• Charging
  • 1% Charge voltage accuracy
  • 10% Charge current accuracy
  • Pin selectable USB 100-mA and 500-mA maximum input current limit
  • Programmable termination and precharge threshold
• Protection
  • 30-V Input Rating; With 6.6-V input overvoltage protection
  • Input voltage dynamic power management
  • 125 °C Thermal regulation; 150°C thermal shutdown protection
  • OUT Short-circuit protection and ISET short detection
  • Operation over JEITA range through battery NTC - ½ fast-charge-current at cold, 4.06 V at hot
  • Fixed 10-hour safety timer
• System
  • Auto input source detection (D+, D– pins)
    • No device transceiver required
    • USB Friendly
  • Automatic termination and timer disable mode (TTDM) for absent battery pack with thermistor
  • Status indication – charging/done
  • Available in small 2-mm × 2-mm package

• Headphones, speakers, and audio accessories
• Wristbands and wearables
• Smart door locks
• Low-power handheld devices

The BQ2405x series of devices are highly integrated Li-Ion and Li-Pol linear chargers devices targeted at space-limited portable applications. The devices operate from either a USB port or AC adapter. The high-input voltage range with input overvoltage protection supports low-cost unregulated adapters.

The BQ2405x has a single power output that charges the battery. A system load can be placed in parallel with the battery as long as the average system load does not keep the battery from charging fully during the 10-hour safety timer.

The battery is charged in three phases: conditioning, constant current, and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded.

The charger power stage and charge current sense functions are fully integrated. The charger function has high accuracy current and voltage regulation loops, charge status display, and charge termination. The precharge current and termination current threshold are programmed through an external resistor. The fast charge current value is also programmable through an external resistor.

Simplified Circuit