LDO Regulator Feedback Circuit for Wide-Band Ripple Suppression
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Solution Overview
Problem
Conventional low dropout (LDO) regulators in integrated circuits face challenges in maintaining stable voltage and suppressing wide-band noise and ripple signals, particularly in systems-on-chip (SOC) applications, leading to poor power supply rejection ratio (PSRR) and impaired performance of sensitive loads like phase lock loops and oscillators.
Innovation Solution
The implementation of a low dropout regulator circuit that includes an operational amplifier, an output circuit, a feedback circuit, and a compensation circuit, along with divided resistors, which provides feedback signals to the operational amplifier to eliminate ripple and noise, ensuring a stable voltage within a specific dropout range and enhancing PSRR across a wide frequency bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDO regulator structure is used, then device simplicity is maintained, but power supply rejection ratio (PSRR) deteriorates and noise suppression capability is insufficient
Solution Approach 1:
The patent implements a feedback circuit that samples the output voltage and feeds it back to the operational amplifier to cancel ripple and noise signals. The feedback circuit includes capacitors coupled between the output terminal and input terminals of the operational amplifier, creating a feedback path that actively suppresses wide-band noise and ripple, thereby improving PSRR without requiring a fundamentally complex regulator architecture.
Solution Approach 2:
The regulator circuit is segmented into distinct functional blocks: an operational amplifier with multiple input terminals, an output circuit with separate ripple generation and suppression paths, and a feedback circuit with specific capacitor configurations. This segmentation allows each component to address specific aspects of noise suppression while maintaining overall circuit manageability and design clarity.
2Object-affected harmful factors
If feedback circuit with capacitors is added, then noise suppression capability is improved, but device complexity increases
Solution Approach 1:
The operational amplifier is designed with multi-functionality, serving both as the main voltage regulation element and as a noise cancellation element through its multiple input terminals. The same operational amplifier processes both the reference voltage and the feedback voltage containing ripple and noise information, eliminating the need for separate dedicated noise filtering circuits and reducing overall component count.
Solution Approach 2:
The feedback circuit is merged with the operational amplifier structure, where capacitors are directly coupled between the output terminal and specific input terminals of the operational amplifier. This integration combines the voltage regulation function and noise suppression function into a unified circuit architecture, reducing the number of discrete components while achieving effective wide-band noise rejection.
Data Source
AI summary
A device is provided. The device includes an operational amplifier, an output circuit, a first capacitor, and a second capacitor. The operational amplifier is configured to generate an output according to a feedback signal. The output circuit is configured to generate a first current signal in response to a supply voltage and the output of the operational amplifier. The first current signal includes a first ripple signal. The first capacitor and the second capacitor are coupled in parallel between the operational amplifier and the output circuit. The first capacitor is configured to receive the first current signal and feedback to the operational amplifier the first ripple signal.