The LTC4078/LTC4078X are standalone linear chargers that are capable of charging a single-cell Li-Ion/Polymer battery from both wall adapter and USB inputs. The chargers can detect power at the inputs and automatically select the appropriate power source for charging.No external sense resistor or blocking diode is required for charging due to the internal MOSFET architecture. The LTC4078/LTC4078X feature a maximum 22V rating for both wall adapter and USB inputs, although charging stops if the selected power source exceeds the overvoltage limit. Internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. The float voltage is fixed at 4.2V and the charge current is programmed with an external resistor. The LTC4078/LTC4078X terminate the charge cycle when the charge current drops below the programmed termination threshold after the final float voltage is reached.Other features include battery present detection, automatic recharge, undervoltage lockout, charge status outputs, and "power present" status outputs to indicate the presence of wall adapter or USB power. The device is offered in a low profile (0.75mm) 3mm × 3mm 10-lead DFN package.ApplicationsCellular TelephonesHandheld ComputersPortable MP3 PlayersDigital Cameras