Multi-Stage LDO Circuit for High-Voltage Stepdown Stability
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Solution Overview
Problem
Existing low-dropout regulator (LDO) circuits face challenges in regulating high input supply voltages while maintaining a high power supply rejection ratio (PSRR), fast transient response, and reducing reliability issues such as device burnout due to high voltage drops.
Innovation Solution
The implementation of a multi-level LDO circuit with multiple stages, where each stage steps down the voltage in gradual stages across multiple LDOs, allowing for better control of intermediate and overall voltage drops, reducing voltage differences across components, and enhancing reliability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage LDO is used to step down high input voltage, then the circuit structure is simple, but the voltage drop across the regulator causes reliability issues and device burnout
Solution Approach 1:
The voltage regulation process is divided into multiple stages, with the first stage performing coarse voltage reduction and the second stage performing fine regulation. This segmentation reduces the voltage drop across each individual regulator, preventing device burnout and improving reliability while maintaining reasonable circuit complexity.
2Reliability
If a multi-stage LDO circuit is used to reduce voltage drops, then reliability improves, but the device complexity increases
Solution Approach 1:
The circuit is segmented into two functional stages: a first voltage reduction stage and a second regulation stage. Each stage has a specific function, which simplifies the design and analysis of each individual block while achieving the overall goal of reduced voltage drops and improved reliability.
Solution Approach 2:
An intermediate voltage node is introduced between the two stages, serving as a mediator that connects the coarse reduction stage and the fine regulation stage. This intermediate node allows the system to transition from high voltage to low voltage in controlled steps, improving reliability without excessive complexity.
3Device complexity
If a single-stage LDO regulates voltage directly from high input to output, then the circuit is simple, but the power supply rejection ratio (PSRR) is degraded
Solution Approach 1:
The voltage regulation is segmented into two stages, where the first stage handles the bulk of the voltage reduction and the second stage provides precise regulation with high PSRR. This segmentation allows the second stage to operate with a more favorable voltage differential, improving its ability to reject power supply noise.
4Speed
If a single-stage LDO is used, then the transient response is slower, but using a multi-stage circuit increases device complexity
Solution Approach 1:
The transient response improvement is achieved through segmentation into two stages, where the first stage provides a low-impedance voltage source that enhances the transient response of the second stage. This segmentation allows the regulation stage to respond faster to load changes without requiring excessive complexity in a single block.
Data Source
AI summary
Systems and methods as described herein may take a variety of forms. In an example, a circuit includes a first voltage stepdown module and a second voltage stepdown module. The first voltage stepdown module has a supply voltage and a first reference voltage as inputs, and an intermediate stepped down voltage as an output, the intermediate stepped down voltage being electrically coupled to a feedback input of the first voltage stepdown module. The second voltage stepdown module includes a low-dropout voltage regulator having the intermediate stepped down voltage and a second reference voltage as inputs and a target voltage as an output.