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Hello everyone, today we will learn about the 3.8V main power supply circuit in the Apple A2337 circuit

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The name of the 3.8V main power supply is PP3V8_AON_VDDMAIN

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This main power supply mainly provides power to the power chip behind

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This power supply is generated by three inductors at the same time,

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which is controlled by the main chip U5700

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In the real circuit, here are the three inductors

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There are three black current-sense resistors at the rear end of the inductors

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After the power supply is output through the current-sensing resistor,

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it provides power to the following two power chips,

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one is the main power supply and the other is the auxiliary power supply

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Of course, there will be filter capacitors at the back end of the inductors

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The capacitors are on the back of the mainboard, which are these two rows of tank capacitors

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The main chip refers to this chip

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The main chip drives three MOS tubes

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The three MOS tubes at the front end of the inductor are composite tubes,

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which integrate the upper and lower tubes

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Let's take a look at the circuit diagram

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In the circuit diagram, U5700 is the main chip

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The condition of this chip is very simple, only need to meet the VIN main power supply

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The VIN main power supply is provided by the common point voltage PPBUS_AON

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With the mains supply, it produces a linear

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This LDO5 is a 5V linear output

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After the linear output, it returns to supply power to the VDRV pin,

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and then gets the enable signal EN

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It will output the drive of the three upper and lower tubes

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UGATE1, LGATE1, BOOT1, this is the driver of the first road,

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controlling the first road upper and lower tubes

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BOOT2, UGATE2, LGATE2, this is the second road

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UGATE3, LGATE3, this is the third road

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These three set of upper and lower drivers respectively control the three

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groups of upper and lower tubes on this page

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Q5800 is a set, Q5820 is another set, and Q5840 is also a set

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There are inductors behind the three MOS tubes

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The rear ends of the three inductors are all connected together

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The output terminal is PP3V8_AON_VDDMAIN, which is the main power supply output of 3.8V,

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and the maximum current is 30A

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As can be seen from the circuit diagram,

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there is a milliohm-level current-sensing resistor at the back end of each inductor

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After the 3.8V power supply is output, there are voltage detection pins, VSEN and VRTN,

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which are used to detect whether the output voltage at the back end of the inductor is normal

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There are 3 groups of current detection pins here, CSP1 and CSN1 are the current detection of the first set,

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connected to the current detection resistor at the rear end of the first set of inductors

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The following is the current detection of the second set and the third set,

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both of which are connected to the front and rear ends of the current-sensing resistor at the rear end of the inductor

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There is a current detection resistor at the back end of each set of inductors,

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and they are connected to the corresponding current detection pin of the main chip

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to detect whether the output current is normal

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In the maintenance process, if the 3.8V output is abnormal,

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we mainly check the working conditions of the main chip,

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and check whether its power supply, open signal, and linearity are normal

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In the process of maintenance,

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we can also directly connect a voltage above 4.5V to the rear end of the inductor

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through an adjustable power supply,

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and give it a DC power, and it can also display normally

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Ok, this is the main power supply of 3.8V

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The open signal of the main power supply is P3V8AON_PWR_EN,

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which comes from U5340

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It is the open signal sent by the charging chip to turn on the main power supply of 3.8V

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If there is a problem with the charging chip, it will cause the open signal to be abnormal

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Only after the common point voltage is normal, the charging chip will send an open signal

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Ok, this is the 3.8V main power supply generation process