Shared Clock-Switch Multi-Bit Flip-Flops for Lower Power
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Solution Overview
Problem
Conventional digital logic circuits with flip-flops face significant power consumption due to frequent clock signal switching, and existing techniques to reduce this often increase circuit area or lead to performance penalties such as increased set-up or hold times and unstable operation.
Innovation Solution
Implementing inter-cell and intra-cell clock switch sharing in multi-bit flip-flops to reduce the number of clock switches, allowing for lower power consumption and smaller layout size while maintaining performance and avoiding logic contention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional flip-flops use separate clock switches for each stage, then reliable clock signal control is achieved, but power consumption increases due to frequent clock signal switching
Solution Approach 1:
The patent merges clock switches across multiple flip-flop cells by sharing clock switch pairs between adjacent cells. Specifically, the clock switch pair (SP4, SN4) of the first flip-flop cell is shared with the clock switch pair of the second flip-flop cell, reducing the total number of clock switches while maintaining proper clock signal distribution to all stages.
Solution Approach 2:
The shared clock switch pair serves multiple functions simultaneously: it controls both the master and slave latches of the first flip-flop cell and the master and slave latches of the second flip-flop cell. This multi-functional approach allows a single clock switch pair to replace what would traditionally require separate clock switches for each cell.
2Area of stationary object
If more clock switches are used to control each flip-flop stage, then stable operation is achieved, but circuit area increases
Solution Approach 1:
Adjacent flip-flop cells are merged in terms of clock switch resources, where the clock switch pair at the boundary between cells is shared. This merging reduces the total count of clock switches and consequently reduces the layout area while maintaining stable operation through proper clock signal phasing.
3Loss of energy
If clock switches are shared between flip-flop cells, then power consumption and area are reduced, but logic contention may occur
Solution Approach 1:
The shared clock switches control stages in a periodic, non-overlapping manner. During each clock cycle, the clock switches are activated in a specific sequence that ensures only one stage per clock edge is active, preventing logic contention. The clock signal phasing ensures that master and slave latches are controlled at different times, avoiding simultaneous activation that would cause contention.
Data Source
AI summary
A multi-bit flip-flop has first and second one-bit flip-flops. The multi-bit flip-flop employs inter-cell clock switch (CSW) sharing in which the first and second one-bit flip-flops share at least one clock switch. The multi-bit flip-flop may also employ intra-cell CSW sharing in which at least one of the first and second one-bit flip-flops shares at least one clock switch. The inter-cell CSW sharing enables implementation of multi-bit flip-flops with fewer clock switches and possibly fewer data devices, while reducing power consumption, including state retention power gating power reduction.