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TPS2511 is able to charge with no connections on D+/D- lines

mbl
Prodigy 60 points
Other Parts Discussed in Thread: TPS2511

Please read through the previously posted question.  As detailed, I have a TPS2511 in which DCP seems to always be active.

Ed: Hi, my name is Ed. How may I help you? 
me: Hi. As posted, I have a TPS2511 Usb Charger device in my design. During testing, I see that the device provides power without any kind of USB D+/D- configuration. This should not occur. I am trying to understand this... 
Ed: Hello XX. I am not real sure please give me a moment to look into this for you. 
Ed: However I would be inclined to agree with you. 
me: Take your time to review. 
Ed: Thank you. 
Ed: I am not still not real sure. I did locate this post from our Factory apps teams in our E2E forum:https://e2e.ti.com/support/power_management/power_interface/f/204/p/348992/1245335#1245335 
Ed: I would suggest you look at that post and see if that is what you are experiencing. 
me: Mmmm, not that I can decipher. 
Ed: You can also ask the engineers directly at the link here:https://e2e.ti.com/support/power_management/power_interface/f/204#pi239797013=1 
Ed: They will be able to better assist you with the application of this device. 
me: When I place an external load on 5V, I measure the D+/D- pins at 2.0V and 2.7V. When powered off, the D+/D- measure high impedance. Again, this is with no connections on these two pins. 
Ed: Yeah I would definitely recommend you rely on the expertise of our Factory Apps team. We have recently implemented a new escalation process with our forum. If you do not have a response within one full business day please contact us back and let us know so we can reach out to the factory. 
Ed: That link to post is here: https://e2e.ti.com/support/power_management/power_interface/f/204#pi239797013=1 

  • 0
    TI__Intellectual 2685 points
    Hi,

    TPS2511 is a Dedicated Charging Port Controller and Current Limiting Power Switch. And the default voltage on D+/D- is 2.0V and 2.7V. Once TPS2511 is powered on, 2.0V and 2.7V will be applied to D+ and D-. If you plug in cell phones, the D+ and D- voltage will change automatically depending on the cell phones.
  • 0 in reply to Yongqiang Sun
    Prodigy 60 points
    This explains the voltages on the D+/D- lines. The original question remains, though. The port by default provides power without following any DCP protocol. Is this the intent? Is the TPS2511 by default suppose to provide full power on 5V pin and any DCP device would then negotiates less current? This does not seem right. I would expect the 5V to be current limited to 100mA until a device attached properly drives D+/D- to negotiate an allowance of some greater current amount.
  • 0 in reply to mbl
    Prodigy 60 points
    Okay, I suspect my understanding of DCP is not correct. Apparently, the DCP port does indeed provided full power at all times and it is up to the attached device to request an allocated amount of this power via the DCP protocol. Correct?

    Thanks for any clarifications.