Voltage Regulator Frequency Compensation With Small MOS Capacitors
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Solution Overview
Problem
Voltage regulators face challenges in maintaining stable output voltage due to high current limit variation across process, voltage, temperature, and mismatch, and require large capacitors for frequency compensation, which occupy significant silicon area.
Innovation Solution
The proposed solution involves a voltage regulator circuit with a gain stage, two transistors, and current source circuitry to fix the gate-source voltage of the pass transistor, reducing current limit variation and using smaller MOS capacitors for frequency compensation, thereby minimizing silicon area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional frequency compensation methods are used in voltage regulators, then stability is achieved, but large capacitors are required which occupy significant silicon area
Solution Approach 1:
The patent changes the compensation approach by using a small capacitor (7.5 pF) in combination with specific circuit topology (gain stage with transistor feedback) to achieve the same stability function that traditionally required large capacitors. This parameter change in capacitance value, enabled by the circuit architecture, reduces silicon area by 9-67 times while maintaining stability.
2Reliability
If current limit circuitry is used to protect against faults, then protection is provided, but current limit variation across process, voltage, temperature, and mismatch remains high
Solution Approach 1:
The patent implements feedback circuitry that senses the current limit variation and adjusts the gate-source voltage of the pass transistor to compensate for these variations. This feedback mechanism reduces current limit variation to ±15% across process, voltage, temperature, and mismatch conditions while maintaining fault protection capability.
Solution Approach 2:
The patent fixes the gate-source voltage of the pass transistor through the feedback mechanism, changing the operating parameters to achieve more stable current limiting. This parameter control reduces the variation in current limit characteristics across different operating conditions and manufacturing processes.
Data Source
AI summary
Methods, apparatus, systems, and articles of manufacture are described corresponding to a voltage regulator with frequency compensation. An example circuit includes a gain stage having a first input terminal, a second input terminal, and an output terminal; a transistor having a first current terminal, a second current terminal, and a control terminal, the first current terminal of the transistor coupled to a supply voltage terminal, the second current terminal of the transistor structured to be coupled to the second input terminal of the gain stage, and the control terminal of the transistor coupled to the output terminal of the gain stage; and regulator compensation circuitry having a first terminal and a second terminal, the first terminal of the regulator compensation circuitry coupled to the output terminal of the first gain stage, the second terminal of the regulator compensation circuitry coupled to the second input terminal of the gain stage.