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Hello everyone, today we will learn about the generation process

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of the standby power supply PP3V3_G3H in the Apple A2159 circuit

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We can see from the timing diagram that PP3V3_G3H is generated by the control of TPS51980

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and mainly provides main power supply for U7800

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When the power supply chip receives this power supply,

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its crystal oscillator will start to vibrate and generate a clock,

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and then send an open signal EN to the TPS51980

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Let's look at the pin definition of TPS51980 in the circuit diagram

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Its location number is U7650

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The VIN pin of the chip is the main power supply pin,

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and its power supply comes from the common point

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we trace its source

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We found that it was renamed after the common point voltage PPBUS_G3H

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passed through the current-sensing resistor

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With the power supply, it also needs an open signal

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The 12th pin EN is the main open signal,

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we can also call it linear open, the external name is P5VXX_EN

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we trace its source

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It is renamed after PMU_PVDDMAIN_EN passed through the resistor

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Then this signal comes from the VPWR_EN pin of the U7800 power supply chip

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This is the power chip U7800

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When the TPS51980 gets the open signal, first its reference voltage starts to output

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This is a 2V reference voltage output,

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usually used to pull up this SKIP working mode setting

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After the reference voltage is normal, VREG3 and VREG5 linear power supply will be generated

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These two linear voltages are not usually adopted by external circuits

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For example, this VREG3,

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we searched its whereabouts and found that it was not used by external circuits

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The 5V linear is also not used by external circuits,

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but is used internally by the chip

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This chip is a dual PWM controller, it needs to use this 5V power supply

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Including the boost pin of the upper tube and the two VBST boost pins,

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they all need to use this 5V linear as the bootstrap base voltage

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Then, its two lower tube drivers also need to use this 5V linear as the driving source

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There are many modules and many pins that need to use this 5V linear to provide pull-up

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Let's take a look at the generation process of PP3V3_G3H

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After the previous power supply, turn on, reference and linearity are all normal,

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then it needs to get an EN2 open signal

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EN2 is dedicated to open the second PWM power supply

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The left one is the first PWM, which is used to control the generation of 5V power supply

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There are upper and lower tubes and inductors here

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The output name of the rear end of the inductor is called PP5V_G3S

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We're not going to talk about this power supply for now

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We mainly introduce the power supply of PP3V3_G3H

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This power supply is also driven by the chip output upper tube drive and lower tube drive,

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and outputs two pulses to control the external two upper and lower tubes to conduct in turn

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to generate power supply output

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The name of the inductor backend is PP3V3_G3H

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This current is relatively large, with more than ten amperes, and the working frequency is 500KHz

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This open signal is floating and not controlled by an external circuit

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In Apple's circuit, the logo begins with TP indicates a test point, which means floating

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We tracked down this switch and couldn't track down the source

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So as long as the previous master open signal is normal, the linear voltage output is normal,

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and then there will be this PWM output to control the normal output of this PP3V3_G3H

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There are two pins at the bottom, CSP and CSN,

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they are current detection pins

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RF is the frequency setting pin

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VFB2 is the feedback of 3.3V power supply

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COMP is the feedback compensation pin

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The current detection pin is connected to the front and rear ends of the inductor

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for real-time detection of the current flowing through the inductor,

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real-time detection of the energy in the inductor, and used to adjust its output

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After the voltage at the back end of the inductor is divided by resistors in series, this VFB2 is obtained,

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which is used to detect whether the output of the rear end of the inductor is overvoltage or undervoltage,

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and is used to adjust the PWM output

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When it is detected that the output voltage at the back end of the inductor is normal,

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the PGOOD2 power good signal output is finally generated

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This power good signal finally returns to the U7800 power chip,

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which is pulled up by PP3V3_G3H and sent to this pin of U7800

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This is the generation process of standby power supply PP3V3_G3H

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After this power supply is supplied to U7800,

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it mainly supplies power to its VDD_MAIN and VDD_BUCK pins

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This chip has various PWM outputs

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Let's take a look at the real picture

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This is the U7800 power chip, and there are multiple inductors around it,

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which means that there are multiple PWM power supply outputs.

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The source of each power supply is this PP3V3_G3H

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There are two inductors here, one is PP3V3_G3H and the other is PP5V_G3S

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The two next to it are the upper and lower tubes

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The back end of the inductor are filter capacitors

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These two PWMs are controlled by the chip TPS51980,

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which is on the back of the mainboard

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Let's take a look at the circuit diagram

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The power supply of VDD_MAIN and VDD_BUCK of U7800 is provided by PP3V3_G3H

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This U7800 is a multi-PWM controller,

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which integrates LDO and PWM, and switch power supply mode

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The power supply of each PWM is provided by VDD_BUCK

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Ok, this is how PP3V3_G3H is generated and where it goes