Level Shifter Threshold Testing Across Voltage Domains
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Solution Overview
Problem
The variability in voltage thresholds of level shifter circuits during manufacturing poses reliability issues, requiring multiple iterations of process adjustments and characterization steps to ensure operational reliability when transitioning between different voltage domains.
Innovation Solution
An integrated circuit design that includes level shifter modules with detection logic and a control circuit to iteratively change voltage supplies while capturing output values, determining the threshold voltages at which level shifters operate reliably, thereby reducing the need for process adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple iterations of process adjustments and characterization steps are performed to ensure reliable operation, then reliability is improved, but manufacturing time and complexity increase
Solution Approach 1:
The patent incorporates a built-in self-test mechanism that performs voltage threshold characterization during the manufacturing process itself, rather than requiring separate post-manufacturing testing iterations. The test circuit automatically sweeps through voltage ranges and captures threshold values, enabling preliminary characterization that reduces subsequent manufacturing iterations.
Solution Approach 2:
The level shifter circuit includes integrated detection logic and test circuits that enable it to self-characterize its voltage thresholds during manufacturing. The circuit tests itself by applying test signals and measuring its own transfer characteristics, eliminating the need for external manual characterization steps and reducing manufacturing time.
2Reliability
If multiple revisions of silicon are made to ensure fully operational design, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the level shifter functional circuit with its own test and characterization circuits into a single integrated structure. The detection logic, test signal generators, and level shifter circuits are combined on the same silicon, allowing simultaneous testing and operation without requiring separate test chips or additional manufacturing revisions.
Solution Approach 2:
The test circuit is designed to be universal and adaptable to different level shifter configurations and voltage domains. The same test structure can characterize various level shifter designs and process variations, reducing the need for design-specific test revisions and simplifying the overall device complexity.
3Ease of manufacture
If voltage thresholds are not systematically determined, then manufacturing process is simpler, but reliability between different voltage domains deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the detection logic continuously monitors the level shifter output during voltage sweeping. When the output transitions between logic states, the system captures the corresponding input voltage threshold value. This feedback loop systematically determines accurate voltage thresholds, ensuring reliable voltage domain transitions while maintaining manufacturing simplicity.
Data Source
AI summary
An apparatus and method for testing level shifter threshold voltages on an integrated circuit includes one or more level shifter modules each including a number of level shifter circuits. Each level shifter circuit may be coupled to a first and a second voltage supply. Each level shifter circuit may also receive an input signal that is referenced to the first voltage supply, and to generate an output signal that is referenced to the second voltage supply. In addition, each level shifter module may include detection logic that may detect an output value of each of the level shifter circuits. The control circuit may be configured to iteratively change the voltage output from one of the voltage supplies, and maintaining a voltage on the other voltage supply while the input signal is provided to the level shifter circuits. The detection logic may capture the output value upon each change in voltage.