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TPA3140D2: PCB Layout confusions

Fahad Ansari20
Intellectual 480 points
Part Number: TPA3140D2


Hi,

I am designing a PCB using TPA3140D2. I was referring to datasheet as well as EVM user guide for reference Layout designing. I have little confusion on following

1. AVCC pin connection with PVCC: Datasheet suggest 10E resistor, EVM shows direct connection, which should I implement? In case of resistor, what should be the value of resistor/what is current requirement for AVCC pin?

2. Capacitor at AVCC pin (1uf to 10uF) is recommended in datasheet but not implemented in Eval board. Can this be dropped?

3. Do we need a resistor between 1SPW and AVCC?

4. Do we need RC circuit at the Audio output pins? (not there in datasheet but used on EVM). Also, is it ok to have provision for these on board and not mount them? will the open stub cause any issue?

5. Recommended layout shows straight traces for audio out but traces on EVM are not running that straight, is it OK if I follow trace pattern observed in EVM. I am planning to use 0603 components and thus will not be able to run traces straight. Let me know if I can bend them a little (as in EVM) or should change components to 0402.

6. Also, I am planning to connect capacitors at bottom side for Power trace and Audio out traces, connecting them to top traces using Vias, is this OK? Though this is not shown in either of the document, I wanted to know this in order to keep capacitors closer to pins.

  • 0
    TI__Mastermind 24835 points
    Hi Fahad,
    Please find my answer below:
    1. 10Ohm resistor between AVCC and PVCC can be used to keep high frequency class D noise from entering the linear input amplifiers. So you can reserve it in your design.
    2. You are correct that 1uF to 10uF capacitor can be used for AVCC decoupling.
    3. For 1SPW pin, drive it to High level for 1SPW mode and to Low for BD mode. BD mode is more widely used by the customers. You could connect thi pin to GND directly. If you want to use the AMP in 1SPW mode, please drive the pin to High through 100kOhm resistor to protect the pin from damage by too high slew rate on the power supply.
    4. The RC snubber on the ouput pins are used to minimize the ringing on the PWM switching. Please find more info in this document www.ti.com/.../slva255.pdf You could reserve the circuit on the board, there shouldn't be any performance loss if it's not populated.
    5. As you mentioned, the output traces should be straight, and the differential output traces should be as matching as possible. But for most the real application, it's not feasible. Please follow it as much as possible in the PCB design.
    6. I agree with you that the decoupling effect should be better if the distance between the power pin and the decoupling capacitor is short. So you could place the decoupling capacitors on PVCC and Bootstrap capacitors on the bottom. But usually we place them on the top of the board to achieve a integrated GND plane for a better thermal performance.
    Best reagards,
    Shawn Zheng