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TS3A226AE: Switch not working after splitting headset grounds

Sepeedah Zadeh
Expert 3070 points
Part Number: TS3A226AE
Other Parts Discussed in Thread: TS3A225E, TS3A227E, TS3A26746E

Hello team, 

Customer is using regular analog USB-C headset with TS3A226AE and working fine. They are needing to change the regular analog USB-C headset by splitting the headset receiver analog ground from headset microphone analog ground. The change is on the headset side only and needed to avoid crosstalk between receiver and mic.

To do this customer is connecting analog ground of headset receiver to USB-C digital ground. There is no change on TS3A design and no change for headset mic (Ring2 and Sleeve are the same).

The issue now is that the device will not switch to headset mode. So far, it seems that SW detects USB-C headset is plugged and apply mic bias to HS_MIC(MICP) since they can detect the mic bias on Sleeve or/and Ring2. That means S1 is on. However, it seems that either FET1 or FET2 is not on at all because the voltage/waveform of SLEEVE and RING2 is the same.  So this issue seems something to do with TS3A226AE. If it can auto switch SLEEVE and RING2, then it should work because there is no change on SLEEVE and RING2 from mic point view.

Can you please help on what may be going on here?

Thanks,
Sepeedah

  • 0
    TI__Mastermind 45495 points

    Seepedah,

    1) Do you have a diagram or schematic of the headset and TS3A226AE connections?

    2) What does headset mode mean? and what is the other system state its switching from?

    3) What is the impedance from the tip to Sleeve and Tip to ring2?

    The TS3A226AE automatically configures its internal switch matrix based on the impedance it sees on the tip to sleeve and tip to ring2.  This thread goes into more detail on the how the TS3A226AE decides how to configure its switch matrix. 

    Does TS3A226AE support high impendance microphone (like IPhone 6 earphone ) ? (this post also explains...

    e2e.ti.com
    Other Parts Discussed in Thread: TS3A226AE , TS3A227E , TS3A225E Hi, My customer concerns about TS3A226AE can support high impendance microphone or not. They

    The TS3A226AE behaves similar to the TS5A225E.  If you look at the TS3A225E datasheet register map you can see that the device recognizes a range of resistances and assigns it a register value.  The device then compares the register values to determine if the tip to sleeve (Rsleeve) and tip to ring 2 (R2) resistances are >, <, or = to each other.  

    In the case you mention R2 = 100k ohms compared to Rsleeve = 102k ohms the audio jack devices will measure those resistances and place them both in the >2800 ohm bucket. Since both resistances will be in the same bucket the audio jack will determine the resistances are equal and configure itself for a 3 pole device grounding both the sleeve and ring 2.

    If you need to manually configure the internal switch matrix you can use the TS3A225E or the new TS3A227E that have manual control through I2C commands.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 10 points
    Hi Adam,

    Thanks for the information. If my understanding is correct, then your chips will not be able to measure the impedance between Tip and Ring2 or Sleeve if I split the ground between receiver and mic. I don't know whether there is a solution for us.

    I assume that you use the mic bias from pin MICP through S1, SLEEVE/RING2, to TIP for regular analog headset. The reason that this will work is because there is common ground(either SLEEVE or RING2) between mic ground and receiver(TIP) so that there is a loop to measure the impedance between TIP and SLEEVE/RING2. If there is no common ground(the only common ground is through system ground instead of on the headset), there is no loop between TIP and SLEEVE/RING2 from headset point view unless you can use system ground (you will have to turn on FET1 or FET2 as a loop to measure the impedance between TIP and SLEEVE/RING2.

    I also read TS3A225E data sheet to see whether I can switch S1 and FET1/FET2 manually. However, it will still need through the same impedance measurement which will not work. So I don't see any solution so far.

    If my understanding is wrong or you have different idea, please let me know.

    Thanks,

    TJ
  • 0 in reply to TJ Shiau
    TI__Mastermind 45495 points

    TJ,

    That is correct the headset will need to have the same ground path for the audio jack switch devices to make the impedance measurement which is the way it automatically locates the ground and mic nodes.

    If you don't need the automatic detection of the mic and ground lines you can use the manual control feature of the TS3A225E and TS3A227E.

    Another option you could try is using a simple cross point switch like the TS3A26746E which you can toggle switch states using a GPIO signal. 

    Thank you,

    Adam