Power Gating Switch Cell Layout for In-Rush Current Control
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Solution Overview
Problem
Existing power gating circuits face challenges in setting the optimal ratio of weak and strong switch cells, leading to inaccurate designs that require redesign and re-routing, affecting IC timing and routing, and causing potential damage due to localized current concentration.
Innovation Solution
The introduction of weak-strong and strong-only switch cells with similar footprints allows for flexible placement and swapping without affecting IC routing or timing, using dual enable signals to control the transition between weak and strong coupling modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ratio of weak switch cells to strong switch cells is estimated inaccurately in the design phase, then redesign and re-routing are required, but this increases design complexity and affects IC timing and routing
Solution Approach 1:
The patent makes the switch cell configuration dynamic by introducing enable signals that can transition switch cells between weak and strong modes during operation. This allows the ratio to be adjusted after fabrication without redesign, resolving the contradiction between accurate ratio estimation and design complexity.
Solution Approach 2:
The patent changes the operational parameters of switch cells by using enable signals to modify their coupling strength. This allows the same physical cell to function as either weak or strong depending on the enable signal state, eliminating the need for accurate pre-design ratio estimation and subsequent redesign iterations.
2Object-affected harmful factors
If weak switch cells are turned on first to limit in-rush current, then in-rush current peaks are reduced, but the power rail charges slowly and requires strong switch cells to be turned on later
Solution Approach 1:
The patent dynamically controls the coupling strength of switch cells during the power-up sequence. Weak coupling is applied initially to limit in-rush current, then the enable signal transitions to strong coupling to complete the charging, optimizing both current limitation and charging speed throughout the process.
Solution Approach 2:
The patent uses periodic enable signals to control the transition between weak and strong switch cell modes. This periodic activation allows the system to first limit in-rush current with weak coupling, then switch to strong coupling to complete the power rail charging efficiently.
3Object-affected harmful factors
If switch cells are swapped to achieve optimal ratio, then in-rush current is minimized, but re-routing and timing analysis are required which complicates the design
Solution Approach 1:
The patent makes each switch cell universal by enabling it to function as either weak or strong depending on the enable signal. This multi-functionality eliminates the need to swap cells to achieve the optimal ratio, as the same cells can be dynamically configured, greatly simplifying the design process.
Solution Approach 2:
The patent introduces dynamic control through enable signals that allow switch cells to transition between weak and strong modes. This dynamic configuration replaces the static cell swapping approach, eliminating re-routing and timing analysis requirements while still achieving optimal in-rush current minimization.
4Power
If strong switch cells are used to fully couple power rails, then total current demand is met, but in-rush current peaks increase and may damage the IC
Solution Approach 1:
The patent applies preliminary weak coupling through enable signals before full power connection to limit in-rush current peaks. This preliminary action protects the IC from damage, after which the enable signal transitions to strong coupling to meet the total current demand.
Solution Approach 2:
The patent dynamically adjusts the coupling strength of switch cells during the power-up sequence. Initially, weak coupling is applied to protect against in-rush current damage, then the enable signal transitions to strong coupling to satisfy the total current demand of the IC portion.
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.