TIDUFE4 June   2026

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TAS6684-Q1
      2. 2.3.2 LM5125A-Q1
      3. 2.3.3 MSPM0G3507-Q1
  9. 3System Design Theory
    1. 3.1 Boost Output Capacitance and Maximum Output Voltage
    2. 3.2 Peak Power of the Boost Converter
    3. 3.3 Ramp Time and Class-H delay
    4. 3.4 Design of the Class-H Two Stage RC Filter
    5. 3.5 Class-H Tracking with Multiple TAS6684-Q1s
    6. 3.6 TAS6684-Q1 Class-H Parameters
    7. 3.7 Design Parameters
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
      1. 4.3.1 Hardware Setup
      2. 4.3.2 Software Setup
    4. 4.4 Test Results
      1. 4.4.1 Test Results of Audio Amplifier
      2. 4.4.2 Test Results of Boost Converter
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 Layout Prints
    2. 5.2 Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.7 Design Parameters

Table 3-5 shows the quantity, average power of the speakers in the audio system. The k is selected based on Table 3-5.

Table 3-3 Quantity and Average Power of the Speakers
Speaker Type Average Power Quantity k
Woofer 150W 2 2
Middle Range 80W 2 1.5
Twitter 40W 4 1

The peak power of the audio amplifier Pt can be found as,

Equation 35. Pt=150W⋅2⋅2+80W⋅2⋅1.5+40W⋅4⋅1=1kW

Knowing 150W average power of the 4Ω woofer, the maximum voltage across the woofer (Vao) can be obtained from Equation 3,

Equation 36. Vao=2RspPa_avg=34.6V

The woofer peak current Iaocan be found as,

Equation 37. Iao=VaoRsp=8.7A

Vs can be found as,

Equation 38. Vs=IaoRs=2.2V

Assuming Vout_pp = 2V, the minimal output capacitance can be found as,

Equation 39. Cout=Iai∙5LeqIin_maxVin_minVout_pp=1060µF

where Iai is the worst-case audio amplifier total input current which is estimated by Pt / Vao.

Aluminum electrolytic capacitor is preferred due to low cost and high capacitance density. Considering the capacitance derating at low temperature, 6 pcs 330µF electrolytic capacitors are chosen.

Ceramic capacitors are mandatory to handle the current ripple and reduce the switching frequency voltage ripple. 18 pcs 10µF and 8 pcs 0.1µF ceramic capacitors are used. The 0.1µF ceramic capacitors are placed close to the MOSFETs following "vertical loop" concept. Refer to Improve High-Current DC/DC Regulator EMI Performance for Free With Optimized Power Stage Layout for more details.

Considering 2% settling error and 2% tolerance of the output voltage, the voltage margin needs to be higher than 4.8V from Equation 17. 40V maximum output voltage is selected. Minimum output voltage of 9V is selected. When the required output voltage is less than the input voltage, the boost enters bypass mode to further improve light load efficiency.