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[FAQ] TUSB320: Clarify DFP to Type-C 1.0 DRP incompatibility

Prodigy 20 points

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Part Number: TUSB320

The datasheet indicates "A USB Type-C 1.1 compliant DFP can not connect to a Type-C 1.0 DRP" and "This limitation is a result of a backwards compatibility problem between USB Type-C 1.1 DFP and a USB Type-C 1.0 DRP".  (Section 7.2.1.1 in the TUSB320LAI, similar statements in other related parts like the TUSB321 and TUSB322).

Can you explain the incompatibility? Looking through the ECNs between USB Type-C v1.0 and v1.1, I don't see anything obvious.

Thank you. 

  • Hi,

    This statement refers to a limitation of the Type-C spec and not the TUSB320X family. In the Type-C 1.0 spec DRP ports would look for CC termination when trying to become a SRC (DFP). For DRP trying to become a SNK (UFP) a device would look for VBUS when trying to establish a "legitimate" Type-C connection. In the latter case the DRP trying to become a SNK(UFP) port would switch the presented termination on the CC line before VBUS (tVBUSON, allowable time before Vbus reaches tSafe5V) was ready. In this case a DFP or DRP.SRC would be on the other side, thinking that a valid connection was not made. 

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