bqTINY-II 1-Cell Li-Ion Charger w/USB/AC Supply Mgmt in 3x3mm2 QFN-10 w/Enable, Timer/Term Enable# BQ24023 Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The BQ24023 is a highly integrated single-cell Li-ion battery charger IC designed for space-constrained portable applications. Its primary use cases include:
Portable Medical Devices
- Wearable health monitors requiring continuous operation
- Portable diagnostic equipment with battery backup
- Medical sensors needing reliable charging cycles
- Emergency medical devices requiring fast recharge capabilities
Consumer Electronics
- Smartphones and tablets with USB charging
- Wireless earbuds and hearing aids
- Fitness trackers and smartwatches
- Portable gaming devices and multimedia players
Industrial Applications
- Handheld barcode scanners and inventory devices
- Portable data collection terminals
- Industrial sensors with battery backup
- Field service equipment requiring reliable power management
### Industry Applications
Medical Industry
- Advantages: Medical-grade reliability, predictable charging cycles, thermal regulation for patient safety
- Limitations: May require additional certification for critical medical applications
Consumer Electronics
- Advantages: Compact footprint, cost-effective solution, excellent thermal performance
- Limitations: Maximum 1.5A charging current may be insufficient for high-capacity batteries
IoT and Wearables
- Advantages: Low quiescent current (typically 15μA), small package size (3mm × 3mm QFN)
- Limitations: Single-cell Li-ion only, not suitable for multi-cell configurations
### Practical Advantages and Limitations
Advantages:
- Integrated Power Path Management : Allows simultaneous charging and system operation
- Thermal Regulation : Automatic charge current reduction during high temperature conditions
- Small Form Factor : 16-pin QFN package ideal for space-constrained designs
- Wide Input Voltage Range : 4.35V to 6.5V operation with 20V absolute maximum rating
- High Integration : Includes thermal regulation, current sensing, and voltage regulation
Limitations:
- Single Chemistry Support : Limited to Li-ion/Li-polymer batteries only
- Current Limitation : Maximum 1.5A charge current may not suit high-capacity applications
- Temperature Monitoring : Requires external NTC thermistor for optimal battery temperature sensing
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Thermal Management
- Problem : Overheating during high-current charging
- Solution : Ensure proper thermal vias under IC, adequate copper area for heat dissipation
Pitfall 2: Input Voltage Transients
- Problem : Damage from USB hot-plug events or adapter voltage spikes
- Solution : Implement input TVS diode and adequate input capacitance
Pitfall 3: Battery Connection Issues
- Problem : Intermittent battery connection causing charging faults
- Solution : Use robust battery connector, implement proper strain relief
Pitfall 4: Incorrect NTC Implementation
- Problem : False temperature fault triggering
- Solution : Proper NTC selection and placement near battery terminals
### Compatibility Issues with Other Components
Power Management Integration
- Compatible : Most DC-DC converters and LDOs
- Considerations : Ensure system load doesn't exceed available current during charging
Microcontroller Interfaces
- STAT and PG Outputs : Compatible with 3.3V and 5V logic levels
- CE Input : Requires proper pull-up/down configuration
Battery Protection Circuits
- Recommended : External protection MOSFETs for additional safety
- Compatibility : Works well with most battery protection ICs
### PCB Layout Recommendations
Power Path Routing
- Use wide traces for VBUS, SYS, and BAT connections (minimum 40 mil width)
- Place input capacitors (10μF ceramic) within 2mm of VBUS pin
- Battery connection traces
