LDO Bulk Switch Biasing for Transistor Leakage Blocking
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Solution Overview
Problem
Low-dropout regulators (LDOs) face challenges in effectively blocking power leakage across transistors, particularly at ultra-low voltage levels and under varying process corners and temperature conditions, leading to significant leakage currents that affect the reliability and efficiency of electronic devices.
Innovation Solution
A simplified bulk switch structure using a pair of transistors (M1 and M2) with a high side comparator and leakage track bias generator, which compares and controls the gates of the transistors based on the input voltages vcc and vccq, ensuring only one transistor is on at a time to block leakage current, independent of detectors and capable of tracking temperature and process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDO regulator design is used, then voltage regulation function is achieved, but significant leakage current occurs across transistors under varying process corners and temperature conditions
Solution Approach 1:
The patent implements dynamic control of bulk switches M1 and M2 based on real-time voltage comparison between vcc and vccq. The high-side comparator continuously monitors voltage levels and adjusts the bulk switch states accordingly, enabling the LDO to adaptively block leakage current under varying operating conditions including different process corners and temperature levels, thereby resolving the contradiction between maintaining reliability and reducing energy loss.
Solution Approach 2:
The patent changes the operational parameters of the transistors by dynamically switching the bulk connections based on voltage conditions. When vcc > vccq, bulk switch M1 is turned on and M2 is turned off; when vcc < vccq, the states are reversed. This parameter change approach allows the system to optimize leakage current blocking while maintaining voltage regulation functionality across different operating conditions.
2Loss of energy
If bulk switches are always on to block leakage, then leakage current is reduced, but voltage regulation fails when input voltage drops below output voltage
Solution Approach 1:
The patent employs dynamic switching of bulk connections controlled by a high-side comparator that monitors the relationship between input voltage vcc and output voltage vccq. The bulk switches M1 and M2 are turned on or off based on real-time voltage comparison, allowing the system to adaptively maintain leakage blocking when needed while ensuring proper voltage regulation when input voltage drops, thus resolving the contradiction between energy loss reduction and adaptability.
Solution Approach 2:
The patent implements a feedback mechanism where the high-side comparator continuously compares vcc and vccq levels and uses this information to control the bulk switch states. This feedback ensures that bulk switches are only activated when voltage conditions warrant leakage blocking, preventing interference with the LDO's voltage regulation function across the full operating range, thereby resolving the contradiction between leakage blocking and voltage regulation adaptability.
3Reliability
If complex detector circuits are used to control bulk switches, then leakage blocking is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by using the existing high-side comparator, which serves dual purposes: it controls the power good signal and simultaneously controls the bulk switches for leakage current blocking. This eliminates the need for separate detector circuits, reducing device complexity while maintaining effective leakage blocking and improving reliability.
Solution Approach 2:
The patent merges the leakage blocking control function with the existing power good detection functionality by using the same high-side comparator to control both the power good signal and the bulk switches M1 and M2. This consolidation reduces the overall circuit complexity while achieving effective leakage current blocking, thereby resolving the contradiction between reliability improvement and device complexity.
Data Source
AI summary
In certain aspects, a circuit includes an amplifier, a first transistor, a second transistor, a third transistor, a signal pair generation circuit, and a leakage track bias generator circuit connected to the signal pair generation circuit. A gate terminal of the first transistor is connected to an output of the amplifier, and a first terminal of the first transistor is connected to an input of the amplifier. A first terminal of the second transistor is connected to a second terminal of the first transistor. A first terminal of the third transistor is connected to the first terminal of the first transistor, and a second terminal of the third transistor is connected to a second terminal of the second transistor. The signal pair generation circuit is connected to a gate terminal of the second transistor and a gate terminal of the third transistor. The leakage track bias generator circuit includes a resistor, and a first terminal of the resistor is connected to the ground.