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TPA2011D1: TPA2011 Input Mixer Circuit Review

Wayne Chen (ex FAE)
Guru 15950 points
Part Number: TPA2011D1

Hi Sirs,

We are supporting customer in designing a down mix circuit with TPA2011D1 as the picture below.

There are three signal sources, PWM#1, PWM#2, and stereo analog audio, while they will not send signals simultaneously.
A low pass filter will be used on the input path of the PWM buzzer. 

Here we need product line's suggestion of the input filter of the TPA2011. Since the PWM generator does not work with analog audio at the same time.
Should we design the input circuit to achieve R9=R3//R6//R8//R6~=39kR, C9=C3//C6//C7//C8~=0.22uF?
If no, how do we design the input filter with the TPA2011 in this case?


Thank you and Best regards,

Wayne Chen
01/27/2021


  • 0
    TI__Guru* 84915 points

    Hi, Wayne,

    Thank you for sharing the circuit design.

    This is correct. Actually, the TPA2011D1 single-ended inputs impedances must match as mentioned in  section 9.4.1.3 datasheet.

    https://www.ti.com/lit/ds/symlink/tpa2011d1.pdf#page=17

    So, all the input impedance of IN- must be equal to the input impedance of IN+. This includes also the resistors and capacitors of the connected filters. So, the equivalent resistor and the equivalent capacitor of all the single-ended inputs must be equal to R9 and C9.

    This practice is suggested in order to avoid any pop issue in the device.

    Best regards,
    Luis Fernando Rodríguez S.