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TPS65987DDK: Sourcing current is not adjustable via Transmit Source Capabilities (0x32) Registers

Raisa Guenther
Prodigy 10 points
Part Number: TPS65987DDK
Other Parts Discussed in Thread: TPS65988

Hello,

I'm Raisa Guenther and I am working in the software development department.

We currently have problems with the power delivery adjustments for this device.

It is set for source power delivery on PP_HV5.

We take adjustments using the application customization tool and set the following:

Port Control (0x29):

Transmit Source Capabilities (0x32):

The result should have been, that the current on the USB-C-Recaptacle should not got over 2A, but with these settings the sourcing current on the receptacle goes all the way to 3A.

Also attached is the exportet JSON of the configuration:

Configuration_json.txt

What do we adjust wrong?

It would help us if there is any help.

Best regards,

Raisa Guenther

  • +1
    TI__Mastermind 36756 points

    Hi Raisa,

    Do you have a PD analyzer to confirm you are negotiating the 5V/2A PD Contract? We recommend using the Total Phase PD Analyzer as a low cost option.

    Likely what is happening here is that you are not entering a PD contract and instead are stuck in a 5V/3A standard USB-C mode of operation. I would recommend adjusting your Port Control (0x29) setting: Adjust the "Type-C Current" setting from 3A to 1.5A. 

    Please note that in order to negotiate a USB-PD contract with your settings in the Source Capabilities register (0x33), you would need to have a USB-PD capable device connected to the other end of the cable. If not, you would enter a standard USB Type-C mode.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Prodigy 10 points

    Hello,

    thank you for the helping answer about the Type-C-Current and the responsible power draw recommendation when negotiation via the PD contracting.

    This arises a question for me and I will need some answers fot that:

    When an USB device is connected which is not able to negociate the PC contract, like for eample a simple USB2.0 Mass Media device othe others which cannot provide the PD contract -> the hard current limiting factor in that case would be the "USB-C-Current setting" via the pull up characteristic (weak 0,9A, medium 1,5A, strong 3,0A).

    What would be the minimum and maximum current limits for those settings?

    Example: when the setting in medium pullpu (1,5A) what are the maximum limits? 1,7A was seen during testing here before the overcurrent protection turned it off.

    What would it be for these and and on strong pullup setting (3,0A)?

    Thank you for your help.

    Best regards,

    Raisa Guenther

  • 0 in reply to Raisa Guenther
    TI__Mastermind 36756 points

    Hi Raisa,

    Thanks for confirming that this answered the first question.

    For the second question regarding the max/min current limit settings, please refer to section 3.2.2 of the following application note: https://www.ti.com/lit/an/slva994/slva994.pdf

    With a 1.5A current limit setting, the TPS65988 firmware will automatically select the correct current limit setting. For 1.5A, it will select the current limit setting with:


    Min: 1.620A
    Typ: 1.800A
    Max: 1.980A

    For 3.0A, the current limit setting select will be:

    Min: 3.060A
    Typ: 3.400A
    Max: 3.740A

    Thank you,
    Eric