CDI Blog For Engineers

Using Spread-Spectrum Oscillators to Solve EMI Issues

Mercury at CDI
Using Spread-Spectrum Oscillators to Solve EMI Issues
EMI testing is almost always one of the last certification tests that needs to be completed before a product can enter full production. As a result, the product design is “complete” when the testing occurs. In most cases, EMI certification tests are completed without an issue.
But what about those times when it does not?
The pressure is on. Time-to-market is critical, and the design is complete, and just waiting for the stamp of certification to begin production ramp-up. Going back to the drawing board on the electrical or mechanical design (or both!) to solve EMI issues is going to be a problem. Savvy engineers will try simple fixes, such as going to shielded inductors, adding some absorbing, or shielding material where it can be squeezed into the existing design.

Rarely, however, do they try one of the simplest changes that can be made – without having to modify the PCB design. The system clock, which is usually derived from a crystal oscillator, propagates throughout the design. This clock, or perhaps clocks derived from the main clock, are used everywhere, and any noise on those lines contribute directly to unwanted emissions that can cause a design to fail EMI certification. So, if the system clock can be made “quieter”, there is a good chance that the EMI issue can be resolved with a simple part number change.

Mercury Electronics and Component Distributors encourage engineers who are facing EMI challenges to try using a Spread-Spectrum Oscillator (SSXO). The SSXO is fully pin compatible with the existing crystal oscillator (XO) footprint and function, and samples can be obtained in a matter of a day or two. By switching to an SSXO, clock noise can drop by up to 12 dB, as seen below.

Spectrum Comparison
Click here to Download the Mercury Low EMI Oscillators Datasheet
Most common XO package types are available, and prototype turn-around time is usually 24-48 hours. Contact CDI for assistance and see your design fly through the EMI test and get into production quickly.
About Mercury United Electronics
Mercury United Electronics is a quartz crystal manufacturer of frequency control products that includes Crystals, Oscillators, Low EMI Spread Spectrum Clock Oscillators, (Quick-Turn) TCXO’s, VCTCXO’s, VCXO’s, OCXO’s and Monolithic Crystal Filters.
About Component Distributors, Inc. (CDI)
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