LTC4008 Datasheet

• General Purpose Charger Controller
• High Conversion Efficiency: Up to 96%
• Output Currents Exceeding 4A
• ±0.8% Voltage Accuracy
• AC Adapter Current Limiting Maximizes Charge Rate
• Thermistor Input for Temperature Qualified Charging
• Wide Input Voltage Range: 6V to 28V
• Wide Output Voltage: 3V to 28V
• 0.5V Dropout Voltage; Maximum Duty Cycle: 98%
• Programmable Charge Current: ±4% Accuracy
• Indicator Outputs for Charging, C/10 Current Detection, AC Adapter Present, Input Current Limiting and Faults
• Charging Current Monitor Output
• Available in a 20-Pin Narrow SSOP Package

• Notebook Computers
• Portable Instruments
• Battery Backup Systems

The LTC4008 is a constant-current/constant-voltage charger controller. The PWM controller uses a synchronous, quasi-constant frequency, constant off-time architecture that will not generate audible noise even when using ceramic capacitors. Charging current is programmable with a sense resistor and programming resistor to ±4% typical accuracy. Charging current can be monitored as a voltage across the programming resistor. An external resistor divider and precision internal reference set the final float voltage.

The LTC4008 includes a thermistor sensor input that will suspend charging if an unsafe temperature condition is detected and will automatically resume charging when battery temperature returns to within safe limits; a FAULT pin indicates this condition. A FLAG pin indicates when charging current has decreased below 10% of the programmed current. An external sense resistor programs AC adapter current limiting. The I_CL pin indicates when the charging current is being reduced by input current limiting so that the charging algorithm can adapt.