Phase Interpolator Skew Correction for Stable Clock Timing Margins
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Solution Overview
Problem
Conventional phase interpolator circuits experience phase difference shifts between output clock signals due to skew mismatches, leading to reduced timing margins and hindered high-speed operations.
Innovation Solution
A phase interpolator circuit with a first and second generation circuit generating intermediate currents based on input clock signals, a synthesis circuit for combining these currents, and a correction circuit to adjust current amounts using correction codes to correct phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase interpolator circuits are used to generate output clock signals, then phase adjustment is achieved, but phase difference shifts occur due to skew mismatches reducing timing margins
Solution Approach 1:
The patent applies preliminary action by measuring the phase difference between input clock signals before phase interpolation and using this measurement to pre-calculate correction values. The correction circuit proactively adjusts the phase interpolation result based on the measured skew mismatch, preventing phase difference shifts before they occur. This is implemented through a phase difference measurement circuit that continuously monitors input clock signals and feeds correction data to the phase interpolator.
Solution Approach 2:
The patent implements feedback by creating a closed-loop system where the phase difference between input clock signals is measured, and this measurement is fed back to correct the phase interpolation process. The correction circuit uses the measured phase difference information to adjust the output clock signal phase, ensuring that timing margins are maintained despite skew mismatches. This feedback mechanism continuously compensates for phase errors.
2Productivity
If phase interpolation is performed to adjust clock phase, then data acquisition capability is improved, but phase difference shifts reduce high-speed operation capability
Solution Approach 1:
The patent replaces traditional mechanical or conventional electronic phase adjustment mechanisms with a measurement-based correction system. Instead of relying on fixed or manually adjusted phase interpolators, the system uses automated phase difference measurement and digital correction circuits to dynamically adjust the clock phase. This substitution enables more precise and faster phase adjustment, maintaining high-speed operation capability while improving data acquisition accuracy.
3Reliability
If skew mismatch correction is implemented, then timing margin stability is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the phase difference measurement function and the skew mismatch correction function into a single integrated circuit system. The phase interpolator, measurement circuit, and correction circuit are combined to work together as one unified structure. This merging reduces the need for separate independent circuits, thereby limiting the increase in overall circuit complexity while still achieving timing margin stability through coordinated operation of the integrated components.
Data Source
AI summary
A phase interpolator circuit that generates an output clock signal having a phase according to a PI code based on input clock signals, the phase interpolator circuit includes: a first generation circuit configured to generate a first intermediate current based on a first input clock signal according to the PI code; a second generation circuit configured to generate a second intermediate current based on a second input clock signal having a first phase difference from the first input clock signal according to the PI code; a synthesis circuit configured to synthesize the first and second intermediate currents to generate the output clock signal; and a correction circuit configured to correct a current amount of at least one of the intermediate currents based on a correction current according to a correction code set according to at least an amount of shift of the first phase difference from a certain value.