Dual-Loop LDO Regulator With Digital Current Injection for Noise Control
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Solution Overview
Problem
High-speed high-bandwidth input-output applications require a clean power supply to minimize jitter and noise, but existing low-dropout (LDO) regulators are less preferred due to their sensitivity to data patterns and wide current range requirements, which complicates power supply noise management.
Innovation Solution
A dual loop voltage regulator system is introduced, comprising an analog loop for voltage control and a digital loop for current injection, which boosts current for a set interval to reduce peak-to-peak noise without significantly increasing quiescent current, thereby addressing data pattern dependency and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional LDO regulator is used for high-bandwidth applications, then the power supply can provide stable voltage, but the regulator becomes sensitive to data patterns and requires wide current range which increases power supply noise
Solution Approach 1:
The regulator is divided into two independent loops: an analog loop for voltage control and a digital loop for current injection. Each loop handles specific aspects of regulation independently, allowing the analog loop to maintain voltage stability while the digital loop manages current demands and reduces noise sensitivity to data patterns
Solution Approach 2:
A digital current injector is introduced as an intermediary component that pre-charges or pre-discharges the output capacitor based on predicted data patterns. This mediator handles the high di/dt requirements separately from the analog LDO, preventing noise from affecting the voltage regulation while maintaining responsiveness to data transitions
2Adaptability or versatility
If the LDO regulator increases quiescent current to handle wide current range requirements, then it can respond to data patterns, but power consumption increases
Solution Approach 1:
The digital current injector operates periodically or event-driven based on data pattern detection rather than continuously. It activates only when data transitions are predicted or detected, providing wide current range handling capability on-demand while maintaining low quiescent current during steady-state operation
Solution Approach 2:
The system uses data pattern detection and prediction mechanisms that enable the regulator to anticipate current demands and prepare accordingly. This self-service approach allows the regulator to handle wide current ranges efficiently without requiring continuously high quiescent current, as it only activates additional current when needed
3Measurement precision
If high-bandwidth regulation is implemented to reduce sensitivity to data patterns, then timing margin improves, but device complexity increases
Solution Approach 1:
A digital current injector serves as an intermediary that handles the complex task of data pattern detection and prediction, isolating this complexity from the analog voltage regulation path. This allows the analog loop to remain simple and stable while the digital layer manages the sophisticated control needed for high-bandwidth performance and timing margin improvement
Data Source
AI summary
A dual-loop low-drop (LDO) regulator having a first loop which is an analog loop that compares the voltage on the output supply node with a reference, and generates a bias or voltage control to control a strength of a final power switch. The first loop regulates the output voltage relative to a reference voltage by minimizing the error between the two voltages. A second loop (digital loop) that controls a current source which injects current on the gate of the final power switch to boost current for a load. The second loop is an auxiliary loop that boosts the current load for a set interval until the tracking bandwidth of the LDO resolves the error in the output, thereby reducing the peak-to-peak noise. The quiescent current is not increased a lot by the second loop since the second loop circuit is on for a fraction of the entire LDO operation.