Adjustable OCD Driver Resistance for DRAM IO Impedance Matching
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Solution Overview
Problem
High-speed signal transmission in memory devices leads to signal degradation and distortion due to capacitance loading and impedance mismatching issues in OCD drivers, particularly affecting IO pads in DRAM channels.
Innovation Solution
The implementation of a resistance-adjustable means in OCD drivers using triode-mode PMOS and NMOS coupled with adjustable and fixed resistors, allowing for controlled impedance matching through series connections and switch-controlled resistor units, reducing load effects on IO pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed resistors are used in the OCD driver structure, then the impedance can be maintained, but the IO pad bears huge loading effect causing signal transmission distortion
Solution Approach 1:
The patent extracts the resistor from the IO pad connection and places it inside the OCD driver circuit. Specifically, the resistor is connected between the drain of the output transistor and the IO pad, but the IO pad no longer directly bears the loading effect of the resistor combined with all MOS capacitances. This separation reduces the harmful capacitance loading on the IO pad while maintaining the impedance function.
Solution Approach 2:
The patent introduces adjustable resistors that can dynamically change their resistance values based on different operating conditions. The resistance adjustment mechanism allows the driver to adapt to different channel characteristics and impedance requirements, optimizing signal transmission quality under varying conditions while managing capacitance loading effects.
2Power
If multiple MOSs are used in the pull-up and pull-down drivers, then the driving capability is enhanced, but the capacitance loading on the IO pad increases causing signal degradation
Solution Approach 1:
The patent extracts the resistive loading element from the direct IO pad path and relocates it within the driver circuitry. By placing the resistor inside the OCD driver rather than having it directly load the IO pad, the harmful capacitance effect is reduced while the driving capability provided by multiple MOS transistors is preserved.
3Manufacturing precision
If fixed resistors are used for impedance matching, then the channel impedance can be controlled, but the impedance mismatching issues among different DQ channels cannot be resolved
Solution Approach 1:
The patent introduces adjustable resistors with resistance values that can be dynamically changed based on channel-specific requirements. Each DQ channel can have its impedance independently tuned by adjusting the corresponding resistor value, allowing compensation for manufacturing variations and achieving consistent impedance matching across all channels.
Solution Approach 2:
The patent applies different resistance values to different DQ channels based on their individual characteristics. Instead of using a uniform fixed resistor value for all channels, the system allows each channel to have locally optimized resistance settings, addressing the impedance mismatching issues caused by manufacturing process variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces signal loss and distortion during high-speed transmission by minimizing capacitance loading on IO pads, thereby improving signal integrity and matching impedance across DQ channels.
Implementation Method 1
a first triode-mode PMOS coupled between the first PMOS and at least one of one or more first adjustable resistors
Data Source
AI summary
This invention provides a resistance-adjustable means using at a pull-up driver and/or a pull-down driver of an OCD circuit. When the resistance-adjustable means is applicable to the pull-up driver, the resistance-adjustable means includes a triode-mode PMOS coupled to a circuit of the pull-up driver and at least one of one or more adjustable resistors and/or a fixed resistor, which are connected in series and coupled to the triode-mode PMOS, and the at least one of the adjustable resistors or the fixed resistor is coupled to an IO (input/output) pad. When the resistance-adjustable means is applicable to the pull-down driver, a triode-mode NMOS is used to replace the triode-mode PMOS for the resistance-adjustable means.