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Original question:

TLV320DAC3203: Master Clock Input

TLV320DAC3203: Output level driving differential BTL - audio transformer

Johnson John
Intellectual 630 points
Part Number: TLV320DAC3203

Hello,

I would like to understand the Mono output of the TLV320DAC3203 Codec in BTL configuration for driving audio transformer.

Referring to page# 8 in the datasheet of TLV320DAC3203 device, it states that Full scale output is 1778mVrms. Questions, How do we get 1.778Vrms (2.5 Peak or 5Vp-p) with LDIin = 3V ? Can you share more details?

I have attached the our functional block diagram of the circuit. Our requirement is, the output voltage of the transformer (transformer is 1:1, 600 impedance) shall be 1.56Vrms. Question, If I power the codec with 3.3V supply and as per attached circuit, Can I get output 1.56Vrms voltage? Do you see any issues?

Thank you 

  • 0
    TI__Guru* 84915 points

    Hi, Johnson,

    I think there's a typo in this datasheet value.

    This parameter (full-scale output) should refer to Vp voltage instead of Vrms. The maximum output in differential mode is limited by the LDOin level. Which could be up to 3.6V. The device is only capable to reach a Vpp = 3.6V.

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

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 630 points

    Thank you for the response, Luis Fernando Rodríguez S.

    Question, referring to below functional block diagram, can i take differential output from codec to drive differential amp and transformer for 1.56Vrms output? Idea is to remove bulk dc blocking capacitance on input and output? Can you share your feedback? 

     

  • 0 in reply to Johnson John
    TI__Guru* 84915 points

    Hi,

    Regarding the TLV320DAC3203 output capacitors, I think there shouldn't be any problem to remove the DC-blocking capacitors. The idea of having the output capacitors is to eliminate the common-mode voltage at the output (1.25V, 1.5V or 1.65V depending of the registers settings). Usually the differential amplifiers don't support a negative voltage. So, the output signal of the DAC3203 will be fixed at the common-mode level and the minimum value that it can achieve is 0V, which will be good to protect the amplifier inputs. However, if the amplifier requires of input capacitors because an internal bias or a common-mode level, it is recommended to add them.

    In addition, I recommend to add a low-pass RC filter at the DAC3203 outputs. This device has delta-sigma modulation which results in high-frequency output noise. This noise should be eliminated or it could be amplified.

    For more information, please consult this App Note.

    http://www.ti.com/lit/an/slaa313/slaa313.pdf

    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.
    Intellectual 630 points

    Thank you for the response, Luis Fernando Rodríguez S.

    the application note is really helpful.

    One more question, what is the full scale output amplitude of the Codec for default settings of the DAC registers.

  • 0 in reply to Johnson John
    TI__Guru* 84915 points

    Hi, Johnson,

    Sorry for my late response.

    The TLV320DAC3203 default settings set the device headphone output in stereo single-ended configuration. Accordingly to the electrical characteristics, the full-scale output voltage is 0.5Vrms under this configuration.

    Best regards,
    Luis Fernando Rodríguez S.  

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 630 points

    Thank you for the response, Luis Fernando Rodríguez S.