Drive Assist Output Circuit for High-Speed Switching Reliability
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Solution Overview
Problem
Existing output circuits for semiconductor integrated circuit devices face malfunctions when the speed of circuit operation is increased, particularly due to issues with signal frequency and transition timing in drive assist circuits.
Innovation Solution
The output circuit incorporates a p-type output transistor, a pre-driver, and a drive assist circuit with a pulse generation circuit that includes a logic gate, delay circuit, and inverter, where the delay circuit has different transmission delays for rising and falling signal transitions, ensuring reliable assist operations even at high speeds without increasing transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the circuit operation speed is increased to achieve high-speed operation, then the productivity is improved, but the reliability deteriorates due to malfunction at high frequencies
Solution Approach 1:
The drive assist circuit performs preliminary action by temporarily bringing down the potential at the output node before the output transistor switches on. This advance preparation ensures that when the transistor conducts at high speed, the gate-source voltage is already optimized, preventing malfunction while enabling high-speed operation.
Solution Approach 2:
The drive assist circuit acts as an intermediary between the power source and the output transistor. It mediates the voltage potential at the output node, temporarily reducing it to assist the transistor switching operation, thereby enabling reliable high-speed operation without directly modifying the transistor itself.
2Productivity
If the gate-source voltage is temporarily increased to enhance driving capability, then the productivity is improved, but the device complexity increases due to additional drive assist circuit
Solution Approach 1:
The drive assist circuit is merged with the existing output circuit structure. The assist operation integrates with the normal switching operation of the output transistor, combining the power source connection with the assist function to reduce overall circuit complexity while maintaining enhanced driving capability.
Solution Approach 2:
The drive assist circuit operates periodically only during the transition phase when the output transistor switches on. By applying the assist operation temporarily and periodically rather than continuously, the circuit achieves enhanced driving capability during critical moments without requiring complex continuous control mechanisms.
3Speed
If the potential at output node is brought down temporarily to assist switching, then the speed is improved, but the use of energy increases due to additional current flow
Solution Approach 1:
The drive assist circuit rushes through the potential adjustment process by temporarily bringing down the output node potential only during the critical switching transition moment. This brief, focused intervention speeds up the transition without sustaining additional energy consumption, as the assist operation is skipped for the remainder of the transistor conduction period.
Data Source
AI summary
A drive assist circuit includes a pulse generation circuit which outputs a pulse to control an assist operation when an assist signal makes a first transition corresponding to a transition of a gate signal from a high level to a low level. The pulse generation circuit includes a delay circuit provided in one of two inputs of a logic gate. The delay circuit is configured such that a delay is greater when an input makes a transition corresponding to the first transition of the assist signal, as compared to a case where the input makes a transition corresponding to an inverse of the first transition.