A Low Dropout Linear Regulator's Design And Research On Fast Response And Low Noise

Power and power regulation,are the most basic functions in an electrical system.The role of the power management chip is to adjust these unpredictable,noisy supply voltages to a stable,accurate,load-independent supply voltage that attenuates these unwanted ripples to a lower,acceptable level.With the development of semiconductor process and technology,power management chips developing toward high integration or system-on-chip integration,how to achieve low noise,low power consumption,low supply voltage supply,fast transient response,high stability and high integration will become a focus research area.This article will use a 0.6?m,12 V bipolar process to design a fast-responding,lownoise low-dropout linear regulator LDO based on Candence's Spectre simulation software.The input voltage range is 3~12V,the rated output voltage is 2.5V,and the load range is 1mA~3.5A.First,a new symmetrical two-stage cascode-co-basis error amplifier and a resistive load are used to increase the common-mode rejection ratio and supply-voltage rejection ratio of the circuit and reduce LDO noise.In the load current of 400 mA,10Hz~100kHz,the output noise voltage of the chip is 4.78?V/?Hz,and the corner frequency is 1Hz.Secondly,the chip adopts the double-zero compensation technology of the output terminal feed-forward capacitor zero point and ESR zero point to ensure that the loop has a phase margin of more than 52 degrees in the full load range.Thirdly,the design adds a buffer stage and a Darlington driver stage circuit between the error amplifier and the power stage to improve the driving capability of the circuit,and at the same time separate the high resistance node and the capacitor node of the loop,so that the LDO loop is more stable.For the load step of 1A,the undershoot voltage is 54.1mV,the overshoot voltage is only 18.7mV,and the transient response time is 0.32?s.Finally,auxiliary protection circuits such as over-temperature protection,current-limit protection,overload monitoring identification and anti-power tube saturation are added in the chip design process to avoid the chip working in extreme environments and damage the device.Among them,the over-temperature protection has added a hysteresis of 30 °C to avoid insufficient heat dissipation of the chip and frequent startup.At the same time,the traditional resistor feedback current limiting protection is abandoned,and an externally adjustable current limiting protection structure is adopted.When the load exceeds the threshold set by the current limiting protection,the chip will externally identify that the current chip is in an overload working environment.The anti-saturation circuit prevents the LDO's power tube from entering an undesired saturation state,making the chip more robust.The chip is a PNP pass element low-dropout linear regulator that will be available in a flat,flat package with an area of 2.79 mm × 3.86 mm,primarily for noise-sensitive analog or RF circuit modules.