Low pass filter and low dropout regulator

A low-pass filter, low-dropout linear technology, applied in the field of filters, can solve the problem of sacrificing the startup time of the circuit

Active Publication Date: 2013-09-25
KUNSHAN BRANCH INST OF MICROELECTRONICS OF CHINESE ACADEMY OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the RC filter is directly applied to the LDO, although the noise is reduced and the high-frequency power supply rejection ratio is improved, the start-up time of the circuit is sacrificed.

Method used

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Embodiment Construction

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0038] The invention discloses a low-pass filter applied to an LDO, which can shorten the start-up time of the circuit on the premise of ensuring the performance of the LDO circuit.

[0039] see figure 1 , figure 1 It is a structural schematic diagram of a low-pass filter disclosed by the present invention. The low-pass filter includes a first resistor R1 , a first capacitor C1 , a controllable switch 100 and a feedback circuit 200 .

[0040...

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Abstract

The invention discloses a low-pass filter. A controllable switch and a feedback network are further arranged on the basis of an RC (resistor-capacitor) filter, the input end of a first field-effect tube in the controllable switch is connected with a first end of a first resistor, and the output end of the first field-effect tube in the controllable switch is connected with a second end of the first resistor; when the voltage at a first end of a first capacitor does not reach a first voltage threshold, the first field-effect tube is connected to short circuit the first resistor and to fast charge the first capacitor; when the voltage of the first end of the first capacitor reaches the first voltage threshold, a second field-effect tube is connected to begin to fast charge a second capacitor; when the voltage at a first end of the second capacitor reaches a second voltage threshold, the first field-effect tube is disconnected to restore to an RC filter state. Based on the low-pass filter, not only is the quick start of an LDO (Low Dropout Regulator) circuit guaranteed, but also the effect that an LDO has low noises and a high power supply rejection ratio is guaranteed. The invention further provides a low dropout regulator.

Description

technical field [0001] The invention relates to the technical field of filters, in particular to a low-pass filter and a low-dropout linear regulator using the low-pass filter. Background technique [0002] Low dropout linear regulators (LDOs) can provide very low dropout voltages. In the circuit design of LDO, the noise and power supply rejection ratio characteristics of LDO are very important to the application of the circuit, especially in the power supply of some high-frequency circuits. [0003] In order to achieve low noise and high power supply rejection ratio, in addition to optimizing the main devices in the LDO, an RC low-pass filter is usually added between the reference circuit and the error amplifier. This can not only eliminate certain low frequency noise, but also improve the power supply rejection ratio at high frequency of the circuit. The current LDO mainly includes a reference circuit, a low-pass filter, an error amplifier, a power transistor, and a volt...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G05F1/56
Inventor 杨少丹阴亚东牟荣增阎跃鹏
Owner KUNSHAN BRANCH INST OF MICROELECTRONICS OF CHINESE ACADEMY OF SCI
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