Phase Mixer Non-Linearity Measurement in CDR Clock Recovery
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Solution Overview
Problem
Phase mixer circuitry in clock and data recovery systems experiences non-linearity due to PVT variations and architecture mismatches, leading to phase errors and jitter in received data signals, which existing mitigation methods fail to fully address.
Innovation Solution
A method and system for measuring differential non-linearity of phase mixer circuitry by counting the occurrence of phase mixer codes within specific time periods and determining non-linearity values, allowing for improved alignment of clock signals and reduced errors in data reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase mixer circuitry is used in clock and data recovery systems, then clock signal phase adjustment is achieved, but non-linearity occurs due to PVT variations and architecture mismatches
Solution Approach 1:
The patent applies preliminary action by measuring and storing non-linearity values of the phase mixer circuitry before actual data reception. The system pre-characterizes the non-linear behavior across different phase codes and PVT conditions, creating a lookup table that compensates for non-linearity during operation. This advance preparation eliminates the need for real-time complex calculations and ensures accurate phase compensation is available when needed.
Solution Approach 2:
The patent utilizes parameter changes by varying process, voltage, and temperature conditions during factory testing to characterize the phase mixer's non-linear behavior across different operating points. Multiple non-linearity measurements are taken at different PVT conditions and combined to create a comprehensive compensation model that adapts to changing environmental conditions during device operation.
2Measurement precision
If non-linearity measurement is performed during factory testing, then non-linearity values are obtained, but additional test time and complexity are introduced
Solution Approach 1:
The patent implements periodic action by using a pseudo-random sequence of phase codes that systematically cycles through all possible phase mixer code values during the measurement process. This periodic excitation pattern ensures complete characterization of the non-linear behavior while optimizing the measurement duration. The structured periodic approach is more efficient than arbitrary or sequential code sweeping.
Solution Approach 2:
The patent applies self-service by implementing an automated measurement system that uses the device's own internal resources (phase mixer, clock circuits, counters) to perform the non-linearity characterization. The system self-tests and self-characterizes without requiring external specialized equipment, reducing factory test complexity and time while maintaining measurement accuracy.
3Measurement precision
If non-linearity values are stored in memory for each phase mixer code, then compensation accuracy is improved, but memory requirements increase
Solution Approach 1:
The patent extracts only the essential non-linearity information from the complete set of phase mixer code measurements. Instead of storing all raw measurement data, the system processes the measurements to extract representative non-linearity values that capture the dominant error characteristics. This extraction reduces memory requirements while maintaining sufficient compensation accuracy for practical applications.
Solution Approach 2:
The patent applies partial action by implementing selective measurement and storage of non-linearity values. Rather than measuring and storing data for every possible phase code under all PVT conditions, the system measures a representative subset that captures the essential non-linear behavior. This partial characterization achieves adequate compensation accuracy with reduced memory requirements compared to exhaustive measurement.
Data Source
AI summary
A system and method that measures the code non-linearity of a phase mixer (PMIX) during active operation of a clock and data recovery (CDR) circuitry. The PMIX circuitry generates a clock signal based on the PMIX codes. The PMIX circuitry receives a plurality of codes and based on the code value, adjusts the phase of the PMIX output clock signal. A number of times each of the plurality of PMIX codes occurs within a respective time period is determined. Non-linearity values are determined based on the number of times. The non-linearity values are stored in a memory.