1

00:00:00,933 --> 00:00:03,166

High current occurs when iPhone starts up

2

00:00:03,566 --> 00:00:07,533

In this video, we're going to learn how a high current circuit works

3

00:00:09,066 --> 00:00:12,433

This works for the iPhone 6 to iPhone 12Promax

4

00:00:14,000 --> 00:00:15,200

Here's how it works

5

00:00:17,233 --> 00:00:24,033

The first step, when we connect the adjustable power supply or battery, it will generate the main power supply

6

00:00:24,166 --> 00:00:27,766

The main power supply provides the operating voltage for the IC

7

00:00:28,166 --> 00:00:31,033

Second, after the main power supply,

8

00:00:31,366 --> 00:00:36,200

it will preferentially generate a PP1V8_ALWAYS standby power supply

9

00:00:37,200 --> 00:00:40,400

Third, after the standby power supply is generated,

10

00:00:40,633 --> 00:00:44,233

a pull-up power supply will be provided for the switch pin

11

00:00:44,566 --> 00:00:47,600

Step four, when we short the switch pin,

12

00:00:48,366 --> 00:00:51,233

this signal will be sent to the main power supply

13

00:00:53,733 --> 00:00:58,000

The main power supply will output power after receiving this start signal

14

00:00:58,666 --> 00:01:02,566

The main power supply will output about 30 power supplies,

15

00:01:02,833 --> 00:01:06,733

including about 15 power supplies for BUCK with high current

16

00:01:07,500 --> 00:01:10,800

and 15 power supplies for LDO with low current

17

00:01:13,400 --> 00:01:16,700

We can confirm the specific model through the drawing

18

00:01:18,766 --> 00:01:21,100

After the output of this power supply,

19

00:01:21,600 --> 00:01:26,500

it will provide the operating voltage for the application part of the chip in the mainboard

20

00:01:27,033 --> 00:01:33,266

Such as CPU, temporary storage, hard disk, audio, Wifi, etc

21

00:01:34,666 --> 00:01:38,800

When we press the switch, these chips have an operating voltage

22

00:01:40,066 --> 00:01:46,233

If there is a short circuit on the BUCK power supply and the LDO power supply of the IC output,

23

00:01:46,733 --> 00:01:49,566

it will result in a high startup current

24

00:01:50,400 --> 00:01:54,200

The output current of a BUCK power supply is usually high,

25

00:01:55,700 --> 00:01:59,433

so when it shorts out, we call it high current

26

00:02:01,100 --> 00:02:04,433

LDO power supply output current is relatively small,

27

00:02:04,900 --> 00:02:09,266

if it shorts circuit, it is called the startup current is too high

28

00:02:11,566 --> 00:02:15,433

As long as there is a short circuit in the output power supply IC,

29

00:02:15,733 --> 00:02:19,600

the current after starting will be larger than the normal current

30

00:02:20,333 --> 00:02:25,700

After this problem occurs, we need to measure all the power supply IC output

31

00:02:27,866 --> 00:02:32,766

If there is a short circuit, we remove the connection components of the short circuit

32

00:02:33,066 --> 00:02:34,866

Then the fault can be fixed

33

00:02:35,833 --> 00:02:37,833

So that's all for this lesson