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TPA2006D1 Class D audio amplifier Gain Control

Vini
Intellectual 895 points
Other Parts Discussed in Thread: TPA2006D1, TPS65930

Hi,

I am driving 0.5W 8 Ohm mono speaker from TPA2006D1. The max power rating for speaker is 0.8W.

Single ended input configuration is used for amplifier and it is driven from TPS65930 which consists of audio pre-drivers.

I am not sure how to configure TPA2006D1 for 0.5W output. I am using 5V supply for chip. Now max amplitude across speaker will be 5V (neglecting voltage drop across driving FETs in audio amplifier) which theoretically gives more than 3W (V*V/R). Now based on PWM duty cycle average power will be less. Is it correct way to drive 0.5W speaker in this manner or supply voltage of audio amplifier be decreased such that max output power applied to speaker should not be more than 0.8W.

Regards,

Vini

  • 0
    TI__Guru**** 189399 points

    Hi, Vini,

    I think this app note will answer your questions: http://www.ti.com/lit/an/sloa105a/sloa105a.pdf

    There is nothing magical about a class-D amplifier. It works identical to a class-AB amplifier, but with much higher efficiency.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 895 points

    Hi Don,

    Thanks for the app note. It was really helpful. Actually, volume was very less with my speaker. So, I wanted to increase the power but I was not sure what max power I should deliver to 0.5W speaker which I am using. I have asked speaker vendor about max power this speaker can handle.

    Additionally, I would like to point out that as per TPA2006D1 datasheet, it is a filter less amplifier. So I did not provide any option for output filter and sound quality without filtering was not that good. After searching on web for class D audio amplifier designs, I found out that when using filter less class D amplifier, speaker should be selected such that the speaker inductance and load resistance can filter the high frequency noise without damaging itself. Otherwise, an output filter is recommended at output. I reworked my board and used an external LC filter between TPA2006D1 and speaker and sound quality improved a lot.

    I think TI should mention about speaker selection for a filter less class D amplifier (and filter requirements if speaker parameters are unknown) in amplifier datasheet itself or at least include a reference to some application note which describes these requirements.

    BR,

    Vini

  • 0 in reply to Vini
    TI__Guru**** 189399 points

    Vini,

    I am sorry for the trouble you had with the filterless operation. What speaker are you using? I have never seen this issue before.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 895 points

    Hi Don,

    I am using PUI Audio's SMS-1508MS-R speaker.

    BR,

    Vini

  • 0 in reply to Vini
    TI__Guru**** 189399 points

    Hi, Vini,

    Do you have any measurement data from that speaker with and without the filter?

    -d2