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LM48511: Select proper audio source

Cevdet Bozkurt
Prodigy 110 points
Part Number: LM48511
Other Parts Discussed in Thread: TPA2011D1

Tool/software:

Hi TI expert,

I have a CPU board. It can deliver 1.8 watt into 8-ohm speaker as you can see in the picture. It also has headphone output for earphone. I don't need neither headphone nor 1.8W speaker output for my project.

I only need deliver 5W into 4ohm speaker as mono. Which one should i amplify? speaker output or headphone output? Which one is the correct way in terms of engineering?

Note: I used LM48511 before to amplify 1.8W to 5W, but i haven't achieved.

I listen your suggestions and apricate your guidance.

Regards.

Cevdet.

  • 0
    TI__Guru** 100525 points

    Hi Cevdet,

    I would suggest using the headphone output rather than speaker output signal.
    Speaker output may be a PWM-like signal, while headphone should be analog signal which is better for analog input amplifiers such as LM48511 or TPA2011D1.

    Best regards
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 110 points

    Hi Ivan 

    Yes, the speaker output is PWM since the amplifier type is class D while headphone is analog in our SoC. 

    However, isn't it beter to use PWM-like signal for amplifying Analog may contain more noise.

    Which circuit type or IC you can recommend in case we prefer to amplify class D output? (to drive 5W 4Ohm load)

    I deeply appreciate your assistance.

    Thank you.

    Cevdet 

  • 0 in reply to Cevdet Bozkurt
    TI__Guru** 100525 points

    Hi Cevdet,

    Class-D switching signal is not used to amplifier the signal further when using an analog input amplifier. The analog input amplifier won't work OK with such signal. Perhaps you're thinking about a PWM input (output stage) amplifier such as these: Speaker amps product selection | TI.com, although these are used mostly for high power systems.

    If you still want to use Class-D signal to drive analog input amplifiers, you can add RC or LC low-pass reconstruction filter in-between.

    Best regards
    -Ivan Salazar
    Applications Engineer