Dynamic Gate Bias Pass Switch for Overvoltage Without Signal Clipping
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Solution Overview
Problem
Multifunctional integrated circuits face challenges in protecting low voltage rated circuitry from overvoltage conditions without compromising performance, as existing protection devices can affect linearity and cause clipping of rail-to-rail input signals.
Innovation Solution
A dynamic gate bias circuit combined with an input pass switch, comprising a voltage level shifter, current mirror, and regulator, is used to maintain relatively constant resistance across the input pass switch over process, supply voltage, and temperature variations, ensuring effective protection from overvoltage while preserving circuit performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection devices are used to prevent overvoltage damage to low voltage rated circuitry, then reliability is improved, but linearity and signal performance deteriorate due to resistance variation and clipping
Solution Approach 1:
The patent implements a dynamic resistance control mechanism where the resistance of the input pass switch is actively adjusted based on the input voltage level. A control circuit monitors the input voltage and dynamically modifies the gate voltage of the switch transistor to maintain constant resistance across varying conditions, thereby resolving the contradiction between protection reliability and signal linearity
Solution Approach 2:
The patent employs a feedback control circuit that continuously monitors the input voltage and adjusts the switch resistance accordingly. The control circuit uses the input voltage signal itself as feedback to regulate the gate voltage, ensuring that the resistance remains constant even when protecting against overvoltage conditions, thus maintaining both reliability and signal accuracy
2Device complexity
If a simple pass switch is used for overvoltage protection, then device complexity is reduced, but performance linearity deteriorates due to resistance variation
Solution Approach 1:
The patent introduces a control circuit as an intermediary between the input voltage and the pass switch. This intermediary circuit processes the input voltage signal and generates an appropriate gate voltage to maintain constant resistance, effectively mediating between the conflicting requirements of simple structure and precise resistance control
3Object-affected harmful factors
If the input pass switch resistance varies with voltage, then overvoltage protection is achieved, but rail-to-rail input signal clipping occurs
Solution Approach 1:
The patent dynamically changes the electrical parameters of the pass switch, specifically the gate voltage, in response to varying input voltage conditions. By adjusting the gate voltage parameter, the switch resistance is maintained constant across the full rail-to-rail input range, preventing signal clipping while still providing overvoltage protection capability
Data Source
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AI summary
A protection device (100) includes a dynamic gate bias circuit (110). The dynamic gate bias circuit (110) includes an input pass switch (MN1) configured to receive a first input VIN (102) and a first control signal VINT (119); a voltage level shifter (120) coupled to the input pass switch (MN1); a current mirror (130) coupled to the voltage level shifter (120) at a first node (121); a regulator (140) coupled to the current mirror (130) at a second node; and a transistor (ΜΝ0) coupled to the first node (121). The transistor (ΜΝ0) is configured to receive a second control signal (VG) from the first node (121) and to receive the first input VIN (102).