SSZTDE7 October   2026 TAS2573 , TAS2781

 

  1.   1
  2. 1 Introduction
  3. 2 The physics of microspeaker vulnerability
  4. 3 Traditional versus smart approaches to audio design
  5. 4 Integrated IV-sense circuitry
  6. 5 The temperature protection algorithm
  7. 6 Thermal modeling and control
  8. 7 The excursion protection algorithm
  9. 8 Look-ahead limiter
  10. 9 Integrating the audio tuning chain
  11. 10Conclusion
  12. 11About the authors
  13. 12Additional resources
  14. 13Trademarks

5 The temperature protection algorithm

Thermal protection in a smart amplifier relies on the physical law that the electrical resistance of a metal conductor changes predictably with temperature. This is known as the temperature coefficient of resistance (α).

As a voice coil heats up, its RE increases linearly, and the smart amplifier’s IV-sense hardware isolates this resistance from the measured impedance. Equation 1 solves for the coil’s internal temperature:

Equation 1. R d c ( T ) = R E ( T 0 ) [ 1 + α ( T - T 0 ) ]

where RE (T) is the measured resistance at current time T, RE (T0) is the baseline resistance from factory calibration, and α is the coil material’s temperature coefficient of resistance (such as copper).

This eliminates the need for bulky, slow-responding physical thermistors.

This measurement is invoked only periodically – a checkpoint reading rather than a continuous stream – for two reasons: it is less trustworthy at low output levels or during low-to-high power transitions (noise-limited signals, settling error and offsets), and running the sense ADC and its analog front end continuously would consume unnecessary power, especially in battery-powered, low-volume listening.