AC-Coupled Buffer Feedback for Stable Differential Clock Duty Ratio

Solution Overview

Problem

AC coupling circuits in integrated circuit devices face challenges in effectively buffering differential clock signals across varying frequencies, leading to issues with duty ratio consistency, noise sensitivity, and bias variation, especially when handling both high and low frequency signals.

Innovation Solution

The implementation of a variable resistive feedback circuit with a feedback resistance controller that adjusts resistance values based on frequency, providing different resistances for high and low frequency signals, coupled with capacitors and buffers to ensure consistent duty ratio and reduced noise sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed resistance feedback circuit is used in AC coupling circuits, then the circuit structure is simple, but the duty ratio consistency and noise sensitivity performance deteriorate when handling signals across varying frequencies

Engineering Contradiction:

Improveduty ratio consistencyVSAvoidfeedback circuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The feedback circuit transitions from a fixed resistance configuration to a dynamic, frequency-selective configuration. Multiple feedback paths with different resistance values are provided, and the appropriate path is selected based on the input signal frequency, enabling the circuit to adapt its feedback characteristics dynamically rather than using a single static resistance value

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The feedback resistance value is changed based on the frequency parameter of the input signal. Different resistance values are selected for different frequency ranges (e.g., first resistance for first frequency range, second resistance for second frequency range), allowing the circuit to optimize its performance for each frequency band by adjusting the feedback parameter

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a fixed resistance feedback circuit is used in AC coupling circuits, then the circuit structure is simple, but the noise sensitivity performance deteriorates across varying frequencies

Engineering Contradiction:

Improvenoise sensitivityVSAvoidfeedback circuit structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The feedback circuit transitions from a fixed resistance configuration to a dynamic, frequency-selective configuration. Multiple feedback paths with different resistance values are provided, and the appropriate path is selected based on the input signal frequency, enabling the circuit to adapt its feedback characteristics dynamically rather than using a single static resistance value

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The feedback resistance value is changed based on the frequency parameter of the input signal. Different resistance values are selected for different frequency ranges (e.g., first resistance for first frequency range, second resistance for second frequency range), allowing the circuit to optimize its performance for each frequency band by adjusting the feedback parameter

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If different resistance values are provided for different frequencies, then the buffering performance across frequencies is improved, but the device complexity increases

Engineering Contradiction:

Improvefrequency adaptabilityVSAvoidfeedback circuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The feedback circuit is segmented into multiple independent feedback paths, each with a different resistance value optimized for specific frequency ranges. Instead of using a single complex adjustable circuit, the feedback function is divided into separate parallel paths that can be independently selected based on the input signal characteristics

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback circuit structure is designed to perform multiple functions through different feedback paths. The same feedback circuit topology can handle different frequency ranges by selecting appropriate resistance values, making the circuit multi-functional rather than requiring separate circuits for each frequency band

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS7778097B2AC coupling circuits including resistive feedback and related methods and devices

Publication Date: 2010.08.17 SAMSUNG ELECTRONICS CO LTD

AI summary

An integrated circuit device may include an amplifier having an amplifier input configured to receive an input signal with the amplifier being configured to provide an amplifier output signal at an amplifier output responsive to the input signal received at the amplifier input. A capacitor may be coupled to the amplifier output, and a buffer may be coupled to the capacitor so that the capacitor is coupled in series between the amplifier output and an input of the buffer with an output of the buffer being coupled to a buffered signal terminal. A variable resistive feedback circuit may be coupled between the input and output of the buffer with the variable resistive feed back circuit providing a variable resistance between the input and output of the buffer. A feedback resistance controller may be coupled to the variable resistive feedback circuit with the feedback resistance controller being configured to select a first resistance for the variable resistive feedback circuit for a first frequency of the input signal and to select a second resistance for the variable resistive feedback circuit for a second frequency of the input signal different than the first frequency with the first and second resistances being different.