ESD Protection Circuit Using Diode Strings and RC Triggering
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Solution Overview
Problem
Conventional electrostatic discharge (ESD) protection circuits suffer from high leakage current and inefficient power usage due to the increased leakage current of metal-oxide-semiconductor field effect transistors (MOSFETs) as they shrink in size, requiring larger thick oxide devices that increase mask costs and reduce protection effectiveness.
Innovation Solution
The proposed ESD protection circuit incorporates a p-type field effect transistor, an n-type field effect transistor, and a capacitance device, along with a parasitic silicon controlled rectifier, which forms an RC circuit with a diode device to reduce area and leakage, and includes diode strings to further reduce leakage currents by tuning voltage differences across the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If MOSFET size is reduced to nanometer order, then device integration density is improved, but leakage current increases
Solution Approach 1:
The protection circuit is divided into multiple functional modules: a first protection circuit branch with p-type MOSFET and first diode, a second protection circuit branch with n-type MOSFET and second diode, and a triggering circuit. This segmentation allows each module to be optimized independently, enabling the use of smaller MOSFETs while maintaining low leakage through proper circuit configuration and voltage control.
2Object-generated harmful factors
If thick oxide device is used to reduce leakage current, then leakage current is reduced, but mask cost increases and protection ability decreases
Solution Approach 1:
The invention changes the operating parameters of standard-thickness MOSFETs by controlling the voltage differences across them. By maintaining voltage differences below threshold values through the diode-based triggering circuit, standard-thickness devices operate in a low-leakage regime without requiring thick oxide processes, thereby avoiding increased mask costs while achieving low leakage current.
3Area of moving object
If MOSFET size is reduced, then integration density is improved, but protection effectiveness is reduced
Solution Approach 1:
Diodes are introduced as intermediary components that mediate the triggering action. The diodes detect voltage conditions and provide controlled current paths to trigger the MOSFETs only when electrostatic discharge conditions are present. This intermediary mechanism ensures that smaller MOSFETs are fully activated for protection when needed, compensating for their reduced size and maintaining protection effectiveness.
4Object-generated harmful factors
If diode strings are added to reduce leakage, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The diodes in the circuit serve multiple functions simultaneously: they act as voltage detectors for triggering, provide controlled current paths for activation, and function as protection elements themselves. This multi-functionality allows the circuit to achieve low leakage current without requiring additional dedicated components, thereby reducing overall device complexity despite the sophisticated operation.
Data Source
AI summary
One embodiment of the disclosure provides an electrostatic discharge protection circuit. The electrostatic discharge protection circuit includes a p-type field effect transistor, a capacitance device and an n-type field effect transistor. The p-type field effect transistor has a source coupled to an input/output terminal, a gate coupled to a first node and a drain coupled to a second node. The capacitance device has a first terminal coupled to a first rail and a second terminal coupled to the first node. The n-type field effect transistor has a source coupled to the first rail, a gate coupled to the second node and a drain coupled to the first node.