Power Gating Switch Cell Layout for In-Rush Current Equalization
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Solution Overview
Problem
The design of power gating circuits for integrated circuits faces challenges in setting the proper ratio of weak switches to strong switches, leading to unpredictable in-rush current peaks that can exceed safety thresholds, requiring redesign and re-routing, and causing potential damage due to localized current concentration.
Innovation Solution
The introduction of weak-strong switch cells and strong-only switch cells with similar footprints allows for flexible placement and 'hot swapping' during the design phase, enabling equalized in-rush current peaks without affecting routing or timing, and distributing weak switches to reduce current concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ratio of weak switch cells to strong switch cells is estimated inaccurately during design, then in-rush current peaks exceed safety thresholds, but redesigning the power gating circuit requires re-routing and timing analysis, increasing design complexity
Solution Approach 1:
The switch cells are segmented into weak switch cells and strong switch cells with distinct functions. Weak switch cells are used to control in-rush current during power-up, while strong switch cells provide full current capacity during normal operation. This segmentation allows independent optimization of each cell type's characteristics.
Solution Approach 2:
The invention changes the parameters of switch cells by creating different types (weak and strong) with different transistor sizes and current capabilities. By adjusting the ratio and distribution of these cell types, the in-rush current profile can be controlled without affecting the overall circuit functionality or requiring re-routing.
2Object-affected harmful factors
If weak switch cells are used to limit in-rush current, then current peaks are reduced, but the total current supply capability is insufficient during normal operation
Solution Approach 1:
Weak switch cells are activated first during power-up to preliminarily charge the internal power rail and limit in-rush current. After this preliminary action completes safely, strong switch cells are activated to provide full current supply capability. This sequential activation ensures both current protection and adequate power delivery.
Solution Approach 2:
The power gating circuit dynamically switches between weak and strong switch cell configurations. During power-up, weak cells are used to protect against in-rush current. During normal operation, strong cells are activated to meet full current demand. This dynamic reconfiguration allows the system to adapt its characteristics based on operational phase.
3Reliability
If the ratio of weak to strong switch cells is changed to optimize in-rush current, then current peaks are equalized, but re-routing connections and performing timing analysis are required
Solution Approach 1:
Both weak and strong switch cells share a universal interface and connection scheme to the power gating circuit. This universality allows the ratio of cell types to be adjusted for optimal in-rush current control without requiring changes to routing or timing analysis, as both cell types can be swapped in place of each other.
4Ease of manufacture
If switch cells are concentrated in one location, then routing is simplified, but localized current concentration causes potential damage
Solution Approach 1:
The invention applies local quality by distributing weak switch cells to specific locations where in-rush current control is most needed, while placing strong switch cells in locations optimized for current supply. This spatial distribution of different cell types with appropriate local characteristics prevents localized current concentration while maintaining routing simplicity through standardized interfaces.
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
A power gating circuit including a set of weak-strong switch cells and strong-only switch cells daisy chained together. Each of the weak-strong cell is layout (footprint) compatible with the strong-only cell such that swapping a weak-strong cell for a strong-only cell or vice-versa during the design phase of the power gating circuit does not affect routing to or the timing operation of the circuit to which the power gating circuit supplies power. This allows the ratio of weak to strong switches for minimizing in-rush currents to be optimally set during the design phase of an IC. Each of the weak-strong cells couples power rails together via a weak transistor in response to a weak enable signal, and via a strong transistor in response to a strong enable signal. Each of the strong-only cell couples the power rails together via weak and strong transistors in response to the strong enable signal.