HDMI Transmitter ESD Protection Circuit Leakage Control

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Solution Overview

Problem

Conventional ESD protection schemes, such as double diode and N-channel Field Effect Transistor circuits, fail to effectively manage leakage current during power-down conditions in High-Definition Multimedia Interface (HDMI) applications, leading to suboptimal ESD performance and compliance issues with leakage specifications.

Innovation Solution

The proposed solution involves a three-circuit architecture that includes a first circuit to selectively switch a bonding pad between power and discharge rails, a second circuit to clamp ESD between the discharge and power rails, and a third circuit to bias the discharge rail, creating a separate ESD rail for controlling leakage and filtering it to AC ground for noise isolation, thereby ensuring effective ESD protection compatible with HDMI specifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If double diode ESD protection is used, then ESD protection is provided, but significant leakage current occurs when system is powered down

Engineering Contradiction:

ImproveESD protectionVSAvoidleakage current

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The ESD protection function is segmented into two independent parts: a double diode circuit for ESD protection and a separate ESD rail with switching circuitry for leakage control. This segmentation allows each part to optimize its function without compromising the other - the diodes provide robust ESD protection while the switching circuitry eliminates leakage when powered down.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ESD rail is dynamically connected or disconnected from the power rails using switching circuitry controlled by a control signal. When the system is powered down, the switching circuitry disconnects the ESD rail to prevent leakage current. During ESD events, the switching circuitry connects the ESD rail to provide protection. This dynamic configuration resolves the contradiction between providing ESD protection and preventing leakage.

Inventive Principle:

Principle #15Dynamics

2Loss of energy

If N-channel Field Effect Transistor is used to block leakage, then leakage current is reduced, but ESD performance becomes weaker

Engineering Contradiction:

Improveleakage currentVSAvoidESD performance

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

A separate ESD rail acts as an intermediary between the bonding pad and the power rails. This intermediate rail allows the system to achieve both low leakage and strong ESD protection by providing a dedicated path for ESD current that does not pass through the power supply network, while still maintaining electrical isolation when powered down.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If separate ESD rail is created to control leakage, then leakage current is reduced, but device complexity increases

Engineering Contradiction:

Improveleakage currentVSAvoidcircuit architecture

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The separate ESD rail serves multiple functions: it provides a dedicated path for ESD current, isolates the bonding pad from power rails when powered down to prevent leakage, and can be dynamically connected or disconnected based on system state. This multi-functionality justifies the additional complexity by resolving multiple problems simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach effectively reduces leakage current to levels compliant with HDMI specifications, enhances ESD performance, and simplifies implementation, meeting both Human Body Model and Machine Model ESD criteria while maintaining excellent electrical performance.

Implementation Method 1

a first circuit (128, 130) configured to selectively switch a bonding pad (112) to (i) a first rail (120) of a power source and (ii) a discharge rail (116) in response to an electrostatic discharge

Methodology Applied

Scientific EffectElectrostatic discharge: Electrostatic Discharge

Implementation Method 2

a second circuit (104, 106) configured to clamp the electrostatic discharge between the discharge rail (116) and the first rail (118)

Methodology Applied

Scientific EffectElectrostatic discharge clamping: Electrostatic Discharge

Implementation Method 3

a third circuit (114) configured to bias the discharge rail (116) to a second rail (116) of the power source

Methodology Applied

Scientific EffectElectrical biasing: Electric Field

Data Source

PatentUS8659859B1Electrostatic discharge protection scheme for high-definition multimedia interface transmitters

Publication Date: 2014.02.25 AMBARELLA INT LP

AI summary

An apparatus generally having a first circuit, a second circuit and a third circuit is disclosed. The first circuit may be configured to selectively switch a bonding pad to (i) a first rail of a power source and (ii) a discharge rail in response to an electrostatic discharge. The second circuit is generally configured to clamp the electrostatic discharge between the discharge rail and the first rail. The third circuit may be configured to bias the discharge rail to a second rail of the power source.