Oscillator Frequency Compensation Using Ratio-Based Voltage Trimming

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Solution Overview

Problem

The existing semiconductor integrated circuit oscillators face challenges in achieving high-precision frequency compensation due to variations in the reference voltage supplied to the analog-digital converter, leading to deviations in the temperature compensation code and subsequent trimming inaccuracies.

Innovation Solution

A semiconductor integrated circuit design that includes a signal voltage output unit generating both temperature-dependent and temperature-independent signal voltages, an A/D converter for digitalizing these voltages, and a compensation code generation unit that calculates a compensation code based on the ratios of these signals to accurately compensate the oscillator frequency, even with deviations in the reference voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single signal voltage is used for frequency compensation, then the circuit structure is simple, but the compensation precision deteriorates due to reference voltage variations

Engineering Contradiction:

Improvecircuit structureVSAvoidfrequency compensation precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The signal voltage output unit is segmented into two independent signal generation paths: one generating a temperature-dependent signal voltage and another generating a temperature-independent signal voltage. This segmentation allows the system to separately handle compensation for temperature effects and reference voltage variations, thereby improving frequency compensation precision without significantly increasing circuit complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A ratio calculation mechanism is introduced as an intermediary between the signal voltages and the compensation code generation. By calculating the ratio of temperature-dependent signal voltage to temperature-independent signal voltage, the system eliminates the influence of reference voltage variations, achieving high-precision frequency compensation despite variations in the reference voltage supplied to the A/D converter.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If temperature compensation is implemented using conventional methods, then the oscillator frequency can be stabilized against temperature changes, but the compensation accuracy deteriorates when reference voltage varies across different substrate manufacturers

Engineering Contradiction:

Improveoscillator frequency stabilityVSAvoidcompensation code accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system changes the parameter used for compensation from absolute temperature-dependent signal voltage to the ratio of temperature-dependent signal voltage to temperature-independent signal voltage. This parameter transformation makes the compensation code generation immune to reference voltage variations across different substrate manufacturers, thereby maintaining both frequency stability and compensation accuracy.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the A/D converter uses a fixed reference voltage for digitalization, then the conversion process is simple, but the trimming precision deteriorates due to reference voltage deviations

Engineering Contradiction:

Improveconversion processVSAvoidtrimming precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The system implements a feedback mechanism where the temperature-independent signal voltage serves as a reference that is continuously compared with the temperature-dependent signal voltage. The ratio of these two voltages provides feedback information that compensates for reference voltage deviations, enabling high-precision trimming without increasing the complexity of the A/D conversion process.

Inventive Principle:

Principle #23Feedback

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

This approach enables high-precision frequency trimming of oscillators, ensuring consistent performance across different substrate manufacturers' voltage settings, thereby stabilizing the oscillation frequency despite variations in the reference voltage.

Implementation Method 1

an A/D converter for digitalizing the temperature-dependent signal voltage and the temperature-independent signal voltage

Methodology Applied

Scientific EffectAnalog-to-Digital Conversion:

Data Source

PatentUS7515008B2Semiconductor integrated circuit having oscillator frequency compensation function

Publication Date: 2009.04.07 RENESAS ELECTRONICS CORP

AI summary

It is desired that the temperature dependency of the frequency of a oscillator in a semiconductor IC is compensated in high precision. First signal voltage having temperature dependency and second signal voltage set to be constant independently from the temperature are outputted and A/D converted into first and second converted signals. And the compensation code is generated in response to the ratio between the first and second converted signals. The temperature dependency of the frequency of the oscillator can be compensated by using the compensation code.