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USB Type-C USB 2.0 Power

dlh
Prodigy 50 points

Other Parts Discussed in Thread: BQ24190, TPS65982, TPS6598X-CONFIG, TPS2544

We have a USB 2.0 device that we would like to add a USB Type-C UFP to, which seems easy enough using some pull-downs on the CC lines. However, is it possible with USB Type-C using USB 2.0 only devices to request more than 500mA? Ideally our design would like to use USB 3.0 power (5V @ 900mA), but with USB 2.0 data.

Any information on how such a design can be achieved would be much appreciated.

  • 0
    TI__Intellectual 1710 points

    In order to use USB3.0 power, the device would need to identify the host port as being a USB3.0 capable port. This is done by negotiating a USB3.0 connection. Since your device doesn't have this capability you won't be able to determine the port speed. One way a USB2.0 device could request more power is by implementing the battery charging 1.2 specification.

  • 0 in reply to Lee E Myers
    Prodigy 50 points

    Thanks for the response Lee.

    Regarding the Battery Charging 1.2 spec, the following is unclear to me:

    • Is there the BC 1.2 spec mandatory in USB 2.0 or 3.0 hosts? What I am trying to determine is if there is some guaranteed minimum power I can expect from a given port (that is hopefully greater than 5V @ 500mA). 
    • Are there any issues with peripherals using this spec and not using it to charge a battery? i.e. is this a hack or do other peripherals do this to source more power?

    Also, does TI have a part which is appropriate for the BC 1.2 Spec implementation for a UFP device? 

    Thanks again for the information.

  • 0 in reply to dlh
    TI__Intellectual 1710 points

    BC 1.2 is not mandatory and not all hosts will support it. I think most USB ports today will provide at least 900mA, so if a USB2.0 device were to draw more current than the USB2.0 specification specifies then that device would probably work in most cases, but there are no guarantees. Furthermore the sweet spot for type-C host ports will be 1.5A.

    TI does off some BC1.2 devices that could be used in a UFP such as the bq24190.

  • 0 in reply to Lee E Myers
    TI__Mastermind 30310 points

    dlh,

    Hi, I support the TPS65982 and other TPS6598X parts, and from a Source's perspective there is a clear way to advertise "Default" USB Current for Type-C.

    When acting as a Type-C source, your are required to provide a Pull-up in the form of a resistance (Rp) or a current source (Ip). The 3 Amp current advertisement is 330uA, which connects to a 5.1kOhm Rd pull-down resistor and creates 1.683 Volts on the CC pin. The Source knows it was offering 3 Amps, and the Sink should be able to detect this. Similarly advertising 1.5 Amps has a lower current value (Ip = 180 uA), and advertising "default" has an even lower Ip value (Ip = 80uA). We use the TPS6598X-CONFIG Configuration tool to select these options for our part.

    When acting as a source advertising "Default", the TPS65982 assumes 900mA can be used by the Sink for USB3, but USB2 devices will be limited to 500mA.

    To advertise 1.5A on Type-C and additionally support BC1.2 as a Host, another IC like the TPS2544 can be used as described in this App Note: