Multi-mode LDO Regulator Voltage Transition Stability
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Solution Overview
Problem
Existing multiple-mode regulators experience voltage dips or overshoots during power mode transitions due to mismatches in regulation between high-power and low-power LDO modules, potentially causing device resets.
Innovation Solution
A multiple-mode voltage regulator using replica devices, where a first and second voltage regulator are configured with error amplifiers and replica pass transistors to accurately regulate output voltage during transitions, with transition logic controlling the multiplexer to select the appropriate input for the error amplifier, ensuring stable voltage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both HP LDO module and LP LDO module are enabled during mode transition, then both modules regulate Vout simultaneously, but voltage dip or overshoot occurs due to mismatch in regulation decisions
Solution Approach 1:
A replica device is introduced as an intermediary to sense the output voltage during mode transitions. The replica device provides a reference voltage to the error amplifier, which then controls both LDO modules during the transition period. This intermediary mechanism ensures coordinated regulation between HP and LP LDO modules, preventing voltage dips or overshoots that would otherwise occur due to their independent regulation decisions.
Solution Approach 2:
The system performs preliminary action by enabling both LDO modules before the actual mode transition occurs. The transition logic detects the mode change and activates both modules simultaneously during a transition period, allowing them to work together in a controlled manner before one module fully takes over. This preliminary coordinated operation prevents sudden voltage changes during the switch between power modes.
2Reliability
If transition period is extended to allow both LDO modules to stabilize, then voltage stability improves, but transition response time increases
Solution Approach 1:
The error amplifier continuously monitors the output voltage through the replica device and provides feedback control during the transition period. This feedback mechanism allows the system to maintain stable voltage regulation dynamically, enabling a shorter transition period while still ensuring voltage stability. The feedback loop adjusts the regulation of both LDO modules in real-time, preventing voltage dips or overshoots even during rapid mode transitions.
Data Source
AI summary
Aspects of the present disclosure generally relate to multi-mode voltage regulators. For example, the regulator may include a first voltage regulator configured to operate in a first power mode. The first voltage regulator is further configured to selectively adjust an output voltage using one of a voltage output of a replica pass transistor of the first voltage regulator or a voltage output of the pass transistor of the first voltage regulator based on a transition from a second power mode to the first power mode.