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TLV320AIC3254EVM-K: Analog Input Configuration

Trevor Hsu
Genius 4435 points
Part Number: TLV320AIC3254EVM-K

Hi 

There are three analog input configuration examples on the AIC3254 CS Tool.  The first one "High Performance Stereo Recording", the second one is "Low Power Stereo Recording" and the third one is "On-Board Differential Microphone".

My question is why only the  "On-Board Differential Microphone" example doesn't need to set the "common mode"? We don't understand what "common mode" is,  and we don't know whether we need to set it?(Our analog input is using a differential microphone) 

 

Thanks.

BR

Trevor

  • 0
    Genius 4435 points

    The following  analog input scripts can all capture the correct microphone data, do you know which one is correct?

    //Without CM
    P1 R52 0x00
    P1 R54 0x00
    P1 R55 0x40
    P1 R57 0x10
    P1 R58 0x00


    //With CM
    P1 R52 0x00
    P1 R54 0x40
    P1 R55 0x40
    P1 R57 0x40
    P1 R58 0x40

    BR

    Trevor

  • 0 in reply to Trevor Hsu
    TI__Expert 8900 points

    Hi,

    Our TI experts are out of office today for US holiday so please be patient as responses are delayed.

    Thank you for your patience.

    Regards,

  • 0 in reply to Trevor Hsu
    TI__Expert 8900 points

    Hi,

    Please reference TLV320AIC3254 Application Reference Guide (Rev. A) for more details on common mode and configuration.

    'The common-mode voltage setting of the device is determined by the available analog power supply and the desired PowerTune mode. This common-mode (input common-mode) value is common across the ADC, DAC and analog bypass path. The output common-mode setting is determined by the available analog power supplies (AVDD and LDOIN) and the desired output-signal swing.'

    Section 3.5 of reference guide detail setting common mode voltage.

    Common mode needs to be set for maximizing performance of analog input SNR and determines what full-scale input voltage(Vrms) is, table 3-1 highlights the input swing once programmed.