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How to use the schematic diagram

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This video mainly demonstrates how to view the meanings of the marking in the schematic diagram

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Let me take the iPhone schematic diagram as an example to demonstrate

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After opening in the drawing, the first page is the catalog page

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The catalog page is dedicated to introducing the page numbers of different chips in the mainboard

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After the schematic diagram is opened,

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if we see a circle marked SB or BS,

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it represents the screw column in the real object

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All those starting with FD, TP, or PP in the schematic diagram represent test points

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In the actual object, the small yellow dots represent test points

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A box in the schematic diagram represents a chip

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If the position numbers in the boxes are same,

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it means that all the introductions are the same chip

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For example, the location number of the iPhone 12 CPU is U1000

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After searching, we can find that there are many identifiers U1000

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As long as U1000 is marked, it means that the whole introduction is CPU

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In the Apple drawing, we can also identify it according to the SYM2OF21 below the position number

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2 represents the second box of the CPU,

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and 21 represents a total of 21 boxes for the CPU

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Each line in the schematic diagram represents each solder point in the physical diagram

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The English identification in the schematic diagram is the manufacturer's English logo

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The English logo of the internal is the chip manufacturer logo

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When we search for a signal, we search for the external English name

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The letters and numbers at the junction of the line and the box represent the coordinates

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Because BGA chips have solder points horizontally and vertically,

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they cannot be directly identified by numbers

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Generally, the vertical row will be identified by letters,

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and the horizontal row will be identified by numbers

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the coordinate point represents the foot position

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For example, point F5 in the bitmap,

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it will have a corresponding point in the schematic diagram

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In the schematic diagram, the line is marked IN,

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and the arrow facing inward represents that the signal is input

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If the arrow marks OUT outward, it means that the signal is output

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If there are arrows on both sides of the line identification BI,

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it means that the signal can be output or input

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In Apple's drawings, the line marked NC,

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like the unused signal in the schematic diagram of iPhone 11, will be marked NC

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And the line will be crossed, then both cases belong to the signal is not used

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The inside of the box is divided into areas,

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which belong to the subdivision module

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Because the CPU is an integrated body,

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its different solder points handle different functions

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In the schematic diagram, the solder points with the same functions will be marked together

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The number below the position number generally represents the model of the chip

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For example, CBTL1614A1 is marked under U9300,

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which means it is the model of this chip

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In general, we are based on the model marked on the physical chip,

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and the model marked in the schematic diagram is only for reference

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In Apple's schematic diagram, the thick line is usually the power supply,

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and the thin line is usually the signal

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But there are also special cases

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In the Apple model,

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if we see the NOSTUFF mark on the top of the component,

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it means that the component is not installed

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When we look at the physical picture,

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we can see that there are many components that are not installed

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We can't make up for this kind of component,

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There are dots crossed in the schematic diagram,

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which means that the line is connected in actual measurement

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If the intersection has no dot, it means that the lines are not connected

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Ok, that's it for this lesson