AM335x USB VBUS

It forms a low-pass filter together with the 0.1uF capacitor that's between it and the USB1_VBUS pin. Purpose is to eliminate noises that could be transferred over the VBUS rail.

In the VBUS rail, a 220ohm 2A bead is placed. Is it enough for eliminating noise ? 

Also, does the 1.2K,1/4W resistor mentioned has any current limiting functionality?

The primary function of this resistor is to limit current through D6 (Zener clamp diode) in case there is a transient voltage on VBUS that exceeds the absolute maximum input voltage of 5.25 volts.  However, D6 was not installed on the starter kit so it is important your application does not cause VBUS to exceed 5.25 volts.

Regards,
Paul 

Please confirm the attached connection. Do we need an RC circuit in addition to this for VBUS line?

The USB specification defines the following capacitors on VBUS.

A standard USB host must have a minimum of 120uF on VBUS.

A USB peripheral must have less than 10uF on VBUS.

A Dual-role USB OTG device must have between 1uF  and 6.5uF on VBUS.

This allows a USB peripheral to be hot plugged with a uncharged 10uf VBUS capacitor and the 120uF host capacitor provides enough charge sharing capacity to prevent VBUS from dropping below the specified voltage.  You should perform the VBUS droop test as defined by USBIF test procedures to make sure the ferrite bead in this path does not cause you to fail this test.

The original USB specification did not define a minimum VBUS capacitance for a USB peripheral but I think they published a recommendation several years ago to use at least a 1uF capacitor on VBUS to prevent transient events on the peripheral VBUS signal when the cable is hot plugged/unplugged.

I have seen other customers use a ferrite bead on VBUS, but think this was done to minimize conducted emissions from coupling onto the VBUS cable and becoming radiated emissions.

Regards,
Paul

You will need to add a power switch on the Host VBUS rail, which must be controlled by USB0_DRVVBUS.