Pad-Tracking Output Buffer for High-Voltage GPIO Protection
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Solution Overview
Problem
Conventional GPIO designs face stability and reliability issues due to weak voltage endurance of transistors, particularly when input signals with large swings exceed the supply voltage, risking damage to low-side transistors.
Innovation Solution
A circuit design incorporating a pad-tracking mechanism that uses a tracking circuit and pre-driver to control the output buffer, featuring P-type and N-type transistors, where the tracking circuit generates control signals to manage transistor states, preventing damage by fully turning off P-type transistors and using N-type transistors as voltage dividers to reduce gate-drain voltages during high-swing input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional GPIO designs use transistors in output and input buffers to handle large input signal swings, then the circuit can process high-voltage input signals, but the transistors may be damaged due to high gate-drain voltages exceeding their voltage endurance
Solution Approach 1:
The patent introduces a pad tracking circuit as an intermediary mechanism that generates control signals based on the pad voltage level. This mediator monitors the input signal and dynamically adjusts the output buffer operation, enabling the circuit to handle large voltage swings while protecting transistors by preventing them from operating in dangerous voltage conditions.
Solution Approach 2:
The output buffer operation is made dynamic through the pad tracking mechanism. Instead of static transistor switching, the control signals are dynamically adjusted based on the real-time pad voltage level. This dynamic operation allows the buffer to adapt to varying input conditions, enabling high-voltage tolerance while maintaining transistor safety through continuous adaptation of operating states.
2Adaptability or versatility
If the supply voltage is charged by high voltage from the pad, then the circuit can accept high-voltage input signals, but the low-side transistors may be damaged due to high gate-drain voltages
Solution Approach 1:
The pad tracking circuit implements a feedback mechanism where the control signals are generated based on the pad voltage level. This feedback loop continuously monitors the input signal conditions and adjusts the output buffer operation accordingly, preventing harmful high gate-drain voltages from damaging low-side transistors while maintaining the ability to accept high-voltage inputs.
Solution Approach 2:
The circuit applies preliminary protective action by using the pad tracking mechanism to preemptively control the output buffer operation before damaging conditions can occur. The tracking circuit anticipates potentially harmful voltage conditions and adjusts transistor operation in advance, preventing gate-drain voltage damage before it can occur.
Data Source
AI summary
The present invention provides a circuit including an output buffer, a tracking circuit and a pre-driver, where the output buffer includes at least one P-type transistor and at least one N-type transistor, the at least one P-type transistor is coupled between a supply voltage and a pad, and the at least one N-type transistor is coupled between a ground voltage and the pad. In the operations of the circuit, the tracking circuit is configured to generate a tracking signal control signal according to a voltage level at the pad, and the pre-driver is configured to generate a control signal to control the at least one P-type transistor or the at least one N-type transistor according to the tracking signal.