I have a PL2303HX and I just etched my board with a USB to Serial IC (PL2303HX). The problem is that it requires a 12 MHZ crystal but I don't currently have.
Just a side note, the IC is on the same circuit with the Atmega328. When I plug the USB cable the LED on pin 13 blinks once. (it means it's working.)
I tested the board but it didn't work but the PC showed a notification that an Unknown Device has been plugged. The problem might be from the circuit or from the crystal, so I'm just interested in knowing if an IC doesn't have a built in oscillator, will it work without one ?
Edit: Actually it does include one but it needs an external one also. "PL-2303HXD already has an integrated clock generator. There is no need for the external 12MHz crystal oscillator used in HXA/XA PCB."