Shared LC Tank VCO Switching Between Phase Noise and Power Modes

Solution Overview

Problem

Existing voltage-controlled oscillators (VCOs) face challenges in balancing high-performance and low-power operation due to intrinsic relationships between phase noise and current consumption, with NMOS LC VCOs drawing excessive current and CMOS LC VCOs failing to meet phase noise standards, necessitating separate VCOs that occupy substantial silicon die area.

Innovation Solution

A switchable NMOS-CMOS VCO with a shared LC tank, utilizing a cross-coupled differential pair of NMOS transistors and selectively coupled CMOS transistors, allows for switching between high-performance and low-power modes by sharing an LC tank, reducing current draw and die area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an NMOS LC VCO is used to meet high-performance phase noise requirements, then phase noise performance is improved, but current consumption increases excessively

Engineering Contradiction:

Improvephase noise performanceVSAvoidcurrent consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The VCO circuit dynamically switches between NMOS and CMOS operating modes based on performance requirements. The circuit includes switching mechanisms that allow it to transition from high-performance NMOS mode (for low phase noise) to low-power CMOS mode (for reduced current consumption), making the power consumption adaptive rather than static

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operating parameters of the VCO by switching between different transistor types (NMOS and CMOS) and different operating modes. This allows the circuit to adjust its characteristics - using NMOS for high-performance applications and CMOS for power-sensitive applications - without requiring separate dedicated circuits

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If a CMOS LC VCO is used to reduce current consumption, then power efficiency is improved, but phase noise standards are not met

Engineering Contradiction:

Improvecurrent consumptionVSAvoidphase noise performance

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The VCO circuit dynamically switches between NMOS and CMOS operating modes based on performance requirements. The circuit includes switching mechanisms that allow it to transition from high-performance NMOS mode (for low phase noise) to low-power CMOS mode (for reduced current consumption), making the power consumption adaptive rather than static

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operating parameters of the VCO by switching between different transistor types (NMOS and CMOS) and different operating modes. This allows the circuit to adjust its characteristics - using NMOS for high-performance applications and CMOS for power-sensitive applications - without requiring separate dedicated circuits

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If separate NMOS and CMOS VCOs are used to cover both high-performance and low-power requirements, then operational versatility is improved, but silicon die area increases substantially

Engineering Contradiction:

Improveoperational versatilityVSAvoidsilicon die area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The VCO circuit is designed as a universal multi-functional oscillator that can operate in both high-performance NMOS mode and low-power CMOS mode using the same core LC tank circuit. This single circuit serves multiple purposes - acting as both a high-performance VCO and a low-power VCO - eliminating the need for separate dedicated circuits for each application scenario

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention merges the functionality of separate NMOS and CMOS VCOs into a single integrated circuit. The LC tank circuit is shared between both operating modes, and the switching mechanisms combine both transistor types in one unified structure, reducing the total die area compared to implementing separate independent VCO circuits

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12388401B2Switchable NMOS-CMOS voltage-controlled oscillator (VCO) with shared inductor-capacitor (LC) tank

Publication Date: 2025.08.12 INFINEON TECHNOLOGIES AMERICAS CORP

AI summary

A voltage-controlled oscillator (VCO) includes a cross-coupled differential pair of n-type metal-oxide semiconductor (NMOS) transistors. The VCO further includes an inductor-capacitor (LC) tank circuit coupled to the cross-coupled differential pair of NMOS transistors. The VCO further includes cross-coupled pairs of complementary MOS (CMOS) transistors selectively coupled to the LC tank circuit.