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TLV320ADC3101: How much current can MICBIAS supply if it's supplying AVDD instead of 2.5v?

Mark Calder
Prodigy 80 points
Part Number: TLV320ADC3101

Hi, I can see on page 6 of the datasheet that Microphone Bias pin can source 4mA when it's set to supply 2.5v. If I'm using MICBIAS = AVDD how much can the transistor source? I'm guessing it's more than 4mA since it's not loading down an internal reference like the 2.5v is. Is there a spec for this anywhere? AVDD is 3v on my circuit if that makes a difference.

Thanks, Mark

  • 0
    TI__Guru* 84915 points
    Hi, Mark,

    Welcome to E2E and thank you for your interest in our products!

    Effectively, when MICBIAS is configured as a programmable voltage (2V, 2.5V), this pin can source 4mA. When MICBIAS is configured as AVDD voltage, it would be a different case. This configuration is actually a switch to AVDD. So, the MICBIAS pin is directly connected to AVDD. You may find more information in the link below:

    e2e.ti.com/.../1088.should-i-connect-a-capacitor-to-a-micbias-pin-what-should-i-do-about-noise

    This connection allows higher current consumption. We don't specify this value since it depends of your AVDD power supply current capability.

    Please let me know if you have additional questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.
  • 0 in reply to Luis Fernando Rodriguez S.
    Prodigy 80 points

    Thanks Luis. Often datasheets show the source / sink currents for I/O lines and the voltage at that current. I thought maybe TI knew the range that the MIC BIAS transistor could source but just had forgotten to put it on the datasheet. There is a graph of AVDD and the voltage drop across the transistor coming out of MIC BIAS but no mention of what current that was sourcing. Was it driving a multimeter or 4mA? I guess I'll go put a 750R resistor on that pin and see what the voltage is and hope that's typical. A spec for a typical range and a note to say that it's not tested is still potential useful on a datasheet. I disagree with this statement "We don't specify this value since it depends of your AVDD power supply current capability" . Of course you can't supply more current than is available at AVDD's power supply but if my AVDD can supply 1 amp does that mean mic bias can too? I doubt it.

    Best regards, Mark

  • 0 in reply to Mark Calder
    TI__Guru* 84915 points
    Hi, Mark,

    I apologize for the confusion. You are right. I was searching for more information about the MICBIAS pin. MICBIAS output is able to support 6mA without AVDD current constraints.

    Best regards,
    Luis Fernando Rodríguez S.