USB power on a PIC

Discussion in 'The Projects Forum' started by KansaiRobot, Apr 26, 2015.

  1. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    Hello everybody and thanks always for your help.

    I have a question regarding USB powering for a PIC. I am using the 18F2550 and the 18F2553 that have USB capabilities. Now, in the past -using a development board that had incorporated a crystal oscillator of 20MHz I had communicated the PIC and the PC.

    Right now, I am not using that board but just a simple IC. Now, I am using the internal oscillator for A/D etc, so no problem there but I ve read in the datasheet that you need a crystal for the USB data communication to work, because the USB functions are timed by that.

    But how about if I just want to only power my IC from the USB? I have the schematics of where to put the Vusb and the GND pins but do I still need a crystal for this too??? (notice I am not going to pass data in or out)

    Thanks for the help
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    No. However, if the USB is from a PC, you will not be able to enumerate the USB, and so will be limited to 100mA.