Memory Output Driver Slew-Rate Correction Under Impedance Variation
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Solution Overview
Problem
Semiconductor memory apparatuses face signal integrity issues due to impedance variations in data output devices, leading to jitter and a narrowed data eye, as the slew rate of the output signal is not effectively controlled.
Innovation Solution
A data output device with a pre-driver unit that adjusts its driving force in response to impedance control signals, and a main-driver unit that controls impedance through pull-up and pull-down resistance, allowing for correction of the slew rate of the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main-driver impedance is controlled to match transmission channel impedance for high-speed operation, then operation speed is improved, but the slew rate of the output signal varies depending on impedance changes, generating jitter and narrowing the data eye
Solution Approach 1:
The pre-driver unit adjusts its driving force in advance based on the impedance control signal before the main-driver outputs the signal. This preliminary adjustment ensures that the signal maintains appropriate slew rate characteristics regardless of subsequent impedance variations in the transmission channel, thereby preventing jitter and maintaining signal integrity while supporting high-speed operation
Solution Approach 2:
The system uses impedance control signals that provide information about the main-driver impedance state to the pre-driver unit. This feedback mechanism allows the pre-driver to adapt its driving force dynamically, ensuring optimal signal quality across varying impedance conditions while maintaining high-speed performance
2Device complexity
If the pre-driver applies output signal to the main-driver irrespective of impedance variation, then device complexity is reduced, but signal integrity is deteriorated and data eye is narrowed
Solution Approach 1:
The pre-driver unit performs preliminary adjustment of its driving force based on impedance control signals before signal transmission. This advance preparation enables the system to maintain signal integrity without requiring complex real-time impedance matching circuits, achieving a balance between simplicity and reliability
Solution Approach 2:
The invention applies localized quality adjustment by modifying the driving force characteristics of the pre-driver unit specifically tailored to the impedance conditions. This targeted adjustment maintains signal integrity without requiring global system redesign, preserving overall device simplicity while improving local signal quality
Data Source
AI summary
A data output device includes a pre-driver unit configured to control a driving force according to an impedance control signal and to drive output data using the driving force. The data output device includes a main-driver unit configured to control an impedance according to pull-up and pull-down resistance control codes having values that correspond to the impedance control signal provided to the pre-driver unit and to drive an output of the pre-driver unit by utilizing the controlled impedance.