Wideband LDO Voltage Regulator Feedforward PSR Boost
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Solution Overview
Problem
Legacy low dropout (LDO) voltage regulator designs face challenges in achieving high power supply rejection (PSR) across a wide bandwidth while minimizing power consumption and die area, particularly in high-speed data communication systems, as they require high gain and bandwidth operational amplifiers, leading to increased noise and costly decoupling capacitance.
Innovation Solution
The implementation of a wideband LDO voltage regulator with a power supply feed-forward injection module that delivers an injection signal to the voltage regulator core, offsetting supply voltage variations using a supply voltage sense circuit, low pass filter, and selectable transconductance amplifiers, thereby reducing the intrinsic effects of supply voltage variations and enhancing PSR without increasing power consumption or die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high gain and bandwidth operational amplifiers are implemented to achieve high PSR, then power supply rejection is improved, but power consumption increases
Solution Approach 1:
The invention segments the PSR enhancement function into two independent paths: a feedforward path that directly senses and compensates for supply voltage variations, and a feedback path that maintains voltage regulation. This segmentation allows the feedback operational amplifier to operate at lower gain and bandwidth, reducing its power consumption while the feedforward path handles the high-frequency PSR rejection.
Solution Approach 2:
The feedforward path performs preliminary action by sensing supply voltage variations before they affect the regulated output and injecting compensating signals in advance. This preliminary compensation reduces the burden on the feedback operational amplifier, allowing it to operate with lower power consumption while maintaining high overall PSR performance.
2Reliability
If high gain and bandwidth operational amplifiers are implemented to achieve high PSR, then power supply rejection is improved, but noise increases
Solution Approach 1:
The invention segments the signal processing functions into feedforward and feedback paths. The feedforward path handles high-frequency supply rejection without requiring high-gain amplification, while the feedback path operates at lower bandwidth with inherent noise filtering. This segmentation prevents the noise that would otherwise be generated by high-bandwidth operational amplifiers.
Solution Approach 2:
The feedforward path acts as an intermediary that directly compensates for supply voltage variations before they propagate to the output. By injecting compensating signals through this intermediary path, the system achieves high PSR without relying on high-gain feedback amplification that would generate excessive noise.
3Reliability
If large amount of decoupling capacitance is used to suppress peak PSR, then power supply rejection is improved, but die area increases
Solution Approach 1:
The feedforward path serves as an intermediary mechanism that actively compensates for supply voltage variations, replacing the need for large passive decoupling capacitance. By injecting compensating signals in advance, the system achieves peak PSR suppression without requiring extensive capacitance, thereby reducing die area.
Solution Approach 2:
The invention changes the approach from passive PSR suppression using large capacitance values to active compensation using feedforward signal injection. This parameter change from passive to active control enables high PSR performance with minimal capacitance, significantly reducing the required die area.
4Reliability
If wide bandwidth is achieved in LDO voltage regulator, then power supply rejection bandwidth is improved, but power consumption increases
Solution Approach 1:
The invention segments the bandwidth requirements between two paths: the feedforward path provides wide bandwidth for PSR rejection by directly sensing and compensating supply variations, while the feedback path operates at narrower bandwidth for stable voltage regulation. This segmentation achieves wideband PSR without requiring the feedback operational amplifier to consume excessive power for wideband operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables a wideband LDO voltage regulator to achieve high PSR with reduced power and die area consumption, allowing for efficient power management and noise rejection in high-speed data communication systems, while allowing for a lower bandwidth error amplifier and smaller decoupling capacitance, thus addressing the limitations of legacy designs.
Implementation Method 1
the injection signal is determined from the supply voltage variation and a gain factor that is based on various design attributes of the output stage of the voltage regulator core
Implementation Method 2
the power supply feed forward injection module comprises a supply voltage sense circuit, a low pass filter, and one or more selectable transconductance amplifiers
Data Source
AI summary
The present disclosure provides a detailed description of techniques for implementing a wideband low dropout voltage regulator with power supply rejection boost. More specifically, some embodiments of the present disclosure are directed to a voltage regulator comprising a voltage regulator core powered by a supply voltage and providing a regulated voltage output, and a power supply feed forward injection module delivering an injection signal to the voltage regulator core to effect a power supply rejection of the supply voltage variation from the regulated voltage. In one or more embodiments, the injection signal is determined from the supply voltage variation and a gain factor that is based on various design attributes of the output stage of the voltage regulator core. In one or more embodiments, the power supply feed forward injection module comprises a supply voltage sense circuit, a low pass filter, and one or more selectable transconductance amplifiers.