Switchable Pass-Gate LDO Circuit for Stable Low-Dropout Regulation
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Solution Overview
Problem
Existing low dropout (LDO) voltage regulators face challenges in maintaining stable output voltage across varying load currents and input voltage fluctuations, while also minimizing dropout voltage and power loss.
Innovation Solution
The proposed LDO circuit employs a switchable pass gate circuit with multiple current paths, controlled by an operational amplifier and voltage divider circuit, to adjust the drain-to-source resistance and maintain stable output voltage. This configuration allows for efficient regulation without wide voltage ranges and reduces leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional LDO regulator uses a single pass gate with fixed resistance, then the circuit structure is simple, but the output voltage cannot be stabilized across varying load currents and input voltage fluctuations
Solution Approach 1:
The pass gate is divided into multiple parallel current paths with different resistance values. Each path contains a transistor with specific gate control, allowing selective activation based on operating conditions. This segmentation enables the regulator to maintain stable output voltage across varying loads by choosing the appropriate resistance path, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The circuit dynamically switches between different current paths based on real-time operating conditions such as load current and input voltage. The control logic activates specific transistors in the parallel paths to adjust the effective resistance, enabling the pass gate to adapt its characteristics dynamically. This dynamic behavior maintains output stability while managing circuit complexity through intelligent control.
2Reliability
If the LDO regulator uses multiple current paths with different resistances, then output voltage stability improves, but the dropout voltage and power loss increase
Solution Approach 1:
The control logic dynamically selects and activates only the necessary current paths based on real-time operating conditions. By switching between different resistance configurations, the circuit optimizes the balance between maintaining output stability and minimizing power loss. The system chooses lower resistance paths when high current is needed and higher resistance paths when precision is prioritized, thereby managing energy loss effectively.
Solution Approach 2:
The circuit changes the effective resistance parameter of the pass gate by selectively activating different transistor paths. This parameter adjustment allows the regulator to optimize performance for different operating modes - using lower resistance for high-current applications to reduce power loss and higher resistance for precision regulation scenarios, thus resolving the energy loss contradiction.
3Adaptability or versatility
If the LDO regulator operates with wide voltage ranges, then adaptability improves, but leakage current increases
Solution Approach 1:
The pass gate is segmented into multiple parallel current paths, each with transistors optimized for specific voltage ranges. By selectively activating only the paths appropriate for the current operating voltage, the circuit maintains adaptability across wide voltage ranges while keeping leakage current low. Unused paths remain inactive, preventing unnecessary leakage.
Solution Approach 2:
The control logic dynamically determines which current paths to activate based on the input voltage level and load conditions. This dynamic switching ensures that the circuit operates in the optimal resistance configuration for each voltage range, maintaining adaptability while minimizing leakage current by keeping unnecessary paths deactivated.
Data Source
AI summary
A circuit includes a voltage divider circuit configured to generate a feedback voltage according to an output voltage, an operational amplifier configured to output a driving signal according to the feedback voltage and a reference voltage and a pass gate circuit including multiple current paths. The current paths are controlled by the driving signal and connected in parallel between the voltage divider circuit and a power reference node.