Emi Reduction by Using Low Power Digital Controlled Oscillator

The increases of operating frequency of electronic systems, electromagnetic interference (EMI) effect becomes a serious problem, especially in consumer electronics, microprocessor based systems, and data transmission circuits. Many approaches have been proposed to reduce EMI, such as shielding box, skew-rate control, and spread spectrum clock generator (SSCG). However, the SSCG has lower hardware cost compared with other approaches. As a result, the SSCG becomes the most popular solution among EMI reduction techniques for system-on-chip (SoC) applications. In the proposed technique, a novel portable and all-digital spread spectrum clock generator (ADSSCG) suitable for system-on-chip (SoC) used as a application with low-power consumption. Thus it can provide different EMI attenuation performance for various system applications. Furthermore, the proposed ADSSCG employs a low-power digitally controlled oscillator (DCO) to save overall power consumption significantly. Measurement results show that power consumption of the proposed ADSSCG is 1.2 mW (@54 MHz), and it provides 9.5 dB EMI reductions with 1% spreading ratio.