LDO Wakeup Circuit With Peak Current Control to Prevent Overshoot
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Solution Overview
Problem
Low dropout regulator (LDO) circuits face challenges in achieving fast wakeup times without risking overshoot into breakdown voltage levels, particularly in applications requiring low standby voltage and high active voltage transitions.
Innovation Solution
A wakeup circuit that controls peak current by adjusting impedance between the voltage supply and LDO output, enabling or disabling parallel paths based on supply voltage levels to manage the transition rate, and disabling the circuit at a threshold voltage to prevent overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the LDO transitions quickly from standby mode to active mode to reduce wakeup time, then the wakeup time is decreased, but the output voltage may overshoot into breakdown voltage levels which stresses components
Solution Approach 1:
The wakeup circuit dynamically adjusts the transition rate from standby to active mode based on the supply voltage level. When the supply voltage is high, the circuit enables a faster transition rate; when the supply voltage is low, it reduces the transition rate. This dynamic adjustment allows the system to achieve fast wakeup times when safe, while preventing voltage overshoot that would occur during rapid transitions from low supply voltages, thereby resolving the contradiction between wakeup speed and component protection.
Solution Approach 2:
The system changes the transition rate parameter based on the supply voltage level. By monitoring the supply voltage and adjusting the transition rate accordingly, the circuit optimizes the balance between fast wakeup and preventing overshoot. This parameter change strategy allows the LDO to adapt its behavior to different operating conditions, achieving both fast response when possible and safe operation when supply voltage is limited.
2Device complexity
If the LDO uses a fixed transition rate from standby to active mode, then the circuit design is simplified, but the wakeup time cannot be optimized for different supply voltage conditions
Solution Approach 1:
Rather than using a fixed transition rate, the wakeup circuit implements dynamic control that adjusts the transition rate based on real-time supply voltage conditions. This dynamic approach adds some circuit complexity but enables optimal wakeup performance across different operating conditions, particularly allowing fast wakeup when supply voltage permits while adapting to slower transitions when voltage is limited.
Solution Approach 2:
The wakeup circuit incorporates feedback from the supply voltage level to control the transition rate. By continuously monitoring the supply voltage and using this information to adjust the transition characteristics, the system optimizes wakeup time based on actual operating conditions. This feedback mechanism enables the circuit to achieve the fastest possible wakeup time that is safe for the given supply voltage level.
Data Source
AI summary
Technologies related to transient response of low dropout regulator (LDO) circuits are described. The LDO circuit has a lower standby output voltage and a greater active output voltage. When transitioning to the greater active output voltage, a wakeup circuit controls peak current between voltage supply and LDO output.