Impedance Code Calibration for Accurate On-Chip Termination

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Solution Overview

Problem

Existing impedance code generation circuits in semiconductor devices often fail to accurately match impedance values due to errors in impedance code generation or layout differences between termination and reference units, leading to incorrect termination impedance values and signal distortion.

Innovation Solution

An impedance code generation circuit with a code modification unit that adjusts impedance codes using a setting value, stored in a fuse circuit, to correct impedance values and ensure matching with external circuits, by adding or subtracting values from the initial impedance codes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If impedance code generation circuits are used to match impedance values, then signal transfer quality is improved, but errors in impedance code generation or layout differences cause incorrect termination impedance values and signal distortion

Engineering Contradiction:

Improveimpedance matching accuracyVSAvoidtermination impedance accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by performing impedance calibration before actual signal transmission. The ZQ calibration circuit pre-determines the correct impedance code by comparing reference voltages and storing the calibrated code in a register, ensuring that the termination impedance is accurately set before data transmission begins. This preliminary calibration eliminates impedance mismatching issues during actual operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through the ZQ calibration mechanism where the calibration circuit continuously monitors and adjusts the impedance code based on voltage comparisons. The comparison unit compares reference voltages and feeds back adjustment signals to modify the termination impedance until optimal matching is achieved, creating a closed-loop control system that ensures accurate impedance termination.

Inventive Principle:

Principle #23Feedback

2Speed

If swing widths of signals are reduced to minimize delay time, then signal transfer speed is improved, but influence of external noises increases and signal reflection becomes more severe

Engineering Contradiction:

Improvesignal transfer speedVSAvoidsignal reflection and noise influence

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the termination impedance value based on calibrated measurements. The system changes the impedance parameter to match the specific characteristics of the transmission line and external circuitry, optimizing signal transmission by minimizing reflections and noise effects while maintaining high-speed operation with reduced swing widths.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8344751B2Impedance code generation circuit, semiconductor device including the same, and method for setting termination impedance

Publication Date: 2013.01.01 SK HYNIX INC

AI summary

An impedance code generation circuit includes a first code generation unit configured to compare a voltage of a calibration node with a reference voltage and generate a first impedance code, a code modification unit configured to generate a modified impedance code by performing an operation on the first impedance code according to a setting value, and a second code generation unit configured to generate a second impedance code based on the modified impedance code.