Low-Dropout Regulator Compensation for Stable Low-Noise Operation
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Solution Overview
Problem
Prior-art low dropout regulators (LDOs) suffer from poor noise performance due to a low transconductance upper limit of the error amplifier, which compromises system stability and noise reduction capabilities.
Innovation Solution
The introduction of a second compensation circuit in the LDO, which includes a compensation resistor connected to the error amplifier and a transistor, allows for the regulation of the gain-bandwidth product and phase margin, increasing the secondary dominant pole and reducing the dominant pole, thereby enhancing system stability and noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the transconductance of the error amplifier is increased to improve noise performance, then noise performance is improved, but system stability is compromised
Solution Approach 1:
The patent introduces a second compensation circuit with a compensation resistor that dynamically adjusts the dominant pole and secondary dominant pole positions. This dynamic adjustment allows the system to maintain stability while enabling higher transconductance values in the error amplifier, thereby resolving the contradiction between noise performance and system stability.
Solution Approach 2:
The patent changes the compensation parameters by introducing a compensation resistor in the second compensation circuit. This modifies the pole-zero configuration, allowing the system to achieve both high transconductance for noise performance and appropriate phase margin for stability through parameter optimization.
2Stability of the object's composition
If a compensation circuit is added to improve stability, then system stability is improved, but noise performance deteriorates due to limited transconductance upper limit
Solution Approach 1:
The patent segments the compensation function into two distinct circuits: a first compensation circuit for basic stability and a second compensation circuit with a compensation resistor for fine-tuning the dominant and secondary dominant poles. This segmentation allows independent optimization of stability and noise performance without mutual interference.
Solution Approach 2:
The compensation resistor in the second compensation circuit acts as an intermediary element that mediates between the error amplifier and the load. It provides the necessary phase compensation to maintain stability while allowing the error amplifier to operate at higher transconductance values for improved noise performance.
3Speed
If the gain-bandwidth product is increased to improve response speed, then response speed is improved, but phase margin decreases compromising stability
Solution Approach 1:
The second compensation circuit with the compensation resistor dynamically adjusts the dominant pole position to optimize the gain-bandwidth product while maintaining adequate phase margin. This dynamic pole placement allows the system to achieve fast response speed without sacrificing stability.
Data Source
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AI summary
Embodiments of the present invention disclose a low dropout regulator, a method for improving stability of the low dropout regulator, and a phase-locked loop. The low dropout regulator includes: a reference voltage source, an error amplifier, a regulating circuit, a load, a first compensation circuit, and a second compensation circuit. The first compensation circuit is coupled to the regulating circuit, and is configured to regulate a dominant pole and a secondary dominant pole of the low dropout regulator, to regulate a phase margin. The second compensation circuit is configured to: regulate and decrease the dominant pole of the low dropout regulator and further increase the secondary dominant pole on the basis that the first compensation circuit has regulated the dominant pole and the secondary dominant pole of the low dropout regulator, so as to regulate the phase margin; and regulate a gain-bandwidth product of the low dropout regulator. By using the low dropout regulator according to the embodiments of the present invention, a value of the gain-bandwidth product and a size of the dominant pole can be significantly reduced, and a size of the secondary dominant pole can be increased, so that the error amplifier has better noise performance.