Clock dithering for electromagnetic compliance using spread spectrum phase modulation

摘要: As more electronic systems operate at higher frequencies and bandwidths, they tend to emit electromagnetic interference (EMI). Due lack of shielding, portable such as notebook computers have come under increasing pressure comply with strict EMI emission regulations, FCC CISPR. The data bus the clock are major sources because conduct high currents form large loops. This paper focuses on spreading frequency-spectra signals reduce their peak emissions for EM compatibility. In a similar work, noise is intentionally injected onto VCO control voltage in PLL achieve effect frequency modulation. this case, phase dithered varies unpredictably so mixing both non-dithered clocks within same system avoided. proposed scheme, difference between two arbitrary edges limited half period. Hence, it practical real applications. Since implemented delay-locked loop (DLL), there no problems accumulated error, difficulties designing stable filters, or area costs.