DDR5 Duty Cycle Training for DQS Jitter Reduction
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Solution Overview
Problem
DDR5 SDRAMs face challenges in minimizing jitter associated with DDR5 DRAM transmitters due to duty cycle errors in the 4-phase internal clock scheme, which can lead to system failures.
Innovation Solution
The implementation of Duty Cycle Adjuster (DCA) optimization training algorithms, which include Basic and Advanced DCA training algorithms, to adjust the DQS clock tree and DQ duty cycle by setting DCA code values in mode registers, thereby reducing duty cycle errors and phase mismatch-induced jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DDR5 SDRAM supports increased I/O switching rate (up to 6400 MT/s), then bandwidth is improved, but duty cycle errors and jitter increase causing system failures
Solution Approach 1:
The patent implements preliminary training algorithms (Basic DCA Training and Advanced DCA Training) that execute before normal DDR5 operations to pre-adjust the duty cycle of internal clocks (QCLK, IBCLK, QBCLK) and optimize the DQS clock tree. This preliminary calibration of duty cycle adjuster codes prevents jitter and duty cycle errors from occurring during high-speed data transfers, thereby maintaining both the 6400 MT/s bandwidth and system reliability
2Measurement precision
If duty cycle adjuster codes are adjusted to minimize jitter, then signal quality is improved, but training complexity increases
Solution Approach 1:
The patent segments the duty cycle adjustment process into two distinct training algorithms: Basic DCA Training that independently optimizes each internal clock (QCLK, IBCLK, QBCLK) one at a time, and Advanced DCA Training that performs joint optimization. This segmentation allows the complex jitter minimization problem to be broken down into manageable steps, reducing overall training complexity while achieving high signal quality through systematic duty cycle calibration
Data Source
AI summary
Methods and apparatus for duty cycle adjuster optimization training algorithms to minimize jitter associated with DDR5 DRAM transmitters. Basic and Advanced Duty Cycle Adjuster (DCA) training algorithms are implemented to reduce duty cycle error and hence reduce phase mismatch translated jitter in the transmitter DQS signals. In accordance with aspects of the Basic DCA training algorithm, duty cycles for QCLK, IBQCLK, and QBCLK are adjusted by a memory controller that utilizes a DCA function implemented on a memory module (e.g., DDR5 SDRAM DIMM) to obtain a first set of optimized DCA code settings. The first set of optimized DCA code settings are then used as initial settings for the Advance DCA training algorithm to further optimize the DCA code settings for QCLK, IBQCLK, and QBCLK. A similar technical may be employed to reduce duty cycle error and jitter for DQ signals.