Local Write Receiver Circuit for SRAM Power and Variability
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Solution Overview
Problem
Static random access memory (SRAM) devices face challenges in reducing power consumption during write operations while maintaining process variability resilience and cell stability, with conventional methods leading to complex timing and increased power consumption.
Innovation Solution
The implementation of a memory device with hierarchical bit-lines and a non-strobed local write receiver using cross-coupled inverters to convert a reduced voltage swing on global bit-lines to a full voltage swing on local bit-lines, along with differential VSS biasing to mitigate process variations and reduce transistor count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If reduced voltage swing is used on global bit lines to save power, then power consumption is reduced, but write margin deteriorates
Solution Approach 1:
The bit line system is segmented into global bit lines operating at reduced voltage swing for power savings and local bit lines operating at full voltage swing for reliable writing. The local write receiver acts as an intermediary that converts between the two voltage levels, allowing each segment to operate optimally for its specific function.
Solution Approach 2:
The local write receiver serves as an intermediary device between the reduced swing global bit lines and the full swing local bit lines. It receives the low swing signal, converts it to full swing through its inverter circuitry, and drives the local bit lines, thereby preserving write margin while enabling reduced power consumption on the global lines.
2Reliability
If strobed local write receiver is used to convert reduced voltage swing to full voltage swing, then write margin is preserved, but device complexity increases
Solution Approach 1:
The strobe function is extracted from the local write receiver and implemented separately through the write enable signal that controls the connection mechanism. This allows the voltage conversion function to be simplified while maintaining the timing control needed for proper operation, reducing overall device complexity.
Solution Approach 2:
The connection mechanism between global and local bit lines is made dynamic through the write enable signal, which connects the lines only during the write operation. This dynamic connection allows the system to use simple inverters for voltage conversion while maintaining proper timing, as the conversion only needs to occur during the enabled window.
3Reliability
If conventional local write receiver is used, then voltage swing conversion is achieved, but power consumption increases
Solution Approach 1:
The local write receiver uses a pair of cross-coupled inverters that provide just enough gain to convert the reduced swing signal to full swing, without excessive amplification. This partial action approach achieves the necessary voltage conversion while minimizing the power consumed by the conversion circuitry itself.
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 approach reduces power consumption, enhances process variability resilience, and simplifies timing, achieving up to 10 times less energy consumption and 31% area overhead reduction compared to conventional methods, while maintaining write-ability and read performance.
Implementation Method 1
a pair of cross-coupled inverters directly connected to the complementary local bit lines for converting said reduced voltage swing, passed on by said connection mechanism, to said full voltage swing on said complementary local bit lines
Data Source
AI summary
A memory device having complementary global and local bit-lines, the complementary local bit-lines being connectable to the complementary global bit-lines by means of a local write receiver which is configured for creating a full voltage swing on the complementary local bit lines from a reduced voltage swing on the complementary global bit lines. The local write receiver comprises a connection mechanism for connecting the local to the global bit-lines and a pair of cross-coupled inverters directly connected to the complementary local bit lines for converting the reduced voltage swing to the full voltage swing on the complementary local bit lines.