Power Controller IC Does Double Duty On USB August 2004 Issue Published Date: August 12, 2004
Power management and battery charging are the dual roles performed by the LTC4055 USB power controller and Li-Ion linear charger IC in portable battery-powered applications. The device provides power to a USB peripheral and charges the peripheral’s single cell Li-Ion battery from the USB VBUS or from a wall adapter when one is present. It has the ability to detect the presence of a wall adapter and use it as an alternate power source to charge the battery while providing power to the battery’s load. To comply with USB current limit specifications, the chip automatically reduces battery charge current as the system load increases. To ensure that a fully charged battery remains fresh when the bus is connected, the IC directs power to the load through the USB bus rather than taking power from the battery. Once external power is removed, current flows from the battery to load through an internal low-loss diode, minimizing voltage drop and power dissipation. The device is supplied in a 16-pin low-profile QFN (4 mm x 4mm) package guaranteed for operation from -40°C to +85°C. Price is $2.20 each/1,000. LINEAR TECHNOLOGY CORP., Milpitas, CA. (408) 432-1900, ext.2593.
