ICs Manage Power And Protect Batteries

A duo poised for use in a myriad of portable products, the LP3947 manages battery power and the LM3655 provides battery protection. The LP3947 charges and maintains a Li-Ion battery from either a USB power source or an ac adaptor. Via USB power, it supports low- or high-power charging. In either arrangement, charge current, regulation voltage, and the end-of-charge point are selectable via an I2C interface. Other features include temperature monitoring, under-voltage and over-voltage protection, a 5.6-hr. timer, four operating modes, and the ability to operate as a linear regulator, providing up to 1.2A. The other chip, the LM3655, provides charge and discharge control for a single Li-Ion cell and performs current-control chores using an external PNP transistor. Operating current from the battery passes through the device, allowing the battery to disconnect should overload, short-circuit, or low-battery events occur. Prices for the LP3947 and LM3655 are $1.05 and $1.65 each/1,000, respectively. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959