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LTC1986 - 3V/5V SIM Power Supply in ThinSOT

The LTC1986 is a micropower charge pump DC/DC converter that provides power for either 3V or 5V GSM SIM cards. It operates in one of three modes: VOUT = 5V (5V mode), VOUT = VIN (3V mode) or shutdown. The input voltage range is 2.6V to 4.4V and the part can provide 10mA of output current. The LTC1986 allows VIN to drop as low as 2.6V by providing a boost feature in 3V mode. In 3V mode, VOUT is connected directly to VIN through a 2.5W switch until VIN drops below 2.85V. When VIN is below 2.85V, the part automatically boosts VOUT to maintain a regulated 2.9V output, thereby ensuring VOUT stays within the 3V SIM VCC specification.

Extremely low operating current (14µA typical with no load) and low external parts count make the part ideally suited for small, light load battery-powered applications. The total PCB area of the application circuit shown below is less than 0.045in². Protection features include inrush current limiting, undervoltage lockout, short circuit and thermal overload protection. The LTC1986 is available in a low profile (1mm) SOT-23 package.

Features VIN Range: 2.6V to 4.4V Ultralow Power Operating Current: 14µA Shutdown Current: <1µA No Inductors Short-Circuit/Thermal Protected Ultrasmall Application Circuit (<0.045in² ) Low Profile (1mm) ThinSOT™ Step-Up Charge Pump Generates 5V Output Current: 10mA VIN to VOUT Direct Connection for 3V SIMs Switching Frequency: 900kHz Soft-Start Limits Inrush Current at Turn-On Output Driven to Ground During Shutdown Typical Application

Applications GSM Cellular Telephones PCS/DCS Cellular Telephones Portable POS Terminals Packaging