bqSWITCHER(TM) Synchronous, Switch-Mode Li-Ion Charger w/ 2-A FET in QFN, 1 to 3 cells, Standalone# BQ24105RHLR Technical Documentation
Manufacturer : Texas Instruments (TI)
## 1. Application Scenarios
### Typical Use Cases
The BQ24105RHLR is a highly integrated single-cell Li-ion and Li-polymer battery charger IC designed for space-constrained portable applications. Key use cases include:
- Smartphones and Tablets : Provides complete charging solution with integrated power path management
- Portable Medical Devices : Enables safe charging for handheld medical equipment with precise termination control
- Wearable Electronics : Compact solution for fitness trackers and smartwatches with minimal external components
- Portable POS Systems : Supports frequent charge/discharge cycles in commercial handheld devices
- Bluetooth Speakers : Manages battery charging while supporting simultaneous device operation
### Industry Applications
- Consumer Electronics : Mobile devices, digital cameras, portable gaming systems
- Medical Technology : Portable monitors, diagnostic equipment, patient monitoring devices
- Industrial Equipment : Handheld scanners, data collection terminals, portable test instruments
- IoT Devices : Smart home sensors, connected wearable devices, remote monitoring systems
### Practical Advantages and Limitations
Advantages:
- High Integration : Combines synchronous switching charger, power FETs, and current sensor in single package
- Flexible Input Sources : Supports 4.35V to 6.45V input range from USB or adapter sources
- Thermal Regulation : Automatic charge current reduction to maintain optimal die temperature
- Small Form Factor : 2.5mm × 2.5mm QFN package ideal for space-constrained designs
- High Efficiency : Up to 92% efficiency with 1.5MHz switching frequency
Limitations:
- Single-Cell Only : Limited to 4.2V/4.35V battery configurations
- Maximum Charge Current : 1.5A maximum may be insufficient for high-capacity batteries
- Input Current Limit : External resistor programming required for input current limiting
- Thermal Constraints : Power dissipation may limit maximum charge current in high-temperature environments
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Thermal Management
- Issue : Overheating during high-current charging reduces efficiency and reliability
- Solution : Implement proper thermal vias under package, ensure adequate copper area for heat dissipation
Pitfall 2: Input Voltage Transients
- Issue : Voltage spikes from poor-quality adapters can damage the IC
- Solution : Include input TVS diode and ensure proper input capacitor selection
Pitfall 3: Battery Detection Failures
- Issue : Incorrect battery presence detection leading to charging faults
- Solution : Proper BAT pin pull-up configuration and battery detection threshold setting
### Compatibility Issues with Other Components
Microcontroller Interface:
- Ensure I²C bus pull-up resistors (typically 10kΩ) are properly sized
- Verify logic level compatibility between host processor and charger IC
Power Management Integration:
- Coordinate with system power sequencing to avoid conflicts
- Ensure compatible voltage levels with system DC-DC converters
Battery Protection:
- Works with standard battery protection circuits but requires careful timing coordination
- May conflict with some advanced fuel gauge ICs without proper configuration
### PCB Layout Recommendations
Power Path Layout:
- Place input capacitors (C₁, C₂) as close as possible to VIN and GND pins
- Use wide traces for BAT, SYS, and VIN paths to minimize voltage drop
- Implement star grounding for power and analog grounds
Thermal Management:
- Use thermal vias in the exposed thermal pad connected to large ground plane
- Ensure minimum 2oz copper weight for power traces
- Provide adequate copper area around the package for heat spreading
