RC Oscillator Switching Matrix for Process-Induced Frequency Drift

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Solution Overview

Problem

RC-type oscillator circuits integrated in semiconductor chips experience undesired frequency shifts due to manufacturing processes and mechanical stresses during packaging, which are difficult and costly to compensate.

Innovation Solution

An oscillator circuit design that includes multiple current generators and a switching matrix, allowing for selective connection configurations to reduce frequency variations by iteratively charging and discharging capacitors, thereby minimizing the impact of manufacturing-induced errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If RC-type oscillator circuits are integrated in semiconductor chips using internal resistors and capacitors, then the device complexity is reduced and integration is improved, but frequency accuracy deteriorates due to manufacturing process variations and mechanical stresses

Engineering Contradiction:
Improvecircuit integrationVSAvoidfrequency accuracy
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent implements a feedback mechanism where the oscillator frequency is continuously monitored and compared against a reference frequency. A control signal adjusts the oscillation frequency based on the detected deviation, compensating for manufacturing variations and mechanical stress effects. This closed-loop feedback system maintains frequency accuracy despite the integrated circuit's susceptibility to process variations.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent employs variable parameters in the RC circuit elements, allowing dynamic adjustment of resistance and capacitance values. By changing these parameters in response to detected frequency deviations, the system compensates for manufacturing tolerances and environmental effects, maintaining accurate frequency output while keeping the circuit integrated on the semiconductor chip.

Inventive Principle:
Principle #35Parameter changes

2Manufacturing precision

If calibration steps are added to compensate for frequency shifts, then frequency accuracy is improved, but the manufacturing process complexity and cost increase

Engineering Contradiction:
Improvefrequency accuracyVSAvoidcalibration process
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements a self-calibrating oscillator that automatically compensates for its own frequency deviations without requiring external calibration equipment or additional manufacturing steps. The built-in feedback mechanism continuously monitors and adjusts the frequency, enabling the circuit to self-correct manufacturing variations and maintain accuracy throughout its operational life without human intervention or complex calibration procedures.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The automatic feedback control system eliminates the need for manual or external calibration by continuously detecting frequency deviations and applying real-time corrections. This self-regulating approach replaces complex multi-step calibration processes with a simple automated control loop that maintains frequency accuracy during normal operation.

Inventive Principle:
Principle #23Feedback

3Stability of the object's composition

If multiple current generators and switching matrices are used to reduce frequency variations, then frequency stability is improved, but the circuit complexity increases

Engineering Contradiction:
Improvefrequency stabilityVSAvoidcircuit structure
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent divides the current generation function into multiple separate current generators, each responsible for a specific portion of the total current. This segmentation allows independent optimization and control of each current source, improving frequency stability by reducing the impact of variations in any single generator while keeping the overall circuit manageable through modular architecture.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent employs dynamic switching between different current generator configurations using switching matrices. By dynamically reconfiguring which current generators are active based on operating conditions, the system optimizes frequency stability for different scenarios while maintaining reasonable circuit complexity through controlled adaptability rather than static over-engineering.

Inventive Principle:
Principle #15Dynamics

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

The design achieves a more accurate and reliable clock signal frequency by reducing the impact of manufacturing-induced errors, with error terms minimized through the use of offset effects and iterative connection sequences.

Implementation Method 1

a first capacitor c1, having a nominal capacity C, is provided with a first terminal 16 connected to a first output of the switching matrix 13

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP2541769B1Oscillator circuit and electronic system comprising oscillator circuit
Publication Date: 2014.02.26 STMICROELECTRONICS SRL
  • EP2541769B1 patent drawingFigure 1
  • EP2541769B1 patent drawingFigure 2
  • EP2541769B1 patent drawingFigure 3

AI summary

It is described an oscillator circuit (1) comprising a first capacitor (c1) provided with a first terminal (16); a resistor (r) provided with a reference terminal (18); a first current generator (g1) provided with a connection terminal (14); a second current generator (g2) provided with a second connection terminal (15). Further, the circuit comprises a switching matrix (13) between the first (g1) and second generators (g2) and resistor (r) and the at least one first capacitor (c1).