• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 33 subscribers
  • Views 1659 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.

TUSB320: UFP charge current value

Camron Vossberg
Prodigy 50 points
Part Number: TUSB320
Other Parts Discussed in Thread: BQ24297

I have a UFP that will be used only to draw power from a Type-C connector to charge a battery and provide a system bus voltage. I will not be enumerating or sending data over the connection. I have been looking at the TUSB320 to communicate to my MCU what the available charge current is, so I can tell the battery charger what the maximum current draw is. I am a little confused as to how I can tell exactly what amount of current is available in all situations, based on the TUSB320 I2C or GPIO registers. In particular, I'm unsure what happens when USB 2.0 or various wall adapters are connected using a type A to type C adapter cable.

- If the TUSB320 shows the default current level, it could be 500mA (USB 2.0 SDP) or 900mA (USB 3.0 SDP). How do I tell which is actually present, so I can set the charger to the correct level?

- Is the 1.5A setting selected whenever a DCP is connected? Some DCPs are rated for less, and some for more. How do I set the charger to draw the maximum amount of power available, without drawing too much?

- Many DCPs are proprietary, and there are battery charger ICs that detect all the BC and common proprietary variations out there, and automatically adjust the current appropriately. For example, the BQ24297 does this. Is it possible to use one of these types of devices with USB-C, instead of something like the TUSB320? If so, would I need to do anything with the CC lines? Would 2.0-to-Type C connections from either 2.0 SDPs or DCPs be supported? Would native Type C supplies (DFPs or wall adapters) be supported?

Thanks,

Camron

  • 0
    TI__Mastermind 36085 points

    Hello Camron,

        The TUBS320 detects the advertised current by the DFP, this can be USB default, 1.5A or 3A. For USB default, the 900mA value is for a super speed connection only, so if your device is not enumerating, then the value for USB default is 500 mA.

        The advertised value establishes the maximum available current on VBUS and thus its over current condition, but the actual value depends on the port load. You can limit the port by configuring a VBUS switch to 1.5A or 3A, depending on the advertised current.

        For Type-C application, you need both devices, the CC controller like the TUSB320 and the power switch that limits the amount of current on VBUS.

  • 0 in reply to Diego Cortes
    Prodigy 50 points
    Thanks, Diego. That clears up my question regarding the 500/900 default limit. I'm still unclear on what happens when interfacing with non-Type C sources using an A-to-C adapter cable, e.g. an AC adapter with a Type A receptacle. I've seen these with output ratings ranging from 1A to 3A. When an adapter cable is used, will the TUSB320 always show this configuration as 1.5A, at either of those values? Does it also detect CDP ports, and does it report them as 1.5A?

    Thanks,
    Camron
  • 0 in reply to Camron Vossberg
    TI__Mastermind 36085 points
    Camron,

    Battery charging is a different protocol, it uses the DP/DM lines to determine the charging profile and it is independent to Type-C. The TUSB320 uses the CC lines to determine the power profile, and the Type-A to Type-C adapters have resistors between the CC pins and VBUS, this resistor determines the advertised current and it is likely to be fixed for USB default (56K), but this value actually depends on the cable´s manufacturer. What the TUSB320 will report in this case is the power profile that corresponds with the detected resistor in the cable/adapter. On the other hand, it is also possible to have the CC controller and a battery charging device on the same port, one will handle the power negotiation when connected to a compliant Type-C port Meanwhile, the second one enables battery charging for legacy ports (BC 1.2).

    Regards,
    Diego.
  • 0 in reply to Diego Cortes
    Prodigy 50 points
    Thanks again, Diego. I wasn't sure how A-to-C adapter cables handled detection of legacy sources and converting the power capability over the Type-C standard. Sounds like it's basically non-existent (ie everything including SDP/CDP/DCP all get reported at the default level). Having the ability to support both legacy and C would be great, so I could use both the TUSB320, and something like the BQ24297. Just had a follow-up question on how to control the BQ24297, based on what I see from the TUSB320:

    - 1.5A or 3.0A advertised: Shows a native Type-C device, so override the charger to 1.5/3.0A.

    - Default advertised: Could mean a native Type-C device or a legacy/BC source. Is there a way to tell which is the case? Can I just let the charger run in automatic mode, meaning will it safely limit power to 500mA when a native Type-C source is connected? When a legacy/BC source is connected, I assume the D+/- lines will still work through the Type-A to Type-C adapter as usual.

    Thanks,
    Camron
  • 0 in reply to Camron Vossberg
    TI__Mastermind 36085 points
    Camron,

    You are cirrect, the Type-C detection should have higher priority, override the charger to 1.5A/3A.

    You are correct again, the automatic mode is the best option for USB default, and that´s right, the D+/- lines will still work through the Type-A to Type-C adapter as usual.

    Best regards,
    Diego.
  • 0 in reply to Diego Cortes
    Prodigy 50 points
    Excellent, thank you so much for the speedy assistance Diego!