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TAS5424A play mode settings

Josef Nevrly
Prodigy 20 points

Hi All,

I'm having hard times making the TAS5424A work. I have the i2C communication ready, but I don't know how to set the outputs to play mode.

At first, I set the hardware pins STANDBY and MUTE to high. Then I use the I2C to set the Output control register(0x0C) to 0x00, which (if I understand the documentation corrrectly, should put all channels to play mode).

However, I'm not getting any output and when I read the status registers 0x05, 0x06, it's values are both 0x00. That should mean all outputs are disabled and in HiZ.

I'm pretty sure I can write to the registers, because I can write any value (which does not cause reset) to 0x0C reg. and then read it back.

Could someone please point out some reliable sequence to start-up the TAS5424 in play mode?

Thanks in advance,

Josef

  • 0
    TI__Expert 6050 points

    Josef,

    It sounds like your problem is with the Mute pin. The TAS54x4 devices use the mute pin to store and pull charge when going through the common mode and gain ramps (these are the ramps that allow the device to start up pop and click free). For proper operation, you need to have no external control attached to the Mute pin - in other words it should not be pulled high or low, it should be left floating with a 330nF capacitor attached.

    [The Mute pin can be used to apply an emergency mute to all outputs, but for regular playing it needs to be left floating]

    Once the Mute pin has been left floating, the proper operation is as follows:

    Apply PVDD
    Pull Standby pin high
    (wait ~1 ms for device to come alive) --> device now in HiZ mode
    Clear faults by reading fault registers 0x00 and 0x01
    Place all channels in Mute mode: Write 0x10 to register 0x0C
    Read register 0x06 until it reports all channels are in Mute mode (when it reads 0xF0)
    Place all channels in Play mode: Write 0x00 to register 0x0C
    Read register 0x06 until it reports all channels are in Play mode (it will read 0x0F)

    To summarize this simply: Hi-Z --> Mute --> Play

    To turn off the device follow this procedure: Play --> Mute --> Low-low --> Hi-Z

    I know this is not the most intuitive order of events if you have never worked with a similar device, but this operation results in excellent pop/click performance. This information can be found in the datasheet in the timing diagrams.

    Please let me know if you have any further questions.

    Best regards,
    Aaron

    Texas Instruments
    Applications Engineer
    Audio Amplifiers

  • 0 in reply to Aaron E.
    Prodigy 20 points

    Aaron,

    thanks a lot for the explanation. Worked like a charm.

    I actually think the order of commands is quite intuitive, and although I'm new to this sort of devices, I ended up deducing a similar sequence just from reading the datasheet.

    What is IMHO counter-intuitive here is the MUTE pin situation. If you write in datasheet:

    "The use of a hard mute with an external transistor does not ensure pop- and click-free operation, and is not recommended unless an emergency hard mute function is required in case of a loss of I2C control. For proper pop- and click-free operation the minimum recommended value of CMUTE is 330 nF."

    then I can understand (quite logically) that I2C control is better and MUTE pin is only for emergency control. However, I have not found anywhere in the datasheet the relation of I2C muting and HW muting, especially the fact that I2C muting will not work at all unless MUTE pin is floating with 330nF on it. That's not recommendation, that's requirement...

    So I think some update of the datasheet would clear things up.

    Thanks again for fast and excellent advice.

    Josef