Master-Slave Flip-Flop Layout for SEU-Hardened Slave Latches
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Solution Overview
Problem
Integrated circuit D flip-flops (DFFs) are prone to soft errors due to radiation effects from cosmic neutrons and terrestrial alpha particles, leading to increased Soft Error Rate (SER) and Failure In Time (FIT) rates, particularly due to mismatches in load at input and output nodes of the master latch.
Innovation Solution
A master-slave flip-flop design is implemented in an integrated circuit, where the slave latch is enhanced for Single-Event Upset (SEU) protection, and an inverter is strategically placed between the master and slave latches to optimize load distribution and minimize mismatch between '0' and '1' states, while the master latch remains non-enhanced for SEU protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the slave latch is enhanced for SEU protection, then the reliability against radiation effects is improved, but the device complexity increases
Solution Approach 1:
The flip-flop is divided into two distinct latches with different protection levels: a non-enhanced master latch and an SEU-enhanced slave latch. This segmentation allows selective application of complexity only where needed (in the slave latch), rather than protecting the entire flip-flop uniformly, thus improving reliability against SEU while controlling overall device complexity.
Solution Approach 2:
SEU protection enhancements are applied locally only to the slave latch rather than uniformly across the entire flip-flop structure. The master latch maintains a simpler, non-enhanced design, while the slave latch incorporates specific protective features (such as additional transistors or modified feedback paths) to resist single-event upsets, optimizing the balance between reliability and complexity.
2Reliability
If modifications are made to the slave latch to reduce failures, then the SEU protection is improved, but the load mismatch between input and output nodes increases
Solution Approach 1:
An inverter is introduced as an intermediary element between the master latch output and the slave latch input. This inverter acts as a buffer that helps balance the load conditions, compensating for the asymmetry introduced by SEU protection modifications in the slave latch, thereby maintaining better load matching and reducing harmful effects on productivity.
3Reliability
If the master latch is enhanced for SEU protection, then the overall SEU resistance is improved, but the clock-to-q delay increases
Solution Approach 1:
The flip-flop is segmented into master and slave latches with differentiated protection strategies. Only the slave latch receives SEU protection enhancements, while the master latch remains simple and fast. This segmentation ensures that the critical clock-to-q delay path (through the master latch) is not degraded, while still achieving adequate SEU resistance through the protected slave latch.
Solution Approach 2:
SEU protection is applied locally only to the slave latch portion of the flip-flop, leaving the master latch with its original fast, simple structure. This localized approach ensures that the time-critical master latch operations remain speedy, while the slave latch provides the necessary radiation hardness for reliable data storage and output.
Data Source
AI summary
A master-slave flip-flop implemented in an integrated circuit comprises a master latch coupled to receive data at an input; and a slave latch coupled to an output of the master latch, wherein the slave latch comprises an SEU-enhanced latch, and the master latch is not enhanced for SEU protection. A method of implementing a master-slave flip-flop in an integrated circuit is also described.