A 64-MHz∼1920-MHz programmable spread-spectrum clock generator

In this work, a spread-spectrum clock generator (SSCG) with triangular modulation is presented. The SSCG can be applied to most microprocessor systems. It has the effect of spreading the energy of frequency harmonics over a wider bandwidth, and hence reducing the amplitudes of the harmonics. The digital programming schemes are implemented in the charge pump current, the voltage controlled oscillator gain, the low-pass filter and the divider, to realize reusable silicon IP. The proposed SSCG can generate clocks of 64 MHz to 1920 MHz; with center spread modulation from ±1 MHz to ±50 MHz and the spread ratios equal to spread modulation divides output frequency. A test fabricated in a 0.18 μm CMOS single-poly six-metal process is fabricated. The area is 1.01×1.14 mm² including the loop filter. It consumes 100 mW of power at 266 MHz. Attenuation as high as 17 dB is presented.