bqSWITCHER(TM) Synchronous, Switch-Mode Li-Ion Charger w/ 2-A FET in QFN, Standalone# BQ24108RHLR Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The BQ24108RHLR 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 fast charging capabilities while maintaining thermal safety
- Portable Medical Devices : Ensures reliable charging for critical healthcare equipment
- Wearable Electronics : Compact solution for fitness trackers and smartwatches
- IoT Devices : Enables autonomous charging for connected sensors and edge devices
- Portable POS Systems : Supports frequent charge cycles in commercial applications
### Industry Applications
- Consumer Electronics : Mobile phones, tablets, digital cameras
- Medical Technology : Portable monitors, diagnostic equipment
- Industrial IoT : Remote sensors, data loggers
- Automotive Accessories : Dash cams, portable navigation
- Military/Defense : Portable communication equipment
### Practical Advantages
Strengths:
- High Integration : Combines power FETs, current sensor, and regulator in 3×3mm package
- Fast Charging : Supports up to 1.5A charge current with thermal regulation
- Flexible Input : Works with USB ports or AC adapters (4.35V to 6.45V)
- Safety Features : Built-in thermal protection, battery temperature monitoring
- Low Power Consumption : 35μA standby current, 1μA ship mode current
Limitations:
- Single Cell Only : Limited to 1-cell Li-ion/Li-polymer batteries
- Input Voltage Range : Maximum 6.45V input restricts some high-voltage adapters
- Thermal Constraints : High charge currents may require thermal management in compact designs
- No Wireless Charging : Requires separate controller for wireless charging implementations
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Thermal Management
- Problem : Overheating during high-current charging
- Solution : Implement proper thermal vias, use copper pours for heat dissipation, monitor IC temperature
Pitfall 2: Input Voltage Instability
- Problem : Voltage spikes from poor quality adapters
- Solution : Add input capacitors (10μF ceramic) close to IC, consider TVS diodes for surge protection
Pitfall 3: Battery Connection Issues
- Problem : Intermittent charging due to poor battery contacts
- Solution : Ensure secure battery connector, implement battery detection circuitry
Pitfall 4: Incurrent Current Setting
- Problem : Overcurrent conditions damaging components
- Solution : Properly calculate and set ISET resistor values, verify with actual measurements
### Compatibility Issues
Input Source Compatibility:
- Works with standard USB (500mA) and charging ports (up to 1.5A)
- May require additional circuitry for USB On-The-Go (OTG) applications
- Compatible with most wall adapters up to 6.45V
Battery Compatibility:
- Designed for single-cell Li-ion/Li-polymer (3.6V-4.2V)
- Not suitable for LiFePO4 or multi-cell batteries
- Requires external protection circuit for some battery chemistries
Microcontroller Interface:
- I²C compatible (400kHz) for charge parameter programming
- Requires pull-up resistors on SCL/SDA lines
- Compatible with 1.8V and 3.3V logic levels
### PCB Layout Recommendations
Power Path Layout:
- Place input capacitors (C1, C2) within 2mm of VIN and GND pins
- Use wide traces for BAT and SYS connections (minimum
