IMXRT USB VBUS

[henry_lovett]

Hi, 

The USB VBUS specification on the IMXRT1064 says it needs 4.4V - 5.5V which is then dropped to 3V using the internal LDO. In my application, I do not have a 5V supply as I don't need to supply it to the USB peripheral (in effect, I'm connecting to a self powered device).

Will the USB VBUS operate to 3.3V? Or can I supply 3V directly to the VCC_USB_CAP pin and not the VBUS pins? If possible, I'd like to avoid putting another entire supply down. 

Many thanks,

Henry 

[jorge_a_vazquez]

Henry Lovett

If I understand correctly, you mention that you want to power VDD_USB_CAP pin with 3 volts, am I correct? There is no need to apply any power to this pin, this pin is the output of the internal LDO.

This regulator supplies only low speed and full speed transceivers of USB PHYs, so you actually need to supply the USB VBUS pin with 5V, as long as you have a device USB, you should take the 5V from the Host.

Reference Manual: When the port operates as USB Device, this input should be supplied by the VBUS voltage from the USB connector

Hope this information could help you, please don't hesitate to contact me if you have any other question about this.

Have a great day,
TIC

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