Word Line Driver Circuit Precharge for Memory Speed
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Solution Overview
Problem
In semiconductor memory apparatuses, a large number of selection devices coupled to a word line increases the time constant (tau=R*C), leading to longer times required to turn on all selection devices and form current paths to memory cells, which affects read and write operations.
Innovation Solution
A word line driver circuit comprising a driving unit, transmission unit, and precharge unit that outputs and transmits a sub word line driving signal in response to a word line select signal and main word line driving signal, with a precharge unit precharging the potential of the word line to quickly drive selection devices, and a resistance variable memory apparatus with a row selection unit that decodes row addresses and supplies the sub word line driving signal to the word line, reducing the parasitic resistance and time constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the size of a word line driver is small and the number of selection devices to drive is large, then the device complexity is reduced, but the time constant (tau=R*C) increases leading to longer turn-on time
Solution Approach 1:
The patent divides the word line driver into a main word line driver and a sub word line driver. The main driver generates a main word line driving signal, which is then processed by the sub driver to generate sub word line driving signals. This segmentation allows the system to drive a large number of selection devices without requiring an excessively large single driver, thus reducing device complexity while maintaining fast turn-on time.
Solution Approach 2:
The patent introduces a precharge unit that precharges the potential of the word line before the sub word line driving signal is applied. This preliminary action reduces the time constant (tau=R*C) by preparing the word line in advance, enabling faster turn-on of selection devices and reducing the overall turn-on time.
2Loss of time
If a precharge unit is added to precharge the word line potential, then the turn-on time of selection devices is reduced, but the device complexity increases
Solution Approach 1:
The precharge unit is integrated into the sub word line driver circuit rather than being implemented as a completely separate component. The precharge unit shares the same word line and is controlled by the same main word line driving signal, merging its function with the existing driver structure. This approach reduces the turn-on time by precharging the word line while minimizing the increase in device complexity through functional integration.
Data Source
AI summary
A word line driver circuit according to an embodiment includes a driving unit configured to output a sub word line driving signal in response to a word line select signal and a main word line driving signal, a transmission unit configured to transmit the sub word line driving signal to a word line in response to a first enable signal, and a precharge unit configured to precharge a potential of the word line.