SLAAEI4 August   2024 TAC5111-Q1 , TAC5212-Q1 , TAC5311-Q1 , TAC5312-Q1 , TAC5411-Q1 , TAC5412-Q1 , TAD5212-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Signal Processing Chain
  6. 3Distortion Limiter
    1. 3.1 Distortion Limiter Parameters
      1. 3.1.1 Threshold Maximum
      2. 3.1.2 Threshold Minimum
      3. 3.1.3 Inflection Point
      4. 3.1.4 Slope
      5. 3.1.5 Attack Rate
      6. 3.1.6 Release Rate
      7. 3.1.7 Hold Counter
    2. 3.2 Limiter Response
  7. 4Brown-Out Protection
    1. 4.1 Brown-Out Protection Parameters
      1. 4.1.1 Critical Level
      2. 4.1.2 Gain Level
      3. 4.1.3 Attack Rate
      4. 4.1.4 Release Rate
      5. 4.1.5 Hold Counter
    2. 4.2 Brown-Out Protection Response
  8. 5Thermal Foldback
    1. 5.1 Thermal Foldback Parameters
      1. 5.1.1 Temperature Threshold
      2. 5.1.2 Maximum Attenuation Threshold
      3. 5.1.3 Slope
      4. 5.1.4 Attack Coefficient
      5. 5.1.5 Release Coefficient
      6. 5.1.6 Hold Counter
        1. 5.1.6.1 Thermal Foldback Response
  9. 6Example
  10. 7Summary
  11. 8References

3 Distortion Limiter

The Distortion Limiter works by scaling down the output signal as a function of the battery voltage and input signal level. When VBAT or AVDD drops below the inflection point, the peak of the output signal is reduced from the threshold maximum to the threshold minimum. This feature is valuable when the battery level starts to drop during prolonged use and prevents more supply voltage than necessary being drained to achieve the desired peak output voltage. The gain is restored to the programmed operating condition once the supply recovers. This design prevents the output from exceeding the threshold maximum when the input signal increases to a level that exceeds the full-scale input signal range to prevent audio clipping.

The output signal for the TAx5xxx-Q1 family is up to 10Vrms differential and 5Vrms single-ended. The Distortion Limiter allows the user to configure the threshold maximum and threshold minimum values in dbFS and the inflection point of the supply voltage. Figure 3-1 displays how the configuration of the limiter block maps the battery voltage to the output peak.

Distortion Limiter Output Configuration Figure 3-1 Distortion Limiter Output Configuration

Figure 3-2 highlights the response of the peak output signal as VBAT fluctuates. By default, the input:output signal ratio is 1:1 relative to full scale.

Distortion Limiter Example Figure 3-2 Distortion Limiter Example

The Distortion Limiter can be customized to end application power specifications without impacting the listening experience. Users can configure the parameters of the limiter to prioritize an extended battery life by restricting the output peak and reducing the gain gradually as VBAT decreases. Conversely, users can create a steeper slope when setting a lower VBAT inflection point threshold. A steeper slope emphasizes an audio signal range in low-battery voltage conditions.