Complementary PTAT Voltage Reference Circuit for Low-Voltage Noise Reduction

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Solution Overview

Problem

Conventional CMOS-based band-gap voltage reference circuits in high-speed Ethernet LANs are prone to noise, power supply rejection problems, and accuracy issues, and struggle to operate at low voltages with minimal current consumption.

Innovation Solution

A voltage reference circuit using complementary PTAT voltage generators, combining PNP and NPN transistors in a low-voltage double-ΔVBE topology, with a fully-cascoded ground-referred architecture and a folded-cascode error amplifier to reduce noise and current consumption, while maintaining high precision and power supply rejection ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional CMOS-based band-gap voltage reference circuits are used, then voltage reference functionality is provided, but the circuit is highly prone to noise, power supply rejection problems, and accuracy issues

Engineering Contradiction:

ImproveaccuracyVSAvoidnoise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The voltage reference circuit is divided into two independent complementary PTAT voltage generators (first and second generators) that operate separately but contribute to the same reference voltage. This segmentation allows each generator to be optimized for specific noise reduction techniques while maintaining overall accuracy through their combined output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines PNP and NPN transistors in a complementary configuration within the PTAT voltage generators. This merging of complementary transistor types allows the circuit to exploit the advantageous characteristics of both transistor families, improving noise immunity and power supply rejection while maintaining accuracy.

Inventive Principle:

Principle #5Merging (Combining)

2Use of energy by moving object

If conventional voltage reference circuits are used, then reference voltage is generated, but current consumption is high and low-voltage operation is difficult

Engineering Contradiction:

Improvecurrent consumptionVSAvoidlow-voltage operation

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The patent employs parameter changes by utilizing the complementary characteristics of PNP and NPN transistors across different voltage ranges. The circuit parameters are optimized to enable operation at lower voltages while maintaining minimal current consumption through the complementary PTAT voltage generator architecture.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional voltage reference circuits are used, then voltage reference is provided, but power supply rejection ratio is poor

Engineering Contradiction:

Improvepower supply rejection ratioVSAvoidpower supply rejection problems

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The error amplifier in the circuit provides feedback to compensate for power supply variations and improve the power supply rejection ratio. The feedback mechanism detects deviations in the reference voltage caused by power supply fluctuations and corrects them, enhancing overall reliability.

Inventive Principle:

Principle #23Feedback

4Reliability

If conventional voltage reference circuits are used, then reference voltage is generated, but temperature variation affects accuracy

Engineering Contradiction:

Improvetemperature stabilityVSAvoidtemperature variation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The PTAT (Proportional to Absolute Temperature) voltage generators are specifically designed to produce a voltage that is proportional to absolute temperature. By using complementary PTAT generators with opposite temperature coefficients, the circuit achieves temperature compensation, where temperature-induced variations in one generator are canceled by the other, maintaining stable reference voltage across temperature ranges.

Inventive Principle:

Principle #35Parameter changes

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 solution improves accuracy and noise reduction while enabling low-voltage operation with minimal current consumption, achieving a high power supply rejection ratio and temperature compensation, thus addressing the limitations of conventional voltage reference circuits.

Implementation Method 1

A voltage reference circuit with complementary PTAT voltage generators and method, the voltage reference circuit generates a reference voltage using two complementary proportional-to-absolute-temperature (PTAT) voltage generators

Methodology Applied

Scientific EffectPTAT (Proportional to Absolute Temperature) voltage generation:

Implementation Method 2

Conventional CMOS-based band-gap voltage reference circuits are highly prone to variations as a result of noise, power supply rejection problems, and other accuracy issues

Methodology Applied

Scientific EffectBand-gap voltage reference:

Data Source

PatentUS7595627B1Voltage reference circuit with complementary PTAT voltage generators and method

Publication Date: 2009.09.29 NAT SEMICON CORP

AI summary

A voltage reference circuit is provided. The voltage reference circuit includes a first PTAT voltage generator and an amplifier. The first PTAT voltage generator is operable to generate a first PTAT voltage. The amplifier, which is coupled to the first PTAT voltage generator, comprises a second PTAT voltage generator that is complementary to the first PTAT voltage generator. The second PTAT voltage generator is operable to generate a second PTAT voltage. The amplifier is operable to generate a reference voltage based on the first PTAT voltage and the second PTAT voltage.