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TAS5782MEVM: Idle Mode Current Consumption

John Fedak
Expert 6715 points
Part Number: TAS5782MEVM
Other Parts Discussed in Thread: TAS5782M,

Hi Audio Team,

My customer is using the TAS5782EVM and is looking at reproducing the idle power consumption information in the datasheet on page 20. In particular the 37mA on the PVDD rail in the 24V PVDD, 4 Ohm load, 768kHz, Idle configuration.

In 2 different configurations, this was measured on the EVM with one (of the two) device enabled (and unmuted) and in both cases the EVM is showing around 120mA PVDD (24V) current. This is a little more than 3x higher than stated.

In the first configuration, the EVM was connected to the PPCMB (Rev F, +4V powered via an external supply) and using the EVM GUI to control the status of the device.

In the second configuration, the EVM was separated from the PPCMB and the I2C/I2S/3.3V were provided directly from an alternate source.\

In both cases a resistive 4Ohm load was used.

We are very interested for your thoughts on why the PVDD current draw would be so much higher than expected.

Please let me know if you have any questions, thank you!

Regards,

~John

  • 0
    TI__Expert 6985 points
    Hello John! Andy will follow up on your question, but can you also verify what gain setting is in place for your configuration? Thanks, Jeff
  • 0 in reply to Jeff Kohnle
    TI__Expert 6715 points

    Hi Jeff,

    Looking at the EVM schematic, I see that it is populated with the 20dB gain setting (and the datasheet states 26dB for the spec). I will check with the customer to see if this has been modified.

    Interested to understand if the lower gain setting would cause a (significant) increase in the idle current.

    Regards,

    ~John

  • 0 in reply to John Fedak
    TI__Expert 6715 points
    Hi Jeff, Andy,

    The customer has pointed out to me that the EVM schematic and the datasheet don't match on the gain calculations. Based on the datasheet table 14, the populated (750k and 150k) resistors are set for 26 dB of gain - matching the idle current spec that is looking to be replicated.

    Regards,
    ~John
  • 0 in reply to John Fedak
    TI__Guru 52115 points

    Hi John,

    The 14dB and 20dB gain settings in the EVM schematic are equivalent to the 20dB and 26dB gain setting in the datasheet. The reason for the difference is that they have different definitions. We can update the EVM schematic to make them consistent. 

    Andy

  • 0
    TI__Guru 52115 points
    Hi John,

    If I remember correctly, the idle power consumption data on Page 20 were not taken using a TAS582MEVM since that board needs quite a few hardware changes if used for idle PVDD current measurement. Let me check with my colleague to find out which board was used and how we got these data.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Expert 6985 points
    Hello John! As discussed Andy will close back with you on the feedback from the design team. Thanks, Jeff
  • 0 in reply to Andy Liu (BMS)
    TI__Guru 52115 points

    Hi John,

    I have confirmed with my colleague that he used another board which we call MTS board to take the measurement data on Page 20.

    In the e2e post, you mentioned the customer tried two different configurations. Did they remove one of the two TAS5782M devices on the EVM in the second configuration?  What’s the I2S input to TAS5782M? Provided by AP? What are the commends sent to TAS5782M via i2c?

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Guru 52115 points
    Hi John,

    I am checking with my colleague again which LC filter we used when we took data. It's probably different from the LC filter on the TAS5782MEVM. Different LC filters may lead to different idle current based on our experience.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Expert 6715 points

    Hi Andy,

    The second device was not removed, however the current was 3x higher. Yes, an AP provided the I2S. Are there any I2C settings to pay close attention to?

    Please let us know the feedback from your colleague on the best way to achieve this idle spec on the EVM.

    Thank you!

    Regards,

    ~John

  • 0 in reply to John Fedak
    TI__Guru 52115 points
    Hi John

    Unfortunately I have not yet got feedback from my colleague who took the data yet since he is on vacation this week. For now I would suggest your customer replace the 4.7uF inductors with 10uF inductors. They should be able to see much better results.

    Andy
  • 0 in reply to Andy Liu (BMS)
    TI__Expert 6985 points
    Hello John! Did this recommendation help your situation? Thanks, Jeff
  • 0 in reply to Jeff Kohnle
    TI__Expert 6715 points

    Hi Jeff,

    Thank you for following up. I believe the inductor change will help with idle current, however we still need to understand the exact settings for the idle current measurements in the datasheet to re-create in this system.

    Regards,

    ~John

  • 0 in reply to John Fedak
    TI__Expert 6985 points
    Hello John! I believe the difference is that some DS data is pulled from a test board (MTS), which would not necessarily be exactly configured like the actual EVM. Idle currents are tough to measure on an EVM, and so in this case the MTS board was used and was configured as:
    Frequency LC Filter
    384k 10uH/0.68uF
    768k 4.7uH/0.68uF

    Audio input -999dBFS, 1kHz

    Registers at default, but 0x02=0x00 to put device in play mode.

    Andy, Do you have any other points that would help John here.

    Thanks, Jeff