Output Driver Transistor Leg Cycling for Lower Electromigration
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Solution Overview
Problem
Integrated circuit output driver circuits face challenges in reducing electromigration in conductors due to high current congestion, which is exacerbated by process variations leading to faster or slower transistor operation, limiting the lifetime of conductors and degrading performance.
Innovation Solution
The output driver circuit employs a control circuit to periodically enable and disable subsets of transistor legs in a repeating cycle, reducing the overall current in conductors and distributing the load, thereby minimizing wear and extending conductor lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all transistor legs are enabled simultaneously to provide high output current, then output signal quality is maintained, but electromigration in conductors increases and conductor lifetime decreases
Solution Approach 1:
The control circuit enables different subsets of transistor legs in periodic phases, switching between them in a repeating cycle. This periodic activation distributes the current load over time, reducing the average current through each conductor and minimizing electromigration effects while maintaining adequate output signal quality.
Solution Approach 2:
The transistor legs are divided into multiple subsets that are controlled independently by the control circuit. Each subset is enabled during specific phases, segmenting the overall current load across multiple groups of transistors. This segmentation allows the circuit to maintain high output current capability while distributing the stress on individual conductors.
2Adaptability or versatility
If more transistor legs are enabled to handle process variations, then output signal quality is maintained across process corners, but current congestion in conductors increases
Solution Approach 1:
The control circuit dynamically adjusts which transistor legs are enabled based on operational phase, creating a time-varying configuration. This dynamic approach allows the circuit to adapt to process variations by ensuring adequate current driving capability is always available while preventing sustained high current density in any single conductor path.
Solution Approach 2:
Different subsets of transistor legs are activated in periodic phases to accommodate process variations. The control circuit ensures that sufficient transistor legs are enabled at any given time to maintain performance across process corners, while the periodic switching prevents cumulative current stress on individual conductors.
Data Source
AI summary
An output driver circuit includes a control circuit and first and second transistor legs that are coupled to an output pad. Each of the first and second transistor legs includes a pull-up transistor and a pull-down transistor. The control circuit is coupled to the first and second transistor legs. The control circuit enables the first transistor leg to generate an output signal at the output pad and disables the second transistor leg during a first phase of a cycle. The control circuit enables the second transistor leg to generate the output signal at the output pad and disables the first transistor leg during a second phase of the cycle. The control circuit repeats the first and the second phases of the cycle.