About USB VBUS pin termination process of i.MX6

[yuuki]

Dear all,

We use USB_OTG only as Device mode.

In this case I want to detect VBUS by GPIO. (The voltage is converted)
And, the VBUS pin is not used.

Is such use possible?
If it is possible, would you teach the termination process of VBUS pins?

Best Regards,
Yuuki

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[igorpadykov]

Hi Yuuki

from i.MX6 side according to USB 2.0 specification USB.org - USB 2.0 Documents

VBUS circuit must limit the inrush current on VBUS. The target maximum droop in the hub

VBUS is 330 mV. This is described in sect.7.2.4.1 Inrush Current Limiting, also

sect.7.2.4.2 Dynamic Detach requires:

"..there must be some minimum capacitance on the device end of the cable to

ensure that the inductive flyback on the open end of the cable does not cause the

voltage on the device end to reverse polarity.

A minimum of 1.0 μF is recommended for bypass across VBUS."

Best regards

igor

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