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 VINto drop as low as 2.6V by providing a boost feature in 3V mode. In 3V mode, VOUTis connected directly to VINthrough a 2.5Ω switch until VINdrops below 2.85V. When VINis below 2.85V, the part automatically boosts VOUTto maintain a regulated 2.9V output, thereby ensuring VOUTstays within the 3V SIM VCCspecification.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.ApplicationsGSM Cellular TelephonesPCS/DCS Cellular TelephonesPortable POS Terminals