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TAS5411-Q1: Application questions

Lanxi Li
Expert 7025 points
Part Number: TAS5411-Q1


Hello team,

What is the maximum supported ohm and power in the case of 3% THD?

Thanks.

Lanxi  

  • 0
    TI__Mastermind 45085 points

    Lanxi

    The overcurrent protection will trip before 3% THD will be reached.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    TI__Expert 7025 points

    Hello Gregg,

    I saw the THD in the datasheet, would you mind help give me a more detailed explain here?

    It would very appreciate if you teach me how to evaluate the power vs THD vs resistance.

    Best regards,

    Lanxi

  • 0 in reply to Lanxi Li
    TI__Mastermind 45085 points

    Lanxi,

    To understand THD thresholds, there are several factors.

    1. 3% would be a clipping distortion in this device.
    2. The clipping level is determined by the power supply voltage.
    3. The current level for over current protection is determined by the load impedence and signal level

    I assumed you had PVDD voltage of 14.4Vdc and a 4-ohm load.  The minimum load for this device is 4 ohms.

    The maximum unclipped voltage for this device will be 14.4*.7071.  Which is 10Vrms with no losses taken into account.

    When we have a 4-ohm load and 10Vrms, the current is 2.5Arms.  The peak current is 2.5*1.414 = 3.53A.  The maximum current allowed is 2.5Ap per the datasheet. Therefore, with this PVDD and load impedance, you cannot clip the amplifier to reach the 3% THD.  

    You can work with your PVDD and load to determine output voltage and output power.  But remember we have an over current shutdown set to 2.5Ap.

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    TI__Expert 7025 points

    Hello Gregg,

    That's very kind of you. Sorry, this is my first time learning Class D. Thank you for the patient

    Sorry, I don't see any 3%THD is related to your calculation. Am I missing something?

    Also I saw one waveform based on your reply, so any difference while using 1% and 3%?

    Best regards,

    Lanxi Li

  • 0 in reply to Lanxi Li
    TI__Guru 52090 points

    Hi Lanxi

       Usually we would think 1% THD is already the largest value for audio using. Larger than 1% THD, you will see clearly clipping and the audio will become very strange. The 3%THD and 10%THD doesn't different too much in the output power, because when audio start to clip, the THD will increase very quickly. You could think 8-W Output Power Into 4 Ω is likely to be the 3% THD results, maybe only a little higher than 8W, like around 8.3W.