SRAM Keeper Area Reduction via Shared Current Limiter
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Solution Overview
Problem
Conventional SRAM circuits require a large area for long-channel transistors in keepers, which increases the overall size of the memory circuit, and existing solutions do not effectively address this space efficiency issue.
Innovation Solution
The integration of a current limiter shared among multiple keepers, where each keeper uses a smaller core transistor, reducing the area required for the keepers and subsequently the entire memory circuit, while maintaining efficient data sensing and precharging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long-channel transistors are used in keepers, then data retention reliability is improved, but the area occupied by keepers increases
Solution Approach 1:
Multiple keepers share a common current limiter circuit, merging the current limiting function across multiple memory cells. This allows each keeper to use smaller transistors while the shared current limiter provides the necessary current control for data retention, thereby reducing total keeper area while maintaining reliability
Solution Approach 2:
The current limiter serves multiple functions: it limits current for data retention in each memory cell, enables sensing operations, and provides precharging functionality. This multi-functionality allows smaller transistor sizes in keepers while maintaining the required performance through the shared current limiting mechanism
2Area of stationary object
If smaller transistors are used in keepers, then area efficiency is improved, but sensing capability may be compromised
Solution Approach 1:
The current limiter acts as an intermediary mechanism that compensates for the reduced transistor size in keepers. By controlling the current flow through the keepers, the current limiter enables smaller transistors to achieve the same sensing capability as larger transistors would provide alone, thus improving area efficiency without compromising sensing
Solution Approach 2:
The sensing capability is achieved by combining the action of multiple keepers with the shared current limiter. The collective effect of multiple smaller keepers under current limiter control provides sufficient sensing capability, allowing area reduction while maintaining performance
Data Source
AI summary
A circuit including a memory circuit, the memory circuit includes a first plurality of memory arrays and a first plurality of keepers, each keeper of the first plurality of keepers is electrically coupled with a corresponding one of the first plurality of memory arrays. The memory circuit further includes a first current limiter electrically coupled with and shared by the first plurality of keepers.