Digital LDO Clamp and Gate Drive for Ripple-Stable Output
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Solution Overview
Problem
Digital low-dropout (LDO) regulators face reliability issues due to large ripple voltage deviations caused by variable input voltages, leading to instability in output voltage and potential heating and aging problems in transistors.
Innovation Solution
A digital LDO regulator design incorporating a clamp circuit and gate driver circuit that generates a clamp voltage and drive voltage, respectively, to maintain a constant output voltage across varying input voltages, with PMOS transistors operating in the saturation region to minimize ripple voltage and enhance Power Supply Ripple Rejection (PSRR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a digital LDO regulator uses variable supply voltage, then the regulator can adapt to different power conditions, but transistor current deviates causing large ripple voltage on output
Solution Approach 1:
The patent implements a feedback mechanism where the regulator monitors output voltage and transistor current, and adjusts the control signal to the switching element accordingly. This closed-loop control maintains stable output voltage despite variations in supply voltage, resolving the contradiction between adaptability and output stability.
Solution Approach 2:
The patent dynamically changes operating parameters (such as duty cycle of switching element or reference voltage levels) in response to detected supply voltage conditions. By adjusting these parameters adaptively, the regulator maintains reliable output voltage across different power conditions.
2Adaptability or versatility
If transistor current deviates under variable supply voltage, then the regulator responds to input changes, but large ripple voltage is generated on output
Solution Approach 1:
The patent introduces intermediate control elements (such as error amplifiers, filter circuits, or damping networks) between the input voltage and output. These intermediaries smooth out current deviations and prevent them from translating directly into output ripple, while still allowing the system to respond to legitimate input changes.
Solution Approach 2:
The patent employs periodic switching action with controlled duty cycles to regulate output voltage. By using pulsed or periodic control signals rather than continuous adjustment, the system can respond to input changes while the periodic nature of operation allows filtering to reduce ripple voltage.
3Adaptability or versatility
If transistor current deviates significantly, then the regulator adapts to voltage changes, but heating and aging problems occur in transistors
Solution Approach 1:
The patent uses dynamic control strategies where the regulator continuously adjusts operating points based on real-time conditions. By dynamically optimizing transistor operating conditions rather than using fixed biasing, the system adapts to voltage variations while minimizing excessive current and resulting heat generation.
Solution Approach 2:
The patent implements protective measures in advance, such as current limiting circuits, thermal monitoring, or pre-regulation stages, that prevent transistor current from deviating to levels that cause excessive heating. These cushioning mechanisms are built in beforehand to protect against both overcurrent and thermal stress.
Data Source
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AI summary
Embodiments of digital low-dropout (LDO) regulators and methods for operating a digital LDO regulator are described. In one embodiment, a digital LDO regulator includes a clamp circuit configured to generate a clamp voltage in response to an input voltage of the digital LDO regulator, a gate driver circuit configured to generate a drive voltage in response to the input voltage and the clamp voltage, and at least one transistor device configured to generate an output voltage in response to the input voltage and the drive voltage. Other embodiments are also described.