Stacked Voltage Reference Circuit for Stable Low-Power Output

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Solution Overview

Problem

Voltage reference circuits face challenges in providing a stable, high output reference voltage with low power consumption and insensitivity to parameter variations such as temperature and supply voltage fluctuations, especially in small devices like IoT devices that operate in sleep mode for brief periods.

Innovation Solution

A voltage reference circuit is designed with a stacked connection of transistors, including additional regulating transistors to compensate for voltage changes, ensuring a stable output voltage level while scaling the reference voltage, and configured to output multiple reference voltages from different nodes based on desired properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If stacked pMOS transistors are used to increase output reference voltage, then the reference voltage level increases, but power consumption increases and noise increases

Engineering Contradiction:

Improvereference voltage levelVSAvoidpower consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent changes the operating parameters by using nMOS transistors instead of pMOS transistors, and by operating in the subthreshold region where transistors conduct very small currents. This parameter change allows achieving the desired voltage level transformation while maintaining extremely low power consumption (picowatt range), directly resolving the contradiction between voltage level and power consumption.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If stacked pMOS transistors are used to increase output reference voltage, then the reference voltage level increases, but noise increases

Engineering Contradiction:

Improvereference voltage levelVSAvoidnoise

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The patent changes the transistor type from pMOS to nMOS and operates in the subthreshold region, which fundamentally alters the noise characteristics. The subthreshold operation mode produces significantly less noise while still achieving the required voltage transformation, thus resolving the contradiction between voltage level and noise.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If voltage reference circuit is always-on to provide stable reference voltage, then voltage stability is maintained, but power consumption increases

Engineering Contradiction:

Improvevoltage stabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent uses subthreshold operation which enables the circuit to consume extremely low power (picowatt range) while remaining always-on. This parameter change allows the voltage reference circuit to maintain continuous operation for stable voltage provision without incurring high power consumption, directly resolving the contradiction between reliability and power consumption.

Inventive Principle:

Principle #35Parameter changes

4Use of energy by moving object

If subthreshold region operation is used to reduce power consumption, then power consumption decreases, but output reference voltage becomes very low

Engineering Contradiction:

Improvepower consumptionVSAvoidoutput reference voltage

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent introduces intermediate nMOS transistors configured in specific arrangements (including diode-connected transistors and current mirrors) that act as mediators to transform the low voltage generated in subthreshold operation into a higher reference voltage. These intermediary structures enable voltage level transformation while maintaining the low power consumption benefits of subthreshold operation, resolving the contradiction between power consumption and output voltage level.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP4266144A1A voltage reference circuit and a power management unit

Publication Date: 2023.10.25 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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AI summary

A voltage reference circuit (100; 200) comprises: first transistor (110; 210), second transistor (120; 220), first regulating transistor (130; 230), and second regulating transistor (140; 240) arranged in a stacked connection, wherein first voltage is provided at first node (150; 250) between first (110; 210) and second transistor (120; 220), second voltage is provided at second node (152; 252) between second transistor (120; 220) and first regulating transistor (130; 230), third voltage is provided at third node (152; 252) between first (130; 230) and second regulating transistor (140; 240); wherein first regulating transistor (130; 230) and second regulating transistor (140; 240) are connected to first node (150; 250) and second node (152; 252), respectively, for compensating changes in first voltage and second voltage, respectively, to maintain stable voltage levels; wherein voltage reference circuit (100; 200) outputs at least one of the first, second or third voltage as a reference voltage.