Integrated Circuit Power Gating Distribution Network
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Solution Overview
Problem
Existing power gating techniques in integrated circuits face challenges in reducing leakage current, particularly when using distribution networks, as they often require both gated supply and ground rails, which increase power routing overhead and are difficult to implement, especially in general-purpose processors, and can lead to floating output voltages affecting correct operation.
Innovation Solution
The solution involves a distribution network with two subsets of circuit elements, where those pulling their outputs to the first voltage level remain connected to the main supply rails, and those pulling their outputs to the second voltage level are connected to a gated supply rail, ensuring the static value is maintained during power gating without contributing to leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power gating techniques are used to remove power supply to reduce leakage current, then leakage current is reduced, but output voltage may float to intermediate levels causing incorrect operation
Solution Approach 1:
The patent introduces distribution networks as intermediary circuits that provide predetermined static values to power-gated circuit elements. These distribution networks act as mediators between the power supply and the gated circuits, ensuring that even when power is removed to reduce leakage, the output voltages are maintained at valid logic levels through the static values provided by the distribution networks, preventing floating outputs and incorrect operation.
2Reliability
If distribution networks are powered during power gating mode to maintain static values, then correct operation is ensured, but leakage current increases
Solution Approach 1:
The patent segments the distribution network into multiple subsets of circuit elements. Some subsets are connected to gated power supply rails and are powered off during power gating mode, while other subsets remain connected to ungated rails and stay powered. This segmentation allows the system to maintain correct operation through the powered subsets while minimizing leakage current by powering off other subsets that don't critical path static values.
Solution Approach 2:
Different portions of the distribution network are assigned different power supply connections based on their specific functional requirements. Circuit elements that must maintain static values are connected to ungated rails and remain powered, while other elements are connected to gated rails and are powered off. This local differentiation of power supply quality allows the system to optimize between reliability and energy loss on a element-by-element basis.
3Loss of energy
If both gated supply rail and gated ground rail are used as in zig-zag power gating, then leakage current is reduced and floating outputs are prevented, but device complexity and routing overhead increase
Solution Approach 1:
The patent extracts and removes the gated ground rail component from the zig-zag power gating approach, retaining only the gated supply rail. By taking out the unnecessary gated ground rail, the patent simplifies the power routing infrastructure while still achieving leakage current reduction through the gated supply rail combined with the segmented distribution network approach. This reduces device complexity and routing overhead compared to full zig-zag implementation.
Data Source
AI summary
An integrated circuit has a first and second voltage supply rails with first and second voltage levels and a gated voltage supply rail. Each of the circuit elements is connected either between the first and second voltage supply rails or between the gated rail and the second voltage rail. A source circuit structure comprising one or more circuit elements provides an input signal maintained at a static value during a power gated mode of operation. At least one recipient circuit structure requires receipt of the input signal at the static value during the power gated mode of operation. A distribution network comprises a first subset of circuit elements which pull their output to the first voltage level then the input signal has the static value, and a second subset of circuit elements which pull their output to the second voltage level when the input signal has the static value.