Digital Switch-Capacitor Bandgap Reference Circuit

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Solution Overview

Problem

Traditional bandgap reference generators require significant circuit area and power for voltage headroom, making them inefficient for low-power digital circuits, and they often rely on continuous time references which are not scalable or power-efficient.

Innovation Solution

A digital switch-capacitor based bandgap reference and thermal sensor system that uses sigma-delta ADCs and forward biased diode circuits with switch-capacitor samplers, eliminating the need for unity gain amplifiers and startup circuits, and providing a scalable, low-power solution with built-in offset cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional analog bandgap reference generators are used, then a constant temperature-independent reference voltage is generated, but the circuit requires significant area and power for voltage headroom

Engineering Contradiction:

Improvetemperature independence of reference voltageVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional analog continuous-time bandgap reference generator with a digital switch-capacitor based system. This substitution transforms the continuous analog voltage generation into discrete time-domain sampling and processing, eliminating the need for high-voltage headroom analog circuits and reducing power consumption while maintaining temperature-independent reference voltage generation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the operating parameters by using switch-capacitor circuits that sample and hold voltages at specific time instances, then process them digitally. This transforms the continuous voltage generation approach into a discrete sampling approach, enabling operation at lower supply voltages and reducing power consumption while maintaining reference accuracy

Inventive Principle:

Principle #35Parameter changes

2Reliability

If traditional analog bandgap reference generators are used, then a constant bandgap reference voltage is generated, but the circuit area is significantly increased

Engineering Contradiction:

Improveconstant reference voltageVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces area-intensive analog continuous-time bandgap circuits with compact digital switch-capacitor circuits. The switch-capacitor implementation uses smaller components and can be integrated more densely, significantly reducing the overall circuit area while maintaining the constant reference voltage function

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention uses periodic sampling action where switch-capacitor circuits sample the bandgap voltage at discrete time intervals rather than maintaining a continuous analog signal. This periodic sampling approach allows the use of smaller capacitors and switches, reducing the total circuit area compared to continuous-time analog implementations

Inventive Principle:

Principle #19Periodic action

3Reliability

If continuous time bandgap reference is used, then reference voltage is provided, but additional regulators and unity gain buffers are required which consume area and power

Engineering Contradiction:

Improvereference voltage stabilityVSAvoidcircuit components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and removes the unnecessary regulators and unity gain buffer components from the traditional bandgap reference architecture. By using digital switch-capacitor sampling and processing, the system directly generates the stable reference voltage without requiring these intermediate analog conditioning stages, simplifying the overall circuit

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The switch-capacitor circuits perform multiple functions: they sample the bandgap voltage, hold it during processing, and provide the stable reference output. This multi-functionality eliminates the need for separate regulators and buffers, reducing device complexity while maintaining reference voltage stability

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Reliability

If traditional bandgap reference generators are used, then proper operation is achieved, but voltage headroom requirements increase power supply needs

Engineering Contradiction:

Improveproper circuit operationVSAvoidpower supply voltage

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent substitutes analog voltage amplification stages with digital switch-capacitor processing. This substitution allows the circuit to operate properly with reduced voltage headroom since the switch-capacitor circuits can function effectively at lower supply voltages, enabling proper operation with reduced power supply requirements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10712875B2Digital switch-capacitor based bandgap reference and thermal sensor

Publication Date: 2020.07.14 INTEL CORP

AI summary

Described is an apparatus of a thermal sensor and/or bandgap reference circuit which is independent of an operational amplifier. The apparatus comprises: a forward biased diode circuit having one or more diodes; a first switch-capacitor sampler coupled to the forward biased diode circuit, the first switch-capacitor sampler to provide a reference voltage which is proportional to absolute temperature; and a second switch-capacitor sampler coupled to the forward biased diode circuit.