Programmable Voltage Reference Circuit with Curvature Compensation

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Solution Overview

Problem

Existing voltage reference circuits in integrated circuits face challenges in generating flexible temperature coefficient voltages while compensating for second-order curvature introduced by bipolar junction transistors (BJTs), which degrades as CMOS technology scales.

Innovation Solution

A programmable temperature coefficient analog second-order curvature compensated voltage reference circuit is developed, comprising a reference circuit with first and second current sources and load circuits that generate sum currents to produce zero and negative temperature coefficient voltages, using p-channel FETs and BJTs to mitigate temperature effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If bipolar junction transistors (BJTs) are used to generate voltage references, then temperature-dependent voltage generation is achieved, but second-order curvature degradation occurs as CMOS technology scales

Engineering Contradiction:

Improvetemperature coefficient flexibilityVSAvoidvoltage reference accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The voltage reference circuit is segmented into multiple functional blocks: a reference voltage generation block using BJTs for temperature dependence, a curvature compensation block that separately generates compensation signals, and a combination block that merges these signals. This segmentation allows independent optimization of each function while maintaining overall performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediary curvature compensation circuit is introduced between the BJT-based reference voltage generator and the final output. This intermediary block generates compensation currents or voltages that counteract the second-order curvature effects, thereby mediating between the temperature-dependent reference generation and the accuracy requirement.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple temperature coefficient voltages are generated, then flexibility for different circuit applications is improved, but circuit complexity increases

Engineering Contradiction:

Improvetemperature coefficient flexibilityVSAvoidvoltage reference circuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The voltage reference circuit is designed with multi-functionality to generate multiple temperature coefficient voltages (zero Tempco, positive Tempco, and negative Tempco) from a single unified architecture. The same BJT-based reference generation core and curvature compensation mechanism serve all three output types, reducing overall circuit complexity compared to implementing separate circuits for each temperature coefficient.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The circuit employs dynamic control mechanisms where current mirrors and switches dynamically route and combine reference currents to produce different temperature coefficient outputs. By dynamically adjusting current distribution and combination ratios, the circuit achieves multiple temperature coefficient functionalities without requiring static separate circuits for each output type.

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

This solution enables flexible generation of temperature-dependent voltages, effectively compensating for second-order curvature and improving the performance of voltage reference circuits in integrated circuits, particularly in CMOS technology.

Implementation Method 1

a first circuit configured to generate a proportional-to-temperature current

Methodology Applied

Scientific EffectProportional-to-temperature current generation:

Implementation Method 2

a second circuit configured to generate a complementary-to-temperature current

Methodology Applied

Scientific EffectComplementary-to-temperature current generation:

Implementation Method 3

the first load circuit generating a zero temperature coefficient (Tempco) voltage from the sum current

Methodology Applied

Scientific EffectZero temperature coefficient voltage generation:

Implementation Method 4

the second load circuit generating a negative Tempco voltage from the sum current and the complementary-to-temperature current

Methodology Applied

Scientific EffectNegative temperature coefficient voltage generation:

Data Source

PatentUS20190172504A1Programmable temperature coefficient analog second-order curvature compensated voltage reference

Publication Date: 2019.06.06 XILINX INC

AI summary

An example voltage reference circuit includes: a reference circuit comprising a first circuit configured to generate a proportional-to-temperature current and corresponding first control voltage and a second circuit configured to generate a complementary-to-temperature current and corresponding second control voltage; a first current source coupled to a first load circuit, the first current source generating a sum current of the proportional-to-temperature current and the complementary-to-temperature current in response to the first and second control voltages, the first load circuit generating a zero temperature coefficient (Tempco) voltage from the sum current; and a second current source coupled to a second load circuit, the second current source generating the sum current of the proportional-to-temperature current and the complementary-to-temperature current in response to the first and second control voltages, the second load circuit generating a negative Tempco voltage from the sum current and the complementary-to-temperature current.