I have TXC 7B 16Mhz Crystal and I am not sure if I need 18pF capacitors between GND pins and GND.
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\$\begingroup\$ That depends as much on your oscillator as on your crystal. \$\endgroup\$– Chris StrattonCommented Oct 4, 2016 at 6:19
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\$\begingroup\$ It says 18pF (or specify) according to the datasheet txccrystal.com/images/pdf/7b.pdf \$\endgroup\$– Adam LeeCommented Oct 4, 2016 at 6:21
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1\$\begingroup\$ if I need 18pF capacitors between GND pins and GND You don't, the two GND pins must be connected to GND. They are only connected to the metal case of the crystal. The crystal itself is between the other 2 pins. You need the 18 pF between these 2 pins ! \$\endgroup\$– BimpelrekkieCommented Oct 4, 2016 at 7:14
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2\$\begingroup\$ @b1gtuna you are looking at the wrong data sheet. You must look at the data sheet of the oscillator you connect the crystal to, not just the data sheet of the crystal. Until you specify what oscillator the crystal is to be connected to, this question is unanswerable. \$\endgroup\$– Chris StrattonCommented Oct 4, 2016 at 8:00
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1\$\begingroup\$ You should stop asking for confirmation on everything and assume that what is written by others is true until proven untrue. Look in the Atmega's datasheet how to connect a crystal or google "Atmega crystal circuit" and look at the images (not the websites). Notice how all circuits are the same. So build that. Notice how there is a cap on each side of the crystal connections. Then remember what I wrote about 18 pf and 36 pF. \$\endgroup\$– BimpelrekkieCommented Oct 4, 2016 at 14:26
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Most of the time crystal oscillator with capacitor combination is used for sample and hold purpose, time required to generate sufficient amount of oscillations for purpose defines your your capacitance values. If lookout in datasheets then you will get it! You can see this also
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4\$\begingroup\$ The text/picture you pasted here is relevant. Your own text is nonsense. used for sample and hold purpose Geez ! Not true at all. \$\endgroup\$ Commented Oct 4, 2016 at 7:11
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\$\begingroup\$ Of interest to me is where you found the picture in your answer. \$\endgroup\$– Andy akaCommented Oct 4, 2016 at 7:40
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\$\begingroup\$ @Andyaka eetasia.com/ARTICLES/2001SEP/… looks like a legit original source. At least it has proper attribution in the PDF. \$\endgroup\$– userCommented Oct 4, 2016 at 9:30
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\$\begingroup\$ @MichaelKjörling - good find but I'm interested in the marked up picture with the red and blue boxes around certain parts of text. It looks like something I might have done but I can't find it. \$\endgroup\$– Andy akaCommented Oct 4, 2016 at 9:34