PCI Express EMI Design GuidePCI Express EMI Design Note 1 Spread Spectrum Clock Method SSC reduces radiated emissions by spreading the radiated energy over a wider frequency band 2 Spread Spectrum Clock Method Note The bit rate clock source for transmitter and receiver must be ± 300 ppm or better During SSC is used, the data rate must be down-spread And modulated no more than 0.5% of the nominal data rate frequency During SSC is used, the modulation rate must not exceed the range of 30KHz ……