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Reconfigurable Clock Distribution Circuitry. Circuit and Systems,2007 .ISCAS 2007.IEEE International Symposium on 27-30 May 2007 Page(s):877 - 880 Atanu Chattopadhyay, Zeljko Zilic Department of Electrical and Computer Engineering, McGill University Montreal, Quebec, Canada
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Reconfigurable Clock Distribution Circuitry Circuit and Systems,2007 .ISCAS 2007.IEEE International Symposium on 27-30 May 2007 Page(s):877 - 880 Atanu Chattopadhyay, Zeljko Zilic Department of Electrical and Computer Engineering, McGill University Montreal, Quebec, Canada Presented by: Ishrath Fatima
Features • Skew ranges from 3.9-5.5ps for a 3-clock domain/15-tap configuration. • Worst case skew under 4% for all frequencies. • Power consumption of about 62.82mW • No de-skewing method used. • Frequency : 1.9GHz • Clock Period: 525ps • Reference-based scheme for skew compensation. • Daisy chaining the clock to distribute clock without distortion and reducing the clock load. • PLL replaced by delay lines, which reduces power consumption. • Reconfigurable & reprogrammable clock distribution network.
Reference Based clock distribution scheme • Device is sub-divided into multiple regions. • H-Tree to distribute clock from tap to leaves. • Bi-directional clock distribution line. • Its scalable and compatible with irregularly shaped distribution areas. • Clock distribution line has a constant delay ‘K’ over its entire length. • Phases : Synchronization, Calibration and operation. • Synchronization: The forward clock is delayed to align with reverse clock, which results in each local clock to a position directly between forward and reverse moving reference clocks, results in skew free clocks at each tap. • Calibration: Disable source delay element for an appropriate “average clock”and align polarity of local clock’s by inverting appropriate taps. • Operation: Unused circuitry disabled to save power. • Each local delay line is required to save the delay settings determined during synchronization. • Clock buffers allow us to re-direct clocks dynamically at certain pre-defined switch points, making distribution reconfigurable.
References • A. Chattopadhyay and Z. Zilic “Reference-based clock distribution architectures,” Proc. MWSCAS 2006. • H. Lee, H. Q. Nguyen, and D. W. Potter, “Design self-synchronized clock distribution networks in an SoC ASIC using DLL with remote clock feedback,” Proc ASICSOC 2000, 248-252