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Audio power amplifier


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Audio power amplifier

  1. 1. Audio Power Amp. PCB Layout Class-D design By : Andri Haryono
  2. 2. Clasess in Audio Amplifier <ul><li>Audio Power amplifier circuits (output stages) are classified as A, B, AB and C for analog designs, and class D and E for switching designs based upon the conduction angle or angle of flow, Θ, of the input signal through the (or each) output amplifying device, that is, the portion of the input signal cycle during which the amplifying device conducts </li></ul>
  3. 4. Class-D <ul><li>Class D – This class of amplifier is a switching or PWM amplifier. This class of amplifier is the main focus of this application note. In this type of amplifier, the switches are either fully on or fully off, significantly reducing the power losses in the output devices. Efficiencies of 90-95% are possible. The audio signal is used to modulate a PWM carrier signal which drives the output devices, with the last stage being a low pass filter to remove the high frequency PWM carrier frequency. </li></ul>
  4. 5. Illustration
  5. 6. Advantages <ul><li>Reduce Heatsink size to minimum </li></ul><ul><li>Low voltage requirement </li></ul><ul><li>Theoritically High in efficiency (90-95%) </li></ul>
  6. 7. Disadvantages <ul><li>High cost </li></ul><ul><li>High EMC, because the design need at least 4 inductor </li></ul>
  7. 8. Comparison
  8. 9. PCB Layout for Audio Quality and EMC
  9. 10. Critical Circuit
  10. 11. Order of Priority <ul><li>Ground Plane </li></ul><ul><li>Decoupling Placement and Connection </li></ul><ul><li>EMC Circuit Placement and Connection </li></ul><ul><li>Input and Analog Control Routing </li></ul>
  11. 12. Ground Plane
  12. 13. Ground Plane (Cont’d) <ul><li>Use ground plane to connect all critical circuits </li></ul><ul><li>This minimizes ground impedance, especially </li></ul>
  13. 14. Ground Plane (Cont’d) <ul><li>Place the IC at the center of the ground plane and ground the PowerPAD with thermal vias (0.33mm diameter on 1.0mm centers). </li></ul><ul><li>Ground decoupling caps and EMC components to the PowerPAD area through ground plane. </li></ul><ul><li>Place inputs on one side of the circuit and power and outputs on another to separate the currents. </li></ul><ul><li>This approach minimizes interference that could reduce audio quality and makes decoupling and EMC filters and snubers work best. </li></ul>
  14. 15. Decoupling Caps
  15. 16. Decoupling Caps (Cont’d) <ul><li>Place high-frequency decoupling caps within 1mm of the IC, and place bulk decoupling caps as close as possible to them. </li></ul><ul><li>G round high-frequency decoupling caps and PGND pins to the PowerPAD. </li></ul><ul><li>Also ground decoupling caps and PGND pins to the ground plane through multiple vias. </li></ul><ul><li>This minimizes impedance and inductance in series with these capacitors. </li></ul><ul><li>This approach stabilizes power supply voltage and improves EMC by minimizing ringing. </li></ul>
  16. 17. Poor vs. Proper Decoupling
  17. 18. EMC Filtering
  18. 19. EMC Filtering (cont’d) <ul><li>Place EMC snubbers& filters very near the IC. </li></ul><ul><li>Ground through ground plane & connect outputs to cap pads, directly or through broad copper, & not to inductors, to minimize stray inductance </li></ul><ul><li>Place EMC filter caps as close to the IC as possible on the ground plane layer and ground them to the IC through the ground plane </li></ul>
  19. 20. EMC Filtering (cont’d) <ul><li>This approach minimizes unfiltered loops and trace lengths as well as stray inductance. </li></ul><ul><li>This makes EMC components function best & gives the widest possible filter bandwidth. </li></ul>
  20. 21. Poor vs. Proper Filter Placement
  21. 22. Inputs, Analog Control
  22. 23. Inputs, Analog Control <ul><li>Shield inputs with top layer ground flood. </li></ul><ul><li>Ground analog control caps (GVDD, PLIMIT & AVCC) through ground plane with multiple vias. </li></ul><ul><li>Ground AGND pin directly to PowerPAD ts with top layer ground flood. </li></ul>
  23. 24. Reference <ul><li>Stephen Crump. Audio Power Amplifier Applications. http:// . Texas Instruments </li></ul><ul><li>Douglas Self . Audio Power Amplifier Design Handbook </li></ul><ul><li>Jun Honda & Jonathan Adams . Class D Audio Amplifier Basics </li></ul>
  24. 25. QUESTION NO ?
  25. 26. Thank You <ul><li>For your attention </li></ul>