TUSB321: DIR transition time clarification

Hi Alder,

1: The TUSB321 will debounce the CC lines and VBUS_DET pin before setting outputs like DIR and ID. This could explain the 113ms transition time you're seeing:

2: I'm not sure whether we've speced min/max values on this parameter. I can follow up on this with our systems engineer when they return to the office. 

3. Since the TUSB321 is GPIO mode only, we do not have a way to adjust the DIR transition time. The TUSB322I has a register in I2C mode to adjust the CC pin debounce time, which may help:

4. The TUSB321 has been used in multiple customer systems that have passed the USB C functional test specification. I am not aware of any waivers needed to pass these tests.

5. We have not run tests with these parts together, however we have tested both parts independently. The TUSB1142 has passed USB TX and RX compliance when paired with a compliant source while the TUSB321 has been tested for type-C compliance by our customers. Since the TUSB1142 is a linear re-driver, it will reproduce whatever signal is received from the host or device. As long as the connected host or device is compliant the TUSB1142 should pass.

6. We do not have compliance data with both of these devices together.

Best,

Shane

Thank you Shane, I saw it is about 100ms++ for ID to react (Figure 5 datasheet) and that is for DFP mode, there will be about same for UFP mode, right ? The spec below should be for all, DRP, DFP and UFP, right ?

Thanks,
Best regards,
Alder

Thank you Shane,

1 more question on TUSB321.

If i have 1 board for TUSB321 set as Source (Both CC lines high, Rps) and 1 board for TUSB321 set as Sink (Both CC lines low, Rd), if i flip the type C cable, how the detection work?

Thanks,
Best regards,

Alder

Hi Alder,

In a standard type-C cable, only one CC line will connect through from plug to plug. The other CC line will be left NC or terminated to Ra within the cable depending on whether it is an active or passive cable. Here is a diagram from the USB-C spec that illustrates this:

The Source TUSB321 will monitor both CC lines to look for the Rd pulldown. Similarly, the Sink TUSB321 will look for Rp on one of the CC lines. Depending on which orientation the cable is in, one CC line on the source side will connect to a CC line on the sink side. Once the appropriate pullup/down is detected, the CC controller knows which orientation the Type-C cable is in.

Best,

Shane

Thank you Shane,

I see there is a cable that have both CC1 and CC2, for those cable, the detection will not working, right? 

Hi Alder,

The USB spec defines one configuration channel in every USB-C cable. The other CC line can optionally be used as VCONN, but should not connect through:

If both CC lines are connected through the cable, its likely that the orientation detection will fail.

Best,

Shane