Bi-directional ESD Protection Circuit with IGBTs

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Solution Overview

Problem

Conventional ESD protection circuits are inadequate for handling bi-directional ESD currents, particularly in systems that require protection against large voltage swings like the CAN bus specification, where they often fail to provide effective protection against negative voltage swings and cannot efficiently manage both positive and negative ESD events.

Innovation Solution

The implementation of a protection circuit comprising a pair of diodes and insulated gate bipolar transistors (IGBTs) connected in opposite polarities, forming embedded parasitic silicon controlled rectifiers (SCRs), which steer ESD currents of different polarities to the appropriate IGBTs for discharge through a reference voltage node, ensuring bi-directional ESD protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional ESD protection circuits are used, then single-direction ESD protection is provided, but bi-directional ESD protection capability is lost

Engineering Contradiction:

ImproveESD protection capabilityVSAvoidbi-directional protection capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The ESD protection circuit is segmented into two separate protection paths: one for positive ESD events and one for negative ESD events. Each path contains its own ESD protection circuitry, allowing independent optimization and operation for each polarity, thereby achieving bi-directional protection capability while maintaining reliable single-direction protection in each path.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a universal ESD protection structure that can handle both positive and negative ESD events through symmetric circuit design. The same protection topology is replicated for both polarities, enabling the system to provide versatile bi-directional protection without requiring fundamentally different circuit architectures for each direction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If diode string size is increased to dissipate worst-case ESD event, then ESD protection capability is improved, but device complexity and component count increase

Engineering Contradiction:

ImproveESD protection capabilityVSAvoidnumber of circuit components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protection circuit is divided into two independent single-direction protection circuits operating in parallel. Each circuit is sized appropriately for its specific polarity, avoiding the need for one oversized circuit that must handle both polarities. This segmentation reduces overall component complexity while maintaining robust ESD protection for both positive and negative events.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If conventional ESD circuits are designed for single direction, then circuit simplicity is maintained, but protection against opposite polarity ESD events is insufficient

Engineering Contradiction:

Improvecircuit structure simplicityVSAvoidvulnerability to negative voltage swings

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent employs asymmetric circuit configuration where two identical single-direction protection circuits are arranged with opposite polarities. This asymmetric arrangement allows each circuit to be optimized for its specific polarity while together providing symmetric bi-directional protection, effectively addressing vulnerability to negative voltage swings without significantly increasing overall circuit complexity.

Inventive Principle:

Principle #4Asymmetry

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 robust protection against both positive and negative ESD currents, capable of handling up to ±10 Amperes of HBM ESD current, effectively safeguarding integrated circuit components from bi-directional ESD events in CAN bus-based systems by utilizing multiple IGBTs and diodes to manage voltage swings within the specified range.

Implementation Method 1

forming embedded parasitic silicon controlled rectifiers (SCRs), which steer ESD currents of different polarities to the appropriate IGBTs for discharge through a reference voltage node

Methodology Applied

Scientific EffectParasitic silicon controlled rectifier (SCR):

Implementation Method 2

Electrostatic discharge (ESD) refers to the phenomenon where an electrical current of high amplitude and short duration is discharged at a package terminal of an integrated circuit (IC) due to static charge build-up

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Data Source

PatentUS11031778B2High-voltage tolerant bi-directional electrostatic discharge protection circuit

Publication Date: 2021.06.08 SILICON LABORATORIES INC

AI summary

In an embodiment, an apparatus includes: a signal pad; a first diode having a first terminal coupled to the signal pad and a second terminal, the first diode having a first polarity; a second diode having a second terminal coupled to the signal pad and a first terminal, the second diode having a second polarity; a first insulated gate bipolar transistor (IGBT) having a first polarity, the first IGBT coupled between the second terminal of the first diode and a reference voltage node; and a second IGBT having the first polarity, the second IGBT coupled between the first terminal of the second diode and the reference voltage node.