Programmable Phase Generator for Precise Clock Shift Alignment
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Solution Overview
Problem
Conventional phase locked loop (PLL) systems face challenges in achieving precise and flexible phase shift adjustments due to fixed percentage limitations, which can lead to timing violations and functional failures in integrated circuits, especially in Systems on Chips (SoCs) and Field Programmable Gate Arrays (FPGAs).
Innovation Solution
A phase shift generator is introduced, comprising a phase-shift enable and disable signal generator, a logic signal generation device, and a feedback element, which uses programmable configuration bits to induce additional phase shifts in the output clock, allowing for fractional and multi-cycle phase adjustments by controlling a down counter and multiplexer to align with the VCO cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional PLL with fixed percentage phase shift is used, then the device complexity is reduced, but the adaptability for precise phase adjustment is limited
Solution Approach 1:
The phase shift adjustment is segmented into two independent parts: a coarse adjustment mechanism using a multiplexer that selects from fixed percentage phase shifts (0%, 50%, 25%, 75% of clock period), and a fine adjustment mechanism using a programmable counter that provides additional phase shift in programmable steps. This segmentation allows each part to be optimized independently, achieving high adaptability without excessive complexity.
Solution Approach 2:
The system transitions from a static fixed percentage phase shift approach to a dynamic programmable phase shift approach. The counter is programmed with a value that determines the number of additional clock cycles for phase shift, allowing the phase generator to adapt dynamically to different timing requirements. The configuration register stores programmable values that enable flexible phase adjustment without hardware changes.
2Measurement precision
If additional phase shift circuitry is added to achieve precise phase control, then the phase adjustment precision is improved, but the device complexity increases
Solution Approach 1:
The counter serves multiple functions: it acts as a programmable phase shift element, a frequency divider, and a timing control unit. The same counter circuitry that provides fine phase adjustment also generates the divided clock signal for the PLL feedback path, eliminating the need for separate dedicated circuits and reducing overall hardware complexity while maintaining high precision.
Solution Approach 2:
The configuration register acts as an intermediary that stores programmable values and interfaces between the user's phase shift requirements and the physical phase generator circuitry. This intermediary layer allows precise phase control through software/configuration bit programming rather than complex hardwired logic, simplifying the overall device architecture.
3Adaptability or versatility
If a programmable counter is used for additional phase shift, then the adaptability for different phase shifts is improved, but the device complexity increases
Solution Approach 1:
The phase generator merges the counter-based fine adjustment mechanism with the existing multiplexer-based coarse adjustment mechanism into a unified phase shift system. The total phase shift is the combination of the multiplexer-selected fixed percentage and the counter-programmed additional cycles, creating a cohesive system that achieves high adaptability without requiring entirely separate control circuits.
Data Source
AI summary
A phase generator includes a phase-shift enable and disable signal generator connected to configuration bits at its first input and connected to a reset signal at its reset input for generating a control signal; the configuration bits corresponding to the phase shift desired. The phase generator includes a logic signal generation device connected at its control input to the output of the phase-shift enable and disable signal generator and connected to a reset signal at its reset input for providing a phase generating signal; and a feedback element connected between the output of the logic signal generation device and control input of the phase-shift enable and disable signal generator for providing controlled clock signal to the phase-shift enable and disable signal generator.