The LTC3448 is a high efficiency, monolithic, synchronous buck regulator using a constant frequency, current mode architecture. Supply current during operation is only 32µA (linear regulator mode) and drops to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3448 ideally suited for single Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. At moderate output load levels, PWM pulse skipping mode operation provides very low output ripple voltage for noise sensitive applications.The LTC3448 automatically switches into linear regulator operation at very low load currents to maintain <5mVP-Poutput voltage ripple. Supply current in this mode is typically 32µA. The switch to linear regulator mode occurs at a threshold of 3mA. Linear regulator operation can be set to on, off or automatic turn on/off.Switching frequency is selectable at either 1.5MHz or 2.25MHz, allowing the use of small surface mount inductors and capacitors.The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. The LTC3448 is available in a low profile 3mm × 3mm DFN package or thermally enhanced 8-lead MSOP.Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131. Others pending.ApplicationsCellular TelephonesPersonal Information AppliancesWireless and DSL ModemsDigital Still CamerasMP3 PlayersPortable Instruments