Application of Epson Programmable Spread Spectrum Crystal Oscillator in EMC Design

Spread spectrum technology has become a common means of reducing EMI

The launch time of terminal products is crucial. Usually, after the product design is completed, it needs to wait for EMC certification before mass production can begin. During this period, redesigning PCBs to solve EMI will be a problem. Developers attempt simple repair methods, such as using shielded inductors, adding some absorbent or shielding materials, in order to incorporate them into existing designs.

However, for the EMI issue caused by clocks, a simple method can be used without modifying the PCB design or adding anti EMI components: the system clock is usually obtained from a crystal oscillator and used throughout the entire design. In other words, the clock may be distributed throughout the entire design, and any noise on the circuit can directly cause harmful interference, resulting in the design not being able to pass EMI certification. Therefore, if the system clock can be made "quieter", the problem can be easily solved. A simple method is to replace the crystal oscillator - the Spread Spectrum Crystal (SSXO) - with an existing crystal oscillator that is fully pin compatible in size and function. The use of spread spectrum technology can effectively reduce EMI.

Programmable Spread Spectrum Crystal Oscillator SG-9101 Series

The Epson Extended Frequency Crystal SG-9101 series is a programmable crystal oscillator that reduces EMI electromagnetic interference by adjusting the clock frequency. The frequency programmable range is 0.67MHz~170MHz (1ppm per step), and the extended frequency range is ± 0.25%~± 4%. The SG-9101 new product offers a wider operating temperature range and reduces current consumption by 50%. When using the SG-9101, it can be optionally paired with an existing SG Writer II dedicated burner to define the center frequency of the SG-9101, which can reduce electromagnetic interference (EMI) and spread spectrum crystal oscillator.

The consumption current of SG-9101 frequency quartz oscillator has been significantly reduced by 75% compared to current mass-produced products. The spread spectrum clock crystal oscillator of SG-9101 provides several types of modulation methods, which can achieve modulation values of ± 0.5%, ± 0.75%, ± 1%, ± 1.5%, ± 2%, and 0.25%. Practice has shown that the introduction of spread spectrum clock crystal oscillator modulation results in minimal clock signal jitter. SG-9101 effectively reduces the electromagnetic radiation power by dynamically changing the clock frequency, reduces the impact of EMI electromagnetic interference, and thus solves the problem of EMC radiation exceeding the standard.

Advantages of SG-9101 frequency oscillator

● Good compatibility, product pin function definition and size are compatible with conventional crystal oscillators;

● Programmable, frequency and spread parameters can be defined through programming tools;

Quickly meet customer sample requirements;

● Flexible adaptation to user products. The EMI test results for different customer products vary, and samples with different indicators can be provided to determine the best fit through testing;

●Save PCB space, no need to add additional filtering components, shielding covers, etc., reducing the overall cost of the product.