Legacy USB Device Detection by Type-C

by <a href="http://community.silabs.com/t5/Welcome-and-Announcements/Community-Ranking-System-and-Recognition-Program/m-p/140490#U140490"><font color="#000000"><font size="2">Hero Employee</font></font> </a> yucheng on ‎12-21-2016 09:48 AM

Question

How do I enable the legacy USB devices to be detected by a Type-C device?

Answer

To enable the legacy USB devices to be detected correctly by a Type-C device, connect one Rd resister between the GND and the CC pin. The recommended value of Rd in the Type-C specification is 5.1 kohm.

 

The figure below illustrates the functional model of this connection.

 22.png

After connecting the legacy device to the Type-C source, the source can detect the pull-down on the CC pin because of Rd, and then the source will turn on VBUS and VCONN.