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This lesson continues with the schematic search to get familiar with this small audio circuit

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In this lesson, we will talk about the MediaTek platform, taking Redmi K50 as an example

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Its line can be found from the speaker connector J6501

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Of course, we can also search for SPK to find

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Open the Xinzhizao intelligent terminal maintenance query system, find the Redmi K series,

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find the Redmi K50, find its schematic diagram, and double-click it

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If we want to know how to look at drawings, we start with looking at schematic diagrams

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The PCB diagram is relatively simple

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Let's see if the speaker is okay

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Enter SPK in the search box, click Search, and see where it will find

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It jumps to this position first, MT6895 is the CPU of MediaTek, the position number is U3100

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first look at what it is

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SPKR is the speaker, PA is the power amplifier, RST is the reset

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This is the reset signal of the speaker amplifier, that is, the reset signal of the small audio

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Let's double-click it to see if we can find the small audio

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This is an audio power amplifier, U6001

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A lower SPK is written on the drawing, indicating the speaker below

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Speakers are usually located under

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This is where we found the speakers really

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It's what drives the speaker, and the signal it outputs is here

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It also has a detection signal, which is connected to the output of the speaker

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Let's look at its power supply first

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In this circuit, U6001 we make sure it is an audio power amplifier

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Why can you be sure?

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It has an input sound signal, which is input by the I2S bus

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Output after amplification, output from E4 and E6 pins

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If the small audio chip wants to work, it must first have a 1.8 volt power supply

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VSYS is the system power supply, also called the second terminal power supply

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There is a 1 uH inductance here, this inductance exists for the boost circuit

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Its pin definition is almost the same as that of HiSilicon

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This is the reset signal for the small audio chip

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B5 pin is an interrupt signal, it is generally to the CPU

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I2C bus SDA, SCL, serial data and serial clock

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This circuit diagram has a similar structure to HiSilicon's

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VBST is the boosted voltage

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There are four capacitors connected outside this line

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They are very important

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If water enters, it will easily cause a short circuit.

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You can't remove these capacitors and don't install them,

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otherwise you won't be able to boost the voltage

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They serve the boost circuit of the power amplifier

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Let's see where this output signal goes

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Speaking of which, we see this arrow

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On Android phones, many of the arrows indicating the direction of the signal are wrong

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The arrow for this output signal should be pointing outward

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It leads directly to this socket J6501

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This socket is actually on the big mainboard

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There is also a cable connected here, leading to the small board of the tail plug,

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but the drawing generally does not have a description of the small board of the tail plug

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Here is the circuit for the small audio that drives the speaker

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That's all for this lesson