High accuracy, Low Power Spread Spectrum Clock Generator to Reduce EMI for Automotive Applications

Abstract

This paper presents a Spread Spectrum Clock Generator (SSCG) based on Relaxation oscillator using Up/Down Counter. The current is controlled by a counter and the spread spectrum of the Relaxation Oscillator. A Relaxation Oscillator with temperature compensation using the BGR and ADC is presented. The current to determine the frequency of the Relaxation Oscillator can be controlled. The output frequency of the temperature can be compensated by adjusting the current according to the temperature using the code that is the output from the ADC and BGR. EMI Reduction of SSCG is 11 dB, and Spread down frequency is 150 kHz. The current consumption is <TEX>$600{\mu}A$</TEX> from 5V and the operating frequency is from 2.3 MHz to 5.75 MHz. The rate of change of the output frequency with temperature was approximately <TEX>${\pm}1%$</TEX>. The SSCG is fabricated in a 0.35um CMOS process with active area <TEX>$250um{\times}440um$</TEX>.