Circuit and Modeling Solutions for High-Speed Chip-to-Chip Communication

• Main Author: Hollis, Timothy Mowry
• Format: Others
• Published: BYU ScholarsArchive 2007
• Subjects: jitter; signaling; digital communication; circuits; channel equalization; filtering; Electrical and Computer Engineering
• Online Access: https://scholarsarchive.byu.edu/etd/1067; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2066&context=etd

This dissertation presents methods for modeling and mitigating voltage noise and timing jitter across high-speed chip-to-chip interconnects. Channel equalization and associated tuning schemes have been developed to target the distinct characteristics and signal degradation exhibited in the clock and data signals of multi-Gigabit/second digital communication links. Multiple methods for generating realistically degraded signals for the purpose of simulation are also presented and used to verify the proposed equalization and filtering topologies. Specifically, a new technique for modeling high-speed jittery clocks in the frequency domain is presented and shown to reduce transient simulation time and memory requirements, while simultaneously improving the timing resolution and accuracy of the simulation by minimizing the dependence on the transient simulation time-step. The technique is further developed to provide unprecedented control over the timing characteristics of the generated signals, and is then extended to the generation of random data signals with definable jitter statistics. Through these techniques,realistic clock and data waveforms are constructible, providing for the visualization of the combined effects of voltage and timing degradation, while at the same time tracking the phase relationship between the clock and data signals as they pass across their respective channels and through the receiving circuitry of the communication link. New methods for the automated tuning of second-order continuous-time channel equalizers are proposed based on the simulated or measured single pulse and double pulse responses of the transmission channel. Using only one degree of freedom, the methods target the reduction of inter-symbol interference (ISI) as identified in the single and double pulses. Through tuning either the circuit quality factor (Q), the peaking frequency, or the frequency zero, the methods are shown to adapt to a variety of channel lengths and datarates from the same original equalizer transfer function, implying a good degree of generality, while offering a simple, yet effective, method for ISI reduction. Finally, the design of an active 5 Gigahertz (GHz) bandpass filter, employed for high-speed clock conditioning, is presented and shown to address both random and deterministic components of the clock signal degradation. The bandpass transfer function is achieved through a combination of AC coupling and a resonant LC tank consisting of on-chip interleaved spiral inductors and a tunable capacitor array. Through adjusting the load capacitance in parallel with the inductors, the center frequency of the filter is tunable over a range of nearly 5GHz. The design targets a supply voltage of 1.2 volts and draws approximately 5.7 milliamps of current.