In a message dated 12/11/2007 15:39:50 Pacific Standard Time, [EMAIL PROTECTED] writes:
>OK, so for the DAC piece, why not just use an NXP LPC ARM chip for the >microcontroller, and use a 32bit PCM output followed by a low pass filter as >the VXCO EFC? The DAC just needs high resolution, not accuracy, right? >Or would the switching noise from the processor modulate the control >voltage? Hi Scott, one problem with using all 32 bits in the NXP LPC PWM output is that the counter can only run at typically 60MHz, the maximum CPU clock. With a full 32 bits count time you would only get 2^32 / 60MHz pulses per second, or in other words (at 50% setting) a square wave with 71.6Hz. That's pretty hard to filter out to get a very clean DC voltage so that there won't be a spur at 72Hz offset on the OCXO output. This would require large-capacitor filters. bye, Said **************************************See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004) _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
