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Shared USB and Pseudo OTG Question

Question asked by John Fielden on Sep 21, 2013
Latest reply on Sep 23, 2013 by Naoum Gitnik

Hi, I have a Tower board and have been looking at the USB documentation deciding how to allow for OTG a special future use case.  I'm only using USB0



1. If the Vybrid is not powered, is it ok for VBUS to come through to USB0_VBUS and VBS_DETECT?

2.  USB0_VBUS is an input, correct?

3. I don't see any clear evidence that the Vybrid has a boost supply built in to supply 5V to an external client, so if I add a 5V supply to supply 5V out, does that also tie into the VBUS_DETECT?  Or, will that cause an issue with detection of external clients?

4.  See the attached block diagram.  It shows that I have a USB mux for routing USB other places besides the Vybrid.   The load switch (blocking from both directions) is intended to keep an external VBUS from driving the Vybrid when it is off (see question 1 above).  The 5V supply is used to drive 5V out to a client when the Vybrid is on, and we sense USB_ID is low.

5.  Any reason I should use the USB_VBUS_EN to activate the external 5V supply rather than use a GPIO?