DESCRIPTION
The LTC®4085 is a USB power manager and Li-Ion battery charger designed for portable battery-powered applications. The part controls the total current used by the USB peripheral for operation and battery charging. The total input current can be limited to 20% or 100% of a programmed value up to 1.5A (typically 100mA or 500mA). Battery charge current is automatically reduced such that the sum of the load current and charge current does not exceed the programmed input current limit.
The LTC4085 includes a complete constant-current/constant-voltage linear charger for single cell Li-ion batteries. The float voltage applied to the battery is held to a tight 0.8% tolerance, and charge current is programmable using an external resistor to ground. An end-of-charge status output CHRG indicates full charge. Total charge time is programmable by an external capacitor to ground. When the battery drops 100mV below the float voltage, automatic recharging of the battery occurs. Also featured is an NTC thermistor input used to monitor battery temperature while charging.
The LTC4085 is available in a 14-lead low profile 4mm × 3mm DFN package.

FEATURES
■ Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and 5V Wall Adapter
■ 215mΩ Internal Ideal Diode Plus Optional External Ideal Diode Controller Provide Low Loss PowerPath™ When Wall Adapter/USB Input Not Present
■ Load Dependent Charging Guarantees Accurate USB Input Current Compliance
■ Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charging Rate Without Risk of Overheating*
■ Selectable 100% or 20% Input Current Limit (e.g., 500mA/100mA)
■ Battery Charge Current Independently Programmable Up to 1.2A
■ Preset 4.2V Charge Voltage with 0.8% Accuracy
■ C/10 Charge Current Detection Output
■ NTC Thermistor Input for Temperature Qualified Charging
■ Tiny (4mm × 3mm × 0.75mm) 14-Lead DFN Package

APPLICATIONS
■ Portable USB Devices: Cameras, MP3 Players, PDAs