The pin connections and functions for “crystals” and “crystal oscillators”

About “crystals”

Crystals are passive devices that can cause carefully constructed circuits to oscillate at a fixed frequency. Most typical crystals only actually have two frequency pins, even ones in a 4-pin package like this.

( 4-pin crystals: pin 2 & pin 4 are connected to the case)

The “GND” pins are actually nothing more than an electrical connection to the case of the package. They don’t typically provide any function other than shielding (as  a shield against EMI or helping ground any RF)to increase its frequency reliability.We would advise that you connect both pins to GND as is suggested in our datasheet.

About “crystal oscillators”

The crystal plus the inverter and the capacitor and the resistor make a “crystal oscillator”.

(pin connections for crystal oscillators)

With the 4-terminal device you don’t need the other components. You hook up Vdd to a voltage source. Read the datasheet for “Absolute Maximum Ratings” and typical operation values. Vdd should have a bypass capacitor to GND. GND should go to Ground. Tri-state can be controlled by a logic signal if you want to turn the oscillator on and off. You can also tie it to Vdd (since Tri-state is active high or left floated, and low would be STOP) to have the oscillator on all the time, and the output is what you really need.