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Precision Gain control of amplifier with Microcontroller

Suyog Vyawahare
Intellectual 965 points
Other Parts Discussed in Thread: TPA6130A2, PGA2311, TPA2028D1

Hi,

Currently I am designing a audio device where I have to precisely control gain of audio amplifier which will drive 8 ohm headphones. (mono headphones)

I have absolutely zero experience in audio amplification. I am going to generate sine wave with DDS (single ended input) and then change gain of amplifier from -10dB SPL to +120 dB SPL and I want to vary gain digitally. Which Amplifier should i use? 

  • 0
    TI__Guru** 108685 points
    Hi Suyog,

    What is the output power you need on the output of the amplifier?(Watts or mW). I understand you'll use 8-Ohm speaker, which is fairly low for headphones that usually go from 16 to 32-Ohm.
    I ask this to make the decision narrower between the available amplifiers. Judging by the speaker impedance you'll use you could even use a low power amplifier, not specifically headphone amplifier.
    There is TPA6130A2. This device has digital volume control through I2C with 64 steps and it can also be configured in a mono BTL mode for the output.
    Another option could be to use a separate volume control. You could use a PGA2311 as volume control, which is controlled through I2C, and then an amplifier stage.
    Please share more details of your application in order to offer a closer match to your needs.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 965 points

    Hi,

    It is a audiometer to test hearing of patient. We need precise and accurate control on audio output in terms of dB and noise free output. Headphones have 10 ohms impedance and have maximum power of 300mW. I am attaching headphone datasheet. headphone model is TDH39.

    Existing product uses Max4364,  Max7490 and DS1801. My aim is to get a single digital chip then to have so many parts. 

    tdhspecs.pdf

  • 0 in reply to Suyog Vyawahare
    TI__Guru** 108685 points
    Suyog,

    You could take a look at TPA2028D1. This is a low-power mono amplifier with digital I2C interface. This amplifier is used mostly with 4 to 8-Ohm loads but there should be no problem driving 10-Ohm load. It comes in the same supply voltage range from 3 to 5V.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 965 points

    Hi

    This looks like a good fit. Only issue is we cant handle bga. We need tssop, ssop, tqfn or qfn. Thanks for pointing me in right direction, now i will search for similar amplifier.

    PS: by any chance you know relation  between  dB and dB SPL?

  • 0 in reply to Suyog Vyawahare
    TI__Guru** 108685 points
    Hi Suyog,

    dB represents the gain of an amplifier which takes the input as reference.
    dB SPL on the other hand comes from "sound pressure level" that has its reference at 20uPa. This is most likely a measurement of the sound that comes out from the speaker.

    Best regards,
    -Ivan Salazar
    Texas Instruments