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Hello everyone, in this lesson we will take a look at the actual circuit application of MOS tubes

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First we observe the circuit diagram

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The ultimate purpose of this circuit is to convert the +3VS power supply into the +LCDVDD power supply

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To convert +3VS into LCDDVDD, the MOS tube Q37 in the middle of them needs to be turned on

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Observing the circuit symbol of Q37, we can know that it is a P-channel MOS tube

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The P-channel MOS tube is turned on at a low level and turned off at a high level.

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Q37 needs to be turned on, so the second pin of Q37 should be low

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Let's continue to observe the circuit diagram and analyze how the second pin of Q37 can become low level

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Observing the circuit, we can know that when Q55 is turned on, the G pole of Q37 can become 0 volts

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When Q55 is off, the G pole of Q37 can be changed to 3.3 volts

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Q37 needs a low level to be turned on, so Q55 needs to be turned on

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Observing Q55, we can know that Q55 is an N-channel MOS tube

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N-channel MOS tube is turned on at high level and cut off at low level

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Q55 needs to be turned on, then its second pin should be high level

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Continue to observe the circuit to know

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When any of the previous two signals is high level, the second pin of Q55 is high level

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So for this circuit diagram, when any of the two signals ENVDD or LCDVCC_TST is high,

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the +3VS power supply can be converted into +LCDVDD power supply