They do not exist as I found out (again) not long ago. The last 7490 made was LS (low power schottky) and I use quite a few of them. Actually, I have seen a datasheet for a 74HC90 and 74HCT90 but they apparently either never went into production or very few were produced.
The closest non-TTL alternative that I found was the 74HC390 or 74HCT390 which is basically two 7490 counters in one package. On Fri, 04 Jan 2013 11:59:01 +1100, Max <vk3...@gmail.com> wrote: >Where can one get some of these mythical 74HC90 's and 74AC90 's that >have been mentioned. > None of the usual places have them, ie ebay, digi-key, farnell, or >even the Chinese. > Also data-sheets are not to be found. >Thanks > > > >On 4/01/2013 5:13 AM, Bill Fuqua wrote: >> One way is to divide by 10 and then multiply by 16. >> Divide by 10 and then follow by 4 tuned frequency doublers. >> This should introduce little phase noise. >> Another way to do it is to divide by 10, then pass the output thru a >> narrow 16 MHz filter and amplify. Sounds difficult but the filter can >> be one >> or two 16 MHz crystals followed by a simple amplifier. Look at the >> reference input circuit for a PTS-160. The output of the divide by 10 >> needs to >> be asymmetrical so it produces even harmonics. If you are using a >> divide divide by 5&2 such as a 74HC90, divide by 2 first then by 5. >> Ideally the pulse width should be a half period of 16 MHz for the >> maximum harmonic content at 16 MHz. >> You can take the output of the frequency divider and send it to a >> NAND gate. >> One input of the gate is directly connected and the other is delayed. >> You can >> use an RC with a variable capacitor to ground to get it just right. >> Just adjust the capacitor to get the maximum output from your >> filter amplifier. >> 73 >> Bill wa4lav >> >> >> >> At 07:41 PM 1/2/2013 +0000, you wrote: >>> What's the simplest way to generate 16 MHz from 10 MHz? This will be >>> for clocking a microcontroller at 16 MHz given 10 MHz (Cs/Rb/GPSDO). >>> Low price and low parts count is a goal; jitter is not a concern but >>> absolute long-term phase coherence is a must. >>> >>> The ICS525 (as in TAPR Clock-Block) is a good candidate but I was >>> wondering if there's something cheaper, less functional, and maybe >>> not SSOP. Any suggestions? >>> >>> Thanks, >>> /tvb >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.