With the launch of the new Redmi Note 11T series as scheduled, Redmi’s two TWS earbuds were released along with smartphones and Xiaomi MI Band 7, including Redmi Buds 4 and Redmi Buds 4 Pro. The two products use different design languages, continuing the unique brand features of Xiaomi‘s TWS earbuds, and both support the active noise cancelling function.
The Redmi Buds 4 Pro that will be teardown this time are Redmi’s flagship TWS noise cancelling earphones. The appearance design is similar to Xiaomi FlipBuds Pro noise cancelling earbuds, and it is highly recognizable. In terms of functional configuration, it mainly focuses on 43dB broadband noise cancelling, supports 3-speed noise cancelling mode AI adaptive adjustment, and has passed the official test certification of China Metrology Institute. It supports dual transparent mode for environment and vocals, noise cancelling for three-microphone calls and anti-wind noise design to meet different application scenarios.
Redmi Buds 4 Pro is also Redmi’s first product equipped with a coaxial dual-unit, which is composed of 10mm aluminum-magnesium alloy + 6mm titanium diaphragm tweeter dynamic, and provides excellent sound quality in different frequency bands. It supports 360° surround sound effects, based on the HRTF sound effect algorithm developed by Xiaomi Audio Lab, to restore the immersive experience at the scene level. Support Bluetooth 5.3, dual device intelligent connection. It supports a new generation of LC3 audio decoding, the full link delay is as low as 59ms, and it has a long battery life of 36 hours.
Previously we have teardown Xiaomi’s products including: Xiaomi Buds 3 Pro, Xiaomi FlipBuds Pro, Xiaomi Air 2 Pro, Xiaomi Air2 SE, Xiaomi Air 2S, Xiaomi Air 2, Redmi AirDots 3 Pro, Redmi AirDots 3, Redmi AirDots 2 , Redmi AirDots and Xiaomi Xiaoai Play speaker, etc. Let’s take a look at the internal structure of this product.
01/ Redmi Buds 4 Pro charging case teardown
Enter the teardown section below to see the internal structure configuration information.
Pry open the charging case cover to take out the internal cockpit structure.
The inner structure of the shell.
The bottom of the cockpit is fixed to the motherboard by screws.
An FPC cable is arranged on one side to connect the indicator light and the Hall element. An independent battery cavity is arranged in the middle of the cockpit, and the battery is covered with a sponge pad for buffer protection.
The structure on the other side of the charging cockpit.
Remove the screws and remove the motherboard.
Peel off the foam cushion, and connect the internal battery unit to the motherboard by wire soldering.
Remove the motherboard and battery cell cavity from the cockpit.
The bottom structure of the cockpit is equipped with four magnets for attracting the charging case cover and earbuds.
The charging case teardown includes the motherboard, battery and an FPC cable.
The charging case has built-in rechargeable lithium-ion batteries Model: 761833QH,charging limit voltage: 4.45V, from EVE Energy Co.,Ltd., made in China.
The silk screen information on the other side of the battery has the product model: EVE 761833QH, battery capacity: 590mAh/2.28Wh, nominal voltage: 3.87V, production date: January 19, 2022.
The circuit on one side of the main board of the charging case, and the metal shrapnel for charging the earphones at both ends.
The circuit on the other side of the charging case motherboard.
The design of the metal shrapnel for charging earbuds on the motherboard is relatively novel, and the customized charging shrapnel is deeply matched with the charging compartment, which can make life waterproof. At the same time, the part of the charging shrapnel in contact with the earphone is silver-platinum composite coating, which can avoid the corrosion of the charging shrapnel when charging with sweat, and can be electrolyzed through sweat-resistant for 30 minutes. It is understood that this charging shrapnel comes from KRCONN co., LTD.
Sinhmicro SS881Q POWER MCU, in 4*4mm QFN24 package, integrates battery charging management and single chip microcomputer, which can realize functions such as power management and charging case control.
SS881X is Sinhmicro’s AD-type Flash microcontroller series with integrated charge and discharge management. It has built-in rich interface functions, flexible configuration modes and different low-power options. This product is mainly used in portable intelligent electronic devices that require charging and intelligent control, bringing streamlined peripheral costs, excellent performance and flexible and convenient development.
