1

00:00:00,433 --> 00:00:04,933

This lesson is about the temperature detection circuit of OPPO mobile phone,

2

00:00:05,300 --> 00:00:09,233

which is related to the circuit that prompts abnormal temperature

3

00:00:09,900 --> 00:00:14,433

In this circuit, the first thing to know is that this is the battery holder

4

00:00:15,066 --> 00:00:19,333

It is connected to the I2C bus through the temperature detection line TEMP,

5

00:00:19,666 --> 00:00:23,666

and connected to the CPU through a 33 ohm resistor

6

00:00:25,800 --> 00:00:29,766

Because the temperature detection is connected to the I2C bus,

7

00:00:29,933 --> 00:00:35,700

if the I2C bus wants to work normally, generally two lines must work at the same time

8

00:00:37,533 --> 00:00:40,900

Let's take a look at the principle of its circuit

9

00:00:42,733 --> 00:00:47,533

R3305 and R3306 are pull-up resistors

10

00:00:48,800 --> 00:00:52,233

This terminal is powered by 1.8 volts

11

00:00:52,766 --> 00:00:57,633

There is a 4.7 k ohm resistor connected to the power supply connection,

12

00:00:58,700 --> 00:01:05,233

then there will be 1.8 volts on the I2C bus, and 1.8 volts on the right end of the resistor

13

00:01:05,933 --> 00:01:11,800

During maintenance, if there is no voltage of 1.8 volts measured at the end of the battery holder,

14

00:01:12,266 --> 00:01:18,400

it is necessary to measure whether there is a voltage of 1.8 volts at the left end of the resistor

15

00:01:19,233 --> 00:01:24,466

If so, just remove the resistor, short the resistor or replace the resistor

16

00:01:25,233 --> 00:01:30,033

If the voltage of 1.8 volts cannot be measured at the left end of the resistor,

17

00:01:30,033 --> 00:01:36,166

it is necessary to measure whether the voltage of the power supply terminal of the pull-up circuit is normal

18

00:01:37,233 --> 00:01:41,100

If the voltage of the power supply end is 1.8 volts,

19

00:01:41,833 --> 00:01:47,266

it is generally caused by the damage of these pull-up resistors, just replace it directly

20

00:01:47,866 --> 00:01:53,066

Generally, it can be repaired by replacing the 2 k to 10 k ohm resistor

21

00:01:53,833 --> 00:01:58,333

If the voltage of 1.8 volts cannot be measured at the power supply end,

22

00:01:58,366 --> 00:02:01,333

you need to check which chip the power supply comes from,

23

00:02:01,566 --> 00:02:03,966

resolder the chip or replace the chip

24

00:02:05,400 --> 00:02:09,366

This is the voltage measurement problem of OPPO's temperature detection pin

25

00:02:11,166 --> 00:02:13,800

In the maintenance, there will be a situation

26

00:02:13,800 --> 00:02:19,600

where the ground value is measured from the two pins of the battery holder, and infinity appears, OL,

27

00:02:19,800 --> 00:02:21,433

how should we analyze it?

28

00:02:22,933 --> 00:02:30,000

We generally measure the ground value on the left side of the resistor R2823 to see if it is normal

29

00:02:30,700 --> 00:02:37,200

If there is a ground value, you only need to short this resistor or replace this resistor to repair it

30

00:02:39,000 --> 00:02:43,566

If the measured value is infinity, then the CPU must be re-soldered,

31

00:02:43,866 --> 00:02:47,233

because it is directly connected to the CPU

32

00:02:49,133 --> 00:02:51,200

In the OPPO mobile phone circuit,

33

00:02:51,533 --> 00:02:56,466

some switch chips of wireless charging chips are connected to the I2C bus

34

00:02:58,200 --> 00:03:03,133

If the switch chip is abnormal, or the line of the I2C bus is abnormal,

35

00:03:03,366 --> 00:03:05,866

it will also cause abnormal temperature

36

00:03:06,700 --> 00:03:08,800

This is the actual chip

37

00:03:10,000 --> 00:03:13,166

This is OPPO's temperature detection circuit

38

00:03:13,466 --> 00:03:15,333

That's all for this lesson