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Lowest part-count oscillator/clock
Lowest part-count oscillator/clock
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Old 12th May 2020, 10:25 PM   #1
KHashmi316 is offline KHashmi316  United States
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Default Lowest part-count oscillator/clock

Say I have std. 2-pin crystal can. (Mine is 11.289 Mhz)
I want to make the simplest osc/clock possible ... hence, fewest parts-count I assume. The performance should be acceptible, but does not have to be audiophile-grade.
Please suggest a circuit.
Thanks!

Last edited by KHashmi316; 13th May 2020 at 12:09 AM.
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Old 12th May 2020, 10:36 PM   #2
MarcelvdG is offline MarcelvdG  Netherlands
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See figure 14 and table 9 of
https://assets.nexperia.com/document...et/74HCU04.pdf
where the frequencies in table 9 are in MHz rather than kHz.
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Old 13th May 2020, 12:08 AM   #3
KHashmi316 is offline KHashmi316  United States
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Quote:
Originally Posted by MarcelvdG View Post
See figure 14 and table 9 of
https://assets.nexperia.com/document...et/74HCU04.pdf
where the frequencies in table 9 are in MHz rather than kHz.
Thanks ... but wouldn't a buffered hex inverter be better than the UNBUFFERED 74HCU04 one you suggested?
Also, would a "high-speed" hex inverter, such as the 74VHC04 , be a better option?
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Old 13th May 2020, 12:15 AM   #4
canvas is offline canvas  Taiwan
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IMHO, unbuffered and faster inverter is better. Try PO74GU04.
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Old 13th May 2020, 01:32 AM   #5
KHashmi316 is offline KHashmi316  United States
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Default PO74GU04

Quote:
Originally Posted by canvas View Post
IMHO, unbuffered and faster inverter is better. Try PO74GU04.
I've seen the Potato chip mentioned on DIYA quite often.

I assume this is one:
74U04 Series GHz TTL CMOS logic IC 14pin SOIC QTY-1 | eBay

Only concern is that requires 3.3v max. I'll have to add separate regulation for voltage that low. The lowest I can provide currently is the std. 5vdc.
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Old 13th May 2020, 05:36 AM   #6
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by KHashmi316 View Post
Thanks ... but wouldn't a buffered hex inverter be better than the UNBUFFERED 74HCU04 one you suggested?
Also, would a "high-speed" hex inverter, such as the 74VHC04 , be a better option?
A buffered inverter consists of three inverters in a row. With the extra gain and phase shift of the two additional stages, the start up of the oscillator becomes quite hard to predict. It might oscillate at a frequency set by the inverters rather than the crystal, or become conditionally stable and not oscillate at all. Even if it does work, the phase noise will be worse than with an unbuffered inverter due to the small size of the input stage of a buffered inverter. In fact the 74HCU04 is meant specifically for crystal oscillators and other analogue applications.

What you can and usually should do, is to connect the output of the oscillator to another inverter from the same package and use the output of that second inverter to drive whatever circuits you want to drive with it. The second inverter converts the signal coming out of the oscillator into a nice square wave.

Regarding other logic families, I did some noise measurements a long time ago and found that the Texas Instruments SN74AHCU04 outperformed the SN74HCU04 by far. The measurements concentrated on the PMOS side of the inverter, though. See SN74AHCU04 as a cheap FET differential pair for details.

Last edited by MarcelvdG; 13th May 2020 at 05:41 AM.
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Old 13th May 2020, 06:13 AM   #7
rfbrw is offline rfbrw
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Quote:
Originally Posted by KHashmi316 View Post
Say I have std. 2-pin crystal can. (Mine is 11.289 Mhz)
I want to make the simplest osc/clock possible ... hence, fewest parts-count I assume. The performance should be acceptible, but does not have to be audiophile-grade.
Please suggest a circuit.
Thanks!
Ditch the 2-pin crystal for an oscillator module. 1 can + power.
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Old 13th May 2020, 11:08 AM   #8
KHashmi316 is offline KHashmi316  United States
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Looking thru my closet, I have both 74HCU04 and 74HC04 in my parts bin. Both Fairchild.
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