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TAS6424EQ1EVM: DC Diagnostics Line Out Impedance

Kessler Kerr
Prodigy 80 points
Part Number: TAS6424EQ1EVM
Other Parts Discussed in Thread: PUREPATHCONSOLE, TAS6424E

Tool/software:

Hi Audio Team,

I am using the TAS6424EQ1EVM for initial evaluation. The evaluation is going well. One of the things I haven't been able to do is prove out the DC Diagnostics. My load is very high > 1K. Reading about the line out impedance it looks like it will be able to handle up to 6kOhm. When I have Line-out enable diagnostics checked I still see an open-load condition when I run the DC Load Diagnostics. In order to play on the high impedance loads I have turned off the DC diagnostics by checking "Bypass LD". Is this the expected behavior? I was hoping to see it would be able to detect the high impedance load. Is there something I should configure differently?

Thanks,

Kessler 

  • 0
    TI__Mastermind 45045 points

    Hi Kessler,

    I assume you are using the GUI with the EVM.  Using the switch on the EVM, keep the device in Standby mode.  Make your changes using the GUI before you take it out of standby mode.  The DC diagnostics will automatically run when taken out of standby.  Automatic DC diagnostics can also be disable while in Standby mode.  

    Regards,
    Gregg Scott

  • 0
    Prodigy 80 points

    Hi Gregg,

    That is right. I am using the PurePathConsole TAS6424E plug in. I followed your directions and placed the EVM into standby mode using the switch. I then selected the "Line-out Enable Diagnostic" and "Bypass LD" options. I left standby mode using the switch and then manually ran DC load diagnostics with the start button. The OL and Line OUT fields failed.

    Also if I turn off "Bypass LD" and change the channel to Play Mode then the speaker makes a small pop sound similar to what the datasheet mentions when using line out. This sound occurs every few seconds and I cannot play audio.

    Using an LCR set to 1kHz, my load impedance is 2K so I am expecting the line out impedance diagnostic to be able to work.

    Does it matter what mode the channel is set to? I've swapped between Line out and Speaker and it does not appear to effect the line out diagnostic result.

  • 0 in reply to Kessler Kerr
    TI__Mastermind 45045 points

    Kessler,

    Even in line out mode, it thinks it has an open load.  What values for the LC did you select?  What is the DCR of the inductor?

    Regards,
    Gregg Scott

  • 0 in reply to Gregg Scott
    Prodigy 80 points

    Gregg,

    Thanks, that explains why it's not playing. I assume for LC you mean the filter on output of the Class D? It should be the default components: 1x 3.3uH inducator and 1x 1uF and 1x 0.01uF cap. The DCR is 38mOhm. 

    Thanks,

    Kessler

  • 0 in reply to Kessler Kerr
    TI__Mastermind 49430 points

    Hi Kessler

    Kessler Kerr said:
    Using an LCR set to 1kHz, my load impedance is 2K

    Could you please check what is the DC resistance value of your load. The Load Diag will get the DC resistance, and sometimes we see at DC have very large resistance.

    On the EVM I quickly tried with 3K resistor, everything seems fine.