Adaptive LDO Load Switch Stability Wide Capacitance
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Solution Overview
Problem
Capacitor-less Low Drop-Out (LDO) and load switch linear voltage regulators face challenges with inferior power supply rejection (PSR) and load transient regulation, limited load capacitance range, and instability, especially when load currents exceed 500 mA or load capacitance exceeds 1 μF, due to placement of the dominant pole in the feedback loop and lack of effective load detection.
Innovation Solution
An adaptive RC network is introduced in the feedback network of the LDO/load switch LVR, which estimates load parameters like time constant and resistor during power-up, adjusts the turn-on time, and detects short circuits, placing the dominant pole at the output without an external capacitor, and includes a load detection circuit to adjust the feedback network and reduce non-dominant pole effects, ensuring stability across a wide range of load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an external capacitor is used to guarantee LDO stability, then power supply rejection and load transient regulation are improved, but device complexity and cost increase due to additional external components
Solution Approach 1:
The patent extracts the stabilizing capacitor function from external components and relocates it to an on-chip capacitor integrated within the LDO circuit. This eliminates the need for external capacitors while maintaining the stability enhancement they provide, thereby reducing device complexity and cost without sacrificing reliability
Solution Approach 2:
The patent merges the function of the external stabilizing capacitor with the on-chip capacitor by configuring the on-chip capacitor to work in conjunction with the feedback network. This integration combines multiple functions into a single chip-based solution, eliminating external components while preserving the stability benefits
2Device complexity
If capacitor-less LDO architecture is used to reduce cost, then external capacitor requirements are eliminated, but power supply rejection and load transient regulation deteriorate
Solution Approach 1:
The patent introduces an adaptive mechanism that dynamically adjusts the feedback network based on detected load conditions. This dynamic adaptation allows the LDO to optimize its performance for different load scenarios, achieving superior power supply rejection and load transient regulation without requiring external capacitors, thus maintaining simplicity while improving reliability
Solution Approach 2:
The patent implements an enhanced feedback mechanism that includes load condition detection and adaptive adjustment of the feedback network. This feedback system enables the LDO to automatically optimize its performance based on real-time load conditions, achieving high power supply rejection and load transient regulation without external capacitors
3Device complexity
If dominant pole is placed in feedback loop for capacitor-less LDO, then external capacitor is eliminated, but stability deteriorates under high load current and capacitance conditions
Solution Approach 1:
The patent employs dynamic adjustment of the feedback network based on detected load conditions. When high load current or capacitance is detected, the system adaptively modifies feedback parameters to maintain stability, allowing the dominant pole placement strategy to work effectively across varying load conditions without external capacitors
Solution Approach 2:
The patent changes feedback network parameters adaptively based on load conditions. By detecting load current and capacitance levels, the system adjusts feedback parameters to optimize stability margins, enabling the LDO to maintain stability under high load conditions while eliminating external capacitor requirements
4Stability of the object's composition
If load detection circuit is added to support wide load capacitance range, then stability across load conditions is improved, but device complexity increases
Solution Approach 1:
The load detection circuit is designed to perform multiple functions: detecting load current, estimating load capacitance, and triggering adaptive feedback adjustments. By consolidating these detection and control functions into a single integrated circuit block, the patent achieves wide load capacitance support without proportionally increasing device complexity
Solution Approach 2:
The load detection circuit automatically detects load conditions and triggers appropriate feedback adjustments without external intervention. This self-service mechanism enables the LDO to adapt to varying load conditions autonomously, improving stability across load ranges while minimizing the complexity overhead of the detection circuit itself
Data Source
AI summary
An architecture and method to maintain stability of a low drop-out (LDO)/load switch linear voltage regulator (LVR). The architecture method support optionally determining during a power-up phase and by using a load detection circuit, the estimated load parameters that represents at least one selected from a group consisting of: the load time constant and the load resistor at an output node of the LDO/load switch LVR, and adjusting, based on the estimated output load parameters, an adaptive RC network in the LDO/load switch LVR, wherein the adaptive RC network produces an adaptive zero in a feedback network transfer function of the LDO/load switch LVR, wherein the adaptive zero reduces an effect of a non-dominant pole in the open loop transfer function of the LDO/load switch LVR, and wherein a frequency of the adaptive zero is adjusted based on the estimated load parameters.