C-PHY Transmitter Jitter Reduction via Multi-Phase Clock Launching
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Solution Overview
Problem
High-speed data communication interfaces, such as the C-PHY interface, face challenges in reducing jitter due to channel bandwidth limitations, leading to inter-symbol interference and limited clock-data recovery capabilities, especially in multi-wire configurations.
Innovation Solution
The implementation of multiple clock phases with different phase-shifts is used to launch symbols on a 3-wire interface, allowing for selective selection of launch clock signals based on signaling state transitions, ensuring that each wire transitions at optimal times to minimize differences in arrival times of signaling state transitions at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-emphasis (feed-forward equalization) is employed at the transmitter to compensate for high frequency attenuation, then signal quality is improved, but it has limited effect on multi-wire interfaces and cannot adequately reduce jitter
Solution Approach 1:
The patent changes the timing parameter of signal transitions by using multiple clock phases (first, second, and third clock signals with different phases) to launch symbols on different wires. This allows optimization of transition timing for each wire based on its specific characteristics, reducing jitter and improving signal quality beyond what pre-emphasis alone can achieve.
2Reliability
If multiple clock phases are used to launch symbols on different wires, then transmitter encoding jitter is reduced and signal integrity is improved, but device complexity increases
Solution Approach 1:
The patent segments the clock signal into multiple phases (first, second, and third clock signals) that are launched at different times. Each wire can be assigned a specific clock phase based on its transition requirements, allowing independent optimization of each wire's timing while managing complexity through systematic segmentation.
Solution Approach 2:
The patent dynamically selects which clock phase to use for launching symbols on each wire based on the required transition type. The system adapts the clock phase selection to match the specific signaling state transitions needed, optimizing timing for each condition rather than using a fixed clock scheme.
3Productivity
If transition timing is optimized for each wire to reduce jitter, then maximum symbol transmission rate is increased, but the complexity of determining and selecting appropriate clock phases increases
Solution Approach 1:
The patent determines the type of transition required for each wire in advance before launching the symbol. By预先 determining the transition type and selecting the appropriate clock phase beforehand, the system optimizes timing for maximum transmission rate while managing complexity through advance planning rather than real-time complex calculations.
Data Source
AI summary
A method for error detection in transmissions on a multi-wire interface includes providing a plurality of launch clock signals, including launch clock signals having a different phase shifts, determining a type of transition in signaling state that will occur on each wire of the 3-wire interface at a boundary between two consecutively transmitted symbols, and selecting one of the plurality of launch clock signals to initiate the transition of signaling state on each wire of the 3-phase interface. Selecting one of the plurality of launch clock signals may include selecting a first launch clock signal when the transition in signaling state terminates at an undriven state, and selecting a second launch clock signal when the transition in signaling state begins at an undriven state. An edge in the first launch clock signal may occur before a corresponding edge in the second launch clock signal.