A low dropout linear regulator and its control circuit

Abstract

The application discloses a low-dropout linear voltage regulator and its control circuit. The control circuit includes an error amplifier, a foldback current limiting protection circuit, an undershoot suppression circuit, and an output detection circuit. The foldback current limiting protection circuit is used to limit the power transistor The output current and short circuit protection, the undershoot suppression circuit is used to pull down the control terminal of the power transistor when the output voltage undershoots, and the output detection circuit is used to judge whether the output voltage has risen to the preset voltage value during the start-up phase, and Turn off the foldback characteristic and undershoot suppression circuit of the foldback current-limiting protection circuit before the output voltage rises to the preset voltage value, which can prevent the malfunction of the foldback current-limiting protection circuit and the undershoot suppression circuit from affecting the normal operation of the circuit during circuit start-up Start, improve the load start capability of the circuit.

Description

technical field [0001] The present invention relates to the technical field of linear regulators, and more particularly, to a low-dropout linear regulator and a control circuit thereof. Background technique [0002] A low dropout linear regulator (Low Dropout Regulator, LDO) converts an unstable input voltage into an adjustable DC output voltage so that it can be used as a power supply for other systems. Linear regulators are often used for on-chip power management of mobile consumer electronic equipment chips due to their simple structure, low static power consumption, and small output voltage ripple. [0003] figure 1 and figure 2 The package schematic diagram and the circuit schematic diagram of the low dropout linear regulator according to the prior art are respectively shown. like 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 connected to the powe...

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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