ESD Protection Circuit Using Transistor Segmentation and Current Limiting
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Solution Overview
Problem
Deep-submicron CMOS Integrated Circuits are increasingly vulnerable to electrostatic discharge (ESD) due to reduced device size and gate oxide thickness, necessitating effective ESD protection circuits that can prevent transistor breakdown and oxide damage.
Innovation Solution
The implementation of an ESD protection circuit comprising a first and second transistor, with a current limiting element, where at least one transistor operates in MOS mode to discharge ESD events at low voltage, preventing breakdown and enhancing discharge efficiency through the MOS body effect, and a two-stage protection scheme with a primary and secondary ESD stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If device size and gate oxide thickness are reduced to improve operating speed and integration density, then operating speed and integration density are improved, but vulnerability to ESD damage increases
Solution Approach 1:
The ESD protection circuit is segmented into multiple functional components: a first transistor for initial ESD discharge, a second transistor for sustained discharge, and a current limiting element. This segmentation allows each component to handle specific aspects of ESD protection, enabling effective protection against ESD damage while maintaining the benefits of scaled-down device dimensions for high operating speed and integration density.
2Reliability
If conventional ESD protection circuits are used to protect against ESD damage, then ESD protection is provided, but transistor breakdown and oxide damage occur during ESD events
Solution Approach 1:
The first transistor is configured to activate before the second transistor during an ESD event. The first transistor provides initial ESD discharge capability, preventing voltage from reaching breakdown levels that would damage the second transistor or protected circuitry. This preliminary action ensures that ESD protection is established before damage can occur.
Solution Approach 2:
The current limiting element acts as an intermediary between the ESD protection transistors and the protected circuitry. It limits the discharge current to prevent excessive current from causing oxide damage or transistor breakdown, while still allowing sufficient current to flow to discharge the ESD event effectively.
3Power
If transistors are operated at high voltage during ESD events to enhance discharge capability, then ESD discharge capability is improved, but transistor breakdown and oxide damage occur
Solution Approach 1:
The ESD protection circuit dynamically transitions between different transistor operating states during an ESD event. The first transistor activates initially to handle the voltage spike, then the second transistor engages for sustained discharge. The current limiting element dynamically adjusts the discharge current to maintain it within safe limits throughout the ESD event, preventing oxide damage while maintaining effective discharge capability.
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
The solution effectively prevents transistor breakdown and oxide damage by ensuring transistors operate in MOS mode at low voltage, enhancing ESD discharge efficiency and protecting circuitry from damaging voltages, even in thin gate oxide transistors.
Implementation Method 1
at least one transistor operates in MOS mode to discharge ESD events at low voltage, preventing breakdown and enhancing discharge efficiency through the MOS body effect
Data Source
AI summary
Implementations are presented herein that include an electrostatic discharge (ESD) protection circuit. The ESD protection circuit includes a first transistor and a second transistor. The first transistor has a first terminal that is coupled to a first supply line and a bulk that is coupled to a second supply line. The second transistor has a first terminal that is coupled to the second supply line, a bulk that is coupled to the first supply line and a second terminal that is coupled to a second terminal of the first transistor to define a protected node. The ESD protection circuit further includes a current limiting element that has a first terminal that is coupled to the protected node.