Oxide Semiconductor Holding Circuit for Power Gating Data Retention
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Solution Overview
Problem
Existing semiconductor devices face challenges in reducing power consumption while maintaining data holding capabilities, particularly when power gating is employed, as conventional flip-flop circuits lose their state when powered off.
Innovation Solution
A holding circuit incorporating oxide semiconductor transistors with extremely low off-state current, which includes a capacitor for data retention and switches to control data input and output, allowing data to be held even when the device is powered off, thereby reducing power consumption and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power gating is applied to reduce power consumption, then power consumption is reduced, but data holding capability is lost
Solution Approach 1:
The invention segments the power supply system into two independent power supply potentials (first power supply potential and second power supply potential), allowing selective powering of different circuit components. The holding circuit can be powered by the first potential while other circuits are powered by the second potential, enabling independent power control that preserves data during power gating.
Solution Approach 2:
The invention introduces a capacitor as an intermediary energy storage element in the holding circuit. This capacitor maintains the electrical charge representing stored data even when the main power supply is cut off, acting as a mediator that bridges the gap between power interruption and data retention requirements.
2Reliability
If conventional flip-flop circuits are used, then data holding is maintained during operation, but power consumption increases when powered on
Solution Approach 1:
The invention employs periodic action through the use of switches that periodically connect and disconnect power supply to the holding circuit. During normal operation, the circuit is powered and can read/write data; during power gating, power is periodically cut off while the capacitor maintains data, reducing power consumption while preserving data holding capability.
3Use of energy by moving object
If oxide semiconductor transistors are used for low off-state current, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The invention changes the material parameter of the transistor semiconductor layer from conventional semiconductor materials to oxide semiconductor materials. This parameter change fundamentally reduces the off-state current by several orders of magnitude, enabling ultra-low power operation while maintaining the same basic circuit architecture and avoiding significant increases in device complexity.
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
The proposed solution enables reduced power consumption and zero area or performance overhead for semiconductor devices by effectively holding data during power gating, allowing for efficient data retention and quick restoration without increasing the number of power supply potentials.
Implementation Method 1
By taking advantage of an extremely low off-state current of a transistor whose semiconductor region is formed using an oxide semiconductor layer
Implementation Method 2
A holding circuit including an OS transistor, leading to power gating of the FF
Data Source
AI summary
A holding circuit includes first to third input terminals, an output terminal, first to third switches, a capacitor, and a node. The first to third switches control conduction between the node and the first input terminal, conduction between the node and the output terminal, and conduction between the second input terminal and the output terminal, respectively. First and second terminals of the capacitor are electrically connected to the node and the third input terminal, respectively. The first to third switches are each a transistor comprising an oxide semiconductor layer comprising a semiconductor region. Owing to the structure, a potential change of the node in an electrically floating state can be suppressed; thus, the holding circuit can retain its state for a long time. The holding circuit can be used as a memory circuit for backup of a sequential circuit, for example.