Dual-loop low dropout regulator

Abstract

The invention discloses a dual-loop low dropout regulator, which comprises a first loop and a second loop, wherein the first loop is a three-level amplifier formed by a first amplifier stage, a second amplifier stage, a third amplifier stage, a first compensation network and a second compensation network, and a second loop is a three-level amplifier formed by a second amplifier stage, a fourth amplifier stage, a fifth amplifier stage and a third compensation network. According to the invention, a constant-voltage output of the LDO (Low Dropout Regulator) is controlled by the first loop, an output current of LDO is limited by the second loop so as to prevent the output current from exceeding an over-current point when an over-current condition appears, and the second compensation network and the output port of the LDO are externally connected with a load capacitor, so that a pseudo ESR (Equivalent Series Resistance) zero setting compensation network is integrated in the first loop, and the frequency compensation of the first loop is realized; and meanwhile, the second amplifier stage of the second loop and the second amplifier stage of the first loop are shared, so that the conventional dual-loop LDO circuit is simplified, and the area and the consumption of a chip are reduced.

Description

technical field [0001] The invention belongs to the technical field of power supply management, and in particular relates to the design of a low dropout linear regulator (LDO, Low Dropout Regulator). Background technique [0002] With the development of integrated circuits towards SoC (System on Chip), the power management unit is gradually integrated into the chip and plays an important role. As an important type in power management modules, LDOs are widely used because they can provide low-noise, high-precision stable power supply voltages for noise-sensitive analog modules. [0003] In terms of LDO reliability, due to factors such as power-on establishment, limited power supply capacity, and LDO overload, the LDO is often in an unstable working state. Based on the above reasons, many problems will occur: (1) During the establishment of the LDO, the loop load The feedback mechanism prompts the power tube to output a large current, which may cause the LDO power supply modu...

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Problems solved by technology

[0003] In terms of LDO reliability, due to factors such as power-on establishment, limited power supply capacity, and LDO overload, the LDO is often in an unstable working state. Based on the above reasons, many problems will occur: (1) During the establishment of the LDO, the loop load The feedback mechanism prompts the power tube to output a large current, and the LDO power supply module may be pulled down, causing other modules in the system to fail; (2) When the LDO output is short-circuited or overloaded, the output current is too large, causing the temperature of the LDO to rise until it burns out

There are three traditional over-current protection designs, one is to use a comparator to detect whether the output of the power tube is over-current, and directly shut off the power tube after the over-current. The disadvantage of this circuit is that it takes a long time for the circuit to recover from the over-current. time; the second is the foldback current limit, which limits the output current after overcurrent to a small value, which will neither consume a lot of power nor take a long time to switch the circuit from overcurrent to It works normally, but its disadvantage is that the current limit value of the foldback current limit is within the normal working output current range of the LDO. When the fault is eliminated, the current limit loop is not easy to exit, resulting in the LDO not working normally, and the foldback current limit usually has an additional current limit. The loop and large adjustment tube increase the chip area; the third is a constant current limiting circuit, which limits the output current to a set overcurrent point when an overcurrent condition occurs. The traditional method is to use an independent The constant current loop of the constant voltage loop is used to monitor the output current of the power tube. When the overcurrent condition is met, the power tube is controlled to make the output current a set constant current value, such as smooth peak current limit technology, but logic is often used The control method is switched between the independent constant voltage loop and constant current loop, the control is complex and the additional adjustment tube in the constant current loop increases the chip area

[0005] In terms of LDO stability design, the LDO using off-chip capacitor compensation utilizes the traditional method of using the equivalent series resistance (Equivalent Series Resistance, ESR) of the external load capacitor to generate an effective zero point to achieve compensation, increasing the peak of the output transient response, and the ESR will Fluctuation, large dispersion, and the required ESR is large, it is difficult to achieve

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