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I don't think a 555 will work reliably at 500KHz
You might find get one to work with a low leakage capacitor but I'd be very cautious about building lots of copys of the circuit and expecting them all to work with variations in leakage current in the 555 and the timing capacitor, paticularly over a wide temperature range.
**broken link removed** says "Maximum frequency: around 300 KHz"
555 timers are available from several different manufacturers in several different versions.
Some of the data sheets show a chart going up to 100KHz but don't specify and maximum frequency that I can see.
The **broken link removed** is only guaranteed to work up to 50KHz in astable mode.
If it does work then you could probably adjust it for
+/-100Hz by having multiturn pots in series with fixed resistors for the timing resistor.
Long term stability and variation with temperature is another matter. The phillips 555 datasheet says up to 500ppm/degC which means 5degrees Centigrade to 55 degrees Centigrade could give a 12.5Khz shift.
hi throwaway18.
if i use its CMOS version i think it can oscillate up to 1 Mega Hertz.
i simulate this oscillator in orcad and it work properly.
is it true?
regards
Wow, that's an improvement. The datasheet is dated october 2003. Now I come to think about it the last time I used a 555 in a non-trivial project was about fifteen years ago...
The Timing Shift with Temperature is a lot better as well.
It now depends on your definition of "precise".
You may need to use a good timing capacitor such as a silver mica type rarther than
a ceramic. If you are really cunning you could try to get the temperature coefficients
of the LMC555, the resistors and the timing capacitor to cancel out to some extent.
If you think about precision frequency reference you should consider a crystal-based generator ..
At that frequency level (500kHz generated by the 555 in astable configuration) you may expect frequency drifts of ≈ +/-1% and that will depend on the quality and type of the used components (mainly C) ..
hi
i found that its bipolar versions can oscillate up to 40khz only and its CMOS versions can oscillate up to 3 MHz!
also you can simulate both types in ORCAD:
bipolar -->> 555B Model
CMOS -->> 555C Model
thanks
regards
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