High-Voltage Switch Circuit to Prevent Low-Voltage Feedback Loops
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Solution Overview
Problem
High voltage switch circuits in semiconductor devices fail to maintain normal operation when internal voltage levels drop, leading to reliability issues due to unintended channel formation in high voltage PMOS transistors and subsequent feedback loop formation.
Innovation Solution
Incorporating a buffer circuit to output control signals, a boost circuit to manage block selection signals, a discharge circuit to manage output terminal voltage, and an initial voltage setup circuit to ensure proper voltage levels, preventing feedback loop formation and maintaining circuit integrity at low voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the high voltage PMOS transistor is used to turn on and off the boost circuit, then the circuit can be simplified, but when the internal voltage level is lowered, the transistor may be slightly turned on causing unintended channel formation and feedback loop formation
Solution Approach 1:
A buffer circuit is introduced as an intermediary between the control signal source and the high voltage PMOS transistor. The buffer circuit ensures that the control signal maintains sufficient voltage level to fully turn off the PMOS transistor even when internal voltage drops, preventing unintended channel formation while keeping the overall circuit structure relatively simple.
Solution Approach 2:
The buffer circuit performs preliminary signal conditioning before the control signal reaches the high voltage PMOS transistor. By preparing the control signal in advance to ensure adequate voltage levels, the system prevents the reliability issue before it can occur during low voltage operation.
2Ease of operation
If the feedback loop is formed in the boost circuit, then the block selection signal level rises, but when the internal voltage is low, the feedback loop may be formed unintentionally causing the circuit to malfunction
Solution Approach 1:
The buffer circuit acts as a mediator that controls the feedback loop formation indirectly. It ensures the feedback loop is only formed when properly intended by maintaining appropriate voltage levels on the control signal, preventing spurious feedback loop formation during low voltage conditions.
3Loss of energy
If the high voltage switch circuit is designed to output block selection signal at high voltage level, then voltage drop of the signal is reduced, but the circuit becomes sensitive to internal voltage variations
Solution Approach 1:
The circuit is segmented into distinct functional blocks: the buffer circuit handles voltage level stabilization and adaptation, while the boost circuit handles the high voltage signal generation. This segmentation allows each block to specialize in its function, reducing voltage drop in the signal path while maintaining adaptability to different internal voltage levels through the buffer's voltage regulation capability.
Data Source
AI summary
A high voltage switch circuit of a semiconductor device includes a buffer circuit configured to output a control signal in response to an input signal and a boost circuit configured to output a block selection signal to an output terminal by connecting a current path between a voltage supply node and the output terminal in response to the control signal, and to block the current path in case where the control signal falls from a high voltage level to a low voltage level.