grosen@amadeus.ucsb.edu (Mark D. Grosen) (04/20/88)
Osciallator Question: I need to generate a 2.048MHz clock. Anybody have a good idea on how to do this? Are there any power of 2 oscillators out there? Thanks for any info. Mark Mark D. Grosen ARPA: grosen@hub.ucsb.edu Signal Processing Lab / Communications Research Lab ECE Dept. University of California Santa Barbara, CA 93106
bill@videovax.Tek.COM (William K. McFadden) (04/28/88)
In article <550@hub.ucsb.edu> grosen@amadeus.ucsb.edu (Mark D. Grosen) writes: >Osciallator Question: > >I need to generate a 2.048MHz clock. Anybody have a good idea on how to >do this? Are there any power of 2 oscillators out there? If you get desperate, you could do what I do and synthesize it from a crystal of a different frequency. For example: Take a 1 MHz crystal oscillator and divide the frequency down to 1 KHz using three decade counters. Feed this into the signal input of a 74HC4046 phase- locked loop. Take the VCO output of the PLL, divide it by 2048 with a 4040 CMOS counter and feed the output into the phase detector input on the 4046. Now, assuming you picked the right components for the 4046, you should get 2.048 MHz out. Hence: +------+ +------+ +------+ | 1 MHz| |divide| | | | OSC. |------->| by |------->| PLL |-------+-------> 2.048 MHz output | | | 1000 | | | | +------+ +------+ +------+ | ^ v | +------+ | |divide| +-------| by | | 2048 | +------+ It should take no more than six cheap IC's to implement this frequency synthesizer. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 UUCP: ...{hplabs,uw-beaver,decvax}!tektronix!videovax!bill GTE: (503) 627-6920 "How can I prove I am not crazy to people who are?"
rona@videovax.Tek.COM (Ronald K. Anderson) (04/29/88)
In article <4979@videovax.Tek.COM> bill@videovax.Tek.COM (William K. McFadden) writes: >In article <550@hub.ucsb.edu> grosen@amadeus.ucsb.edu (Mark D. Grosen) writes: >>Osciallator Question: >> >>I need to generate a 2.048MHz clock. Anybody have a good idea on how to >>do this? Are there any power of 2 oscillators out there? > >If you get desperate, you could do what I do and synthesize it from a crystal >of a different frequency. Or you could build your own PLL using: +------+ +------+ +-----------+ +----+ +-----+ | 1.000| |divide| |Phase | | | |6.144| | MHz |-->| by |-->|Detector |->|F(s)|->| MHz |-+ | OSC | | 125 | |(1496) | | | |VCXO | | +------+ +------+ +-----------+ +----+ +-----+ | ^ | | +------+ +----+ | | |divide| |div | | +-------| by |<-+-|by |<-+ | 256 | | |3 | +------+ | +----+ | +-> 2.048MHz out 1MHz and 6.144MHz crystals are available through DIGIKEY (1-800-344-4539) and probably many other sources. Motorola has a nice ap note on using their 10116 in a VCXO circuit: See page 228 of their MECL System design handbook. Design your filter to reject the sum and pass the difference frequencies. CYPRESS makes a registered PROM that makes a great Sequential Finite state machine. You can program them to divide by any integer under the sun, greater than 0 and less than 257: CY7C225. Just feed back the outputs to the respective inputs, and take your output from the SFSM msb. An 8 bit counter will divide by 256 nicely with no messing around with programming. Try a 4040 12-bit counter and tap off pin 13. A 4018 can be simply made into a divide by 3 counter by connecting the appropriate pins together. It should take no more than six IC's to implement this frequency synthesizer. Of course, if you have enough volume, you can get almost any of the crystal makers to customize your own, and if you don't care about stability, make an oscillator out of R's, L's, C's and Q's and design in some tunability! ;*) Disclaimer: I have no brother(s)-in-law(s) at any of the companies mentioned. R.K.Anderson-Gibson-Kappel-Heist-Wood-Galbreath-Olson-Heinz Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 (503)627-2375 ----------------------------------------------------------------------------- new: rona@videovax.tv.Tek.com old: {decvax | hplabs | ihnp4 | uw-beaver | cae780}!tektronix!videovax!rona
kab@hotlr.ATT ( K A Becker hotlv) (04/29/88)
In article <4979@videovax.Tek.COM> bill@videovax.Tek.COM (William K. McFadden) writes: >In article <550@hub.ucsb.edu> grosen@amadeus.ucsb.edu (Mark D. Grosen) writes: >>Osciallator Question: >> >>I need to generate a 2.048MHz clock. Anybody have a good idea on how to >> do this? Sure: just pick one out of a catalog! AT&T, Valprey-Fisher, Austron, Bliley, Colorado Crystal Corp, Conner-Winfield Corp, Croven Crystals, CTS Corp, and probably a dozen others make "canned" crystal oscillators. Look in the EEM Master catalog, available in your local (large) library. Attach +5 at one end, ground at the other, and get TTL levels out, to the precision you pay for. The "standard" ones (100 ppm or so) go for roughly $5 a pop. 2.048-Mhz is one of those "standard" values that phone companies like to use, so you probably will be able to get what you want off the shelf! VXCO's are also avaliable. Have fun! Ken Becker hotlv!kab Any opinions expressed above are my own, and not those of any company I may hack for!
ward@cfa.harvard.EDU (Steve Ward) (04/29/88)
[bite here] In the case of 2.048MHZ it should be easy to find microprocessor-type crystals for 4.096MHZ from one of the mail order places like Jameco, Advanced Computer Products, JDR Microdevices, Active Electronics, Jade, California Digital, Priority One, etc. In any case, JAN Crystals Co., 2341 Crystal Drive, POB 06017, Fort Meyers, FL 33906-6017, tel(800)237-3063, (813)936-2397 will make most any crystal for a very reasonable price, even in quantities of 1-10. Example: Microprocessor crystal, +/- .005% at 25 deg. C for 2.0480 MHZ in HC33/U metal case is $6.00 quantity one. The HC18/U can is smaller and can had for crystals above 2.90MHZ, so you might want to go the 4.0960 MHZ route (and divide by 2) in the HC18/U package for a whopping $6.50 These prices were effective about six months ago, so you might encounter a slight variance. Shipping/handling must be paid, too. Many crystal types at custom frequencies, as well as stock off-the-shelf crystals, are available, including crystals suitable for communications, digital, and general applications. Give them a call and request a catalog/flyer. I have no connection with them except as a satisfied customer. PS - you can get quite specific with them in specifying the crystal parameters if needed. For those less familiar with the technical aspects of specifying crystals, just describe your application. Happy oscillating :-) Steven Ward '