Gain-Boosted LDO Compensation for Capacitor-Free Load Steps
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Solution Overview
Problem
Conventional low dropout regulators (LDOs) face challenges in maintaining accuracy and stability during load steps due to the need for external load capacitors, which are impractical for small, integrated circuits due to size and cost constraints, and achieving high gain for stability often compromises accuracy.
Innovation Solution
The LDOs incorporate an error amplifier and a gain boost amplifier to increase DC gain in response to load steps, providing high accuracy and stability without the need for external load capacitors by dynamically adjusting gain based on the difference between input and output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external load capacitors are used to maintain accuracy during load steps, then voltage accuracy is improved, but device size and cost increase
Solution Approach 1:
The patent extracts the load capacitor function from external components and implements it using on-chip circuitry, specifically using the gain boost amplifier and its associated capacitors to provide the necessary compensation and stability without requiring external capacitors
Solution Approach 2:
The gain boost amplifier serves multiple functions: it boosts the DC gain of the error amplifier, provides compensation for the LDO, and acts as a load capacitor substitute, thereby eliminating the need for separate external load capacitors while maintaining voltage accuracy during load steps
2Area of stationary object
If multiple LDOs are integrated on a single chip to reduce size, then device area is reduced, but the practicality of using external capacitors for each LDO decreases
Solution Approach 1:
The patent merges the load capacitor function with the gain boost amplifier circuitry, allowing multiple LDOs to share common compensation mechanisms and eliminating the need for individual external capacitors for each LDO, thereby making high-density integration practical
Solution Approach 2:
The gain boost amplifier is nested within the LDO control loop, with its capacitors and circuitry integrated into the existing LDO structure, allowing multiple LDOs to be densely packed on the chip without proportionally increasing external component count
3Stability of the object's composition
If high DC gain is achieved for stability during load steps, then stability is improved, but accuracy may be compromised without proper compensation
Solution Approach 1:
The gain boost amplifier is configured within the feedback loop of the LDO, using the output voltage feedback to dynamically adjust its gain, thereby maintaining both high DC gain for stability and accurate voltage regulation through continuous feedback control
Solution Approach 2:
The patent implements dynamic gain adjustment where the gain boost amplifier's gain varies with operating conditions, providing high gain when needed for stability during load steps while maintaining accuracy through dynamic adaptation to changing load and voltage conditions
Data Source
AI summary
Low dropout regulators (LDOs) are disclosed herein. An example of an LDO includes an error amplifier having a first input and a second input, wherein the first input is for coupling to an output of the LDO and the second input for coupling to a reference voltage. The error amplifier has an output with a voltage that is proportional to the difference between the output voltage and the reference voltage. A second amplifier is coupled between the error amplifier and the output of the LDO. A gain boost amplifier is coupled between the error amplifier and the second amplifier. The gain boost amplifier increases DC gain of the LDO in response to a load step on the output.