boost regulator designed for DC to DC conversion in multiple cell battery power systems. Continuous conduction allows the regulator to maximize output current for a given inductor. The maximum switching frequency can exceed 200kHz, allowing the use of small, low cost inductors. The ML4770 is capable of start-up with input voltages as low as 1.8V. The output voltage can be set anywhere between 3.0V and 5.5V by an external resistor divider connected to the SENSE pin. 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 current and variable frequency operation result in high efficiency even at light loads. The ML4770 requires only a few external components to build a very small regulator capable of achieving conversion efficiencies approaching 85%. The SHDN input allows the user to stop the regulator from switching, and provides complete isolation of the load from the battery. FEATURES s Guaranteed full load start-up and operation at 1.8V input Continuous conduction mode for high output current Pulse Frequency Modulation and internal synchronous rectification for high efficiency Isolates the load from the input during shutdown Minimum external components Low ON res...