I designed a powered USB hub that allows me to connect multiple devices to a FPGA development board through a micro USB port. The hub and the FPGA sit inside an enclosure along with some other peripherals connected to the hub. Occasionally I would like to access the hub/peripherals externally using a Windows PC which will be done while the FPGA is powered down. I wanted to incorporate a switch into the hub that will allow me to connect the PC to an external USB port through a 5 pin extension. I discovered the FSUSB30 IC in this post where the user is trying to accomplish a similar task to mine. I've revised my schematic to include it, but wanted feedback to see if I have any gaps/flaws in the design. The FSUSB30 requires a supply voltage between 3 and 4.3VDC. I added the LD1117V33 voltage regulator to drop 5V to 3.3V. This supplies the IC and is also switched to provide the "high" voltage to the S pin of the chip in order to access the data lines of the external USB port. When the switch is disabled, the OE and S pins will be grounded to be "low" so that the data lines for the FPGA will be active. I've seen mention of pulldown resistors on those pins to ensure the "low" logic is enforced. Is that necessary? If so, are the 2K ohm resistors from the article I referenced adequate? By the way my hub uses external 5V from a power supply and I do not plan to have the power pins connected on the internal micro USB or the external USB ports to avoid power feedback to the hosts.




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