Voltage Reference Circuit With Near-Zero TC and High PSRR

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Solution Overview

Problem

Existing voltage reference circuits struggle to provide a stable voltage reference with low output noise and low sensitivity to supply variations, especially at low supply voltages, which is crucial for IoT devices to conserve power and reduce die area and power dissipation.

Innovation Solution

A voltage reference circuit design that combines transistors with positive and negative temperature coefficients to generate an output voltage across a resistor, using amplifiers to improve power supply rejection ratio (PSRR) and achieve a near-zero temperature coefficient, allowing operation at low supply voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional voltage reference circuits are used, then voltage reference stability is achieved, but power consumption increases and supply voltage headroom is reduced

Engineering Contradiction:

Improvevoltage reference stabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The circuit changes the operating parameters by using transistors in triode region instead of saturation region, allowing the reference circuit to operate at lower supply voltages (0.4V-0.6V) while maintaining temperature stability through the specific combination of PTAT and CTAT current paths

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical filtering components (LC filters, RC filters) with an active circuit implementation that achieves superior power supply rejection through the differential amplifier configuration and complementary transistor pairs, eliminating the need for external filtering components

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional voltage reference circuits are used, then voltage reference stability is achieved, but sensitivity to supply variations increases

Engineering Contradiction:

Improvevoltage reference stabilityVSAvoidsensitivity to supply variations

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The differential amplifier configuration provides negative feedback that actively compensates for supply voltage variations. The amplifiers adjust the gate voltages of the transistors to maintain constant current flow through the reference transistors, thereby rejecting supply noise and variations

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The circuit combines transistors with complementary temperature coefficients (PTAT and CTAT) in a composite configuration where the opposite temperature dependencies cancel each other out, achieving temperature independence while the differential structure provides supply rejection

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If low supply voltage is used, then power consumption is reduced, but temperature coefficient stability deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidtemperature coefficient stability

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Different parts of the circuit are designed with different temperature coefficient characteristics - some transistors and current paths are designed to produce PTAT behavior while others produce CTAT behavior, and these are locally optimized to cancel out in the overall reference voltage

Inventive Principle:

Principle #3Local quality

4Object-affected harmful factors

If additional filtering components are added, then supply noise rejection is improved, but die area increases

Engineering Contradiction:

Improvesupply noise rejectionVSAvoiddie area

Core Design Contradiction:

Object-affected harmful factorsVSArea of stationary object

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12591263B2Voltage and current reference circuits providing voltage and currents with near zero temperature coefficients

Publication Date: 2026.03.31 SILICON LABORATORIES INC

AI summary

A voltage reference circuit can operate in a large supply voltage range, including a low supply voltage, and can operate with high PSRR. The voltage reference circuit supplies a voltage reference with a near zero temperature coefficient (TC) across a wide-temperature range. The voltage reference circuit develops a first current with a positive temperature coefficient from a first transistor and a second current with a negative temperature coefficient from a second transistor. The control terminals of the two transistors are supplied by respective outputs of two error amplifiers. The two currents are combined to develop a voltage reference across a resistor. The voltage reference has a near zero temperature coefficient.