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TLV320ADC3101: Whether can PGA always be closed?

Lian Wu
Genius 5250 points
Part Number: TLV320ADC3101


Dears：

Pls. check the below ADC_Loopback  schematic, and want to know whether can PGA always be closed?

amixer cset numid=6,iface=MIXER,name='Mic PGA Switch' 1 is open


  • 0
    TI__Guru 57800 points

    Hi, Lian,

    I reviewed the schematic and my only comment is that the differential input labels seems incorrect. in differential mode, the corresponding pairs are IN1L(P)/IN1R(M), IN2L(P)/IN3L(M) and IN2R(P)/IN3R(M). In the schematic, IN2L(P) is paired with IN3R(M), while IN2R(P) is paired with IN30L(M).

    Can you please elaborate more on your question about the PGA?.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Genius 5250 points

    Hi Diego Meléndez López:

    Thanks for your suggestion.

    We want to compare the MIC input and the ADC loopback through algorithm for reducing harmonic.

    And the schematic as follows:

    Pls. kindly help to check and there are some questions about ADC PGA Switch for realizing loopback as follows:

    1. Whether need ADC PGA  SWITCH open at the same time when we record through MIC.

    2. When need we open or close ADC PAG SWITCH? Could you give some conditions?

    3.Could we always close ADC PGA SWITCH?

    Pls. help!

  • 0 in reply to Lian Wu
    TI__Guru 57800 points

    HI, Luck,

    Could you please provide details about the definition of open and close the PGA switch?. I assume you are referring to the input connections to each PGA at the input of the ADC. If so, there is no special requirement to open or close it for an application like this, you can connect the differential signals of each channel to the corresponding PGA and keep it connected at all times.

    It is mentioned in Q1 that a mic record option is also available, if so, you would need to disconnect the inputs from the Amp output to the PGA and route the mic signals (which are not in the schematic) to the corresponding PGA.

    The conditions to change the input routing basically consist in muting the device ADC before any change and unmute once all the changes are applied.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer