I need to clock an Arduino Pro Mini 328 (3.3V) at 10 MHz using an LPRO Rubidium Oscillator. I can’t find the electrical specs for the External Clock on the 328.
The specs for the LPRO are:
10 MHz sine-wave
.55 Vrms +/- .05 Vrms into
50 ohm [+7.8 +/- 0.8 dBm]
Any help would be appreciated!
thanks,
glenn
http://www.avrfreaks.net/index.php?name … 736#643736
MBedder
PostPosted: Dec 01, 2009 - 01:19 AM
Location: Zelenograd, Russia
Set the CKSEL to 0111 (Full swing xosc) and feed your LPRO output to XTAL1 pin via the 1…10 nF capacitor. Check the XTAL2 output with an scope - you should get a clean and almost square waveform out there which indicates the Mega is clocked properly.
This trick makes an amplifier out of the XTAL1->XTAL2 invertor which is self biased to a linear gain region due to an internal feedback resistor which is connected only in internal crystal CKSEL modes.
–
I’ll be testing this soon and posting the results!
-glenn
Rubidium oscillator, something I haven’t had a chance to play with :).
Have a link?
LPROs were the first atomic frequency standard designed for mass production by Efratom (then Datum, now Symmetricom). They have a design life of 20+ years. New, they were about $2,250 + $250 for a warranty (IIRC). Now, they can be had for <$100 on ebay:
http://shop.ebay.com/?_from=R40&_trksid … Categories
They have been replaced by the XPRO:
http://www.symmetricom.com/products/fre … dard/XPRO/
Design notes:
-run on ~24 volts dc
-use 15-20 watts
-have a built-in test indicator (BITE) (aka “Lock”)
-fit in 1U rack mounts
-electrical and mechanical c-field control (neither usually needed)
You just cost me $80 :shock: