Every board design and its characteristics are unique, and for your board to perform at its best, specifications, like crystal specifications, must be appropriately tuned. Most crystal manufacturers have standard parts known to perform well, but that doesn’t always mean those parts will provide optimal performance for your board.
At Suntsu, we offer our customers a service that not many other manufacturers like us do: crystal circuit analysis. We provide this free analysis because it helps determine the best parameters for your board design and is critical to achieving optimal performance. Keep reading below to understand the importance of our crystal circuit analysis.
While there are various types of oscillators, each with its unique characteristics and features, the most common is the crystal oscillator which uses a piezoelectric crystal as a frequency-selective element. What makes crystal oscillators so popular is their ability to maintain frequency stability for long durations and that they are not as affected by temperature drift.
When it comes to the circuit inside these oscillators, the most widely used is the Pierce Oscillator Configuration. In the past, engineers have used other designs, such as the Colpitts oscillation circuit, but they have since been overtaken in popularity by the Pierce design. The Pierce Oscillator Configuration consists of a crystal, two capacitors, one or two resistors, and the IC. It is typically chosen due to its simple design, size, and cost for embedded solutions.
Most designers are used to working with the Pierce circuit, but that doesn’t necessarily mean they fully understand how it works or how to design it for optimum performance. This circuit requires external load capacitors or internal built-in capacitors along with the crystal and resistor(s) to decide the characteristics of the circuit oscillation. Parameters like frequency output, oscillation gain, negative resistance, and drive level will all be affected if not tuned correctly making it even more important to properly match the crystal used in the circuit with the on-board Pierce oscillator.
For Engineers, it’s common to leave the crystal as is and follow the reference design or use off-the-shelf crystal recommendations from crystal manufacturers. Choosing either of these options is fine, and the circuit will generally perform, but it’s possible it may not operate at the optimal performance level. Think of it like a guitar. You can play the guitar whether it’s tuned or not, but the notes never sound their best until the guitar is properly tuned.
If not tuned correctly, your board may experience issues such as crystal overdrive, a shift in output frequency, and low loop gain. Since the recommended off-the-shelf crystals are generic, they will work, but we cannot guarantee they provide the best performance for your specific board design. The same thing can happen with your capacitors. If not correctly matched, the center frequency can shift, affecting the loop gain of the oscillation circuit.
To help customers tune their boards correctly and reach optimal performance, Suntsu offers something that not many other crystal manufacturers do: crystal circuit analysis. It’s possible to use trial and error to optimize the circuit, but doing this takes time and testing. The easiest way to achieve this is by sending your board to us!
Once we get your board, we run tests to determine the best specs for all parameters to optimize the board circuit using various testing tools like an oscilloscope, crystal measurement system, multimeter, and current probe.
After performing our analysis, we provide you with a test report, including recommended crystals, capacitors, and a detailed tuning method that will provide you with the best parameters and performance for your board design. We also show you how to optimize the values of the capacitors in the design and adjust load capacitance on the crystal. By using these in harmony, you’ll achieve the correct frequency in your design.
Don’t waste time testing crystal parameters yourself or contacting the crystal manufacturer.
Let Suntsu’s doctor do the work to diagnose your circuit. We have a lot of experience optimizing designs for frequency control, and our doctor is always on-call!