Semiconductor Memory Device Data Strobe Preamble Timing
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Solution Overview
Problem
Semiconductor memory devices face challenges in accurately transmitting data due to skew between data and system clock signals, particularly due to variations in process, voltage, and temperature (PVT), which affect the definition of the preamble section of the data strobe signal.
Innovation Solution
A semiconductor memory device generates a data strobe signal with a predefined preamble section by using separate enable signals for data output and strobe signal generation, synchronized with the source clock, ensuring accurate timing and minimization of skew regardless of PVT variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a data strobe signal is transmitted to minimize skew between data and system clock, then synchronization accuracy is improved, but the definition of the preamble section becomes uncertain due to PVT variations
Solution Approach 1:
The patent applies preliminary action by generating the data strobe signal DQS in advance before the actual data output. The strobe signal includes a preamble section that is generated ahead of the data valid period, allowing the memory controller to prepare for data reception. This advance generation ensures that the strobe signal establishes the timing reference before PVT variations affect the data signals, thereby maintaining synchronization accuracy while providing a stable preamble definition.
Solution Approach 2:
The patent employs dynamics by making the data strobe signal generation adaptive to PVT variations. The strobe signal generation circuit adjusts the timing and characteristics of the DQS signal dynamically based on detected PVT conditions. This dynamic adjustment ensures that the preamble section maintains its defined characteristics even when process, voltage, or temperature variations occur, thus resolving the contradiction between synchronization accuracy and preamble definition stability.
2Ease of operation
If the data strobe signal is generated early to provide a preamble section, then the memory controller can prepare for data reception, but the timing precision may be affected by PVT variations
Solution Approach 1:
The patent applies preliminary action by generating the data strobe signal DQS in advance before the actual data output. The strobe signal includes a preamble section that is generated ahead of the data valid period, allowing the memory controller to prepare for data reception. This advance generation ensures that the strobe signal establishes the timing reference before PVT variations affect the data signals, thereby maintaining synchronization accuracy while providing a stable preamble definition.
Solution Approach 2:
The patent employs feedback mechanisms where the memory device monitors the actual timing and characteristics of the data strobe signal and adjusts subsequent strobe generations accordingly. This feedback loop compensates for PVT variations that may have affected the preliminary strobe signal, ensuring that timing precision is maintained throughout the data transmission sequence while still providing the memory controller with adequate preparation time.
Data Source
AI summary
A semiconductor memory device includes: an enable signal generation portion suitable for generating a data output enable signal activated at a predetermined first moment corresponding to column address strobe (CAS) latency based on a read command, a strobe signal generation portion suitable for generating a data strobe signal which has a preamble section until the data output enable signal is activated from a predetermined second moment ahead of the first moment based on the read command and toggles based on a source clock during an activated section of the data output enable signal, and a data output portion suitable for outputting internal data in synchronization with the data strobe signal during the activated section of the data output enable signal.