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TPA2016D2: Amplifier output varies without changing the gain

Ujwal Vijaykumar
Prodigy 140 points
Part Number: TPA2016D2
Other Parts Discussed in Thread: TPA2017D2, , TPA2012D2

We're using the TPA2016 class D amplifier for one of the designs. It's powered at 5V and connected to an 8ohm 1Watt load. The AGC and the limit levels are turned off. When heavy metal or rock music is played at full volumes and the gain is increased to about 22dB, we experience a sudden swag in the output level followed by gradual increase and this phenomena repeats. We tried setting the limiter levels to overcome this effect but, don't see much difference. Can you please suggest a solution for this.

  • 0
    TI__Guru** 102335 points
    Hi Ujwal,

    Based on your description, the limiter is most likely reducing the amplifier gain and then, when the source amplitude is reduced, the gain returns to the set value.
    Have you also tried to disable the limiter? Register address 6, bit 7.
    You could use the limiter, compression ratio and other features of the device to increase low amplitude signals and limit larger signals; that is basically the purpose of the AGC/DRC.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Prodigy 140 points

    Hi Ivan,
    Yes, the limiter and the AGC are disabled. Even then, I'm experiencing the fluctuations in the output levels without changing the gain level.

  • 0 in reply to Ujwal Vijaykumar
    TI__Guru** 102335 points

    Hi Ujwal,

    As you can see from TPA2017D2 data sheet (same as TPA2016D2 but HW control) there is still some non-linearity at the top of the curve even when features are disabled.

    If you don't need these features perhaps it would be better to change the device. Although as you may already know, without these features and if the audio and gain are too high, there will be clipping distortion instead of level fluctuations.

    What would be the requirements for the amp? I assume you need analog input and a Class-D amp. Do you need I2C control or Hardware control is OK? TPA2012D2 would be a simpler solution.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators