Battery-Charger IC Works From Wall Adapter Or USB Input

The LTC4097 standalone dual-input linear battery charger from Linear Technology Corp. charges single-cell Li-ion/polymer batteries from either a wall adapter or USB power source. The device uses a constant-current/constant-voltage charging algorithm with programmable charging current up to 1.2 A from a wall adapter or up to 1 A from a USB supply while automatically detecting the presence of voltage at each input. Suitable applications for the charging IC, which features USB current limiting, include PDAs, MP3 players, digital cameras, lightweight portable medical and test equipment, and large color-display cell phones.

The chip delivers a final float voltage accuracy of ±0.6%. It is equipped with a patented thermal regulation scheme that maximizes the charging rate without the risk of overheating. The wall-adapter charge current, USB-supply charge current, and charge termination current are all programmable via a single resistor. As a standalone charger, the IC does not require an external microcontroller to terminate charging. In addition, it does not require an external MOSFET, a sense resistor, or a block diode. Operating temperature range is −40°C to 85°C. The LTC4097 comes in a low-profile (0.75 mm) 12-lead, 2- by 3-mm DFN package.