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TPS65988: BC1.2 Charger Advertise Results

Cory Van Beek
Prodigy 245 points
Part Number: TPS65988

Hello TI Support,

I'm working on a device using the TPS65988 which can charge multiple devices at once.  There is a limited power budget though, so I need to balance that power between ports.  My device currently advertises as a BC1.2 CDP.

I'm wondering if there's a way to determine the results of the advertisement?  If the port on the TPS65988 was acting as a sink, then it could read bits 7:4 of the Power Status Register (0x3F) to determine which charger was detected and therefor how much power it can sink.  However, if the port is acting as a source, then that option doesn't seem to be available.  The Charger Advertise Status bits (9:8) of the Power Status Register just say whether or not charger advertisement is complete or in progress.  I would like to know if the downstream device is going to pull 1.5 A or USB default current (500 mA or 900 mA) so that I can fully allocate my system's power.  Is it possible to figure that out?

I'm also curious about the other advertise modes.  The BC1.2 Charging Support App Note only mentions BC 1.2 CDP and BC 1.2 DCP advertisements.  What are these other options?

Best regards,

Cory

  • +1
    TI__Mastermind 31820 points

    Hello Cory,

    TPS65988 does have a register that can read the current that is currently sourced from the device. The amount of current pulled is determined by the downstream device. The BC1.2 advertisement only advertise the maximum current supported by TPS65988. Since your device is advertising BC1.2 CDP, the maximum current can be supported is 1.5A per port, but how much current is being pulled from each port is determine by the downstream device connected.

    The DCP 1.2V Advertisement is the Samsung charging scheme and DCP Divider3 Advertisement is the Apple charging scheme. DCP Auto Modes advertise the supported charging modes in the parenthesis. You can read the attached documents for more details about the charging mode.

    tps2513.pdf, 4034.tps2546.pdf

    Regards,

    Tommy

  • 0 in reply to Tommy Lin
    Prodigy 245 points

    Hi Tommy,

    Thank you for getting back to me.  Is your first sentence supposed to say does not have a register...? 

    Thank you for pointing me in the direction of the Samsung and Apple proprietary charging schemes.  I now understand how to read the power status register to determine how much current I can pull when acting as a sink.

    For sourcing current, it sounds like I'll need to just advertise as BC1.2 and then allocate 7.5W anytime a non-PD device is plugged in.

    Best regards,

    Cory

  • 0 in reply to Cory Van Beek
    TI__Mastermind 31820 points

    Hi Cory,

    Sorry about the confusion/typo. Yes I was trying to say does not have a register.

    Regards,

    Tommy

  • 0 in reply to Tommy Lin
    Prodigy 245 points

    Sounds good, thanks for clarifying!