The MOS tube is controlled by the error amplifier, and the bandgap reference source (bandgap) is the input of the error amplifier, so the bandgap reference is required to start quickly. To get a fast start-up, the MOS transistor must be turned on as soon as possible. The schematic diagram of the LDO is as follows: The start-up time is affected by the gain, bandwidth, output current, and the voltage drop of Vin and Vout of the feedback loop. The ON state of the linear regulator is when the output voltage reaches 95% of the rated output. In high-performance systems, this requirement is very strict (for example, strict power-up sequence), which requires fast power-up. The startup time of the LDO is also called the initial load response or power-up time. The most important of LDO is the two characteristics of startup and shutdown In response to this situation, chip manufacturers have developed LDO-type voltage conversion chips. But in some cases, such conditions are obviously too harsh, such as 5V to 3.3V, the voltage difference between input and output is only 1.7v, which obviously does not meet the working conditions of traditional linear regulators. Traditional linear regulators, such as 78XX series chips, require the input voltage to be at least 2V~3V higher than the output voltage, otherwise it will not work properly. This is relative to the traditional linear regulator. LDO stands for low dropout regulator, which is a low dropout linear regulator.
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