Introduction To Crystals And Oscillators

At the heart of any FPGA you will have an oscillator that creates a stable clock signal. This signal is generated from a physical crystal (quartz) which once run through with electricity, will oscillate at its resonant frequency.  Oscillators contain both the resonator (crystal) and the electronic component (the amplifier) which are both required to maintain the oscillations.

In reference to the picture above, here is a listing of many commonly used oscillators:

Crystals (2 pins):

• 1. HC-49/SD crystal (SMD)
• 2. HC-49/US crystal
• 3. HC-49/U crystal

Oscillators (4 pins):

• 4. DIL-14 “Full size” metal case (the metal case brought the nickname “canned oscillator”)
• 5. DIL-8 “Half size” metal case
• 6. DIL-8 “Half size” plastic case
• 7. 5x7mm metal case (SMD)

FPGA 4 Fun has a great article up about crystals and oscillators for those of you who like to always keep learning.  If you’re new to FPGAs we try to post little tidbits like this from time to time to help round out your knowledge base of all things FPGA.  Check out the full article:

• Introduction to crystals and oscillators – FPGA 4 Fun

(via FPGA4Fun)