Programmable Oscillator

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
ljbeng
Posts: 99
Joined: Mon Jan 13, 2003 1:01 am
Location: South Central NE
Contact:

Programmable Oscillator

Post by ljbeng » Tue Jan 31, 2006 7:20 am

I have an application where we want the user to select an oscillation frequency with jumpers or dip switches. I want 8 frequencies, spaced 300Khz apart starting at 7.3728Mhz and ending at 9.4728Mhz. I prototyped with the LTC1799 from Linear Technologies. It uses a single resistor to create the frequency. I used .1% resistors. We have 2 board that must talk to each other. My prototypes worked good so we went to a board mfg. The mfg of the boards say they get some that don't communicate. They think it's because the chip has a <1.5% error and this is enough to create an unmatched pair. This is not RS232 communication. Are there any other variable-frequency oscillators that have a better tolerance than 1.5%?

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Programmable Oscillator

Post by Robert Reed » Tue Jan 31, 2006 10:01 am

Looking at each end of your specs--on one hand you need better than 1.5% accurracy ( how much better?). On the other hand your start/stop frequencys are speced at 10 hz precision which for the fundamentals involved would equate to roughly 1PPM. Do you know what your allowable error is? If it is tight, you may have to go with a simple phase lock loop system that will step it in 300Khz increments. R-C oscillators probably wont give you much more than 0.5% stability.

Ron H
Posts: 360
Joined: Tue Dec 18, 2001 1:01 am
Location: Boise, ID
Contact:

Re: Programmable Oscillator

Post by Ron H » Wed Feb 01, 2006 11:07 am

I'm biting my tongue to keep from commenting on this:
My prototypes worked good so we went to a board mfg.
Google "direct digital synthesis".

ljbeng
Posts: 99
Joined: Mon Jan 13, 2003 1:01 am
Location: South Central NE
Contact:

Re: Programmable Oscillator

Post by ljbeng » Wed Feb 01, 2006 11:18 am

.... for more prototype testing.....


will doooooo.

Post Reply

Who is online

Users browsing this forum: No registered users and 35 guests