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TLV320AIC3104: About description of input DC bias on datasheet

Tao_2199
Genius 5660 points
Part Number: TLV320AIC3104

Hello,

 

Regarding to input DC bias on TLV320AIC3104,my customer is asking a question.

 

(Question)

Why isn’t input DC bias(1.3V) described on datasheet?

My understanding is that just AC couple the inputs within analog input range(0.707Vrms), connect their source on the other side of the capacitor and everything will work fine.

So, they don’t need to consider input DC bias on normal using and it isn’t described on datasheet.

My understanding is correct?

 

Could you please give any comment or advice?

 

Regards,

Tao_2199

  • 0
    TI__Guru 62035 points

    Hello,

    The datasheet mentions there is an internal bias voltage which shifts the AC-coupled audio input signals into the linear range of the single-supply powered ADC.  Unless you're trying to accomplish DC-coupled measurements then the exact bias voltage isn't the most important which is maybe why it's left off.  The voltage is roughly 1.35V.

    Your understanding is correct.  AC couple the inputs, keep them less than 0.707Vrms (2Vpp) and things will work fine.  Note there is a non-zero and also non-zero centered gain-error which typically reduces the usable input range to slightly less than the 0.707Vrms levels.

  • 0 in reply to Collin Wells
    Genius 5660 points

    Hello Collin,

     

    Thank you for reply.

     I will inform to my customer your comment.

     

    By the way,

    You mentioned that following in your comment.

    “The datasheet mentions there is an internal bias voltage which shifts the AC-coupled audio input signals into the linear range of the single-supply powered ADC.”

    I couldn’t find out above description in datasheet.

    Could you please tell me where it is described in datasheet?

     

    Regards,

    Tao_2199

  • 0 in reply to Tao_2199
    TI__Guru 62035 points

    Hello,

    Well, to be honest I was unable to find it in the AIC3104 datasheet.  There is more information in the AIC3107 datasheet which features the same input structure (with a few extra input connections).  Take a look at the images in sections 10.3.4 Audio Analog Inputs and also 10.3.7 Input Impedance and VCM Control.  The exact input voltage ~1.35 volts does not look to be mentioned there either.