According to 52audio, there are Xiaomi, OPPO, Honor, Redmi, realme, Nubia, Lenovo, Nokia, HTC, Edifier, Soundcore, 1MORE, FIIL, 233621, JBL, Philips, Skullcandy, Razer, ZMI, etc. Many brands of TWS earbuds have adopted the Sinhmicro solution.
LPS LP6252F synchronous boost chip in SOT23-6 package. The LP6252F has a switching frequency of 1MHZ with internal compensation, which reduces the number of external components and minimizes the size of inductors and capacitors. Allows external resistors to program the output voltage. In shutdown mode, the output is disconnected from the input and current consumption drops below 1µA.
The LP6252 has strong output capability, and the typical value of the current limit of the lower tube is 3A, which can meet the high current demand of customers for charging headphones. At the same time, it satisfies the light-load high-efficiency mode, which makes the system more efficient at the cut-off stage of charging, and the battery in the compartment lasts longer.
According to 52audio, there are audio products from Black Shark, Xiaomi, Honor, OPPO, Huawei, Redmi, realme, Lenovo, Sony, Nokia, Motorola, Edifier, Soundcore, 1MORE, QCY, UGREEN, Razer and many other brands. The product adopts LPS power management chip.
The inductance of silk screen 1R5 is used to charge the earbuds with the boost chip.
Xysemi ⅩB5152UA2SZR integrated lithium battery protection IC. The XB5152 ZR series products are highly integrated solutions for Li-ion/polymer battery protection. Contains advanced power MOSFETs, high-precision voltage detection circuits and delay circuits. Housed in an ultra-small SOT23-5 package with only one external component, it is an ideal solution for limited space in battery packs.
Type-C charging interface female socket, bottom black hard glue protection.
The Type-c female seat is also from KRCONN.
ZIF connector for connecting the cable.
Function buttons on the motherboard.
There are two LED indicators of different colors on the FPC cable.
Silkscreen 1mBo Hall element is used to sense the magnetic field change when the charging case is turned on/off, and then notify the charging case MCU and earbuds to pair or disconnect from the connected device.
02/ Redmi Buds 4 Pro earbuds teardown
Go to the earbuds teardown section. Pry open the earbud head, the internal structure of the cavity.
A battery and a speaker unit are fixed in the front cavity, and are connected to the FPC board in the rear cavity through a cable.
The component cables in the front cavity are connected to the FPC board in the rear cavity through the BTB connector.
Take out the battery, the cavity is provided with a plastic cover to seal, so that the sound cavity space is independent.
The battery is fixed inside the cavity using double-sided tape.
Take out the plastic parts, the internal structure of the cavity.
The cable in the front cavity is fixed on the cavity wall, an in-ear detection sensor is provided, and the two-dimensional code information is screen-printed on the back of the speaker.
Pick up the cable connector.
Disassemble the components inside the front cavity of the earbud, including the coaxial dual unit, battery, microphone and in-ear detection sensor patch.
The back of the coaxial dual unit uses a 10mm aluminum-magnesium alloy dynamic driver.
The front is equipped with a 6mm titanium diaphragm tweeter dynamic. The two units are held together by brackets.
Two dynamic drivers.
A steel shell button battery is used inside the earbud. The silkscreen information on the label has model number: M1154S3, rated voltage: 3.85V, capacity: 0.212Wh, from MIC-POWER.
Tear off the label, the engraved information on the battery is the same as the outer label.
The negative end of the battery.
Laser carving X042M 28415’s MEMS back-feed noise cancelling microphone is used to pick up the noise inside the ear canal, from XINGANG.
Capacitive in-ear detection sensor, which is used to automatically pause when the earbud is removed, and automatically resume the playback function after wearing it.
Male BTB connector for connecting to the FPC board in the rear cavity.
Pry open the back cover of the earphone handle, and the inside of the cover is provided with a sponge pad for protection.
There are touch detection sensors and LDS bluetooth antennas on the inner bracket of the cover.
There are LDS antennas and touch electrodes on the other side of the bracket.
A BTB connector is arranged on the main board in the cavity to connect the rear cavity cable.
The earbud rear cavity and the earphone stem are disassembled.
