Linear Technology has developed the LTC4085, a monolithic autonomous power manager, ideal diode controller, and standalone battery charger for portable USB devices. The device features PowerPath control that provides power to the USB peripheral device and charges the peripheral's single-cell Li-Ion battery from the USB Vbus or a wall adapter power supply. To comply with USB current-limit specs, the LTC4085 automatically reduces battery charge current as the system load current 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 extracting power from the battery. Once the power source is removed, current flows from the battery to the load through an internal 200-mΩ low-loss ideal diode, minimizing voltage drop and power dissipation. On-board circuitry drives an optional external PFET hookup to reduce the overall ideal diode impedance below 50 mΩ if required by the application.
The LTC4085 can detect the presence of a wall adapter and use it as an alternate power source to charge the battery while providing power to the system load. It also offers the option of charging the battery at a higher rate (up to 1.5 A) than USB spec allow. Additional functions include a charge termination timer, automatic recharge, NTC thermistor input, automatic switchover to battery when the ac adapter input is removed, in-rush current limiting, reverse current blocking, undervoltage lockout and thermal regulation.
The part is housed in a tiny 14-pin, 4- by 3-mm DFN package with a 0.75-mm profile. 1000-piece pricing starts at $1.65 each. For more information, visit www.linear.com.