Features

• V_IN 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
• V_IN to V_OUT Direct Connection for 3V SIMs
• Switching Frequency: 900kHz
• Soft-Start Limits Inrush Current at Turn-On
• Output Driven to Ground During Shutdown

Typical Application

Description

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: V_OUT = 5V (5V mode), V_OUT = V_IN (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 V_IN to drop as low as 2.6V by providing a boost feature in 3V mode. In 3V mode, V_OUT is connected directly to V_IN through a 2.5W switch until V_IN drops below 2.85V. When V_IN is below 2.85V, the part automatically boosts V_OUT to maintain a regulated 2.9V output, thereby ensuring V_OUT stays within the 3V SIM V_CC 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.