ML4890

Extend G nge RIN Ra TU erature A p m e E T l F ia c r e m ed Com °C to 70°C ent –20 Equipm ndheld a H le tab for Por April 1997 ML4890 High Efficiency, Low Ripple Boost Regulator GENERAL DESCRIPTION The ML4890 is a high efficiency, PFM (Pulse Frequency Modulation), boost switching regulator connected in series with an integrated LDO (Low Dropout Regulator) that incorporates “Silent Switcher™” technology. This technique incorporates a patented tracking scheme to minimize the voltage drop across the LDO and increase the total efficiency of the regulator beyond that which can be obtained by using a discrete external LDO regulator. The ML4890 is designed to convert single or multiple cell battery inputs to regulated output voltages for integrated circuits and is ideal for portable communications equipment that cannot tolerate the output voltage ripple normally associated with switching regulators. An integrated synchronous rectifier eliminates the need for an external Schottky diode and provides a lower forward voltage drop, resulting in higher conversion efficiency. FEATURES s s Incorporates “Silent Switcher™” technology to deliver very low output voltage ripple (typically 5mV) Guaranteed full load start-up and operation at 1.0V input and low operating quiescent current (<100µA) for extended battery life Pulse Frequency Modulation and internal synchronous rectification for high efficiency Minimum external components Low ON resistance internal switching MOSFETs 5V, 3.3V, an...