Multiphase Clock Recovery Using Programmable Delays for C-PHY Skew
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Solution Overview
Problem
Current clock generation circuits in multi-wire, multi-phase data communication links, such as the C-PHY interface, face limitations in speed and reliability due to variations in signal transition times and timing skews, which affect the ability to accurately recover clock information and maintain high data transfer rates.
Innovation Solution
A clock recovery circuit is adapted to detect transitions in some symbol intervals and suppress detection in others, using programmable delays to generate interpolated pulses, allowing for clock signals with frequencies that are fractions of the symbol transmission frequency, and incorporating a delay-locked loop to ensure reliable symbol capture, thereby improving clock recovery accuracy and data transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If delay circuits are employed to ensure stable signaling states before sampling, then reliability of clock recovery is improved, but transmission rate is limited by the delay values
Solution Approach 1:
The patent implements a dynamic delay adjustment mechanism where the delay value is not fixed but can be programmed and adjusted based on operating conditions. The delay circuit includes programmable delay elements that allow the sampling timing to be optimized for different transmission rates while maintaining reliable clock recovery. This dynamic adaptation resolves the contradiction by enabling the system to achieve both reliability and high transmission rate through configurable delay values.
2Measurement precision
If maximum time variation related to signal transitions is reduced, then clock recovery accuracy is improved, but the ability to function at higher signaling frequencies is limited
Solution Approach 1:
The patent changes the parameter of delay value to optimize performance at different signaling frequencies. By making the delay programmable and adjustable, the system can adapt to higher frequencies by reducing the delay value appropriately, thus maintaining clock recovery accuracy while enabling operation at higher signaling frequencies. This parameter adjustment resolves the contradiction between accuracy and speed.
3Stability of the object's composition
If delay values are increased to accommodate timing skews, then all conductors assume stable states before sampling, but the transmission rate is limited
Solution Approach 1:
The patent implements dynamic adjustment of delay values to accommodate timing skews without limiting transmission rate. The programmable delay circuit allows the system to use larger delays only when needed for stability, and reduce delays when high transmission rates are required. This dynamic behavior resolves the contradiction by enabling the system to achieve both signal stability and high transmission rate through adaptive delay configuration.
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AI summary
Methods, apparatus, and systems for data communication over a multi-wire, multi-phase interface are disclosed. A method of data communication includes configuring a clock recovery circuit to provide a first clock signal that includes a pulse for each symbol transmitted on the interface, where symbols are transmitted on the interface at a first frequency, adjusting a loop delay of the clock recovery circuit to modify the first clock to have a second frequency that is no more that half the first frequency, where the clock recovery circuit generates a pulse in the first clock signal for a first of an integer number of symbols and suppresses pulse generation for other symbols in the integer number of symbols, configuring a clock generation circuit to provide a second clock signal, and capturing symbols from the interface using the first clock signal and the second clock signal.