I’ve designing a new PCB which includes the Overo FIRE COM. I need to connect a camera to the usb host, but it is not an external cam. The cam and its driver are integrated in the board. The problem comes with the USBH_VBUS pin. I’ve read that 5V is needed for the PHY layer (chip SMSC USB3326), but doing some tests I realize that supplying the pin with 3,3V the software recognizes the driver and they can communicate together. The datasheet of USB3326 I’ve found has a really explicit description of its pinVBUS: This pin connects to an external resistor (RVBUS) connected to the VBUS pin of the USB cable. This pin is used for the VBUS comparator inputs and for VBUS pulsing during session request protocol. No electrical characteristics, no more info…


Has anybody tried a design supplying the pin with less than 5V? Would it be reliable to supply the pin with 3,3V or it is necessary 5V? In my board there is no 5V supply, so I’ll need a boost regulator to get it and if I can avoid it…


Thanks to all.




Iker Caballero

Bizintek Innova



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E-mail: i.caballero@bizintekinnova.com