TUSB321AI: Interface forum

toshihiko.hamaya

Prodigy 110 points

Part Number: TUSB321AI
Other Parts Discussed in Thread: TUSB320, TUSB321

Tool/software:

I am considering configuring a DFP and DRP port using TUSB321AI.

I am trying to turn on the output of USB bus power by monitoring the ID pin of TUSB321AI with a microcontroller.

In this case, I am considering whether there will be a collision of USB bus power with the connected USB TYOE-C device.

① The other side is a device that implements a CC controller that complies with TYPE-C.

In this case, if the other side is a UFP, the ID pin will be asserted LOW and it is thought that bus power output is possible.

If the other side wins the DFP or DRP source first, the ID pin will not be asserted LOW and bus power will not be output.

② If the other side is a legacy AC adapter that implements Rp and always outputs bus power, the ID pin will not be asserted even if it is connected and bus power will not be output.

③ If the other side is a legacy AC adapter that does not implement Rp and always outputs bus power, the ID pin will not be asserted even if it is connected

　(it will be determined to be unconnected) and bus power will not be output.

With this in mind, can we assume that there will be no bus power conflicts?

Tank you

3 months ago

0 Ryan Kitto 3 months ago

TI__Mastermind 38655 points

Hello,

The ID pin should only ever go low in the event where the TUSB320 is set as a DFP, or as a DRP/Source, and a successful CC negotiation is completed, causing the ID pin to go low and indicate VBUS should be sent.

toshihiko.hamaya said:
① The other side is a device that implements a CC controller that complies with TYPE-C.

In this case, if the other side is a UFP, the ID pin will be asserted LOW and it is thought that bus power output is possible.

If the other side wins the DFP or DRP source first, the ID pin will not be asserted LOW and bus power will not be output.

Correct.

toshihiko.hamaya said:
② If the other side is a legacy AC adapter that implements Rp and always outputs bus power, the ID pin will not be asserted even if it is connected and bus power will not be output.

③ If the other side is a legacy AC adapter that does not implement Rp and always outputs bus power, the ID pin will not be asserted even if it is connected

　(it will be determined to be unconnected) and bus power will not be output.

For scenario 2, if the TUSB321 is set as a DFP, then I believe both sides will have Rp, which will result in no CC negotiation and cause the ID pin to stay high, meaning no VBUS to be sent. However, if set as a DRP, then the TUSB321 will toggle down to Rd at some point, resulting in a UFP connection for the TUSB321 where it will receive that VBUS.

For scenario 3, if there is no Rp or Rd, then I believe no CC negotiation will be completed, resulting in no VBUS supplied from the TUSB321. However, if Rd is detected, then its possible the CC negotiation will result in VBUS being supplied.

As long as the TUSB321 does not see and Rd to match the Rp the TUSB321 presents in DFP mode, then I believe there should be no issues with VBU power conflicts.

Thanks,

Ryan