SLAA996A June   2021  – June 2021 TPA6304-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Understanding the Thermal Flow
  4. 3Understanding the Test and System Conditions
    1. 3.1 Device Efficiency
    2. 3.2 Test Signals
      1. 3.2.1 Sinusoidal Signal
      2. 3.2.2 Pink Noise
      3. 3.2.3 Music File
    3. 3.3 Ambient Temperature
    4. 3.4 Junction Temperature
    5. 3.5 Thermal Interface Material and Heatsink
  5. 4Calculating Dynamic Thermal Dissipation
  6. 5Designing a Realistic Thermal Test
  7. 6Thermal Tests
    1. 6.1 Test Setup
    2. 6.2 5W 1kHz Sine Wave Test
      1. 6.2.1 Calculations
      2. 6.2.2 Dynamic Calculation Results
      3. 6.2.3 Tested Results
      4. 6.2.4 Summary of Results
    3. 6.3 10W 1kHz Sine Wave Test
      1. 6.3.1 Calculations
      2. 6.3.2 Dynamic Calculation Results
      3. 6.3.3 Tested Results
      4. 6.3.4 Summary of Results
    4. 6.4 5W Pink Noise Test
      1. 6.4.1 Calculations
      2. 6.4.2 Dynamic Calculation Results
      3. 6.4.3 Tested Results
      4. 6.4.4 Summary of Results
    5. 6.5 10W 1kHz 85°C Test
      1. 6.5.1 Calculations
      2. 6.5.2 Dynamic Calculation Results
      3. 6.5.3 Tested Results
      4. 6.5.4 Summary of Results
  8. 7Overall Summary
  9. 8References
  10. 9Revision History

3.5 Thermal Interface Material and Heatsink

The final factor for determining the device's thermal capabilities within a system is the materials used for the thermal dissipation path. This path consists of the thermal interface material and the heatsink. The thermal resistive properties of these materials will have a direct result on the maximum output power the amplifier can drive without shutting down.

An easy way to determine what the maximum thermal resistance allowed from θCH and θHA is by looking at Equation 1 and Equation 2. Merging both equations gives the following:

Equation 3. (TJ - TA)/PD = θJC + θCH + θHA

Simplifying it further by having θCA = θCH + θHA gives the following equation:

Equation 4. (TJ - TA)/PD = θJC + θCA

Using this formula in an example where the total output power desired is 80W into 4Ω loads with an ambient temperature set at 75°C. At 80W output power, the power dissipation will be approximately 13.6W. Using θJC = 0.6 °C/W and deciding that the junction temperature should never rise above 130°C , θCA can be found by:

(130 - 75)/13.6 = 0.6 + θCA
θCA = 3.44°C/W

Thus, the total thermal resistance of the thermal solution cannot be higher than 3.44°C/W.