On-Chip Noise Filter Circuit for ESD Immunity

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Solution Overview

Problem

CMOS ICs face challenges in integrating large discrete noise-bypassing components for system-level ESD immunity due to process limitations and die size requirements, making it difficult to achieve high system-level ESD specifications without consuming excessive silicon area.

Innovation Solution

A noise filter circuit with a decoupling unit and a current amplifier circuit is integrated into the IC, where the decoupling unit generates a current in response to transient voltages, and the current amplifier circuit drains additional current to increase discharge currents, effectively providing a larger equivalent capacitor value to bypass transient disturbances without requiring large physical space.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large discrete noise-bypassing components are integrated into the IC, then system-level ESD immunity is improved, but die size requirements and process limitations make it difficult to achieve

Engineering Contradiction:

Improvesystem-level ESD immunityVSAvoidchip area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent changes the effective capacitance parameter dynamically by using a current amplifier circuit that activates during ESD events. The amplifier circuit multiplies the discharge current capability, effectively increasing the noise-bypassing capability without physically enlarging the capacitor component on-chip.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The current amplifier circuit acts as an intermediary between the small on-chip capacitor and the ESD current. It senses the transient voltage and amplifies the discharge current through the capacitor, enabling a small physical capacitor to perform the function of a large discrete noise-bypassing component.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If discrete noise filter circuits are used, then transient voltage decoupling is improved, but integration into a single chip is difficult due to process limitations

Engineering Contradiction:

Improvetransient voltage decouplingVSAvoidchip integration

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent merges the noise filter function with standard CMOS circuit elements. The current amplifier circuit is implemented using conventional CMOS transistors and the decoupling capacitor is integrated into the chip fabric, combining ESD protection functionality with standard manufacturing processes.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces mechanical/discrete noise filter components with an electronic implementation using CMOS circuits. The current amplifier circuit electronically achieves the noise-bypassing function that would traditionally require large discrete capacitors or inductors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Power

If large area components are used for noise bypassing, then ESD current discharge capability is improved, but total cost requirements and die size constraints are violated

Engineering Contradiction:

ImproveESD current discharge capabilityVSAvoidcost efficiency

Core Design Contradiction:

PowerVSProductivity

Solution Approach 1:

The noise-bypassing capability is made dynamic rather than static. The current amplifier circuit remains inactive during normal operation and activates only during ESD events, providing high discharge capability when needed while consuming minimal area and power during normal operation.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The current amplifier circuit serves multiple functions: it amplifies the discharge current from the decoupling capacitor, provides a low-impedance path for ESD current, and can be implemented using standard CMOS transistors that are already present in the IC, making the solution universally applicable to various IC designs.

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 configuration enhances system-level ESD immunity by efficiently discharging ESD currents and decoupling transient voltages, improving the reliability of CMOS ICs without increasing the chip's area, thus meeting stringent ESD specifications.

Implementation Method 1

a decoupling unit coupled to a power pad of the IC and a current amplifier circuit coupled to the decoupling unit and the power pad of the IC. The decoupling unit generates a first current in response to a transient voltage being on the power pad of the IC.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

The current amplifier circuit drains a second current from the power pad of the IC according to the first current.

Methodology Applied

Scientific EffectCurrent amplification: Magnetic Amplifier

Data Source

PatentUS8649135B2On-chip noise filter circuit

Publication Date: 2014.02.11 HIMAX TECH LTD

AI summary

A noise filter circuit for an IC is provided. The noise filter circuit comprises a decoupling unit coupled to a power pad of the IC and a current amplifier circuit coupled to the decoupling unit and the power pad of the IC. The decoupling unit generates a first current in response to a transient voltage being on the power pad of the IC. The current amplifier circuit drains a second current from the power pad of the IC according to the first current.