Fingerprint Detection Circuit Chip Area Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Fingerprint information detection circuits occupy large chip areas and are costly due to the clock feedthrough and electric charge injection effects, which affect voltage signal output and increase production costs.

Innovation Solution

A fingerprint information detection circuit design that utilizes a built-in reset transistor to generate and inject electric charge, eliminating the need for additional input units, and places the reset unit beneath the feedback unit to reduce chip area and cost, while purifying the source of electric charge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a conventional fingerprint information detection circuit is used with separate reset unit and charge injection unit, then the circuit can perform fingerprint detection, but the chip area occupied is large and production cost increases

Engineering Contradiction:

Improvechip areaVSAvoidproduction cost

Core Design Contradiction:

Area of stationary objectVSEase of manufacture

Solution Approach 1:

The patent combines the reset unit and charge injection unit into a single integrated structure. The reset transistor's drain electrode is directly connected to the feedback unit, eliminating the need for a separate charge injection unit. This merging of functions reduces the number of components and decreases chip area occupancy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The reset transistor serves dual functions: it acts as a reset switch for the feedback unit and simultaneously serves as the charge injection unit. By making the reset transistor multi-functional, the patent eliminates redundant components and reduces overall circuit complexity and chip area.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If additional input unit is added to generate injected electric charge, then charge injection can be achieved, but device complexity and chip area increase

Engineering Contradiction:

Improvecharge injection effectivenessVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reset transistor generates and injects its own electric charge into the feedback unit through its inherent clock feedthrough effect and charge storage capability. The transistor uses its own operational characteristics to provide the charge injection function, eliminating the need for external charge generation circuits.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The feedback unit serves as an intermediary that receives electric charge from the reset transistor and transfers it to the amplification unit. This intermediary structure allows efficient charge transfer without requiring additional dedicated charge injection circuitry.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If reset unit is placed separately from feedback unit, then circuit functionality is maintained, but chip area usage increases

Engineering Contradiction:

Improvecircuit functionalityVSAvoidchip area

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The reset unit is nested within or directly integrated with the feedback unit structure. The reset transistor's drain electrode is positioned to directly interface with the feedback unit's capacitor, creating a compact nested arrangement that minimizes spatial separation while maintaining functional independence.

Inventive Principle:

Principle #7Nested doll (Nesting)

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

The design reduces chip area usage, saves production costs, and improves the accuracy of fingerprint detection by eliminating adverse effects of clock feedthrough and electric charge injection, while ensuring electrostatic protection.

Implementation Method 1

When the reset signal is high, the reset transistor inside the reset unit is on and stores the electric charge, while resetting the feedback unit; when the reset signal is switched from the high level to a low level, the reset transistor is off, and the electric charge stored is injected to the feedback unit and the amplification unit

Methodology Applied

Scientific EffectElectric charge storage and injection: Capacitance

Implementation Method 2

the clock feedthrough effect and the electric charge injection effect generated by the reset unit affect the voltage signal outputted by the circuit

Methodology Applied

Scientific EffectClock feedthrough effect: Parasitic Capacitance

Data Source

PatentUS9922230B2Fingerprint information detection circuit

Publication Date: 2018.03.20 SILEAD

AI summary

A fingerprint information detection circuit comprises an amplification unit, a source follower unit, a reset unit, and a feedback unit. The amplification unit is coupled to the source follower unit. The reset unit is coupled to both the feedback unit and the amplification unit. The feedback unit and the amplification unit are coupled. The reset unit includes a first transistor and a reset transistor, wherein source and drain electrodes of the first transistor are coupled, wherein one of source and drain electrodes of the reset transistor is coupled to the source and drain electrodes of the first transistor.