Current Regulating Circuit for LDO Standby-to-Active Response
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Solution Overview
Problem
Current low dropout regulators (LDOs) experience slow response speed when switching from standby to active mode, leading to voltage drops and incorrect logic operations in connected circuits due to slow current variance of the inner amplifier.
Innovation Solution
A current regulating circuit comprising a first inverter, a second inverter, a PMOS, an NMOS, and a capacitor is used to enable the PMOS and disable the NMOS when the control signal changes, pulling the voltage level of a node to a high level, thereby increasing the speed of the voltage level change at the reference node, thus enhancing the response speed of the LDO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LDO is switched from standby mode to active mode, then the current of the inner amplifier increases to meet high current demand, but the response speed is slow due to slow voltage level change at the reference node
Solution Approach 1:
The patent applies preliminary action by pre-charging the reference node voltage to a high level before the LDO needs to switch to active mode. The control circuit detects the standby state and activates the first switching element to charge the reference node through the second switching element, so when mode switching is needed, the voltage is already prepared and ready for immediate current increase.
Solution Approach 2:
The patent introduces an intermediary control circuit that mediates between the power management unit and the LDO's reference node. This control circuit includes switching elements and capacitors that act as intermediaries to rapidly transfer charge to the reference node, enabling fast voltage level changes without directly modifying the LDO's internal amplifier structure.
2Device complexity
If the voltage level of the reference node changes slowly, then the circuit structure remains simple, but the response speed of the LDO is slow causing voltage drops
Solution Approach 1:
The control circuit performs preliminary charging of the reference node voltage in advance when the LDO is in standby mode. By preparing the voltage level beforehand through the switching elements and capacitors, the system ensures rapid response capability is pre-established without requiring complex continuous control mechanisms during normal operation.
Solution Approach 2:
The control circuit automatically detects whether the LDO is in standby or active mode and self-regulates the charging of the reference node accordingly. When standby mode is detected, the circuit activates to charge the reference node; when active mode is detected, it stops charging. This self-service mechanism maintains reliability without requiring external intervention or complex control systems.
Data Source
AI summary
A current regulating circuit is provided in the invention. The current regulating circuit includes a first inverter, a second inverter, a PMOS, an NMOS and a capacitor. The first inverter receives a control signal. The second inverter receives the control signal. A first gate of the PMOS is coupled to the first inverter. The NMOS is coupled to the PMOS and a second gate of the NMOS is coupled to the second inverter. The capacitor is coupled to the PMOS and the NMOS at a node, and is coupled to a low dropout regulator at a reference node.