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TLV320AIC3105: HPOUTs voltage on power-up

jerome d.
Expert 1255 points
Part Number: TLV320AIC3105

Dear all
I'm observing HPOUTs voltage at power up (causing audible pop), HP outs are used in single ended mode; connected to the headphones connector through 47uF electrolytic caps.
HPCOMs are left unconnected.
 
My power up sequence is as follow :

1- Keep reset pin low
2- Start power supply 3.3V digital IOVDD
3- Start power supply 3.3V analog + 1.8V Digital (DRVDD+AVDD+DVDD)
4- Wait about 30ms then Start I2S clocks 
5- Wait about 5ms then Set reset pin high 
6- Wait about 5ms then Configure codec registers

I'm observing a voltage ramp up on HPOuts about 5 to 6ms after step 3; once the analog power supply is provided.
By default all HPOut amps should be powered off, I do not understand why I observe those voltage on HPOUTs pins ?
Any idea would be greatly appreciated.
Thanks.

  • 0
    TI__Mastermind 22950 points

    Hello Jerome,

    This is quite odd. You are correct that by default, the DACs and HP drivers should be powered off. What voltage are you reading at the HPOUTs? Is this occurring on HPLOUT and HPROUT? Even though HPCOM outputs are not connected, is there a voltage there as well?

    Can you also please share scope shots of your power up sequence? We want to be sure that nothing is being violated in the power up sequence.

    Regards,

    Aaron

  • 0 in reply to Aaron Estrada
    Expert 1255 points

    Thanks for your prompt reply.
    Yes it is weird.

    I observe one strange thing, the voltage on DRVDD=AVDD=3.2V is ramping up to 4V few milliseconds after it was applied to the codec. Then it goes back to 3.2V about 50ms later.
    I attach my schematics so you can see how I generate this voltage.

    Below are some plots, as requested; please note IOVDD is 3.3V (not 3.2V) and always present, so it is not shown in the below plots.






    I attach the schematics in a next post.
    Thanks

  • 0 in reply to jerome d.
    Expert 1255 points

    On thing I noticed, if I set RESET = 1 before applying power to the codec, the 3.2V no longer ramps up to 4V.
    But the codec hangs once I start writing registers (I guess it is normal since the reset is not properly done).
    But reset = 1 before power supply no longer results in the 4V on the power supplies.
    Weird

    Schematics :




  • 0 in reply to jerome d.
    TI__Mastermind 22950 points

    Hi Jerome,

    Thank you for providing the scope shots and schematic. This is still very puzzling. Some more questions:

    1. It is not possible for the codec to reach 4V by itself. It seems as if one of the supplies is becoming unstable and it can only happen before the regulator, on VCC33. Could you please share ALL power supplies during start-up via scope (VCC33 included)? If possible, could they all be on the same scope? 

    2. What voltage are the SDA and SCL lines getting pulled up to?

    Regards.

    Aaron

  • 0 in reply to jerome d.
    TI__Mastermind 30030 points

    Jerome, 

    We didn't receive a response from you,  are you still having issues with the AIC3105?  please let us know and we can continue to assist. 

    if you were able to resolve, we'd also be interested in hearing what the issue was

    best regards,

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    Expert 1255 points

    Hi

    Sorry for the late answer.

    I noticed the issue appears when the 12V audio power supply is enabled on the board.
    This audio power supply supplies the opamps that are connected to the different inputs as well as to the line outputs.

    I'm waiting for the new prototypes to come, where I delayed the enable pin of the 12V, I'll let you know once I will have results of the tests on this new version.

    regards

  • 0 in reply to jerome d.
    TI__Mastermind 22950 points

    Hello Jerome,

    Thanks for your response!

    Looking forward to hearing back from you about this issue. 

    Regards,

    Aaron