2 Power Amplifier 18 W# AN7188K Technical Documentation
## 1. Application Scenarios
### Typical Use Cases
The AN7188K is a dual-channel audio power amplifier IC primarily designed for stereo audio applications in consumer electronics. Typical implementations include:
- Stereo Audio Systems : Driving 4-8Ω speakers with 5-10W per channel output
- Portable Audio Devices : Battery-powered applications requiring efficient audio amplification
- Television Audio Systems : Built-in speaker amplification for modern flat-panel displays
- Computer Multimedia Systems : Desktop and laptop computer audio subsystems
- Automotive Audio : Secondary audio systems and auxiliary amplification
### Industry Applications
Consumer Electronics
- Home theater systems and soundbars
- Portable Bluetooth speakers
- Gaming console audio systems
- Smart home device audio output
Professional Audio
- Conference system amplifiers
- Public address (PA) systems
- Musical instrument practice amplifiers
Industrial Applications
- Industrial alarm and notification systems
- Machine status audio indicators
- Test equipment audio output stages
### Practical Advantages
Strengths:
- High Efficiency : Class AB operation provides good power efficiency (typically 65-75%)
- Thermal Stability : Built-in thermal shutdown protection prevents damage from overheating
- Low Standby Current : Typically <10mA in shutdown mode for battery conservation
- Simple Implementation : Minimal external components required for basic operation
- Good THD Performance : Total Harmonic Distortion typically <0.1% at 1W output
Limitations:
- Power Output : Limited to approximately 10W per channel, unsuitable for high-power applications
- Frequency Response : Roll-off above 20kHz may affect high-fidelity applications
- Heat Dissipation : Requires adequate heatsinking at maximum output power
- Supply Voltage Range : Limited to maximum 18V DC operation
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Thermal Management Issues
- Problem : Insufficient heatsinking causing thermal shutdown during sustained operation
- Solution : Implement proper thermal vias, adequate copper area, and consider external heatsink for high-power applications
Oscillation Problems
- Problem : High-frequency oscillation due to improper decoupling or layout
- Solution : Place 100nF ceramic capacitors as close as possible to power pins, use proper ground plane techniques
Power Supply Rejection
- Problem : Audible hum from poor PSRR performance
- Solution : Implement LC filtering on power supply lines, ensure clean and stable power source
### Compatibility Issues
Input Signal Compatibility
- Works well with standard line-level signals (0.5-2V RMS)
- May require input attenuation for higher-level sources
- Compatible with most digital audio codec outputs
Speaker Compatibility
- Optimized for 4-8Ω speakers
- Not recommended for 2Ω loads without current limiting
- Can drive 16Ω speakers with reduced power output
Power Supply Requirements
- Single supply operation: 8-18V DC
- Incompatible with dual-supply configurations
- Requires stable, low-noise DC source
### PCB Layout Recommendations
Power Supply Routing
- Use star grounding technique with separate analog and power grounds
- Implement wide traces for power supply lines (minimum 40 mil width for 2A current)
- Place bulk capacitors (100-470μF) near power input pins
Signal Integrity
- Keep input traces short and away from output and power lines
- Use ground plane for improved noise immunity
- Route output traces directly to speaker connectors
Thermal Management
- Provide adequate copper area for heatsinking (minimum 2in² for full power operation)
- Use thermal vias under the IC package to transfer heat to bottom layer
- Consider exposed pad connection to ground plane for improved thermal performance
Component Placement
