Capacitor-Less LDO Regulator for Stable Fast Transient Response
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Solution Overview
Problem
Conventional low dropout (LDO) regulators require an output capacitor, which occupies significant board space, is costly, and affects stability and transient response, while also consuming high current.
Innovation Solution
A capacitor-less LDO regulator design incorporating an error amplifier, pass transistors, resistor feedback networks, and an overshoot protection circuit with a folded cascode amplifier and driver, which compensates for slow response and provides stability without an output capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an output capacitor is used in conventional LDO regulators, then loop stability and noise filtering are improved, but board space occupation increases, cost increases, and current consumption increases
Solution Approach 1:
The patent removes the output capacitor from the LDO regulator circuit, eliminating the need for external capacitor components. This extraction resolves the contradiction by eliminating board space occupation and current consumption associated with capacitors while maintaining loop stability through alternative compensation techniques using resistors and feedback networks
Solution Approach 2:
The patent integrates the stability compensation function directly into the feedback network resistors and control circuitry, merging previously separate functions (capacitor filtering and resistor feedback) into a unified capacitor-less design. This integration eliminates the need for external capacitors while maintaining regulatory stability
2Reliability
If an output capacitor is used in conventional LDO regulators, then loop stability is improved, but current consumption increases
Solution Approach 1:
The patent extracts and eliminates the output capacitor from the circuit, removing the source of excessive current consumption. The design achieves stability without relying on capacitor-based compensation, thereby reducing quiescent current to less than 120 microamps while maintaining regulatory function
Solution Approach 2:
The patent changes the compensation parameters from capacitor-based to resistor-based feedback networks, altering the circuit's operational characteristics to achieve stability through resistive division and feedback rather than capacitive energy storage, thereby reducing current consumption
3Object-affected harmful factors
If an output capacitor is used in conventional LDO regulators, then noise filtering is improved, but device complexity and cost increase
Solution Approach 1:
The patent removes external capacitor components from the circuit, simplifying the overall device structure. The noise filtering function is maintained through integrated feedback networks and control circuitry, reducing both component count and circuit complexity while eliminating the need for external passive components
Solution Approach 2:
The feedback network resistors and control circuitry perform multiple functions simultaneously: voltage division, noise filtering, and stability compensation. This multi-functionality eliminates the need for separate capacitor components, reducing device complexity while maintaining noise rejection capabilities
4Area of stationary object
If the LDO regulator operates without an output capacitor, then board space and current consumption are reduced, but transient response and loop stability become problematic
Solution Approach 1:
The patent implements preliminary compensation actions through resistive feedback networks and control circuitry that anticipate and correct transient disturbances before they affect output stability. This proactive compensation mechanism maintains fast transient response without requiring external capacitor energy storage
Solution Approach 2:
The patent employs enhanced feedback mechanisms through resistor networks that continuously monitor and adjust the output voltage in response to transient load changes. This feedback control system maintains stability and fast transient response by dynamically adjusting the control signal based on output deviations, eliminating the need for capacitor-based energy buffering
Data Source
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AI summary
An integrated circuit including a low drop out (LDO) regulator configured to implement transient response and loop stability in a capacitor-less configuration, including an error amplifier configured to receive a bandgap reference input; first and second pass elements configured to receive outputs from the error amplifier; first and second resistor feedback networks, the first resistor network configured to provide a feedback output as an input to the error amplifier; an overshoot protection circuit; and an output connected to the pass transistors; wherein the capacitor-less low dropout (LDO) regulator is operable without an output capacitor.