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TPS25750: About behavior negotiation and VBUS at sink

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Guru 21045 points
Part Number: TPS25750
Other Parts Discussed in Thread: BQ25792

Hi Team,

 

I would like to use TPS25750 at sink only.

Therefore, I would like to know the behavior of TPS25750 and VBUS when an unusual source device is connected(3 cases).

 

------

[Q1]

Source device is not compliant USB PD.

 

I guess that negotiating continues, VBUS repeats 5V and 0V.

Is my understanding correct?

------

 

[Q2]

Source device is before USB PD Revision 2.0 version1.1.

So, it is a different version from TPS25750(USB PD 3.0).

 

<For example>

-Sink request of TPS25750 is 15W (Set with GUI)

-Maximum source capability of source device is 10W(5V/2A)

 

I guess that TPS25750 can complete negotiation so VBUS is 5V/2A.

So, TPS25750 can communicate even if the versions are different.

Is my understanding correct?

------

 

[Q3]

Source device is 20V/2A setting.

 

If request sink power of TPS25750 is “45W(15V)” by GUI, will VBUS be 20V?

(I'm worried that VBUS will be limited to 15V.)

If no, is there a setting method that can handle 20V with the sink request 20W?

------

 

Regards,

Hide

  • 0
    TI__Mastermind 32901 points

    Hide,

    We are fixing this issue as part of the next GUI release.  We will be adding the ability to configure the Current and Voltage for 4 PDOs to any user selected value.  This will support your request once it is released.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Guru 21045 points

    Hi Chuck-san,

     

    Thank you for the information.

    if current GUI, is my understanding correct of [Q1],[Q2],[Q3]?

     

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 32901 points

    Hide,

    You are correct on all 3 questions.  The PDO negotiation set set by voltage, not current.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Guru 21045 points

    Hi Chuck-san,

    Thank you for the information.

    Could you please let us know release timing of new GUI?

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 32901 points

    Hide,

    We have found an issue with how we interface with the BQ25792 charger that we need to address as part of this release.  Because I am activly debugging this, it is difficult to provide a specific timeline.

    Regards,

    Chuck

  • 0 in reply to Chuck Branch
    Guru 21045 points

    Hi Chuck-san,

    Thank you for the information.

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 32901 points

    I will keep you updated

  • 0 in reply to Chuck Branch
    Intellectual 850 points

    Hello Chuck:

    I have similar questions on TPS25750. Now the configuration can only select one of the W/V. Based on your explanation, in the next GUI we could select multiple. So what will happen at this point,

    1. if 45W(15V) is selected in the configuration, but the source is only 15W(5V)?

    2. if 45W(15V) is selected, but the source is only 30W(15V,2A)?

        2.1. if it works at 30W, but the system requires 45W, this may cause the system not fully functional. So it may be worse than doesn't work at all?

    3. if 15W(5V) is selected, but the source is 45W(15V)? I guess this should be fine and the TPS should handle the gap.

    Thank you!

    Chen.

  • 0 in reply to Chen Jia
    TI__Mastermind 32901 points

    Chen,

    1. In order to be compliant with usb PD systems, you need to support a 5V PDO, so we require one to be present which is why you cannot change PDO1 from 5V, but are allowed to change the current to match your system.  This is not something that we can address unless you have a Microcontroller and wish to use the host interface to address the case where you require a 45W contract to operate.

    2.  This is called a compatibilities mismatch.  We are configured to accept the 30W/2A contract and not cause a disconnect.  Again, we report the contract configuration via our host interface.

    3.  For this case, the source is require to support a 5V PDO, so it is extremely rare that a 45W source would not support a 5V/3A contract in the sources that I have seen, so I would be surprised if this comes up as an issue.

    I will pass your concerns onto our systems team to see if we can address them in the future.

    Regards,

    Chuck