Electronics > Microcontrollers

PIC18F25k50 USB without crystal

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ptricks:
Just got some of the PIC18F25k50 chips and am impressed with everything that is included, pdf sheet is here:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en558862

 One feature I have wanted on pic parts for a long time, usb without having to use an external crystal. It isn't that big of an issue, more an annoyance, but when you want to throw something together quick it can be difficult to keep stock of the right crystals for everything so I have been moving away from crystal requiring parts when possible.
I find it amazing how much can be crammed in such a low cost device.

PA0PBZ:
And then you changed the model while I was replying that it did not have USB  :P

jerry507:
What's more amazing is that they cost so little yet every device has factory trimming done to the oscillator to keep it within spec for USB. They're certainly not the first to do this, but it is nice to see them adopting it.

PA0PBZ:
It looks like they synchronise the clock to the USB host:

Active Clock Tuning: This option allows the internal oscillator to automatically tune itself to
match USB host or external 32.768 kHz secondary oscillator clock sources. Full-speed
USB operation can now meet specification requirements without an external crystal, enabling
lower-cost designs.

Very interesting, I also always hated the need for an external crystal when using USB.

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