LTC1911-1.5

` Low Noise Constant Frequency Operation
` 2.7V to 5.5V Input Voltage Range
` No Inductors
` Typical Efficiency 25% Higher Than LDOs
` Shutdown Disconnects Load from V<sub>IN</sub>
` Output Voltage: 1.8V ±4% or 1.5V ±4%
` Output Current: 250mA
` Low Operating Current: I_IN = 180A Typ
` Low Shutdown Current: I<sub>IN</sub> = 10A Typ
` Oscillator Frequency: 1.5MHz
` Soft-Start Limits Inrush Current at Turn On
` Short-Circuit and Overtemperature Protected
` Available in an 8-Pin MSOP Package

· Handheld Computers
· Cellular Phones
· Smart Card Readers
· Portable Electronic Equipment
· Handheld Medical Instruments
·Low Power DSP Supplies

V_IN to GND .......................................................0.3V to 6V
SS/SHDN to GND............................... 0.3V to (V_IN + 0.3V)
VOUT Short-Circuit Duration ................................ Indefinite
Operating Temperature Range (Note 2) .. 40°C to 85°C
Storage Temperature Range ................. 40°C to 150°C
Lead Temperature (Soldering, 10 sec)..................... 300°C

The LTC^®1911 is a switched capacitor step-down DC/DC converter that produces a 1.5V or 1.8V regulated output from a 2.7V to 5.5V input. The part uses switched capacitor fractional conversion to achieve high efficiency over the entire input range. No inductors are required. Internal circuitry controls the step-down conversion ratio to optimize efficiency as the input voltage and load conditions vary.* Typical efficiency is over 25% higher than that of a linear regulator.

A unique constant frequency architecture of LTC1911 provides a low noise regulated output as well as lower input noise than conventional charge pump regulators. High frequency operation (f_OSC = 1.5MHz) simplifies output filtering to further reduce conducted noise. To optimize efficiency, the part enters Burst Mode^® operation under light load conditions.

Low operating current (180A with no load, 10A in shutdown) and low external parts count (two 1mF flying capacitors and two 10mF bypass capacitors) make the LTC1911 ideally suited for space constrained batterypowered applications. The part is short-circuit and overtemperature protected, and is available in an 8-pin MSOP package.