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This lesson goes on to check the schematic diagram to understand the circuit of the small audio

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We talked about Hisilicon and MediaTek in the previous lessons,

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and this lesson is about Qualcomm, taking Mi 11 as an example

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The circuits of Xiaomi 11, Xiaomi 10 and Xiaomi 12 are the same, so we will choose one of them

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To find a small audio circuit, you can start from the seat J6502

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We open Xinzhizao intelligent maintenance query system, find Mi 11, and click on the drawing

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Double click on the schematic

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We found that it has the same name as the audio amplifier of the Redmi K50

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The PA here is the power amplifier, the power amplifier of the speaker

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Basically we find the speaker circuit

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It belongs to the double speakers. Could it be the top speaker that we found?

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We double click it

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This is the output signal of the small audio, it leads to J6502,

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which means we searched correctly

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Let's take a look at the circuit of this little audio chip

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Its model number is CS35L 41B

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This audio chip is different from the model of Redmi K50

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It's just that their position numbers are the same

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Let's look at its power supply first

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The small audio chip has a 1.8-volt power supply and a main power supply VPH PWR

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Generally, there are two power supplies

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There is also a circuit after boosting

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There are several capacitors on this circuit, and these capacitors are relatively large

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Pay special attention to whether there is a short circuit in the machine that enters the water

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One end of this inductor L6001 is connected to SW,

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and the other end is connected to the main power supply input

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What is the function of this inductance?

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It is mainly energy storage, we usually call it a boost, it is used in a boost circuit

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Let's look at its signal

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E2 pin is the reset signal of the small audio power amplifier

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F4 pin is an interrupt signal

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Pins B4, C4, C5 and B5 are the input sound signals, which are the sound signals input from I2S

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Pins E5 and E3 are the I2C buses, which are used to control this small audio

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What is the main function of this little audio?

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It processes the input sound signal,

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that is, it undergoes digital-to-analog conversion internally, and then performs power amplification.

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After the power is amplified, the electrical signal is output from the D2 and C2 pins to drive the speaker

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Where did the signal go?

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It leads to the socket J6502

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This seat is the seat on the big mainboard

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This is not the end of the speaker

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Where is the end of the speaker?

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There is a cable installed here, and the other end is installed on the small board of the tail plug

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Contact the speaker through the tail plug to make the speaker emit sound

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This line is no different from the MediaTek and HiSilicon we talked about earlier.

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This is Xiaomi's driver circuit of Qualcomm's small audio

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That's all for this lesson