Before being able to give any type of answer at all the forum readers would need to know some rather important details. Do you need the MCU to be a USB host? Does it need to be a USB target? Does it need to support OTG ("on the go") technology? Do you need it to be a low speed device? Full speed device? Or does it need to scream at 480 mpbs as a High speed device? Does the target application want to be recognized as a USB 1.1 device. Does it have to be operational as a USB 2.0 device? Will it need to be a bus powered device? Will it need to be self powered? Will the MCU be part of an aggregate device that actually looks like multiple devices back to a host?

Michael Karas

PS When I do work with USB as a target device I always consider the SiLabs C8051F344 part. It works as a USB 2.0 target full speed device that can support either bus powered or self powered operation. Mouser has a few in stock. Digikey has several hundred in stock. Main line distributors may have more. MJK