Master-Slave Flip-Flop Layout for Low-Voltage Hold Stability
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Solution Overview
Problem
Existing master-slave flip-flop memory circuits face challenges in maintaining low voltage nominal hold and variability characteristics, leading to erratic transistor behavior and increased power consumption, which can result in thermal failures and spurious signals.
Innovation Solution
A re-architectured transistor layout is introduced, reducing the number of transistors in the nominal hold critical path by coupling the input of the master latch to a low output of the test switch around a partial pass gate, and using a specific inverter configuration to improve low voltage nominal hold and variability without increasing circuit area or dynamic power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the source voltage is decreased to prevent thermal failure, then power consumption is reduced, but transistor behavior becomes more erratic as threshold voltage approaches source voltage
Solution Approach 1:
The patent changes the structural parameters of the flip-flop circuit, specifically reducing the number of transistors in the critical path from 6 to 4 transistors. This structural parameter change allows the circuit to maintain reliable transistor behavior at lower source voltages by reducing the cumulative effect of threshold voltage variations across multiple transistor stages.
Solution Approach 2:
The patent segments the flip-flop circuit into distinct functional blocks (master latch, slave latch, test switch) with optimized transistor arrangements in each segment. The master latch uses a specific 2-transistor configuration that minimizes the impact of threshold voltage variations, allowing the overall circuit to operate reliably at lower voltages.
2Productivity
If switching speed is increased to improve productivity, then power consumption increases, but thermal failure risk increases
Solution Approach 1:
The patent optimizes the transistor count and arrangement parameters to achieve a balance between switching speed and power consumption. By using exactly 4 transistors in the critical path with specific connectivity, the circuit achieves adequate switching speed while minimizing dynamic power consumption proportional to the number of switching elements.
3Reliability
If the number of transistors in the critical path is reduced to improve low voltage hold, then circuit area is reduced, but manufacturing precision requirements may increase
Solution Approach 1:
The patent employs asymmetric transistor arrangements within the master and slave latches, where transistors are deliberately positioned with different connectivity patterns rather than symmetric configurations. This asymmetric design optimizes the voltage transfer characteristics and hold behavior at low voltages while maintaining robustness against manufacturing variations through careful asymmetry management.
Data Source
AI summary
The present disclosure is directed to a master-slave flip-flop memory circuit having a partial pass gate transistor at the input of the master latch. The partial pass gate transistor includes a pull-up clock enabled transistor for selectively coupling a high output of a test switch to the input of the master latch. The input of the master latch is also directly coupled to a low output of the test switch around the partial pass gate. In addition, a revised circuit layout is provided in which the master latch has three inverters. A first inverter is coupled to the input of the master latch. Second and third inverters are coupled to an output of the first inverter, with the second inverter having an output coupled to the input of the first inverter, and the third inverter having an output coupled to an output of the master latch. The first and second inverters are clock enabled, and the third inverter is reset enabled.