Semiconductor Memory Device with Replica Cell Timing Control
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Solution Overview
Problem
Static random access memory (SRAM) devices face challenges in reducing power consumption and increasing operating speed due to high bit line amplitude and variation in cell current, especially when operated at low voltages, leading to unnecessary power consumption and inefficiencies.
Innovation Solution
A semiconductor memory device with a programmable replica cell array that adjusts the activation timing of sense amplifiers based on stored information for each row of the memory cell array, optimizing the timing for each word line to match the operating speed of memory cells and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the bit line amplitude is increased to ensure proper sensing, then the sensing accuracy is improved, but the power consumption increases
Solution Approach 1:
The sense amplifier is activated in advance before the bit line signal reaches the required amplitude level. The replica cell predicts the optimal activation timing based on stored characteristic information, allowing the sense amplifier to be ready exactly when needed, thus avoiding unnecessary power consumption while ensuring accurate sensing.
Solution Approach 2:
The replica cell uses feedback from the actual cell operation characteristics to adjust and store optimal timing information. By monitoring and comparing actual cell performance with stored characteristics, the system refines the activation timing to minimize power consumption while maintaining sensing accuracy.
2Use of energy by moving object
If the power supply voltage is decreased to reduce power consumption, then the energy efficiency is improved, but the cell current variation increases
Solution Approach 1:
Different rows of memory cells are assigned different sense amplifier activation timings based on their specific operating characteristics. This local optimization allows each row to operate at the optimal timing for its cell current characteristics, reducing overall power consumption while maintaining stable operation even when power supply voltage varies.
Solution Approach 2:
The system changes the timing parameter of sense amplifier activation based on stored characteristic information from replica cells. By adjusting this timing parameter according to actual cell performance, the system can maintain stable cell current operation across varying power supply voltages while reducing power consumption.
3Speed
If the sense amplifier activation timing is delayed to match the slowest cell, then the operating speed is improved for all cells, but the power consumption increases for faster cells
Solution Approach 1:
Each row is assigned a customized sense amplifier activation timing based on its specific cell speed characteristics. Faster cells in each row are activated at their optimal earlier timing, while the timing is adjusted for slower cells, allowing each row to operate at its optimal speed without causing unnecessary power consumption across the entire array.
Solution Approach 2:
The replica cell stores characteristic information about each row's operating speed in advance. This pre-stored information allows the sense amplifier activation timing to be optimized for each row before actual operation occurs, enabling faster cells to operate at their optimal speed while ensuring slower cells are also properly supported, thus reducing overall power consumption.
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes a memory cell array including memory cells, word lines connected to the memory cell array to select rows of the memory cell array, first bit lines connected to the memory cell array to select columns of the memory cell array, a replica cell array including replica cells respectively connected to the word lines, and storing information on characteristics of the rows of the memory cell array, and a second bit line connected to the replica cells. An operation is changed for each row of the memory cell array based on the information in the replica cells.