Clock Network State-Transition Gating for Dynamic Power Reduction
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Solution Overview
Problem
Existing clock gating methods are inefficient in managing power consumption in sequential circuit designs with high clock loading, as they either disable entire blocks or domains, leading to increased dynamic power dissipation due to higher switching capacitance.
Innovation Solution
State Transition Gating (STG) dynamically gates clock signals for groups of sequential elements based on data transitions, enabling finer granularity in power management by disabling local clock networks when data remains unchanged, using XNOR and NAND gates to control clock distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional clock gating methods disable entire blocks or domains, then power consumption is reduced, but dynamic power dissipation increases due to higher switching capacitance
Solution Approach 1:
The patent divides the clock network into hierarchical levels (global clock network and local clock networks), allowing selective gating of local networks while maintaining global clock distribution. This segmentation enables finer-grained power management where only specific local networks are disabled when their associated sequential elements have unchanged data, rather than disabling entire blocks or domains.
Solution Approach 2:
The patent implements state transition gating at the local clock network level, where each local network can be independently gated based on the data transition status of its associated sequential elements. This local quality approach allows different parts of the circuit to have different clock gating states simultaneously, optimizing power consumption without causing widespread switching activity.
2Reliability
If clock signals are continuously distributed to all sequential elements, then data transition reliability is maintained, but dynamic power consumption increases
Solution Approach 1:
The patent implements dynamic clock gating control where the gating state of local clock networks is continuously adjusted based on real-time data transition detection. The system dynamically enables or disables clock signals to sequential elements based on whether their input data has changed, ensuring reliable data transitions only when necessary while minimizing unnecessary clock activity and power consumption.
Solution Approach 2:
The patent uses feedback mechanisms where the output of XNOR gates (comparing current and previous data states) controls the gating of local clock networks. This feedback ensures that clock signals are maintained when data transitions are detected (ensuring reliability) and gated when no transitions occur (reducing power consumption).
3Adaptability or versatility
If finer granularity clock gating is implemented, then power management precision is improved, but circuit complexity increases
Solution Approach 1:
The patent implements a nested hierarchical structure where local clock networks are nested within functional blocks, and each local network is controlled by its own state transition gating logic. This nesting allows the system to achieve fine-grained power management by controlling individual local networks while maintaining a manageable overall structure through the hierarchical organization of clock distribution.
4Loss of energy
If local clock networks are dynamically gated, then leakage power is reduced, but clock network switching activity increases
Solution Approach 1:
The patent implements periodic evaluation of data transition status through the XNOR gate logic that continuously compares current and previous data states. This periodic action allows the system to detect when data has changed and accordingly enable or disable local clock networks, reducing leakage power during stable periods while maintaining necessary clock activity when data transitions occur, without causing excessive switching activity.
Data Source
AI summary
An integrated circuit (IC) is described. The IC includes a clock distribution network for distributing a clock signal. The IC includes a first sequential circuit having a clock input to receive the clock signal to generate an output. The output of the first sequential circuit is coupled to an input of a first logic group comprising combinatorial logic circuitry. The IC also includes first circuitry to compare logic states of the input and the output and to inhibit the clock signal from propagating to the clock input if the logic states are the same. The IC also includes a second sequential circuit having a second clock input to receive the clock signal to generate a second output. The second output of the second sequential circuit is coupled to an input of a second logic group comprising combinatorial logic circuitry. The IC also includes second circuitry to compare logic states of the input and the output of the second sequential circuit and to inhibit the clock signal from propagating to the second sequential circuit if the logic states are the same.