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In this lesson, we talk about the channel of the handset signal in the circuit diagram

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We start with the earpiece and we can go back to find the big audio, or we can find the small audio

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Let's take Huawei P40 as an example, Huawei P40 uses HiSilicon's solution

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We can start to search from the J3202 earpiece signal

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We open Xinzhizao intelligent query system, find Huawei, find P40, and open its drawings

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Enter the code name SPK of the handset in the search bar

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We have learned about the speaker before, and the code name of the speaker is also SPK PK

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If we look along this SPK, this should be the speaker, J3701

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But what we're looking for is the handset J3202

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Here is RCVOUT

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There are several code names for the handset, including RCV, EAR, and SPK

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RCV is used here

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RCVOUT indicates the signal output of the handset, so here is the line of the handset

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We look back from this touchpoint

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A SG element and an inductor are connected in series on this line

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We need to regard this SG element as a 0 ohm resistor, and its s pole and g pole are turned on

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Let's see which circuit a signal comes from

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Let's search for RCVOUT_S_P_1 directly to see where it comes from

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The other end of this resistor is C3 pin and C5 pin from a chip

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This is the detection, the positive detection and the negative detection are the feedback pins

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The real output pins are pins E6 and E5

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These two are the output of the handset signal

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Let's look at the U3201 circuit

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It's exactly the same circuit as the speaker

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It has reset, I2S bus clock, synchronization and I2S input and output

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It also has control signals for the I2C4 bus

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Here it has the main power supply and 1.8 volts power supply,

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and there are 4 more important capacitors

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If these capacitors are corroded by water, they will easily cause a short circuit

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This inductor works in a boost circuit, because one end of it is connected to the power supply,

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and the other end is connected to SW

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Its circuit is the same as that of the small audio U3202,

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but the code name of the speaker and the earpiece are different

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This is the drive circuit of the Huawei P40 earpiece

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It is mainly driven by the small audio U3201

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The output signal of the small audio is output from the E6 pin and the E5 pin,

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and the two inductors L3263 and L3262 are connected in series in the middle

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The final output is given here,

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and then 2 inductors are connected in series to this contact

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That's all for this lesson