Dual Error Amplifier LDO Voltage Regulator for High Current Sinking
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Solution Overview
Problem
Conventional low-dropout (LDO) voltage regulators struggle to effectively sink currents from the output that are orders of magnitude greater than the quiescent current of the feedback network while maintaining the regulated output voltage.
Innovation Solution
The design incorporates two separate error amplifiers and pass-FETs, with a current source transistor and a current sink transistor, allowing for efficient sourcing and sinking of currents, and a feedback network that maintains the regulated output voltage even under conditions of significant current sinking, such as leakage from other regulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO voltage regulator with a single error amplifier and feedback network is used, then the circuit is simple and quiescent current is low, but the regulator cannot effectively sink currents that are orders of magnitude greater than the quiescent feedback current while maintaining regulated output voltage
Solution Approach 1:
The single error amplifier is segmented into two separate error amplifiers: a first error amplifier connected to the current source transistor and a second error amplifier connected to the current sink transistor. This segmentation allows each amplifier to independently control its respective transistor, enabling the regulator to handle both current sourcing and sinking operations effectively while maintaining regulated output voltage.
Solution Approach 2:
The voltage regulator is designed with dual functionality through the parallel error amplifier configuration. The first error amplifier handles current sourcing operations while the second error amplifier handles current sinking operations. This multi-functional design allows the same regulator circuit to effectively perform both sourcing and sinking of currents that are orders of magnitude greater than quiescent feedback current.
2Loss of energy
If the feedback network quiescent current is kept low for efficiency, then power consumption is reduced, but the regulator cannot sink significant leakage currents from other regulators or circuits
Solution Approach 1:
The feedback network is functionally segmented into two independent control paths through the parallel error amplifiers. The first error amplifier maintains low quiescent current for efficiency during normal sourcing operations, while the second error amplifier is specifically activated to handle leakage current sinking when needed. This segmentation allows the system to maintain energy efficiency while gaining adaptability to handle various current conditions.
Solution Approach 2:
The regulator dynamically switches between the first and second error amplifiers based on operating conditions. During normal current sourcing, the first error amplifier operates with low quiescent current. When leakage currents or other sinking conditions occur, the second error amplifier is activated to handle the sinking operation. This dynamic operation allows the system to adapt to different current conditions while maintaining power efficiency.
Data Source
AI summary
A voltage regulator is arranged to receive an input voltage (Vin) and produce a regulated output voltage (Vout) and comprises: a current source transistor (Msource) and a current sink transistor (Msink) arranged to provide the output voltage at a node therebetween; a first error amplifier; and a second error amplifier. The first error amplifier is arranged to apply a first control voltage to the gate terminal of the current source transistor, wherein the first control voltage is dependent on the difference between the feedback voltage (Vfb) and the reference voltage (Vref). The second error amplifier arranged in parallel to the first error amplifier, the second error amplifier being arranged to apply a second control voltage to the gate terminal of the current sink transistor, wherein the second control voltage is dependent on the difference between the feedback voltage and the reference voltage. The feedback voltage is derived from the output voltage.