Level Shifter ESD Protection Circuit With Lower Gate Stress
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Solution Overview
Problem
Existing integrated circuit designs face challenges in efficiently protecting against electrostatic discharge (ESD) events, which can damage gate oxide layers and require large areas for ESD protection circuits, leading to voltage drops and potential breakdowns of transistor gates.
Innovation Solution
The integration of an ESD protection circuit within the level shifter circuit, utilizing transistors to discharge ESD currents and reduce voltage drops between gate and source terminals, without occupying additional area, by configuring transistors to operate in different voltage domains and using feedback circuits to manage voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large numbers of NMOSs/PMOSs are used for ESD protection, then ESD protection capability is improved, but area occupied by the protection circuit increases
Solution Approach 1:
The ESD protection circuit is merged with the level shifter circuit by integrating the ESD protection transistors (first and second transistors) directly into the level shifter structure. The first transistor is coupled between the input terminal and the gate of the third transistor, while the second transistor is coupled between the output terminal and the gate of the fourth transistor, allowing simultaneous ESD protection and level shifting functions within the same circuit footprint without requiring separate dedicated ESD protection area.
2Reliability
If ESD protection circuit is added, then reliability against ESD events is improved, but voltage drops occur between gate and source terminals
Solution Approach 1:
The circuit dynamically adjusts operating parameters based on conditions. During normal operation, the level shifter transistors (third and fourth transistors) operate in linear region to minimize voltage drops. During ESD events, the ESD protection transistors (first and second transistors) activate and operate in saturation region to shunt ESD currents, with their gate voltages dynamically adjusted through coupling with input/output terminals to optimize protection while minimizing impact on normal signal levels.
3Area of stationary object
If ESD protection circuit is integrated into level shifter circuit, then area usage is optimized, but circuit complexity increases
Solution Approach 1:
The integrated circuit achieves multi-functionality where the level shifter circuit simultaneously provides both level shifting and ESD protection functions. The third and fourth transistors perform level shifting while the first and second transistors provide ESD protection, with all four transistors sharing common control nodes and voltage domains. This universal design eliminates the need for separate dedicated ESD protection circuits, reducing overall area while maintaining distinct functional capabilities through clever transistor arrangement and coupling.
Data Source
AI summary
An integrated circuit is provided and includes a first active region of a first conductivity type coupled to a first voltage terminal and corresponding to a first terminal of a first transistor and a first terminal of a second transistor included in an inverter of a level shifter circuit, wherein the first transistor is configured to discharge electrostatic charges to the first voltage terminal; and second and third active regions, corresponding to a third transistor, of a second conductivity type different from the first conductivity type, wherein the second active region is coupled to a second voltage terminal, and the third active region is coupled to a first terminal, different from the second voltage terminal, of the level shifter circuit. The third transistor is configured to transmit a first supply voltage from the second voltage terminal for the integrated circuit.