Cascode LDO Power Stage for Wide-Input Stable Regulation

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Solution Overview

Problem

LDO circuits face challenges when used in wide range input applications, requiring improved voltage regulation and stability.

Innovation Solution

The proposed electronic device includes a low dropout (LDO) circuit with a power stage utilizing core transistors, which provide a strong driving capability and a wider input range, along with a compensation and feedback circuit to enhance stability and noise reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional LDO circuits are used, then voltage regulation function is provided, but input voltage range is limited

Engineering Contradiction:

Improveinput voltage rangeVSAvoidcircuit stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The power stage is divided into two separate transistors (first transistor and second transistor) connected in series. The first transistor handles the input voltage regulation while the second transistor provides output stabilization. This segmentation allows each transistor to operate within its optimal voltage range, enabling the circuit to handle wider input voltage ranges while maintaining stability through distributed voltage management.

Inventive Principle:

Principle #1Segmentation

2Power

If core transistors are used in power stage, then driving capability is improved, but vulnerability to high-voltage conditions increases

Engineering Contradiction:

Improvedriving capabilityVSAvoidtransistor reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

A second transistor is introduced as an intermediary protective element between the high-voltage input and the core first transistor. This second transistor acts as a voltage buffer and protection device that prevents high-voltage conditions from reaching the first core transistor, thereby protecting it from damage while allowing the first transistor to maintain its high driving capability within safe operating parameters.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If power stage is designed for wide input range, then adaptability is improved, but noise increases

Engineering Contradiction:

Improveinput voltage rangeVSAvoidnoise

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The power stage is segmented into two transistors that share the voltage regulation task. This segmentation allows for better noise distribution and management, where each transistor operates in a more stable voltage region, reducing the overall noise generated by the power stage while maintaining wide input voltage adaptability.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12204357B2Low drop-out circuit, electronic device, and method of manufacturing the same

Publication Date: 2025.01.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a low dropout (LDO) circuit. The LDO circuit includes an input terminal, an output terminal, a cascode operational amplifier, and a power stage. The cascode operational amplifier is electrically connected to the input terminal. The power stage has a first terminal electrically connected to the input terminal, a second terminal electrically connected to an output node of the cascode operational amplifier, and a third terminal electrically connected to the output terminal.