It isa requirement by FCC that allelectronic devices including game-consoles, PCs, and high speed compute servers, limit Electromagnetic Interference (EMI) when they distribute high-speed signals.
Analog Bits’ spread spectrum clock generation macro is capable of generating fine clock spreads that help reduce EMI. The precision spread-spectrum clock spreading is achieved by a combination of integer and fractional multiplication. The fractional divider generates a programmable triangular waveform to precisely control the degrees of spread. Programmable options allow the user to control the degree of spread in fine steps of +0/-0.5% and up to +0/-1.5% of the output clocks.
The spread spectrum macro is integrated with the PLL macro and is implemented in Analog Bits’ proprietary architecture. The combined spread-spectrum generation and PLL is the smallest PLL in the industry. Eliminating band-gaps and integrating all on-chip components such as capacitors and ESD structures, helps the jitter performance significantly and reduces stand-by power. The spread spectrum generation PLL macro may be either IO pad ring or core integrated.
Silicon Proven Analog Bits’ spread spectrum architecture is in volume production in Xbox 360.
FNOM Frequency Spreading FNOM - % TMOD = 31.25 μs Figure 1: Precision Modulation Creating Spread Spectrum Clocks and Typical Layout of SSCG PLL