SLOS907C April   2015  – December 2017 TPA3144D2

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Gain Setting via GAIN Pin
      2. 9.3.2  SD Operation
      3. 9.3.3  Gain Limit Control, LIMTHRES and LIMRATE
      4. 9.3.4  SPEAKERGUARD Automatic Gain Limit, AGL
      5. 9.3.5  Thermal Foldback, TFB
      6. 9.3.6  PLIMIT
      7. 9.3.7  LIMTHRES
      8. 9.3.8  Spread Spectrum and De-Phase Control
      9. 9.3.9  GVDD Supply
      10. 9.3.10 DC Detect
      11. 9.3.11 PBTL Select
      12. 9.3.12 Short-Circuit Protection and Automatic Recovery Feature
      13. 9.3.13 Thermal Protection
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Design Requirements
        1. 10.2.1.1 PCB Material Recommendation
        2. 10.2.1.2 PVCC Capacitor Recommendation
        3. 10.2.1.3 Decoupling Capacitor Recommendations
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Ferrite Bead Filter Considerations
        2. 10.2.2.2 Efficiency: LC Filter Required with the Traditional Class-D Modulation Scheme
        3. 10.2.2.3 When to Use an Output Filter for EMI Suppression
        4. 10.2.2.4 Input Resistance
        5. 10.2.2.5 Input Capacitor, Ci
        6. 10.2.2.6 BSN and BSP Capacitors
        7. 10.2.2.7 Differential Inputs
        8. 10.2.2.8 Using Low-ESR Capacitors
      3. 10.2.3 Application Performance Curves
        1. 10.2.3.1 EN55013 Radiated Emissions Results
        2. 10.2.3.2 EN55022 Conducted Emissions Results
  11. 11Power Supply Recommendations
    1. 11.1 Power Supply Decoupling, CS
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Community Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10.2.2.2 Efficiency: LC Filter Required with the Traditional Class-D Modulation Scheme

The main reason that the traditional class-D amplifier needs an output filter is that the switching waveform results in maximum current flow. This causes more loss in the load, which causes lower efficiency. The ripple current is large for the traditional modulation scheme, because the ripple current is proportional to voltage multiplied by the time at that voltage. The differential voltage swing is 2 × VCC, and the time at each voltage is half the period for the traditional modulation scheme. An ideal LC filter is needed to store the ripple current from each half cycle for the next half cycle, while any resistance causes power dissipation. The speaker is both resistive and reactive, whereas an LC filter is almost purely reactive.

The TPA3144D2 modulation scheme has little loss in the load without a filter because the pulses are short and the change in voltage is VCC instead of 2 × VCC. As the output power increases, the pulses widen, making the ripple current larger. Ripple current could be filtered with an LC filter for increased efficiency, but for most applications the filter is not needed.

An LC filter with a cutoff frequency less than the class-D switching frequency allows the switching current to flow through the filter instead of the load. The filter has less resistance but higher impedance at the switching frequency than the speaker, which results in less power dissipation, therefore increasing efficiency.