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TLV320AIC23B Bad Voice Quality

Hello everybody,

I am using the TLV320AIC23B as speech data converter with LPC2368 micro-controller for configuring the codec device, when i am giving speech data packets to the codec using I2S interface form micro-controller, it generating an output of 2.8V pk-pk and 1.6V mean on LOUT and ROUT, But according to Data sheet the mentioned value is 1V RMS. I observed that the 1.6V mean is generating from the LOUT,ROUT,LLINEIN,RLINEIN pins default.

For Better voice quality the mean should be zero please suggest me how get out of this mean coming from IC default.

Thanks & Regards,

Goutham Kumar.

  • Hi, Goutham,

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

    Is it possible to provide a schematic and registers configuration? We recommend to add DC-blocking capacitors (0.1uF) at the LOUT, ROUT, LINE_IN pins. These capacitors will remove the common-mode voltage at these pins.

    Best regards,
    Luis Fernando Rodríguez S.
  • Hi, Rodriguez

    first of all thanks for your response,

    the following details are the codec registers configuration sequence and  the schematic of codec block section pdf

    Registers configuration:

    SPI_Write_Byte(0x1E00); //Reset

    SPI_Write_Byte(0x011B); //Left line input channel volume control //0x011B ....+6dB

    SPI_Write_Byte(0x031B); //Right line input channel volume control //0x031B .....+6dB

    SPI_Write_Byte(0x05F9); //Left channel headphone volume control //0x05F9 .....0dB

    SPI_Write_Byte(0x07F9); //Right channel headphone volume control //0x07F9 ......0dB

    SPI_Write_Byte(0x08B8); //Analog audio path control //0x08B0 ......-12dB for loopback

    SPI_Write_Byte(0x0A00); //Digital audio path control //0x0A00 ......ADCHP enabled,Deemphasis disabled

    SPI_Write_Byte(0x0C00); //Power down control //0x0C00 ......ALL are in 'ON'

    SPI_Write_Byte(0x0E52); //Digital audio interface format //0x0E52 ......I2S format

    SPI_Write_Byte(0x100D); //Sample rate control //0x100D .....MCLK=12 MHz,sampling rate = 8KHz

    SPI_Write_Byte(0x1201); //Digital interface activation //0x1201 .....Activate interface

    we are using  10 uf at the LOUT,ROUT,LINE_IN pins we will try with your suggested 0.1 uf also,the main thing is we are getting the 1.6V DC-level on the LOUT,ROUT,LINE_IN pins itself

    Thanks & regards,

    Goutham Kumar.

  • Goutham,

    Our codec devices generate a DC level around the 1.65V (common-mode voltage) . This is made to accept the negative values at the codec input/output. This common-mode voltage is generated once the ADC/DAC is enabled. I suggest to make some tests without the DC-block capacitors. This capacitors help to generate the DC-level at the input and output.

    Please let me know if you have questions or comments.

    Best regards,
    Luis Fernando Rodríguez S.
  • Luis Fernando Rodríguez S,

    Thanks the information about the DC level (1.65V) purpose on the Codec pin itself. we have evaluated the codec performance with 100 KPF and 10 UF on LINEIN and LINEOUT pins and observed the better quality in voice with 10UF only, also tested the codec without DC-block capacitors as you suggested in the previous mail and observed that noise is more and low voice quality.

    Regards,

    Goutham Kumar.

  • Hi, Goutham,

    Regarding the codec I2S lines, how are they being configured? I mean, which frequency values are you using for WCLK, LRCIN, LRCOUT?

    Best regards,
    Luis Fernando Rodríguez S.