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    27. How to quickly find the power supply of a chip
    In this lesson, we talk about the description of trigger small currents in circuit diagrams.
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    In this lesson,

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    we talk about the description of trigger small current in the circuit diagrams

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    We talked about the two power supply lines from the power supply to the CPU in the last class,

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    we will continue to see

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    The power output from the U4200 power supply chip is the power supply begins with VREG

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    For example, VREG_S6A_0P9, 0.9V power supply

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    And this, 0.75V power supply

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    And this, VREG_S10_A0P75

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    This is the power output from the switching power supply module

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    integrated inside the power chip

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    Does it power the CPU?

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    We have another way to determine

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    Our last lesson was by looking at the wiring that goes to the CPU,

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    which goes to the U4200, to the U2400,

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    and back again

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    We found that it doesn't go to the CPU,

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    then it's not powering the CPU

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    Let's see if the power supply goes to the CPU

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    This power supply goes to page 38

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    What is this chip called?

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    It is called SM8250

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    It is the seventh part of the description of this chip

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    U3100 is the CPU

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    OK, here we say another way to determine the CPU power

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    First, we need to know which chip is the CPU

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    The chip is generally rectangular on the circuit diagram,

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    the position number will be marked on the top of it,

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    and the model number will be marked on the bottom

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    For example, this CPU,

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    U3100 is its position number,

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    SM8250 is its model

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    From this, we can know that this is the CPU

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    So what about the power supply to    the CPU?

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    We can search for the position number of the CPU in the circuit diagram

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    For example, this power supply is supplied to the W29 pin of the CPU,

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    then this power supply is the power supply of the CPU

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    In the same way,

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    the 0.75V power supply begins with VREG is given to the A22 pin of the CPU

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    This is also the CPU power supply,

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    this is also the CPU power supply,

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    and this one is also the CPU power supply

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    This is the description page of the chip

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    This 0.88V power supply is supplied to the AC33 pin of the CPU

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    Similarly, this is also the CPU power supply,

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    and this one is also the CPU power supply

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    If the CPU wants to work, it needs to be powered,

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    and the power is provided by other chips

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    The CPU itself does not output power,

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    it can only output control signals

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    Therefore, its power supply is provided by the power chip,

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    the main power supply or the auxiliary power supply

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    This is how to quickly find the power supply on a chip,

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    that is to find the chip first,

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    and then see which power supplies are connected to this chip

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    Okay, that's it for this lesson

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