SLAA701B October   2016  – June 2026 TAS5342A , TAS5342LA , TAS5352 , TAS5630B , TPA3220 , TPA3221 , TPA3251 , TPA3255 , TPA3255-Q1

 

  1.   1
  2.   Trademarks
  3.   Abstract
  4. 1LC Filter Design
    1. 1.1 Class-D Output Configurations
      1. 1.1.1 Bridged-Tied Load (BTL)
      2. 1.1.2 Parallel Bridge-Tied Load (PBTL)
      3. 1.1.3 Single-Ended (SE)
    2. 1.2 Class-D Modulation Schemes
      1. 1.2.1 AD (Traditional) Modulation
      2. 1.2.2 BD Modulation
    3. 1.3 Class-D Output LC Filter
      1. 1.3.1 Output LC Filter Frequency Response Properties
      2. 1.3.2 Class-D BTL Output LC Filter Topologies
      3. 1.3.3 Single-Ended Filter Calculations
      4. 1.3.4 Type-1 Filter Analysis
        1. 1.3.4.1 Type-1 Frequency Response Example
      5. 1.3.5 Type-2 Filter Analysis
        1. 1.3.5.1 Type-2 Frequency Response Example
      6. 1.3.6 Hybrid Filter for AD Modulation
        1. 1.3.6.1 Hybrid Filter Frequency Response Example
      7. 1.3.7 AD Modulation With Type-1 or Type-2 Filters
      8. 1.3.8 LC Filter Quick Selection Guide
    4. 1.4 Inductor Selection for High-Performance Class-D Audio
      1. 1.4.1 Inductor Linearity
      2. 1.4.2 Ripple Current
        1. 1.4.2.1 Calculating Ripple Current for a Single-Supply Class-D Amplifier
      3. 1.4.3 Minimum Inductance
      4. 1.4.4 Core Loss
      5. 1.4.5 DC Resistance (DCR)
      6. 1.4.6 Inductor Study With the TPA3251 Device
        1. 1.4.6.1 Results
        2. 1.4.6.2 Conclusion
    5. 1.5 Capacitor Considerations
      1. 1.5.1 Class-D Output Voltage Overview
        1. 1.5.1.1 Ripple Voltage
        2. 1.5.1.2 37
      2. 1.5.2 Capacitor Ratings and Specifications
        1. 1.5.2.1 Maximum Voltage or Rated DC Voltage
        2. 1.5.2.2 ESR and Dissipation Factor
        3. 1.5.2.3 Maximum Temperature Rise (Rated AC Voltage and AC Current)
        4. 1.5.2.4 Pulse Rise Time (dv/dt) or Peak Current (Ipeak)
      3. 1.5.3 Capacitor Types
        1. 1.5.3.1 Selecting a Capacitor Type
        2. 1.5.3.2 Metalized Film Capacitors
          1. 1.5.3.2.1 AC Voltage or Current Rating
          2. 1.5.3.2.2 Temperature Coefficient
        3. 1.5.3.3 Ceramic Capacitors
          1. 1.5.3.3.1 Size
          2. 1.5.3.3.2 DC Bias Voltage
          3. 1.5.3.3.3 Temperature Coefficient
          4. 1.5.3.3.4 Reliability
    6. 1.6 Related Collateral
  5. 2Reference
  6. 3Reference
  7. 4Revision History

1.3.3 Single-Ended Filter Calculations

Since the goal is to use the single-ended equivalent of each filter type for easy analysis, the frequency response of the single-ended filter must be known.

Single-Ended LC FilterFigure 1-7 Single-Ended LC Filter

The equations for the single-ended LC filter shown in Figure 1-7 follow:

Equation 1.
Equation 2.
Equation 3.
Equation 4.

As previously mentioned, it is usually desirable to design a filter that is critically damped with a Butterworth response. For this type of filter, Q = 0.707 = 1 / √ 2. By substituting Q = 1 / √ 2 into equations for Cut-off Frequency and Quality Factor previously listed, L and C values can be derived for a critically damped system assuming the desired cut-off frequency, ωo, is known.

Equation 5.
Equation 6.