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TLV320AIC3206: State if HPx and LOx when driver is disabled

Stefan Burstrom
Prodigy 140 points
Part Number: TLV320AIC3206

Hi!

I am designing a system where I would like to be able switch between driving a 32 ohm headset and outputting an attenuated signal that can drive a microphone input (using an L pad)

What is the state of these outputs when they are not powered? Are they high impedance when they are not powered. I was thinking of combining the output into 1 audio jack and if the pins are high impedance when they are not active, I will be able to combine the line outputs and headset outputs without any external analog muxes.

Best regards,

Stefan

  • 0
    TI__Mastermind 30210 points

    Stefan, 

    The HPL or HPR could be used for both of these...that is to say, you wouldn't need to use the "line out" to drive the mic input, you could use the HPOUT.

    best regards,

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    Prodigy 140 points

    Hi Steven!

    Unfortunately, I dont think that it is that simple.

    The mic input will not work with a ground centered HP signal, it has to be attenuated and AC-coupled. I have a cable where I put the resistor divider + a cap as a prototype and it works fine. I was just hoping to be able to incorporate that in the design right away to avoid having to put any electronics in the cable.

    See below for the schematic. The left side is the audio driver and the right side is the mic input / headset.

    The attenuation network is only needed when there is a mic connected, so I was playing with the idea of using the line out signal to drive the attenuated signal to avoid having to add electronics to make the attenuation switchable.  It is possible that I can simply attenuate the HP-signal enough for the output to be small enough to not overload the mic, but I am not sure what will happen if I drive the mic with a ground centered signal. If there is an ESD diode on the line, it is possible that a negative signal will be clamped to ground.

    Right now, the design has 0-ohm resistors in strategic places so it will be possible for me to try the different options, but it would be great to get some more insight in how the chip works too.

    Best regards,

    Stefan