• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 33 subscribers
  • Views 599 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65987D: Help selecting the correct chip for our application.

Michael Mihalka
Prodigy 20 points
Part Number: TPS65987D
Other Parts Discussed in Thread: TUSB322I

Hello,

I am looking for assistance selecting the correct USB Power Delivery chip for our application.  First, let me start off by saying I am a mechanical engineer and therefore my understanding of the USB spec is limited and some of the terminology goes a bit over my head.

I am trying to design a cable to go from a mobile device (EUD) to a tactical hub.  The EUD in this case is a Galaxy S8 but that shouldn't matter as I want to design the cable such that it is compatible with most if not all USB Type-C ready devices.  The tactical hubs are capable of communicating via the 2.0 standard as well as the 3.0 standard and can supply 5V power at 2.5amps.  It should also be noted these tactical hubs are not yet 3.2 compliant and therefore provide no means to communicate via the CC pin or provide any power regulation at the higher PD voltages. 

The idea for the cable is that we have an inline PCBA with the PD chip on it which allows the EUD to go into sinking host mode or more appropriately said we want the EUD to be the data source and the power sink.  Previously our end users would accomplish this with either a custom ROM on the EUD or a specific resistor value between ID and GND (assuming the device had built in support for that mode) or a combination of both.  With the new PD protocol we can achieve this without the custom ROM, which is very attractive to our customers.

Since I am an ME and work for a mechanical design firm we have partnered with a firm to help develop the PCBA.  Unfortunately they are not well versed in the latest USB specification and as a result we are struggling a bit to move the design forward (ideally we partner with someone else but that isn't an option).  In an effort help I am reaching out to this community to see if I can gather the information needed and educate myself well enough to move development along.  There is one other high level goal beyond what was stated above and that is we would like the design to allow for the future integration of a USB hub circuit so that we may integrate other capabilities such as analog audio, or an Ethernet to USB adapting, or simply connecting another USB peripheral.  It's not absolutely critical that this additional feature makes use of the same PD chip.  In fact this secondary requirement may be the source of our issues...

Finally, the partner firm's initial thought was to move forward with the chip identified above, TPS65987D.  We have managed to work through most of the issues but there is one final sticking point.  They have indicated there is an issue with power regulation and from what I understand it has to do with how the PD spec defines the need to be able to handle 5V, 9V, 12V, and 20V and therefore needing a buck/boost circuit.  I understand what buck and boost circuits do but if I have a constant 5V source I am not sure why we need to concern ourselves with these higher voltage capabilities.  Could it be that this isn't the correct chip for our application?  Any help here would be much appreciated.

Thanks in advance,

Mike

  • 0
    TI__Expert 6430 points

    Hi Michael,

    Thanks for reaching out to us.

    From your description, I understand that you want to design a USB hub whose one port supports USB Type-C/PD to connect to a Samsung S8 phone or similar and there are multiple other ports which are standard Type-A (the bigger USB port seen in existing devices). I also understand that you're not looking for anything other than basic USB 2.0/3.0 communication.

    If all the above statements are true then I would suggest you to use TUSB322I or similar device, which is just enough to add Type-C functionality to your system and will support 5V@3A for the phone to charge.

    TPS65987D supports USB PD along with Alternate Mode and Thunderbolt, which is not required in your system, therefore it will be an overkill for your system.


    Thanks,
    Rahul

  • 0 in reply to Rahul Sharma16
    Prodigy 20 points
    Hello Rahul,

    Thank you for the response. I have just a few follow up questions. First, to be clear, the chip you've proposed will allow the device to accept a charge while in host mode but it is NOT doing this via the PD protocol, correct? If true, can you elaborate on how this is achieving the "sinking host mode"? Would it be an automatic function once the handshake with the device is complete? Second, based on what I have been able to relay can you maybe help me to understand why our partner firm is having challenges with the PD chip they are trying to use? I understand it may be overkill but I think there is value in understanding what is challenging them. Finally, I realize TPS65987D may be overkill for our application but we are trying to get ahead of the curve in the space we are in and while there currently are no requirements for video out or alternate mode there may be requirements in the future. The integrator's in this industry are always evolving and once they fully grasp the power of the USB-C spec they will likely want to take advantage of the expanded capabilities.

    Regards,
    Mike
  • 0 in reply to Michael Mihalka
    TI__Expert 6430 points
    Hi Mike,

    TUSB322I will use USB Type-C to enable 5V@3A power source, there will not be any PD communication in the process.

    This chip can work as a DRP, which means it can provide power to phone and can take power from phone depending on the situtation. All of the Type-C negotiations will happen automatically.

    TPS65987D is comparatively an expensive chip and there's no harm in using it, it will enable future updates in your product with minimal hardware changes.

    Thanks,
    Rahul