Sub-Threshold LDO Regulator Stabilization via Source Degeneration

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Solution Overview

Problem

Sub-threshold region-based low dropout (LDO) regulators face instability due to current mismatch caused by process variations, making it challenging to maintain ultra-low quiescent current.

Innovation Solution

Incorporating resistors with large resistance values between elements operating in the sub-threshold region and the power line, which reduces current mismatch and stabilizes the LDO regulator by using source degeneration technology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If sub-threshold technology is applied to achieve ultra-low quiescent current, then power consumption is reduced, but current mismatch due to process variation increases

Engineering Contradiction:

Improvequiescent currentVSAvoidcurrent mismatch

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces resistors as intermediary elements between the sub-threshold transistors and the power line. These resistors act as mediators that stabilize the current paths and reduce the impact of process variations on current matching, thereby resolving the contradiction between low power consumption and current mismatch reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the operating parameters by introducing resistors with specific resistance values into the current paths. This parameter modification allows the circuit to maintain ultra-low quiescent current while compensating for process variations, thus resolving the contradiction between energy efficiency and current matching accuracy

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If elements operate in sub-threshold region to reduce power consumption, then energy efficiency is improved, but stability deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidcircuit stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The resistors serve as intermediary elements that stabilize the sub-threshold operating region. By introducing these resistive elements into the current paths, the circuit maintains stability while operating in the sub-threshold region, thus resolving the contradiction between energy efficiency and circuit stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies beforehand cushioning by pre-positioning resistors in the circuit paths to compensate for potential instability issues before they occur. These resistors provide a stabilizing effect that cushions against the inherent instability of sub-threshold operation, allowing the circuit to maintain both low power consumption and stability

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10915132B1Sub-threshold region based low dropout regulator

Publication Date: 2021.02.09 HIMAX TECH LTD

AI summary

A low dropout (LDO) regulator is configured to generate an LDO voltage. The LDO regulator includes at least one current mirror and at least one resistor. The at least one current mirror operates in a sub-threshold region. A first terminal of the at least one resistor is directly coupled to the at least one current mirror. A second terminal of the at least one resistor is directly coupled to a power line.