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Not connecting Vbus | Cypress Semiconductor

Not connecting Vbus

Summary: 2 Replies, Latest post by PRJI on 23 Jul 2013 09:05 AM PDT
Verified Answers: 0
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GalS's picture
1 post

 In a self powered USB device based on PSOC3 (CY8C3245LTI-144) I cannot connect the Vbus.

What problems can I expect?

NIKL's picture
Cypress Employee
283 posts

Is the USB connector loose? try probing the vbus of USB connector to check if there is 5v.

Please ask more specific question.

Maybe you can expect better answers if you post in PSOC forum

prji's picture
Cypress Employee
473 posts


 There should be a Vbus detect mechanism. A USB-IF specification requirement is to never drive the USB pins when they are not connected to the bus; they may only be driven when VBUS is present. Refer to section 7.2.1 of the Universal Serial Bus Specification, Revision 2.0. Violating this requirement may cause several failures to the system. One documented failure is reset problems on the upstream devices, which in turn may result in PC cold boot problems, or it causes hubs to fail to enumerate downstream devices. Other failures include the inability to properly resume from a suspend state and forcing other enumerated devices off the bus.

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