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TS3A225E: Special Note On Power off Noise Issue

user5975063
Prodigy 80 points
Part Number: TS3A225E
Other Parts Discussed in Thread: TS3A227E

Dear TI fellow

1, My design is a sort of docking, which device does not support ACPI, so there is no RTC_Bat in my system. (no any other power after shut down). And then the Noise is coming running off the speaker.

2, Could I connect the 'SLEEVE' to GND directly? Why not?

3, In fact, I did connect the 'SLEEVE' to GND directly.  What made I confused is that there is nothing serious happened during the testing of two sorts of headsets ( both standard and OMPT, both listening and recording through the Microphone)

4, I want to know why both kinds of headset could work correctly (at least without any noticeable malfunction)

5, If the 'SLEEVE' could be connected to GND directly, why did the datasheet advise the user to add the circuit below, instead of telling us to connect the SLEEVE to GND directly?

 

  • 0
    TI__Expert 5660 points

    Hello,

    The recommended circuitry for noise reduction that you provided from the datasheet is included to give SLEEVE a path to GND, ONLY while the device is powered off (VDD = 0V). SLEEVE carries the microphone signal if Standard TRRS is detected, so it should not be tied to GND in this case.

    Could you describe more about the results you observed when connecting SLEEVE to GND directly? What do you mean that nothing serious happened (with both Standard and OMPT)? Do you have waveforms from these tests in both cases? Could you provide a schematic of your system?

    I would also like to point out that the newer TS3A227E device includes internal circuitry to combat this issue of noise at power-off. The internal depletion FETs ensure a connection to ground while the device is powered off, so no external path from SLEEVE to GND is necessary. You may want to consider using this device instead.

    Regards,
    Kate

  • 0 in reply to Kate Dickson
    Prodigy 80 points

    Dear Kate

    1, My project is on PVT stage, and the TS3A227E is not pin-matched with TS3225E. So, please forget this solution for this project.

    2, I knew that 'It SHOULD NOT be tied to GND'. What do you think that it will happen if I Tied it to GND? That is what I confused.

    a), causing device damaged

    b), No voice out meanwhile can't record anything through the microphone

    c), Nothing at odds? You could hear the voice from the speaker while you play a song and you could record your voice through the microphone. NO matter which kind of TRRS you used.

    3, I don't have waveform, but I could hear the sound while playing video, clearly.(Again both kind of TRRS) No matter the media source was downloaded through the Internet or recorded by myself.

    4, My schematic is quite the same as the one in the datasheet. I only tied the sleeve pin on the Audio jack to the shielding which is tied to GND directly through a soldering wire(AKA, flying wire).

  • 0 in reply to user5975063
    Prodigy 80 points

    Attach the snapshot of Audio Jack to illustrate the medal cover on the Jack

  • 0 in reply to user5975063
    TI__Expert 5660 points

    Hello,

    Thank you for the additional information.

    For Standard TRRS, if you tie SLEEVE to GND, this will short the resistance between the microphone signal (SLEEVE) and ground (RING2). The device will not be able to detect that the microphone is present. It will interpret this connector as TRS and will operate exclusively as a 3-pole headset. The mic switch will not conduct the mic signal. A way to double check this is to read the /MIC_PRESENT output pin, which will remain high if there is no microphone detected.

     

    For OMTP TRRS, shorting SLEEVE to GND should not be an issue, as Sleeve is the ground of the connector.

    Shorting SLEEVE to GND will not damage the device.

    Best regards,

    Kate

  • 0 in reply to Kate Dickson
    Prodigy 80 points

    Dear Kate

    1, Theratically, My understanding of the Audio system is the same as yours.

    2, But practically, The principal is NOT true.

    3, As shown in the snapshot below,  No matter I use the switcher (Standard/ OMPT TRRS) or NOT, I could record my voice through the Mic of the Headset.

        That is what confused me and why I raised my question here.

    4, There must be some knowledge we mised ( I suppose)

        Any way, thank you for your help! It is very kind of you to answer my question patiently.

    Accidentally, the Pic below was lack of EMC shielding, who tied sleeve to GND.

  • 0 in reply to user5975063
    TI__Expert 5660 points

    Hello,

    Thanks for the picture & additional information! This is definitely an interesting scenario.

    I'll keep looking further into it. In the meantime, could you let me know what you read on the /MIC_PRESENT pin for both Standard and OMTP? If you have a TRS headset as well, it could be helpful to test all three of these configurations and confirm that the mic detection switch is working properly.

    Thank you!

    Kate

  • 0 in reply to Kate Dickson
    Prodigy 80 points

    Dear kate

    1, I am shamed to say that I made a low-level mistake while seting up the DUT. ( The voice I recorded was came from the Mic within the NoteBook)

    2, Your dipicting about the function of  the headsets is right. (*For now, I find that both kind of Headset can't  work correctly after having tied the sleeve to GND directly, which means not only the Standard TRRS

    Thank you for your kind help!

    Churbill