High-Density Latch Arrays for Register File Implementation
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Solution Overview
Problem
Conventional SRAM cells face challenges in sub-micron technologies due to transistor variations, leading to operational issues and increased complexity in power delivery and energy consumption, particularly in deeply scaled CMOS fabrication processes.
Innovation Solution
The implementation of high-density latch cells with a transmission gate, pair of inverters, and an output buffer, which allows for a smaller footprint and reduced energy consumption by decoupling internal nodes from external outputs during read and write operations, eliminating the need for relative transistor strength reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional 6T SRAM cells are used, then fast on-chip storage is achieved, but device complexity increases due to reliance on precise transistor strength matching
Solution Approach 1:
The patent extracts the problematic transistor strength matching requirement from the SRAM cell design by using a latch-based architecture with transmission gates. The latch cell structure separates the storage function from the access function, eliminating the need for precise transistor sizing and matching that plagues conventional 6T SRAM cells.
Solution Approach 2:
The invention changes the fundamental operating parameters of the memory cell by transitioning from a static latch-based design to a dynamic SRAM design. This involves changing the access mechanism from transmission gate control to word line-driven MOSFET switching, and altering the storage mechanism from level-triggered latch to edge-triggered flip-flop behavior.
2Reliability
If SRAM cells operate at higher supply voltage to ensure reliable operation, then operational reliability improves, but energy consumption increases
Solution Approach 1:
The patent introduces dynamic operation to the memory cell by using clocked transmission gates and enable signals. The latch cell transitions between transparent and opaque states dynamically, allowing the cell to operate reliably at lower supply voltages by controlling when data is captured and held, rather than requiring continuous high-voltage operation.
Solution Approach 2:
The invention employs periodic clocking signals to control the transmission gates and enable periodic sampling of data. This periodic action allows the memory cell to operate reliably during specific time windows when the transmission gates are enabled, reducing the need for continuously high supply voltage and thereby lowering overall energy consumption.
3Stability of the object's composition
If transistor sizes are increased to compensate for manufacturing variations, then operational stability improves, but die area increases
Solution Approach 1:
The patent uses a replicated latch structure where the storage function is achieved through cross-coupled feedback paths rather than relying on individual transistor characteristics. This copying approach distributes the stability requirement across multiple identical components rather than demanding high precision from each individual transistor, allowing smaller device sizes while maintaining operational stability.
4Reliability
If redundancy and error-correction codes are implemented to handle failed bits, then reliability improves, but device complexity and storage density decrease
Solution Approach 1:
The patent builds inherent fault tolerance into the latch cell design itself through cross-coupled feedback and complementary transistor pairs. This beforehand cushioning approach prevents single-transistor failures from propagating, eliminating the need for external redundancy circuits and error-correction codes, thereby maintaining high density while ensuring reliability.
Data Source
AI summary
A system and device are provided for implementing memory arrays using high-density latch cells. The device includes an array of cells arranged into columns and rows. Each cell comprises a latch cell that includes a transmission gate, a pair of inverters, and an output buffer. Each row of latch cells is connected to at least one common node for addressing the row of latch cells, and each column of latch cells is connected to a particular bit of an input signal and a particular bit of an output signal. A register file may be implemented using one or more arrays of the high-density latch cells to replace any or all of the banks of SRAM cells typically used to implement the register file.