Sense Amplifier Bootstrap Write Assist for SRAM Arrays
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Solution Overview
Problem
The semiconductor industry faces challenges in designing SRAM cells that are both stable and fast, as device scaling issues lead to increased power consumption and leakage, particularly in larger arrays where long wires require larger devices, affecting write ability and stability.
Innovation Solution
A method and circuit for implementing sense amplifiers with bootstrap write assist for SRAM arrays, using a sense amplifier in both read and write operations, along with limited swing drivers and a write assist boost circuit, to reduce device area and leakage, and enable full transmission gate data driving, thereby improving SRAM cell write ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If larger devices are used to drive long data lines in larger SRAM arrays, then the data lines can be driven to full rail, but power consumption increases and device leakage increases
Solution Approach 1:
The patent segments the data driving function by introducing local write drivers at each SRAM cell that only need to drive local bit lines rather than global data lines. This segmentation allows smaller devices to be used locally, reducing power consumption while maintaining drive capability for the local region.
Solution Approach 2:
The patent introduces sense amplifiers as intermediary components between the global data lines and local bit lines. These sense amplifiers receive data from global lines and amplify it for local driving, eliminating the need for large devices all along the data path and reducing overall power consumption.
2Speed
If larger devices are used to drive long data lines in larger SRAM arrays, then the data lines can be driven to full rail, but device leakage increases
Solution Approach 1:
The patent segments the data driving function by introducing local write drivers at each SRAM cell that only need to drive local bit lines rather than global data lines. This segmentation allows smaller devices to be used locally, reducing power consumption while maintaining drive capability for the local region.
Solution Approach 2:
The patent introduces sense amplifiers as intermediary components between the global data lines and local bit lines. These sense amplifiers receive data from global lines and amplify it for local driving, eliminating the need for large devices all along the data path and reducing overall power consumption.
3Stability of the object's composition
If SRAM cell is skewed to be more stable, then stability improves, but write ability deteriorates
Solution Approach 1:
The patent changes the parameter of write assist by introducing a boost circuit that temporarily modifies the voltage conditions during write operations. This allows the SRAM cell to maintain its stable skewed design while the boost circuit provides the additional drive strength needed for successful writes.
Solution Approach 2:
The patent makes the sense amplifier work continuously in both read and write operations, eliminating the need for separate dedicated write circuits. This continuous operation allows the same stable skewed cell design to be used for both reading and writing, with the write assist boost providing necessary support during write operations.
4Area of stationary object
If sense amplifier is used in both read and write operations, then device area and leakage are reduced, but circuit complexity increases
Solution Approach 1:
The patent makes the sense amplifier universal by enabling it to perform both read and write operations. This multi-functionality eliminates the need for separate dedicated write circuits, reducing overall device area and leakage despite the added complexity of making the sense amplifier handle both functions.
Data Source
AI summary
A method and circuit for implementing sense amplifiers for sensing local write driver with bootstrap write assist for Static Random Access Memory (SRAM) arrays, and a design structure on which the subject circuit resides are provided. The circuit includes a sense amplifier used in both read and write operations with a write assist boost circuitry. The sense amplifier captures and amplifies write data at a selected SRAM cell column and drives the write data onto local bit lines. The write assist boost circuitry temporarily supplies an increased device voltage differential to the SRAM cell during write operations to significantly increase SRAM cell write ability.