LTC3549

LTC3549 250mA Low VIN Buck Regulator in 2mm × 3mm DFN U U FEATURES ■ 1.6V to 5.5V Input Voltage Range ■ Internal Soft-Start ■ Low Ripple Burst Mode® Operation Output Ripple: <20mVP-P IQ: 50µA ■ 2.25MHz Constant-Frequency Operation ■ High Efficiency: Up to 93% ■ 250mA Output Current (VIN = 1.8V, VOUT = 1.2V) ■ 450mA Peak Inductor Current ■ No Schottky Diode Required ■ Low Dropout Operation: 100% Duty Cycle ■ 0.611V Reference Voltage ■ Stable with Ceramic Capacitors ■ Shutdown Mode Draws <1µA Supply Current ■ Current Mode Operation for Excellent Line and Load Transient Response ■ Overtemperature Protection ■ Available in a Low Profile (0.75mm) 6-Lead (2mm x 3mm) DFN Package U APPLICATIO S ■ 2 AA-Cell Applications ■ Cellular Phones ■ Digital Cameras ■ MP3 Players DESCRIPTIO The LTC®3549 is a high efficiency, monolithic synchronous buck regulator using a constant-frequency, current mode architecture. The output voltage is adjusted via an external resistor divider. A fixed switching frequency of 2.25MHz is supported. This switching frequency allows the use of small surface mount inductors and capacitors, including ceramics. Supply current during Burst Mode operation is only 50µA dropping to < 1µA in shutdown. The 1.6V to 5.5V input voltage range makes the LTC3549 ideally suited for single cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH battery-powered applications. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. Burst M...