VCO CTAT Offset Current for Wide-Band PLL Frequency Drift

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Solution Overview

Problem

Wide band PLLs suffer from frequency drift issues due to temperature changes, which are not effectively addressed by conventional PTAT/CTAT methods, limiting frequency correction range and signal gain, especially at lower frequency bands.

Innovation Solution

Introduce a fixed offset current with CTAT behavior in the V2I output current, mirrored to the CCO, to reduce frequency drift at lower bands without affecting loop dynamics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional PTAT/CTAT temperature compensation methods are used in wide band PLLs, then frequency drift at higher frequency bands is reduced, but frequency correction range is limited and signal gain is reduced at lower frequency bands

Engineering Contradiction:

Improvefrequency stabilityVSAvoidfrequency correction range

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies different temperature compensation strategies to different frequency bands. A first temperature compensation circuit (PTAT-based) is used for higher frequency bands, while a second temperature compensation circuit (CTAT-based) is used for lower frequency bands. This local differentiation allows each band to receive optimized compensation, resolving the contradiction between frequency stability and correction range across the wide band spectrum.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The frequency band is segmented into multiple ranges, with different compensation circuits activated for different segments. The wide band PLL is divided into at least two frequency bands, each handled by a specialized compensation mechanism. This segmentation enables the system to achieve both high stability in upper bands and adequate correction range in lower bands simultaneously.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If control voltage range is increased to correct frequency drift at lower frequency bands, then frequency correction range improves, but the available control voltage range is reduced due to supply scaling at lower technology nodes

Engineering Contradiction:

Improvefrequency correction rangeVSAvoidcontrol voltage range

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the compensation mechanism parameter based on frequency band. Instead of using a single compensation method across all bands, it switches between PTAT and CTAT compensation approaches. This parameter change allows the system to achieve effective frequency correction at lower bands without requiring increased control voltage range, thus avoiding the supply scaling limitation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If temperature compensation is applied to reduce frequency drift, then frequency stability improves, but device complexity increases due to additional compensation circuits

Engineering Contradiction:

Improvefrequency stabilityVSAvoidcompensation circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent designs the temperature compensation system to serve multiple frequency bands with a unified architecture. The compensation circuits are integrated into the existing PLL structure, allowing them to handle both upper and lower frequency bands through selective activation. This multi-functional approach reduces overall complexity compared to having separate compensation systems for each band.

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

Extends the fine tune frequency correction range of the VCO, reducing temperature-induced frequency drift and improving communication signal quality by correcting frequency deviations at lower bands.

Implementation Method 1

introducing a conversely proportional to absolute temperature (CTAT) in a V2I output current to a ring oscillator (RO)

Methodology Applied

Scientific EffectConversely Proportional to Absolute Temperature (CTAT):

Data Source

PatentUS12592666B2Methods and systems for reducing a frequency drift in a voltage controlled oscillator (VCO)

Publication Date: 2026.03.31 SAMSUNG ELECTRONICS CO LTD

AI summary

A circuit for reducing a temperature-induced frequency drift in a voltage to current (V2I) converter based voltage-controlled oscillator (VCO) for at least one wide band phase-locked loop (PLL), the circuit includes a V2I resistor node of the V2I converter, the V2I resistor node being at one end of a resistor, the VCO, and a current controlled oscillator (CCO), and the circuit is configured to provide a fixed offset current to the V2I resistor node to cause at least one V2I output current to have a value conversely proportional to absolute temperature (CTAT), the at least one V2I output current being output by the V2I converter, and mirror the at least one V2I output current to the CCO to reduce the temperature-induced frequency drift at a lower frequency band of the VCO.