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TPS65983B: Power in a Thunderbolt 3 Daisy Chain

Patobravo
Prodigy 230 points
Part Number: TPS65983B

Are there any reference designs or app notes available detailing how power delivery works in a TB3 daisy-chain?

---John

  • 0
    TI__Genius 10370 points

    Hi John,

    Welcome to E2E! Unfortunately, we do not have any reference designs/app notes on TBT3 daisy-chain. With respect to PD, I believe both daisy-chained monitors are powered externally from an outlet. The monitor that's connected directly to a laptop should provide a 20V contract to charge the laptop battery. Since the other two monitors are powered externally, the PD contract between them will probably be a 5V contract on VBUS. 

    The magic of Thunderbolt is that it allocates bandwidth on the USB3.1 superspeed lanes to support 40Gbps on one lane or 20Gbps on two lane. This is how TBT3 can support two 4k 60Hz monitor displays.

    Just an FYI, Thunderbolt is an Intel product and you might be able to find more info on their webpage (https://thunderbolttechnology.net/, and/or ask an Intel representative for more details.

    I hope this helps and If this answers your question, PLEASE select  This resolved my issue 

  • 0
    Prodigy 230 points

    Thanks Aramis,

    We've been waiting for a couple of months for approval from Intel to get TB3 developers access, the latest go-round for approval was rejected because "Two ports cannot be BPD (Bus powered device)", the topology submitted was basically lifted from a TI presentation (the picture below).  

    In the meantime our design progresses the best we can with the information available to us.  My initial read of the the available information for TB3 and power delivery was conceivably you could have a chain of several bus-powered/self powered devices, all powered from a single USB-C power adapter like shown below, true?  Stupid question?

  • 0 in reply to Patobravo
    TI__Genius 10370 points

    Hi John,

    You're correct about self-powered devices (bus-powered devices) with TBT3 ecosystems, but when it comes to monitors this falls under a different protocol. Each monitor is powered externally through a power adaptor to a wall. The laptop, of course, doesn't need to be powered from a wall outlet. The main purpose of daisy chaining two monitors is for the data and not the power.

    For more questions on TBT3, please contact an Intel representative. They have the latest specs and can help you your TBT3 ecosystem :-)

    If this answers your question, PLEASE select  This resolved my issue 

  • 0 in reply to Aramis P. Alvarez
    Prodigy 230 points

    Thanks Aramis,

    I'm not sure why monitors are brought up, our product application involves multiple data protocols in the field, TB3 would support this better than say USB and daisy chaining is attractive.  What's not attractive is the prospect of each unit being externally powered.  I was sort of hoping TI had considered the scenario above and had a solution to offer, or at least some guidance.  

    ---John

  • 0 in reply to Patobravo
    TI__Genius 10370 points

    Hi John,

    If you're connecting non-monitor bus-powered devices (like your drawing above), this should work. I believe you can daisy-chain up to six 15W devices to a laptop. In reference to the monitor, monitors consume a ton of power and hence the need to connect them externally.

    When building a TBT3 ecosystem, one must first contact Intel for a reference design that suits your application.  Secondly, TI will provide the exact FW to flash the PD controller needed for your exact reference design (no customization on the GUI).  Intel tells customers using TBT that customization is NOT allowed in order to have TBT certification. One must follow the reference design and copy all of the components used.

    With TBT devices, TI must follow what Intel tells us. I hope this answers your question, and for more details on TBT ecosystems, please contact an Intel Representative for assistance.  

    If this answers your question, PLEASE select  This resolved my issue

  • 0 in reply to Aramis P. Alvarez
    Prodigy 230 points

    Thank you Aramis, this answer is very helpful!

    ---John