DESCRIPTION
The LTC®3544B is a quad, high efficiency, monolithic synchronous buck regulator using a constant frequency, current mode architecture. The four regulators operate independently with separate run pins. The 2.25V to 5.5V input voltage range makes the LTC3544B well suited for single Li-Ion/polymer battery-powered applications. 100% duty cycle provides low dropout operation, extending battery runtime in portable systems. At moderate and low output load levels PWM pulse skip mode operation provides very low output ripple voltage for noise sensitive applications.

FEATURES
■ High Efficiency: Up to 95%
■ Four Independent Regulators Provide Up to 300mA,
   200mA, 200mA and 100mA Output Current
■ 2.25V to 5.5V Input Voltage Range
■ 2.25MHz Constant Frequency Operation
■ No Schottky Diodes Required
■ Low Dropout Operation: 100% Duty Cycle
■ Pulse Skipping at Low Load for Minimum Ripple
■ 0.8V Reference Allows Low Output Voltages
■ Shutdown Mode Draws <1µA Supply Current
■ Current Mode Operation for Excellent Line and Load
   Transient Response
■ Overtemperature Protected
■ Low Profile (3mm × 3mm) 16-Lead QFN Package

APPLICATIONS
■ Cellular Telephones
■ Personal Information Appliances
■ Wireless and DSL Modems
■ Digital Still Cameras
■ Media Players
■ Portable Instruments