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TUSB320: Necessary IC/components for DFP capability detection

David Bongiorno
Prodigy 10 points
Part Number: TUSB320


Hello,

I am trying to alter the design of an existing device so that it could utilize power given by a USB-C charger/supply. I'm quite new to USB/USB-C power supplies/devices so I want to make sure I have the correct understanding!

So far I understand that I need to attach each CC pin on the receiving UFP to individual to 5.1k resistors such that it can be recognized as a sink. At this point I believe I need a comparator or CC controlling IC to determine the power delivered to the device. My goal is to receive a steady (5 V @  ~0.5 -1.0 A) if I know nothing about the supply/source of power. I anticipate that users of my device may attempt to use USB-C charging adaptors, plug their cable straight into a laptop port, etc.

I still have a couple questions on the subject: 

1) Is a comparator circuit/CC controller within the UFP absolutely necessary to ensure this desired power application (i.e. is it possible to just rely on having the CC pins connected to individual, grounded Rd resistors?

2) If it is necessary to utilize a CC controller, I was wondering is it possible to have a CC Controller IC preconfigured before shipment to request a certain power profile below 15 W (i.e. 5V @ X Amps, where X<= 1.5)? Ideally I'd like to avoid messaging between the USB-C CC Controller and the processor on board as the main power to the board would be provided by the USB-C port.

3) Is there a recommended method for configuring a USB-C CC Controller?

  • 0
    TI__Guru 64326 points

    Hi,

    Let me give some background here, in USB-C the connected host (DFP) advertises the available power over Vbus. A compliant USB-C device (UFP) is responsible for not consuming more than what is advertised on CC pin. By default, meaning without extra configuration on CC, the DFP must accommodate 500 mA (USB2) or 900 mA (USB3) current consumption on Vbus. This is the case for all USB-C DFP and DRP ports. In USB-C (non-PD) application a UFP does not request a certain power level, the UFP is only responsible for not consuming more power than what is advertised. 

    If your design can stay under these defined limits for USB-C default current advertisement then Rd resistor can be acceptable. I would still recommend using a CC controller especially in a USB 3 application so that cable reversal can be easily supported. If you want to support high current operation (1.5A or 3A) you should also use a CC controller as you would need a comparator for each CC level, VBUS and flipped cable state.

    CC controllers can be pre-configured over GPIO mode using resistor option.

  • 0 in reply to Malik Barton57
    Prodigy 10 points

    Hey Malik!

    Thanks for the quick reply! Hmm a preliminary analysis of our device showed a maximum current draw of about 700mA, so perhaps we could get away with relying on the USB-C compliancy standards of supporting up to 900mA.

    However we are considering expanding the capabilities of our device to power larger peripherals (e.g. speakers) or secondary USB-C devices, so a CC controller sounds like a logical choice. Could you expand a bit more on the pre-configuration via GPIO mode?

    Regards,

    Dave B

  • 0 in reply to David Bongiorno
    TI__Guru 64326 points

    Hi Dave,

    Keep in mind that 900mA is only if you are enumerating over USB3. USB2 limit is 500mA. TUSB320LAI has pins that can be configured via pull-up or pull-down resistors For example PORT chose the CC controller mode such as DFP, UFP or DRP.