Digital LDO Clamp Circuit for Stable Output Under Variable Input
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Solution Overview
Problem
Digital low-dropout (LDO) regulators face reliability issues due to large ripple voltage deviations in output voltage caused by variable input voltage, leading to heating and aging problems in transistors.
Innovation Solution
A digital LDO regulator design incorporating a clamp circuit and gate driver circuit to generate a constant output voltage, where the clamp circuit includes PMOS transistors and current sources, and the gate driver circuit uses inverters to control PMOS power transistors, ensuring the transistors operate in the saturation region, reducing ripple voltage and improving 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 clamp circuit dynamically adjusts the gate voltage of the PMOS transistor based on the input voltage level. When input voltage varies, the clamp circuit modifies the gate drive voltage accordingly to maintain the transistor in saturation region, ensuring stable output voltage despite dynamic input conditions.
Solution Approach 2:
The clamp circuit changes the gate voltage parameter in response to input voltage variations. By adjusting this critical parameter, the circuit maintains optimal transistor operation across different supply voltage conditions, preventing current deviation and ripple voltage generation.
2Power
If the transistor operates with high current to deliver power, then the power delivery capability is improved, but heating and aging problems occur reducing reliability
Solution Approach 1:
The clamp circuit optimizes the gate voltage parameter to maintain the transistor in saturation region operation. This parameter optimization enables the transistor to deliver required power while minimizing excessive current and power dissipation, thereby reducing heating and aging effects.
3Reliability
If the clamp circuit is added to generate clamp voltage, then the output voltage stability is improved, but the device complexity increases
Solution Approach 1:
The clamp circuit acts as an intermediary between the variable input voltage and the PMOS transistor gate. It mediates the voltage relationship by generating an appropriate gate voltage that maintains transistor saturation, thereby stabilizing output without requiring complex control systems.
Solution Approach 2:
The clamp circuit is designed to automatically adjust the gate voltage in response to input voltage changes without external control. The circuit self-regulates to maintain optimal transistor operation, eliminating the need for complex external control mechanisms while achieving output voltage stability.
Data Source
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.