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TAS5733L: Audio Throughput without MCLK

Faizul Bacchus
Intellectual 1895 points
Part Number: TAS5733L
Other Parts Discussed in Thread: TAS5733,

I am posting the following customer issue

 

We are trying to get some audio out of a TAS5733.  We are under the impression that we should be able to get audio through this amplifier without an MCLK input.  (3rd bullet on the first page).  We have not been able to achieve this.  Could you give some assistance here?  The I2S signals going into the 5733 also are fed back into the Codec and do successfully drive an analog output to headphones, so we know that the I2S signaling is correct.  We are able to get audio through the 5733 when we apply the RMCK from the Codec but we don’t want to do this.  The datasheet says that you need a resistor between pins 16 & 17 in order to put the amplifier into I2S autodetect mode and refers you to Table 18 to know what the value is…  Table 18 says nothing about the resistor, but I am thinking that this is somehow involved with our problem.

 

 Thanks

Faizul Bacchus

  • 0
    TI__Guru 57800 points

    Hi, Faizul,

    The TAS5733L requires a MCLK to operate properly, if MCLK is not provided, the amplifier’s internal oscillator will generate the internal clock required for the amplifier’s operation. In this operation mode, the amplifier will not stream audio content through the outputs until a valid MCLK is provided. 

    This device is capable of working in 3-wire I²S mode. This operation mode can be implemented as this amplifier accepts the same frequency for SCLK and MCLK (64×Fs) when Fs=44.1KHz/48KHz. In order to make this, MCLK and SCLK should be tied externally. 

    The information from the datasheet's third bullet implies that 3-wire I²S mode is achievable without the need of a different clock for MCLK (i.e. 128×Fs or 256×Fs).

    The reference filter for autodetect mode should follow the typical application diagram, If the filter components are not followed properly, the devcie might not work as expected.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 10 points

    Hello Diego,

    In your first sentence you say "The TAS5733L requires a MCLK to operate properly"...  but then you say "if MCLK is not provided, the amplifier's internal oscillator will generate the internal clock required for the amplifier's operation". These two ideas are opposite one another. 

    But, again, the second sentence seems to imply that I do need an MCLK to do I2S audio, but the 3rd sentence seems to say that I do not need a MCLK (from external pin).

    I appreciate you trying to help but I am confused by what you are saying.  

    We have the RC circuit as shown in Figure 49 between pins 16 and 17 but we are not able to get audio through the amplifier unless we provide an external MCLK on the chip MCLK pins.

    thanks,

    david coburn

  • 0 in reply to Diego Melendez
    Prodigy 10 points
    Hi Diego,

    This is my second reply... We did the amplifier to pass audio data. We implemented your comment "In order to make this, MCLK and SCLK should be tied externally". That did work but I do not see this documented in the datasheet anywhere. Can you direct me to this information in the datasheet, please.

    thank you,
    david coburn
  • 0 in reply to David Coburn
    TI__Guru 57800 points

    David,

    Sorry for the confusion, by saying ""if MCLK is not provided, the amplifier's internal oscillator will generate the internal clock required for the amplifier's operation" I was meaning that the internal oscillator will generate the internal clock required to keep the amp's internal circuitry running, this is neccesary to keep the power stage ON and avoid noise artifacts. No audio will be streamed until a valid external MCLK signal is provided. There is no direct mention of this in the datasheet, but in table Table 5. Clock Control Register (0x00), you can find the available sample rates when MCLK is 64×Fs (same as BCLK).

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer