[RLCrisp]

I am starting an order for the parts to build one of these up and was wondering about a few of the parts:

I can't seem to find the crystal resonator in the schematic (12MHz 16pf load), I can find 12MHz 18pf which should just require different load caps. This leads to the question of why the schematic has two 20pf load caps with a 16pf resonator. Why put 40pf of load capacitance on an oscillator that specifies 16pf? Part numbers for the oscillator would help if you know which one is intended to be used.

Second - the USB receptacle. Anybody have good/cheap part numbers for this?

Thanks,
Ryan

 

[slowpogo]

Are you aware that you can purchase it assembled and tested? Or do you just really want to build it yourself?

 

[RLCrisp]

Being the DIY forum I would like to build it myself =)

 

[n_maher]

You should probably try Twisted Pear's forums for the answer.

 

[error401]

The load capacitors are in series, so you can't just add the values. Capacitance divides in series, so:

With 20pF load capacitors, you end up with 10pF plus the stray capacitance (a few pF). Perhaps a bit low, but close.

An 18pF crystal will work fine, increase the load capacitors to 24-30pF.

Either way, it's very non-critical. You can pull the crystal a few ppm with the wrong load capitance, but nowhere close to far enough to compromise the USB interface.

See: FAQ Crystals

 

[BrianDonegan]

Quote:

I can't seem to find the crystal resonator in the schematic (12MHz 16pf load)

RAKON (FORMERLY C-MAC FREQUENCY PRODUCTS | XTAL003210- HC49/4HSMX | Frequency Control | Passives | Newark.com

Quote:

Second - the USB receptacle. Anybody have good/cheap part numbers for this?

61729-0010BLF

Our support forum is a better place for these questions.

 

[RLCrisp]

Thanks for the help all. I'll keep any further questions to the proper support forum. Excited to start on this after I finish my pimeta.