LDO Load Transient Detection Circuit for Voltage Regulation
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Solution Overview
Problem
Conventional low-dropout (LDO) linear voltage regulators and load switch regulators experience significant load transient regulation degradation when load current suddenly changes from values lower than 1 mA to higher values, resulting in output voltage drops of over 0.6 V, which is not acceptable for many applications.
Innovation Solution
The proposed architecture includes a load transient detection circuit within the feedback network that senses the difference between the output voltage and the gate voltage of the pass element, generating a control signal to activate a current sink block to mitigate overshoot/undershoot during load transient events, thereby improving load transient regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional LDO and load switch linear voltage regulators are used, then the circuit structure is simple, but the load transient regulation deteriorates significantly when load current changes from less than 1 mA to higher values, resulting in output voltage drops exceeding 0.6 V
Solution Approach 1:
The patent implements a preliminary action by detecting load transient events before they cause significant output voltage drops. The load transient detection circuit monitors the pass element gate voltage and proactively activates the current sink block to counteract the transient effect, rather than waiting for the output voltage to deviate beyond acceptable limits.
Solution Approach 2:
The patent introduces an intermediary mechanism between the pass element and the output node. The current sink block acts as a mediator that can quickly remove excess current from the output node during load transients, preventing large voltage swings without requiring changes to the main LDO regulation path.
2Speed
If the LDO regulator responds to load current changes, then the output voltage can be regulated, but the response time is insufficient to prevent output voltage drops when load current changes occur in 1 μsec
Solution Approach 1:
The patent implements a fast feedback mechanism through the load transient detection circuit that continuously monitors the gate voltage of the pass element. When a load transient is detected (indicated by the gate voltage dropping below a scaled value of the output voltage or a constant voltage level), the feedback immediately triggers the current sink block to activate, providing a rapid response well within the 1 μsec load change timeframe.
Solution Approach 2:
The detection circuit performs preliminary detection of load transients by monitoring the pass element's gate voltage before the output voltage has time to drop significantly. This allows the current sink block to be activated in advance, counteracting the transient effect before it propagates to the output node.
Data Source
AI summary
A method to adjust the load transient regulation of a low drop-out (LDO)/load switch linear voltage regulator (LVR) with an n-type pass element having an open loop transfer function, including determining during a load transient event if the gate of the pass—element goes lower than a scaled value of the output voltage or a constant voltage level, generating a control signal that controls a current sink block if the gate voltage of the pass element is lower than the output voltage, and enabling a current sink block that is controlled by the control signal and connecting the output of the current sink block to the output of the LVR.