Output Circuit Node Control for Analog-Digital Signal Isolation
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Solution Overview
Problem
In semiconductor integrated circuits, the increased speed of A/D conversion can lead to insufficient charging and discharging of capacitors, causing voltage differences that result in erroneous digital signal determination and decreased accuracy, particularly when digital and analog signals share the same terminal, influencing each other's operation and causing malfunctions.
Innovation Solution
An output circuit with a driver circuit and a node control circuit, utilizing transistors and control signals to manage the voltage at the external terminal, ensuring that the transistors are kept in a state that prevents leak currents and maintains the voltage difference between the source and drain terminals at zero, thereby isolating the analog signal from the digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If digital and analog signals share the same terminal to reduce the number of external terminals, then the number of external terminals is reduced, but the digital circuit influences the analog signal causing decreased operation margin and malfunction
Solution Approach 1:
The patent divides the circuit into distinct digital and analog sections with separate signal paths. The digital signal processing circuit and analog signal processing circuit are segmented to operate independently, preventing mutual interference while sharing the same external terminal through controlled switching.
Solution Approach 2:
The patent introduces switching elements and isolation circuits as intermediaries between the digital and analog circuits. These intermediary components control the interaction between digital and analog signals, allowing the external terminal to serve both purposes without direct interference between the circuit types.
2Productivity
If A/D conversion speed is increased to improve productivity, then conversion speed is improved, but the capacitor cannot be sufficiently charged and discharged causing voltage differences and erroneous determination
Solution Approach 1:
The patent implements preliminary charging and discharging phases for the capacitor before the actual comparison operation. This preliminary action ensures the capacitor is properly prepared and charged to the required voltage level, preventing voltage differences that would cause erroneous determination even at high conversion speeds.
Solution Approach 2:
The patent maintains continuous operation of the capacitor charging and discharging cycle throughout the A/D conversion process. By ensuring the capacitor remains actively engaged in the conversion cycle without interruption or insufficient charging time, the system achieves both high speed and high accuracy in digital output signal determination.
Data Source
AI summary
An output circuit includes a driver circuit and a node control circuit. The driver circuit includes a first transistor and a second transistor. The first transistor includes one end coupled to an external terminal and the other end coupled to a first node. The second transistor includes one end coupled to the first node and the other end coupled to a wiring that is supplied with a power supply voltage. When the first transistor and the second transistor are deactivated, the node control circuit supplies a node control signal based on a voltage of the external terminal to the first node.