TIDUA71 January   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TAS6584-Q1
      2. 2.3.2 LM5123-Q1
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Results
      1. 3.2.1 Class-H Tracking Waveform Example
      2. 3.2.2 Thermal Performance
  9. 4Design and Documentation Support
    1. 4.1 Design Files
    2. 4.2 Support Resources
    3. 4.3 Trademarks
  10. 5About the Author

1 System Description

In a traditional high-power audio amplifier system, a boost converter provides a constant voltage to achieve the maximum possible power to be delivered to the speaker load. The dynamic nature of music typically only needs this maximum voltage for short moments, and only when the listener sets the system to full volume. This means the power supply of the amplifier far exceeds typical requirements and there are significant power losses in the boost converter and amplifier system. The total system must be designed for this maximum power use-case but suffers in thermal performance and system efficiency to meet those requirements. This leads to larger heat sinks, inductors, MOSFETs, and copper area on the system to handle the increased thermal load.

These types of system challenges can be solved with a Class-H tracking power supply system. The audio signal sent to the system is analyzed to determine the required power supply voltage at a given moment in the audio stream and the boost converter is adjusted appropriately. The entire system operates to directly match the needs of the audio signal at all times instead of only maintaining the voltage required at the maximum power use-case. Power losses in the system are reduced and power efficiency and thermals improve significantly.

The TIDA-020033 showcases the integrated Class-H features of the TAS6584-Q1. Utilizing the integrated DSP, the TAS6584-Q1 can track the envelope of the incoming audio stream and send a signal to the LM5123-Q1 boost converter to adjust the power supply voltage. This function is self-contained within these two devices. No additional monitoring of the audio signal or external control of the boost converter from a microcontroller is necessary.

Figure 1-1 Simplified Class-H System With TAS6584-Q1 and LM5123-Q1

This self-contained system provides design flexibility to an automotive audio system designer. External amplifiers can operate as more of a “plug-and-play” system rather than one that needs monitoring and control from a remote module (like a head unit or radio tuner) to calculate the audio envelope and control the power supply. Different automotive fleet variants with different audio system requirements will not need significant changes to the delivery of the audio data to the external amp or new software variants for different Class-H envelope tracking needs.

The implementation of Class-H power control in TIDA-020033 also provides several other key benefits at the system level, such as:

  • Smaller LM5123-Q1 power supply inductor due to lower average input currents
  • Smaller heat sink for the TAS6584-Q1 Class-D amplifier due to lower die temperatures
  • Less copper thermal relief area on the PCB due to lower junction temperatures in the system
  • Improved EMI performance due to lower switch-node currents leading to lower electromagnetic energy