Auto-Adjusting Impedance Circuit for Accurate On-Chip Termination

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Solution Overview

Problem

Existing impedance adjustment circuits face challenges with limited adjustment range and accuracy due to variations in process, voltage, and temperature conditions, particularly in on-chip termination, leading to signal distortion and inefficiencies.

Innovation Solution

A circuit design that includes a first and second voltage divider with parallel resistors and reference resistors, combined with a comparator and code selector, to automatically adjust impedance by selecting optimal resistance codes based on comparison values, ensuring wide adjustment range and high accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If off-chip termination is used, then termination resistance can be adjusted relatively accurately, but parasitic components generate reflection signals causing signal distortion

Engineering Contradiction:

Improvetermination resistance accuracyVSAvoidsignal distortion

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The harmful parasitic components are extracted and eliminated by moving the termination resistor from external packaging onto the chip itself, thereby removing the source of reflection signals while maintaining the termination function

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

An on-chip termination resistor serves as an intermediary solution that balances the conflicting requirements of accuracy and signal integrity by providing termination resistance without external packaging parasitics

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If on-chip termination is used, then signal distortion is reduced, but resistance value varies with PVT conditions requiring adjustment circuits

Engineering Contradiction:

Improvesignal distortionVSAvoidresistance adjusting circuit

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The termination resistance is made dynamically adjustable through digital control of transistor switches, allowing the resistance value to be adapted to PVT conditions while maintaining signal integrity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The resistance value is changed by digitally controlling the switching states of transistors in the adjustment circuit, enabling dynamic adaptation to process, voltage, and temperature variations

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If analog resistance adjusting circuit is used, then accurate resistance can be obtained, but adjustment range is small

Engineering Contradiction:

Improveresistance accuracyVSAvoidadjustment range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The resistance adjustment function is segmented into multiple discrete steps using binary-weighted transistor switches, enabling both fine accuracy and wide adjustment range through digital code control

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The analog voltage-controlled resistance adjustment is replaced with a digital switching system using transistor arrays controlled by binary codes, providing both precision and extended adjustment range

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Adaptability or versatility

If digital resistance adjusting circuit is used, then adjustment range is increased, but resistance accuracy decreases

Engineering Contradiction:

Improveadjustment rangeVSAvoidresistance accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

Different regions of the resistance adjustment circuit are assigned different functions: binary-weighted switches provide coarse adjustment for wide range, while fine-tuning elements provide local precision for accurate termination

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20260074678A1Circuit capable of automatically adjusting impedance thereof

Publication Date: 2026.03.12 UNIV OF SEOUL IND COOP FOUND

AI summary

The present invention provides a circuit capable of automatically adjusting impedance thereof having a wide adjustment range and high accuracy by selecting a pull-up code and a pull-down code for obtaining resistances closest to those of a first reference resistor and a second reference resistor, respectively, using a first reference P-code and a second reference P-code, and a first reference N-code and a second reference N-code.