Input Buffer Replica Circuit for Stable Logic Threshold Sensing
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Solution Overview
Problem
Semiconductor devices face challenges in accurately sensing input signals due to shifts in logic threshold voltage caused by process variations and temperature changes, especially when the difference between high and low potential input signals decreases, leading to inaccurate sensing and issues with external clock frequency changes.
Innovation Solution
A semiconductor device configuration that includes an input buffer, a replica circuit with the same configuration, a reference voltage generating circuit, and a comparator circuit to adjust the logic threshold voltage by generating a threshold adjustment signal, allowing the input buffer to accurately sense input signals without relying on external clock signals or frequency comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the logic threshold voltage is set to a specified value intermediate between VIH and VIL, then the input circuit can sense input signals, but the sensing accuracy deteriorates when the logic threshold voltage shifts due to process variation or temperature change
Solution Approach 1:
The patent implements a feedback mechanism where the replica circuit generates a logic threshold voltage that is fed back to the input buffer through a comparator. The comparator continuously monitors the replica circuit's output and adjusts the input buffer's logic threshold voltage to match, ensuring accurate sensing despite process variations or temperature changes.
Solution Approach 2:
The patent uses a replica circuit that is identical in configuration to the input buffer to copy the logic threshold voltage characteristics. This replica circuit serves as a reference model that generates the appropriate threshold voltage under the same process and temperature conditions, which is then applied to the input buffer to maintain sensing accuracy.
2Use of energy by stationary object
If the difference between VIH and VIL decreases due to lower operating voltage, then power consumption is reduced, but the input circuit's ability to accurately sense input signals deteriorates
Solution Approach 1:
The patent dynamically adjusts the logic threshold voltage parameter based on the operating conditions. By using the replica circuit to generate a threshold voltage that adapts to process variations and temperature changes, the system maintains accurate sensing even when the VIH-VIL difference is small due to lower operating voltages.
3Measurement precision
If a ring oscillator is used to adjust the logic threshold voltage, then the threshold can be adjusted in correspondence with input signal levels, but the system becomes dependent on external clock signals and frequency comparisons
Solution Approach 1:
The patent extracts the essential function of threshold voltage adjustment from the ring oscillator's frequency comparison mechanism. Instead of relying on external clock signals and frequency measurements, the system directly uses the replica circuit's output voltage to control the input buffer's threshold, eliminating the need for clock-dependent adjustment mechanisms.
Data Source
AI summary
A semiconductor device, includes an input buffer, first and second PMOS transistors serially interconnected between a first power supply node and an output node of the input buffer. First and second NMOS transistors are serially interconnected between a second power supply node and the output node of the input buffer. A replica circuit includes a third and fourth PMOS transistors serially interconnected between the first power supply node and an output node of the replica circuit. Third and fourth NMOS transistors are serially interconnected between the second power supply node and the output node of the replica circuit. The input node of the replica circuit is connected to the output node of the replica circuit and a comparison circuit compares a voltage at the output node of the replica circuit to a reference voltage.