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TPS2546: Unexpected behavior with Android phone during transition from CDP to DCP

Antony Lin
Genius 13480 points
Part Number: TPS2546

Hi,

TPS2546 is used on a NB for this project.  When the system has a S0 to S5 power state transition, they'll change the setting of TPS2546 from CDP/S0(CTL1/CTL2/CTL3/ILIM_SEL="1111")  to DCP/S5(CTL1/CTL2/CTL3/ILIM_SEL="0011").

There two different result as summarized below,

  • If the this port is connected to Apple iPhone at this moment, there'll be one stop-charge happening which should correspond to VBUS drop happening once as below.

  • If the this port is connected to Android phone at this moment, there'll be two stop-charge happening which should correspond to VBUS drop happening twice as below.


The channel assignment for these two waveforms as below,

  • CH1:VBUS
  • CH2:CTL1
  • CH3:CTL2
  • CH4:STATUS

Do we know why there's one additional drop for Android phone case?  What can be done for further clarification?

Thanks,

Antony

  • 0
    TI__Mastermind 30000 points

    Hi Antony, 

    This is a characteristic of the DCP_Auto functionality and is expected behavior. Hope this helps answer your question

  • 0 in reply to Adam Mc Gaffin
    TI__Genius 13480 points

    HI Adam,

    Thanks for the comments.  May we know why VBUS drop once for iPhone but twice for Android phone?  Do we have related description in datasheet about it?

    Thanks,

    Antony

  • 0 in reply to Antony Lin
    TI__Mastermind 30000 points

    Hi Antony,

    Yes here is the relevant paragraph taken from the datasheet (section 8.4.1)

    As mentioned above the TPS2546 integrates an auto-detect state machine that supports all the above DCP charging schemes. It starts in Divider1 scheme, however if a BC1.2 or YD/T 1591-2009 compliant device is attached, the TPS2546 responds by discharging OUT, turning back on the power switch and operating in 1.2 V mode briefly and then moving to BC1.2 DCP mode

    So the first VBUS drop is for transitioning to DCP_Auto and then the second VBUS drop is the TPS2546 transitioning to 1.2V charging mode