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

1.1.1 Bridged-Tied Load (BTL)

Bridge-tied load (BTL) is the most common output configuration for a class-D amplifier. A BTL configuration consists of one amplifier driving one side of a load and another amplifier, with an inverted signal from the first amplifier, driving the other side of the load. This results in 2× more voltage swing across the load for a given supply voltage when compared to a single-ended configuration where one side of the load is tied to the amplifier output and the other side to ground. Twice the voltage swing across the load equates to a 4× power increase because P = V2 / R. So, a BTL load configuration offers 4× more power to the load than a single-ended configuration from the same supply voltage.

Because each side of the load is driven, the load is not ground-referenced. Therefore, the voltage across the load must be measured differentially relative to ground. The TAS5830 is an example of a TI device operating in a BTL output configuration.

Stereo (Two-Channel) BTL Class-D AmplifierFigure 1-1 Stereo (Two-Channel) BTL Class-D Amplifier