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TAS5727 without MCLK

Oane Kingma
Intellectual 370 points
Other Parts Discussed in Thread: TAS5727, TAS5727EVM

Hello,

we are currently in the process of evaluating hardware for our design and we have been looking at the TAS5727 DAC+Class D amplifier for our design. We have purchased an evaluation kit and are interfacing it to our own hardware. With the TI software we are able to produce sound through the ADC so all components seem to work.

The reason we chose the TAS5727 is that in the datasheet it is stated that:

"The clock section uses MCLK or the internal oscillator clock (when MCLK is unstable, out of range, or absent) to produce the internal clock (DCLK) running at 512 times the PWM switching frequency".

This made use believe that we could actually could get away with just connecting SCLK, LRCLK and SDIN and the amplifier could work (no MCLK connection required).

Is this assumption correct and will the internal oscillator generate MCLK or does the amplifier really need MCLK connected to properly fuction?

Best regards,

Oane

  • 0
    TI__Mastermind 22965 points

    Hi Oane,

    Without an external MCLK, the device will not play audio. The internal clock (DCLK) is used to sustain operations like I2C communication & idle output PWM switching. So in effect what the datasheet statement is saying is "Even in the absence of MCLK, I2C read/write operations can be performed, and the output PWM will continue to switch in idle mode". Sorry about any confusion with the datasheet description.

    That being said, one option to use a single clock on both MCLK & SCLK is if a 44.1KHz/48KHz sample rate (i.e. LRCLK is used). With a 44.1K/48KFs rate, a 64*Fs clock can be used on both SCLK and MCLK pins.

    Also, wanted to clarify, the TAS57xx series devices do not use a DAC. It is a true digital solution, i.e. digital I2S input is converted to PWM, which is then processed by the Class-D.

    -Ravi

  • 0 in reply to Ravi Singh
    Intellectual 370 points

    Hi Ravi,

    thank you for clearing this up.

    I will try the suggestion you gave me with regards to the 64*Fs clock. Crossing my fingers that it works :)

    Best regards,

    Oane

  • 0 in reply to Oane Kingma
    Intellectual 370 points

    Hi Ravi,

    just wanted to let you know that your suggestion works! Using an NXP LPC1778 dev kit and the TI TAS5727EVM dev kit I distributed the SCLK to the MCLK as well and configured the TAS5727 to use 64xFs for MCLK. Et voilà, there was sound.

    Looks like we'll be using the TAS5727 in our design after all! Many thanks for the help.

    Best regards,

    Oane

  • 0 in reply to Oane Kingma
    TI__Mastermind 22965 points

    Hi Oane,

    Thanks for the update. Good to know that you got it working. Please let us know if you have any questions during development.

    For reference, can you please provide the use-case conditions (Vcc, Load, Power) & the application details?

    -Ravi