Low-Leakage ESD Protection Circuit Using Single Current Path
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Solution Overview
Problem
Existing ESD protection circuits suffer from significant leakage current and current noise, particularly in devices with limited current ranges and power supplies, due to non-ideal diodes contributing additive noise current, which degrades signal quality and increases power consumption.
Innovation Solution
The proposed ESD protection circuit employs a primary protection block with a single ESD current path using MOSFET transistors and a secondary protection block with a zener diode, both capacitively coupled to the input, to minimize leakage current and noise, with transistors biased to operate in low-leakage regions and bootstrapping amplifiers to reduce input voltage dependency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse-biased diodes are used in series for ESD protection, then ESD strike protection is provided, but leakage current increases
Solution Approach 1:
The patent changes the operating parameters of the protection circuit by using transistors biased in the subthreshold region instead of reverse-biased diodes. This parameter change enables the circuit to maintain ESD protection capability while operating at extremely low leakage currents, directly resolving the contradiction between protection reliability and energy loss.
Solution Approach 2:
The patent substitutes the traditional diode-based protection mechanism with a transistor-based mechanism operated in the subthreshold region. This substitution fundamentally changes how protection is achieved, allowing the circuit to provide ESD protection through controlled transistor operation rather than reverse-biased diode characteristics, thereby eliminating the inherent leakage current problem.
2Reliability
If reverse-biased diodes are used for ESD protection, then voltage limiting during ESD strikes is achieved, but current noise increases
Solution Approach 1:
The patent changes the operational parameters by biasing transistors in the subthreshold region, which fundamentally alters the noise characteristics. This parameter change enables the circuit to maintain effective voltage limiting during ESD strikes while generating minimal current noise, as subthreshold operation produces significantly lower noise compared to reverse-biased diode operation.
3Reliability
If diodes are used to provide ESD current paths, then ESD current diversion is achieved, but leakage current becomes proportional to input voltage
Solution Approach 1:
The patent substitutes the diode-based current diversion mechanism with transistors operated in the subthreshold region. This substitution eliminates the voltage-proportional leakage characteristic inherent in diodes, as subthreshold transistors exhibit exponentially lower leakage currents that are largely independent of input voltage variations, thereby resolving the contradiction between current diversion capability and voltage-dependent energy loss.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces leakage current and current noise, ensuring effective ESD protection while minimizing power consumption and maintaining signal integrity, especially in low-current applications like portable devices.
Implementation Method 1
The gate of the at least one transistor can be capacitively coupled to the input. In some implementations, the gate of the transistor can be biased above a voltage at a source or a drain of the transistor by a voltage about double the semiconductor Fermi voltage level of the transistor to reduce the leakage current of the transistor.
Implementation Method 2
The primary protection circuit can produce a leakage current at the input, and can use at least one bootstrapping amplifier to provide a reduced voltage across the transistor and to reduce input current dependency of the leakage current on an input voltage at the input.
Implementation Method 3
the ESD current can be directed to a connected core-clamp that limits the voltage of the strike and directs the current to ground, thus protecting the connected circuitry from the strike.
Data Source
AI summary
An electrostatic discharge (ESD) protection circuit, set forth by way of example and not limitation, includes an input operative to receive input signals and a primary protection circuit coupled to the input. The protection circuit is operative to provide a single ESD current path for one or more the input signals that are ESD strikes. The currents of positive ESD strikes and negative ESD strikes flow through the single ESD current path, where the single ESD current path is not used by one or more of the input signals that are non-ESD signals.