Regional Clock Gating With Dithering for Idle Power Savings
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Solution Overview
Problem
Integrated circuits face challenges in power management during idle periods, as existing clock-gating techniques either fully gate the clock signal, leading to inactivity or fail to efficiently save power when functional units are expected to resume operations after latency periods.
Innovation Solution
The implementation of a clock signal dithering method, where the duty cycle and effective frequency of the clock signal are reduced during idle times, allowing functional units to remain active while minimizing power consumption in the clock tree, using a control unit that monitors activity levels and periodically asserts and de-asserts the clock enable signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the clock signal is fully gated during idle periods, then power consumption is reduced, but the functional units cannot resume operations quickly when needed
Solution Approach 1:
The patent applies periodic action by dithering the clock signal at a reduced duty cycle (e.g., 10% or 20%) during idle periods instead of fully gating it. This periodic presence of clock edges maintains the functional units in an active state while significantly reducing power consumption in the clock tree, allowing rapid resumption of operations when needed.
Solution Approach 2:
The patent changes the parameter of the clock signal from full duty cycle to reduced duty cycle (dithering) during idle periods. This parameter change maintains the clock signal's presence to keep functional units active while reducing the energy consumption proportionally to the reduced duty cycle, resolving the contradiction between power savings and operational readiness.
2Reliability
If the clock signal continues at full frequency, then functional units remain fully active and responsive, but power consumption increases
Solution Approach 1:
Instead of continuous full-frequency clock signaling, the patent uses periodic dithering at reduced duty cycles during idle periods. This maintains operational readiness through periodic clock edges while reducing power consumption to a fraction of the continuous full-frequency operation.
Solution Approach 2:
The patent applies partial action by providing clock edges at reduced duty cycles (e.g., 10-20%) rather than continuous full-frequency operation. This partial clocking is sufficient to maintain functional unit readiness while consuming significantly less power than full-frequency continuous operation.
3Loss of energy
If clock-gating logic is added at leaf nodes to save power, then power consumption is reduced during idle times, but device complexity increases
Solution Approach 1:
The patent segments the clock tree into regional clock-gating circuits that can independently control clock distribution to different functional units. This segmentation allows power-saving gating at the regional level without requiring complex logic at every leaf node, reducing overall device complexity while maintaining power savings.
Solution Approach 2:
The regional clock-gating circuits serve multiple functions: they can fully gate the clock signal when functional units are completely idle, and they can dither the clock signal at reduced duty cycles when units are in latency states. This multi-functionality reduces the need for separate control mechanisms, simplifying the overall device complexity.
Data Source
AI summary
A system and method for dithering a clock signal during idle times is disclosed. An integrated circuit (IC) includes a number of functional units and a clock tree. The clock tree includes a root level clock-gating circuit, a number of regional clock-gating circuits, and a number of leaf level clock-gating circuits. The root level clock-gating circuit is coupled to distribute an operating clock signal to the regional clock-gating circuits, while the regional clock-gating circuits are each configured to distribute the operating clock signal to correspondingly coupled ones of the leaf level clock-gating circuits. The IC may further include a control unit configured to monitor activity levels and indications from each of the functional units. The control unit may cause the root clock-gating circuit to dither the clock signal if the IC is idle, wherein dithering includes reducing the duty cycle and the effective frequency of the operating clock signal.