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Hello everyone, today we are going to understand the LDO power supply mode output by the voltage regulator

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First, LDO stands for low voltage differential linear regulator,

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which can achieve very small voltage difference between output and input

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This supply circuit is characterized by its direct output from the chip

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Direct output from this OUT pin, no inductor at the output end, but a filter capacitor

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The disadvantage is low output current and high loss, such as here

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The chip works like this

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The BIAS pin is the operation voltage of the chip

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This IN is the voltage input, provided by PP1V8_S3, 1.8V power supply input

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And then when it gets the third pin EN, it's going to output OUT

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The voltage output from the OUT pin is 1.5V and the maximum current is 0.02A

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The current is very small, 20 mA

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And it is the step-down type, step-down 1.8V to 1.5V

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It has a step-down and low current, and that's an LDO circuit

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Take a look at this chip, U7840,

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which is also an LDO power chip

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Pins 3, 4, and 6

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Its power supply, input voltage and turn on signal are provided by PP3V3_SUS

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This chip can provide power, and has enable signal and input,

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it converts the input voltage into an OUT output

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Here, the output is PP1V05_SUS, indicating 1.05V power output

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It converts 3.3V to 1.05V, which has a vlotage drop

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Its maximum output current is 0.35A, which is very small

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But the current in PP3V3_SUS is very high

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If every power supply uses LDO, the loss is too great

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Therefore, LDO power supply mode is usually used in some low-power circuits

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For example, it provides standby power to the EC and RTC circuits

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In this very low power circuit, LDO is used

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Well, this is the LDO power supply mode of the voltage regulator output