DESCRIPTION
The LTC®3544 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 LTC3544 well suited for single Li-Ion/polymer battery-powered applications. 100% duty cycle provides low dropout operation, extending battery runtime in portable systems. Low ripple Burst Mode® operation increases efficiency at light loads, further extending battery runtime with typically only 20mV of ripple.

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
■ Extremely Low Channel-to-Channel Transient
   Crosstalk
■ Low Ripple (20mVP-P) Burst Mode Operation:
   IQ = 70µA (All Channels On)
■ 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