Output Driver Switching Between LVSTL Drive and On-Die Termination
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Solution Overview
Problem
Existing memory systems face challenges in effectively terminating input data during write operations using low-voltage swing-terminated logic (LVSTL) interfaces, which affects the efficiency and power consumption of semiconductor memory devices and memory controllers.
Innovation Solution
The proposed solution includes an output driver with a pre-driver and an on-die termination controller that generate control signals to manage pull-up and pull-down NMOS drivers, allowing for efficient termination of high and low-level data using internal power supply voltages higher than the output power supply voltage, reducing power consumption and simplifying circuit configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If LVSTL interface is used for data output, then power consumption is reduced, but termination of input data during write operations becomes ineffective
Solution Approach 1:
The output driver dynamically switches between drive mode and termination mode based on operation type. During write operations, the pull-up NMOS driver transitions from driving high-level output data to terminating high-level input data, while the pull-down NMOS driver terminates low-level input data. This dynamic reconfiguration enables effective termination while maintaining low power consumption characteristics of LVSTL interface.
Solution Approach 2:
The pull-up NMOS driver and pull-down NMOS driver are designed to perform multiple functions: during read operations, they generate high-level and low-level output data respectively, while during write operations, they terminate high-level and low-level input data respectively. This multi-functionality allows a single circuit structure to handle both data output and input termination requirements of LVSTL interface.
2Device complexity
If pull-up NMOS driver is used to generate high-level output data, then circuit complexity is reduced, but ability to terminate input data effectively is compromised
Solution Approach 1:
The pull-up NMOS driver dynamically changes its function based on the operation mode. Control signals switch the driver between generating high-level output data during read operations and terminating high-level input data during write operations. This dynamic switching enables a simple NMOS-based circuit to achieve both data output and input termination functions that would traditionally require more complex circuitry.
Data Source
AI summary
An output driver includes a pre-driver receiving a driver control code to generate a pull-up control signal or a pull-down control signal in response to data while a read operation is performed, an on-die termination controller receiving a first on-die termination control code to generate a first on-die termination control signal in response to an on-die termination enable signal while a write operation is performed, and a main driver including a pull-up n-channel metal-oxide-semiconductor (NMOS) driver generating high-level output data in response to the pull-up control signal while the read operation is performed, and terminating high-level input data with a first high voltage and terminating low-level input data with a first low voltage in response to the first on-die termination control signal while the write operation is performed, and a pull-down NMOS driver generating low-level output data in response to the pull-down control signal while the read operation is performed.