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TLV320AIC3107: MIC+Line input

Jerry Chu
Genius 4915 points
Part Number: TLV320AIC3107

Hi Expert,

I want to design the audio input for MIC-IN. But if the line-in with 3.3V bias voltage, does it any risk for AIC3107? 

PS. MICBIAS has 2.2Kohm to connect analog signal.

  • 0
    TI__Guru 62085 points
    Hi Jerry,

    Could you share a rough diagram/schematic of what you're asking about? It's difficult to answer the question without being sure what you're asking. If you're asking if it's okay to have a 2.2k pull-up on the line-in voltage to +3.3V then provided your line driver can drive the required current it shouldn't be an issue.
  • 0 in reply to Collin Wells
    Genius 4915 points

    Hi Collin,

    For example, the TLV320AIC3254EVM-U, if I set the MICBIAS to 2.0V and the phone jack connects a LINE-IN signal with 3.3V DC bias. Does it any risk to damage the codec?

    BTW, if the codec didn't power on, any risk? Thanks!

  • 0 in reply to Jerry Chu
    TI__Guru 62085 points
    First, in our experience it’s much more common for customers to use dedicated line-in / microphone input channels but we understand why the customer is trying to achieve what they’re doing.

    The main issue that will arise is that when the device is configured for microphone inputs with an active MICBIAS and they connect a line-in connection that the two sources will fight against each other. When sourcing MICBIAS from the internal LDO, then the current is internally limited to around 3-4mA so as long as the line-in can over-drive the MICBIAS then there shouldn’t be issues. However, if the MICBIAS is sourced from the internal AVDD through the internal switch then the current will only be limited by the MICBIAS pull-up resistor. If the resistor is large enough then even if the LINE-IN drives to GND then there would only be a few mA of current flow and again this should likely be okay.