Low dropout regulator and control circuit thereof

Abstract

The invention discloses a low dropout regulator and a control circuit thereof, the control circuit comprises an error amplifier, a turn-back type current-limiting protection circuit, an undershoot suppression circuit and an output detection circuit, wherein the turn-back type current-limiting protection circuit is used for limiting the output current of a power transistor and performing short-circuit protection; the undershoot suppression circuit is used for pulling down the control end of the power transistor when the output voltage undershoots, and the output detection circuit is used for judging whether the output voltage rises to a preset voltage value or not in the starting stage and closing the turn-back characteristic of the turn-back type current-limiting protection circuit and the undershoot suppression circuit before the output voltage rises to the preset voltage value. The normal starting of the circuit can be prevented from being influenced by misoperation of the turn-back type current-limiting protection circuit and the undershoot suppression circuit in the starting process of the circuit, and the on-load starting capability of the circuit is improved.

Description

technical field [0001] The present invention relates to the technical field of linear regulators, in particular to a low-dropout linear regulator and a control circuit thereof. Background technique [0002] A low dropout regulator (Low Dropout Regulator, LDO) converts an unstable input voltage into an adjustable DC output voltage, so as to be used as a power supply for other systems. Because linear regulators have the characteristics of simple structure, low static power consumption, and small output voltage ripple, linear regulators are often used for on-chip power management of mobile consumer electronics chips. [0003] figure 1 and figure 2 A package schematic diagram and a schematic circuit diagram of a low dropout linear voltage regulator according to the prior art are respectively shown. Such as figure 1 As shown, the existing low dropout linear regulator includes an input pin IN, an enable pin EN, an output pin OUT and a ground pin GND. The input pin IN is conn...

AI Technical Summary

Problems solved by technology

[0006] The existing low-dropout linear voltage regulator with foldback current limiting protection circuit has the following problems: if the subsequent stage load is slightly greater than the current limit value when the current limiting protection circuit folds back, during the power-on process of the circuit, due to the current output The voltage Vout is low, and the current limiting protection circuit will mistakenly believe that a load short circuit occurs at this time, and clamp the voltage Vgate of the control terminal of the power transistor Mpout to a certain value, resulting in the failure of the circuit to start normally.

[0008] and image 3 There are also some problems in the low dropout linear regulator in the circuit: during the power-on process of the circuit, due to the low output voltage Vout, the undershoot suppression circuit 220 will mistakenly believe that an output voltage undershoot event has occurred at this time, and the power transistor Mpout The control terminal voltage pulls down

Since the loop of the error amplifier has not been established at this time, the control terminal voltage of the power transistor Mpout is at a low potential for a long time, which will cause the output current to increase. For some small load application circuits, the output voltage will overshoot

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