Bootstrap Sampling Circuit for High-Voltage Input Protection
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Solution Overview
Problem
Bootstrap circuits face issues when sampling input signals greater than the power supply voltage, leading to damage or current leakage in sampling switches due to voltage limits, which existing solutions like resistor divider networks or cascoded transistors do not adequately address.
Innovation Solution
A bootstrap circuit design incorporating protection switches, such as NMOS transistors, to prevent voltages exceeding the transistor limit, combined with a driver and level shifter to manage voltage levels during pre-charge and sample operations, ensuring stable sampling of high-voltage input signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bootstrap circuit is used to improve the linearity of the sampling switch, then the linearity is improved, but the sampling switch may be destroyed or current leakage occurs when the input signal voltage exceeds the power supply voltage
Solution Approach 1:
The patent introduces a protection circuit as an intermediary between the high-voltage input signal and the sampling switch. This protection circuit includes voltage clamping elements (such as diodes or transistors) that mediate the voltage relationship, ensuring the sampling switch never experiences voltage exceeding its rating while still allowing accurate sampling of high-voltage signals through the bootstrap capacitor mechanism.
2Adaptability or versatility
If the input signal voltage is greater than the power supply voltage, then high-voltage sampling is achieved, but the sampling switch is destroyed or current leakage occurs
Solution Approach 1:
The patent implements beforehand cushioning by incorporating protection elements (such as clamping diodes or voltage-limiting transistors) that are pre-configured to activate before the sampling switch can be damaged. These elements create a safety margin that cushions the sampling switch from excessive voltage, allowing the circuit to handle input signals greater than the power supply voltage without damage.
3Reliability
If protection switches are added to prevent voltage damage, then transistor protection is achieved, but circuit complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing protection switches that serve dual purposes: they act as protection elements during high-voltage conditions and as normal switching elements during standard operation. The same transistors used for sampling also provide protection when configured with appropriate voltage clamping networks, reducing the need for separate dedicated protection components and minimizing overall circuit complexity.
Data Source
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AI summary
A bootstrap circuit for generating an output signal through a pre-charge operation and a sample operation, includes: a sampler including a sampling switch configured to sample an input signal, a first protection switch connected between an input node and the sampling switch, and a second protection switch connected between the sampling switch and an output node; and a driver configured to drive the sampler based on a power supply voltage and the input signal.