SRAM Word Line Voltage Control for Single Power Supply Access
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Solution Overview
Problem
As semiconductor devices miniaturize, SRAM cells experience increased element variations, leading to deteriorated reading and writing characteristics, necessitating additional power supplies to maintain performance, which increases circuit size and complexity.
Innovation Solution
A semiconductor storage device with a word line control circuit that manages voltage levels of control signals to activate SRAM cells using a single power supply, employing a drive capability control circuit and voltage-boosted power supply to achieve stable operations by controlling voltage levels in three activation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistor size is increased to reduce element variations, then reading and writing characteristics are improved, but SRAM cell size becomes larger
Solution Approach 1:
The patent changes the voltage parameter of the word line signal from a single level to two levels (first power supply potential and second power supply potential). By applying different voltage levels at different operation stages, the patent improves reading and writing characteristics without increasing transistor size, thus resolving the contradiction between reliability and cell size.
2Reliability
If two power supply potentials are used to control word line signals for stable access operations, then reading and writing characteristics are improved, but the number of power supplies increases from one to two
Solution Approach 1:
The patent merges the functions of two separate power supplies into a single power supply by using a voltage conversion circuit. The voltage conversion circuit converts the single power supply potential to generate both the first and second power supply potentials needed for word line control, thus reducing the number of power supplies while maintaining operation stability.
Solution Approach 2:
The voltage conversion circuit acts as an intermediary between the single power supply and the word line control circuit. It converts the single power supply potential into the required two-level voltage signals, enabling the word line to operate with two voltage levels without requiring two separate power supplies.
3Reliability
If three different power supplies are supplied to improve both reading and writing characteristics, then data retention characteristic is improved, but circuit size and complexity increase
Solution Approach 1:
The patent merges multiple power supply functions into a single power supply system. By using a voltage conversion circuit that generates both the first and second power supply potentials from a single power supply, the patent achieves improved data retention characteristics without increasing the number of power supplies or circuit complexity.
Data Source
AI summary
A semiconductor storage device in accordance with the present invention includes a first SRAM cell that stores data, and a word line circuit that outputs a first control signal used to activate the first SRAM cell. The word line control circuit gradually raises the voltage level of the first control signal from a substrate potential to a first power supply potential in a first activation period, maintains the voltage level of the first control signal at the first power supply potential in a second activation period subsequent to the first activation period, and raises the voltage level of the first control signal from the first power supply potential to a second power supply potential in a third activation period subsequent to the second activation period.