ESD Protection Circuit with Floating Diodes for Signal Integrity
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Solution Overview
Problem
Existing ESD protection circuits for semiconductor devices and integrated circuits suffer from signal clipping issues, especially in analog circuitry and RF power amplifiers, due to the asymmetrical nature of conventional ESD clamps, which are difficult to fabricate and increase chip area, thereby increasing manufacturing costs.
Innovation Solution
The use of an ESD protection circuit that combines an asymmetric ESD clamp with multiple floating diode strings, allowing for more symmetric ESD protection by adjusting the doping and width of diodes to prevent signal clipping, while minimizing chip area and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an asymmetric ESD clamp is used for ESD protection, then ESD protection is provided, but signal clipping occurs especially in analog circuitry and RF power amplifiers
Solution Approach 1:
The ESD protection function is divided into two separate components: an asymmetric ESD clamp for handling high-voltage ESD events and one or more floating diodes for clamping normal signal levels. This segmentation allows each component to be optimized for its specific function, preventing signal clipping while maintaining ESD protection capability.
Solution Approach 2:
Floating diodes are introduced as intermediary elements between the asymmetric ESD clamp and the circuit core. These diodes act as mediators that clamp the voltage during normal operation to prevent signal clipping, while allowing the asymmetric clamp to handle ESD events without affecting the signal path.
2Object-generated harmful factors
If a symmetric ESD clamp is used to prevent signal clipping, then signal integrity is improved, but fabrication becomes difficult and chip area increases
Solution Approach 1:
The invention uses an asymmetric ESD clamp configuration that is specifically designed for the particular circuit core geometry and doping profile. This asymmetric design is actually easier to fabricate than a symmetric clamp because it leverages the existing asymmetry in the circuit layout, while floating diodes provide the necessary symmetry for signal clamping functionality.
Solution Approach 2:
The floating diodes serve multiple functions: they clamp normal signal levels to prevent clipping, they work in conjunction with the asymmetric clamp during ESD events, and they can be implemented using standard fabrication processes without requiring additional complex steps.
3Reliability
If conventional ESD clamps are used, then ESD protection is achieved, but chip area increases leading to higher manufacturing costs
Solution Approach 1:
The floating diodes are designed with dynamic characteristics that allow them to be non-invasive during normal low-voltage operation (high impedance state) and become active only when voltage exceeds the diode forward voltage threshold. This dynamic behavior minimizes their impact on normal circuit operation and allows for compact integration.
Solution Approach 2:
The invention optimizes the doping concentration and geometric dimensions of the floating diodes to achieve the desired clamping voltage while minimizing the area occupied. By carefully controlling these parameters, the diodes provide effective signal clamping with minimal impact on chip area and manufacturing cost.
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 solution provides effective ESD protection with reduced signal clipping and minimal increase in chip area, making it suitable for RF power amplifiers and other semiconductor devices, thereby addressing the limitations of existing technologies.
Implementation Method 1
Modern electronic devices, especially semiconductor (SC) devices and integrated circuits (ICs) are at risk of damage due to electrostatic discharge (ESD) events
Implementation Method 2
Zener diode symbol 23′ within ESD clamp 23 indicates that the function of ESD clamp 23 is to limit the voltage than can appear across protected core 22
Implementation Method 3
ESD clamp 23 is forward biased and goes into forward conduction at voltage V=−V2 determined generally by the band-gap of the SC material of which it is formed
Data Source
AI summary
An electrostatic discharge (ESD) protection circuit (40) is coupled across input-output (I/O) pads (21) and common terminals (24) of a circuit core (22) to protect it from ESD events. The circuit (40) comprises, a unidirectional ESD clamp (23) and two or more floating diodes (42, 44) arranged in parallel opposed configuration in series with the ESD clamp (23), the combination coupled between the I/O pads (21) and the reference terminals (24). In a preferred arrangement, the two strings of opposed parallel coupled diodes (42, 44) are used with different numbers of diodes in each string. These diodes (42, 44) operate in forward conduction (43, 45), so the energy dissipated therein during an ESD event is much reduced compared to a reverse biased diode and they can have smaller area. Signal clipping at the I/O pad (21) is reduced, less power is dissipated and less chip area is utilized.