The LTC4055/LTC4055-1 are USB power manager and Li-Ion battery chargers designed to work in portable battery-powered applications. The parts manage and limit the total current used by the USB peripheral for operation and battery charging. Depending on the state of the current select pin (HPWR), total input current can be limited to either 100mA or 500mA. The voltage drop from the USB supply or battery to the USB peripheral is typically less than 100mV at 400mA and 20mV at 80mA. Other management features include: automatic switch over to battery when input is removed, inrush current limiting, reverse current blocking, undervoltage lockout and thermal shutdown.
The LTC4055/LTC4055-1 include 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. Fully discharged cells are automatically trickle charged at 10% of the programmed current until the cell voltage exceeds 2.8V. 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 LTC4055/LTC4055-1 are available in a 16-pin low profile (4mm x 4mm) QFN package.
Feature
- Charges Single Cell Li-Ion Batteries Directly from USB Port
- Load Dependent Charging Guarantees USB Input Current Compliance
- Automatic Battery Switchover When Input Supply is Removed
- Constant-Current/Constant-Voltage Operation with Thermal Feedback to Maximize Charging Rate Without Risk of Overheating*
- Selectable 500mA/100mA Current Limit
- Low Loss Full PowerPath™ Control with Ideal Diode Operation (Reverse Current Blocking)
- Preset 4.2V Charge Voltage with 0.8% Accuracy (4.1V for LTC4055-1)
- 4.1V Float Voltage (LTC4055-1) Improves Battery Life and High Temperature Safety Margin
- USB-Compliant Suspend Mode
- Programmable Charge Current and Termination Timer
- Soft-Start Limits Inrush Current
- NTC Thermistor Input for Temperature Qualified Charging
- Tiny (4mm x 4mm x 0.75mm) QFN Package
Applications
- Portable USB Devices: Cameras, MP3 Players, PDAs
(Picture: Pinout)
