ML4871

Extended C Tem ommercial -20˚C to 70˚C quipment Handheld E for Portable G FEATURIN ge perature Ran July 2000 ML4871 High Current Boost Regulator GENERAL DESCRIPTION The ML4871 is a continuous conduction boost regulator designed for DC to DC conversion in multiple cell battery powered 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 ML4871 is capable of start-up with input voltages as low as 1.8V and is available in 5V and 3.3V output versions with an 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 ML4871 requires only one inductor and two capacitors to build a very small regulator circuit capable of achieving conversion efficiencies approaching 90%. The circuit also contains a RESET output which goes low when the DETECT input drops below 1.25V. FEATURES s Guaranteed full load start-up and operation at 1.8V Input Continuous conduction mode for high output current Very low supply current (20µA output referenced) for Micropower operation Pulse Frequency Modulation and Internal Synchronous Rectification for high efficiency Maximum switching fr...