BQ24298 Battery Charger IC: Complete Guide
Pinout, Working Principle, Testing Procedures & Applications
BQ24298 IC Pinout Diagram showing all functional pins and dimensions
What is BQ24298?
The BQ24298 is a highly integrated single-cell Li-Ion and Li-Polymer battery charger IC from Texas Instruments. It's designed for space-constrained portable applications like smartphones, tablets, and wearable devices. The IC features a power path management system that allows the battery to charge while simultaneously powering the system, similar to the BQ24259 but with some enhanced features.
- Integrated power FETs and current sensors
- USB/AC adapter input with automatic input source selection
- I²C interface for programming charging parameters
- Thermal regulation to ensure safe operation
- Small 4.5mm × 4.5mm package
- Enhanced power path management
- QON pin for quick on functionality
Pin Configuration and Functions
| Pin Name | Function | Description |
|---|---|---|
| VBUS | Power Input | Connects to USB port or AC adapter input (4.5V to 6.5V) |
| BAT | Battery Connection | Connects to the positive terminal of the Li-Ion battery |
| SYS | System Output | Powers the system load; provides power to the system |
| PGND | Power Ground | Ground connection for power circuitry |
| TS | Temperature Sense | Connect to NTC thermistor for battery temperature monitoring |
| SDA, SCL | I²C Interface | Serial communication for programming and status monitoring |
| STAT | Status Output | Indicates charging status (charging, charge complete, fault) |
| PG | Power Good | Indicates when input power is present and valid |
| INT | Interrupt Output | Alerts the host microcontroller of fault conditions |
| CE | Chip Enable | Enables or disables the charger IC |
| ILIM | Input Current Limit | Sets the input current limit through resistor divider |
| OTG | On-The-Go | Enables USB OTG functionality for powering USB peripherals |
| PSEL | Power Path Select | Selects between different power path configurations |
| QON | Quick On | Enables quick system turn-on without waiting for battery communication |
How BQ24298 Works
The BQ24298 operates as a complete battery management system with the following working principle:
1. Power Input Management
The IC accepts power from either a USB port (VBUS pin) or an AC adapter. It automatically detects the power source and adjusts the charging parameters accordingly. The input current limit is set through the ILIM pin using a resistor divider.
2. Charging Process
The IC implements a three-stage charging algorithm:
- Pre-charge: When battery voltage is very low (<3.0V), it applies a small current (about 10% of fast charge current)
- Fast charge: Applies constant current until battery reaches 4.2V
- Constant voltage: Maintains 4.2V while current tapers down until termination
3. Power Path Management
The power path feature allows the system to be powered simultaneously while charging the battery. The IC intelligently manages power flow between:
- Input source (VBUS)
- Battery (BAT)
- System load (SYS)
This ensures the system always has power, even with a dead battery or no input source.
4. Quick On Functionality
The QON pin provides a quick system turn-on feature that allows the system to power up immediately without waiting for the battery communication to complete. This is particularly useful in applications where fast system response is required.
5. Safety and Monitoring
The IC continuously monitors:
- Battery temperature via TS pin
- Input voltage and current
- Battery voltage and charging current
- Die temperature for thermal regulation
If any parameter exceeds safe limits, the IC reduces charging current or stops charging entirely.
How to Test BQ24298
Step-by-Step Testing Procedure:
1. Visual Inspection
- Check for physical damage, burns, or discoloration
- Verify all solder joints are secure and not bridged
- Ensure no components are missing near the IC
2. Power Supply Check
- Measure VBUS pin voltage (should be 4.5V-6.5V when power is applied)
- Check BAT pin voltage (should match battery voltage)
- Verify SYS pin voltage (should be close to battery voltage or system voltage)
3. I²C Communication Test
- Connect an I²C scanner or logic analyzer to SDA and SCL pins
- Verify the IC responds to its default I²C address (0x6B)
- Read key registers to confirm proper communication
4. Charging Function Test
- Connect a known-good battery to BAT pin
- Apply power to VBUS pin
- Measure charging current at BAT pin (should match programmed value)
- Monitor STAT pin for status changes (should indicate charging)
5. Temperature Monitoring Test
- Check voltage on TS pin (should be between 0.3V and 2.7V)
- Simulate temperature change by heating/cooling the thermistor
- Verify charging current adjusts accordingly
6. Quick On Function Test
- Apply a high signal to QON pin
- Verify SYS pin powers up immediately
- Check if system turns on without battery communication
7. Fault Condition Test
- Test overvoltage protection by applying excessive voltage to VBUS
- Test thermal protection by heating the IC
- Verify INT pin signals fault conditions
- Multimeter (for voltage/current measurements)
- Oscilloscope (for signal analysis)
- I²C scanner or logic analyzer
- Variable power supply
- Known-good battery
- Thermometer or temperature chamber
Common Applications
- Smartphones and mobile phones
- Tablets and portable media players
- Wearable devices (smartwatches, fitness trackers)
- Portable medical devices
- Bluetooth speakers and headphones
- Portable gaming devices
- Industrial handheld devices
Differences Between BQ24259 and BQ24298
| Feature | BQ24259 | BQ24298 |
|---|---|---|
| Temperature Sense Pins | TS1, TS2 (dual) | TS (single) |
| Quick On Function | No | Yes (QON pin) |
| Package Size | 4.5mm × 4.5mm | 4.5mm × 4.5mm |
| Power Path Management | Standard | Enhanced |