LDO Regulator Noise-Suppression Circuit for Stable Output Accuracy
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Solution Overview
Problem
Low-dropout regulators face decreased output accuracy due to noise interference from various sources, as they lack effective noise-suppression mechanisms, which affects the reference voltage and subsequently the output voltage.
Innovation Solution
The implementation of an operational amplifier circuit with a differential input circuit, amplifying output circuit, and strategically placed resistive components to increase the power supply rejection ratio (PSSR), thereby isolating the reference voltage from noise and maintaining output voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If no noise-suppression mechanism is added to the LDO, then the device complexity remains low, but the output accuracy decreases due to noise interference
Solution Approach 1:
The patent introduces resistive components as intermediary elements between the power supply and the operational amplifier circuit. These resistors act as noise filters, blocking high-frequency noise from reaching sensitive internal nodes while allowing the regulator to maintain its low-dropout functionality. This intermediary approach suppresses noise without requiring complex active filtering circuits.
Solution Approach 2:
The patent modifies the electrical parameters of the operational amplifier circuit by adding resistive elements that change the noise characteristics of internal nodes. By carefully selecting resistance values, the circuit achieves high power supply rejection ratio (PSRR) at noise frequencies while maintaining proper voltage regulation. This parameter-based approach allows noise suppression without fundamentally redesigning the regulator architecture.
2Object-affected harmful factors
If resistive components are added to suppress noise, then the noise suppression capability improves, but the device complexity increases
Solution Approach 1:
The patent applies noise suppression locally at specific critical nodes within the operational amplifier circuit rather than implementing a global noise filter. Resistive components are strategically placed only at internal nodes where noise would most adversely affect regulation accuracy. This localized approach provides effective noise suppression while minimizing the overall component count and circuit complexity.
3Reliability
If the PSSR of internal nodes is increased, then the reference voltage is protected from noise, but the circuit structure becomes more complex
Solution Approach 1:
The patent uses resistive components as intermediary elements that protect the reference voltage from noise without requiring complex shielding or isolation techniques. These resistors create a high-impedance path that blocks noise from coupling into the reference voltage node, thereby improving reliability through a simple passive component addition.
Data Source
AI summary
The present disclosure discloses a low dropout regulator apparatus having noise-suppression mechanism. An operational amplifier circuit includes a differential input circuit, an amplifying output circuit and a first and a second resistive components. The differential input circuit is coupled between first connection nodes and a ground terminal to receive a reference voltage and a feedback voltage. The amplifying output circuit includes a first and a second transistor pair circuits. The first transistor pair circuit is coupled between a power supply and second connection nodes. The second transistor pair is coupled between the second connection nodes and the ground terminal and has an amplifying output terminal generating an amplified voltage. The first and the second resistive components are coupled between the first and the second connection nodes. A voltage stabilizing output circuit receives the amplified voltage to generate an output voltage and generates the feedback voltage according to a division thereof.