Asymmetric Sense-Amp Flip-Flop for Zero Setup Time
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Solution Overview
Problem
In digital systems, timing delays in flip-flops such as clock-to-Q time, setup time, and hold time contribute to lower circuit operating frequencies as operating frequencies increase, necessitating the reduction of these delays.
Innovation Solution
The Asymmetric Sense-Amp Flip-Flop (ASAFF) achieves zero setup time and short clock-to-Q times by pre-charging nodes and using asymmetric master and slave circuits with delay-dependent responses to input data, allowing for the incorporation of combinatorial logic and balancing delays to maintain the relationship between different hold times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional flip-flop architectures are used, then circuit reliability is maintained, but timing delays (setup time, clock-to-Q time, hold time) increase, reducing circuit operating frequency
Solution Approach 1:
The flip-flop is divided into separate master and slave circuits with distinct functions. The master circuit captures data on the active clock edge, while the slave circuit transfers it to outputs on the inactive edge. This segmentation allows independent optimization of each circuit's timing characteristics, reducing overall timing delays and enabling higher operating frequencies.
Solution Approach 2:
The circuit employs pre-charging of internal nodes before the active clock edge arrives. By pre-establishing voltage levels on storage nodes, the circuit eliminates setup time requirements, as the nodes are already prepared to respond immediately to the incoming data signal when the clock transitions.
2Loss of time
If asymmetric delay paths are implemented to achieve zero setup time, then setup time is reduced, but device complexity increases
Solution Approach 1:
The patent implements asymmetric delay paths within the master and slave circuits, where different internal nodes experience deliberately unequal delays. This asymmetry is engineered to balance the overall timing, allowing one path to achieve zero setup time while another path compensates with extended hold time, thereby resolving the timing contradiction without requiring complete circuit redesign.
Solution Approach 2:
The circuit utilizes controllable delay elements that can adjust their delay characteristics based on operating conditions. By dynamically modifying delay parameters in response to clock transitions and data values, the circuit achieves zero setup time for critical paths while maintaining adequate hold time for non-critical paths, effectively managing complexity through adaptive parameter control.
3Manufacturing precision
If multiple delay elements are added to balance timing paths, then timing precision is improved, but device complexity increases
Solution Approach 1:
Delay elements are strategically placed only in specific locations where timing balancing is critical. Rather than uniformly adding delay throughout the circuit, the patent applies delay elements locally to specific paths that require timing adjustment, thereby achieving precise timing control with minimal additional complexity.
Data Source
AI summary
An Asymmetric Sense-Amp Flip-Flop (ASAFF) is disclosed that may achieve zero setup time and short clock-to-Q delays. The ASAFF captures input data at a clock transition by setting values of a first node and a second node in a manner that is input data value dependent. If the input data is at the first input data value, the first node is set and held at a first storage value after a first delay, and the second node is set and held at a second storage value after a second delay, and if the input data is at a second input data value, the first node is set and held at a third storage value after a third delay, and the second node is set and held at a fourth storage value, after a fourth delay. This internal-path dependent difference in delay enables ASAFF to achieve zero setup time.