USB-C: Adding Data Transmission to USB PD

Question

Background

Texas Instruments' reference design PMP41013 exhibits bidirectional power transmission (DRP) via USB-C USB PD.

This is principally accomplished through an IC:

• TPS25750 — USB Type-C® and USB PD controller

Potential USB-C connection cases include:

• Device receives power (Power: UFP)
• Device provides power (Power: DFP) (USB OTG)

Data Transmission

Data transmission is not referenced in the reference design.

The USB-C data lines:

• SSTX±, SSRX± (USB3) are left floating.
• D± (USB2) are renamed USB_P, USB_N and passed to TPS25750.
  • This is for BC1.2 functionality.

Figures:

• PMP41013 : Schematic : USB-C Connector

• PMP41013 : Schematic : TPS25750

• TPS25750 : Datasheet : USB_P, USB_N

Issue

I would additionally like to perform USB2.0 data transmission.

Question

How can I supplement this design to add optional data transmission to these ports, such that:

• Device receives data (ideally with power) for USB MCU bootloading
  • Ex: TI MSP430F5
• Device receives data (ideally with power) for USB external storage read/write
  • Ex: Flash drive

I am seeking something like a reference design portraying the types of additional USB circuitry needed for such an augment.

• Is it as simple as placing a USB2.0 PHY layer on the D± lines?
  • Do I need to cut the BC 1.2 lines to do so?
  • Can I have USB2.0 data AND BC 1.2?

Note

This was asked here; the respondent stated that the how needed to be asked in a separate question.

I have also asked on the TI forums, in case anything crops up there.

Answer 1

As it stands, you can either permanently put your MCU's data lines onto the USB-C connector (which will allow programming but disallow BC charging), or combine them in some way. This depends on whether you want BC support - TPS25750 supports both charging from BC and charging BC-supporting devices. If you do want BC support, I am guessing that you might be able to actually parallel the BC lines with USB 2.0 lines - the TPS25750 datasheet figure 9-23 shows that its BC detection hardware is flexible enough, so it only depends on how much software control you have over enabling and disabling that BC hardware.

A different, surefire option I see is to use a USB 2.0 2:1 mux that's BC-compatible, and have your MCU expose its programming interface on its own whenever it can detect a data-capable device. The mux's control pin could also be overridden by the powerbank button or a different onboard switch in case the user bricks the powerbank during firmware update. That could be the option you go for in one of the test revisions, so that you can still try combining BC with USB by jumpering both pins of the mux together, bypassing the mux - again, that's assuming that you are looking for BC support. And, of course, there's nothing wrong with a good old pair of 0R in your favourite footprint.

As far as I can see, this mechanism would be quite independent from the USB-C port, save for the fact your downstream device will still need to present CC pulldowns if it wants to take advantage of BC, rendering BC support somewhat moot. Only a few devices require BC support to fully charge from a USB-C PD-compliant connection - sadly, the PS5 controller is one of them, but there's not a lot otherwise.