I have a question about the DFP (downstream facing port) power advertisement logic in the TUSB320.
My customer is using the TUSB320 USB-C configuration logic IC in one of our designs. In this application, the USB-C port is only used as a power supply connection. The TUSB20 is used to detect 3.0 A power advertisement over the CC wire from the attached power supply. The power advertisement is signaled by a 10K impedance from the CC wire to +5. (The application circuit is an “upstream facing port” that expects to get power from the connecting device.)
In the USB-C specification, the CC wire (with the resistor power signaling connection) is supposed to be on the A5 pin of the USB-C plug. The B5 pin is supposed to have VCONN (+5 V) on it. In this way, no matter which way the USB-C plug is connected, the TUSB320 will be able to tell the orientation by looking at the voltages on the CC1 and CC2 signals.
Here is the problem: their power supply vendor seems to have implemented a USB-C cable that has a 10K resistor (3 A power advertisement) on both pins A5 and B5, instead of connecting B5 to +5 V. As a result, both of the TUSB320 CC pins will see a 10K resistor to +5. Will the fact that in either cable orientation, both CC pins see the 10K resistor confuse the logic that controls the OUT1 and OUT2 indications of the DFP power advertisement?