The internal structure of the earphone handle cavity.
Call microphone pickup structure, anti-wind noise design, improve the performance of voice calls. At the bottom are two charging copper post connectors for charging the earbud.
A bracket structure for fixing the cable in the back cavity.
The LDS antenna on the other side of the bracket and two antennas improve the stability of the bluetooth connection.
FPC wiring circuit in the rear cavity.
The MEMS feed-forward noise cancelling microphone of the Laser Engraving 2204 MX05 is used to pick up external ambient noise, also from XINGANG.
ABOV modern microcontroller A96T549D capacitive touch MCU.
Silkscreen EL Cc IC.
Silkscreen 1tVp XySemi DFN1*1 lithium battery protection IC. It has a series of protections such as overcharge and overdischarge, short circuit, overcurrent, and overtemperature.
Female BTB connector for connecting components inside the front chamber.
Male BTB connector for connecting to the motherboard.
Circuit on the motherboard side.
Circuit on the other side of the motherboard.
AIROHA AB1565AM bluetooth audio SoC, AB1565x is Airoha’s new generation bluetooth advanced audio solution, supports Bluetooth 5.3, and has the ability to support LE audio. The latest multi-point for TWS, which can easily switch between laptops and mobile phones at the same time. It provides ultra-low power consumption and ultra-low latency performance, and the average power consumption can reach ~4.x mA, which is the leading power consumption level in the current bluetooth audio market. It also has stable bluetooth connection, clear sound quality and Hybrid active noise cancelling function, providing rich and powerful performance for bluetooth headphones.
Airoha AB1565x has built-in CM4 processor and Tensilica HiFi mini DSP. Embed 4MB/8MB flash memory, integrate lithium battery charge controller and power management IC, and provide a variety of flexible package sizes and other options. In terms of software, it supports Google/AMA/Siri, etc., and provides IOS and Android reference APP development design.
According to 52audio, many bluetooth headphones from Sony, Zepp Health Corporation, 1MORE, realme, FIIL, Edifier and other brands on the market have adopted the AIROHA solution.
A power inductor is integrally formed on the periphery of the main control chip, which is used to supply power to the buck-boost circuit inside the bluetooth chip.
The crystal oscillator that provides the clock for the bluetooth chip.
Another MEMS microphone is used to pick up voice calls.
The pickup hole of the call microphone on the main board is provided with a rubber pad and a dust-proof net for sealing protection.
The two metal shrapnel used to connect the bluetooth antenna inside the earphone handle cover are small in size, only 1.25mm*0.85mm in length and width, from KRCONN.
The metal shrapnel connecting the LDS antenna on the rear cavity bracket is also from KRCONN.
Metal domes for connecting touch detection sensors, also from KRCONN.
The clip connector on the motherboard used to connect the charging copper column to charge the earbud has a novel design, which solves the problem of positioning the traditional charging copper column during production and can also achieve waterproofing at the copper column. It is understood that this clip for holding the copper column comes from KRCONN.
Female BTB connector for connecting components inside the earphone head.
The internal motherboards of the left and right earbuds have two colors of blue and green, which are easy to be distinguished by factory assembly.
All components of Redmi Buds 4 Pro true wireless noise cancelling earphones.
Redmi Buds 4 Pro true wireless noise cancelling earbuds, as a new generation flagship product of Redmi, adopts a new design that is different from previous generations. The charging case is a small oval shape with a matte texture. The earbuds feature an ergonomic handle-like in-ear design and are equipped with soft silicone eartips in a variety of sizes to provide a comfortable wearing experience.
In terms of internal circuit, the charging case adopts Type-C interface input power supply, built-in EVE 590mAh 3.87V high-voltage lithium battery, and is equipped with ⅩB5152UA2SZR integrated lithium battery protection IC. SinhMicro SS881Q POWER MCU is used on the main board, which integrates battery charging management and single-chip microcomputer, and is responsible for power management and charging case control functions. LPS LP6252F synchronous boost IC, with KRCONN custom charging shrapnel, copper posts and clips to charge earbuds.
The interior of the earbud mainly includes three parts. The internal speaker, microphone and main board in the front cavity are connected in series on the same FPC cable, connected to the rear cavity FPC board through the BTB, and then connected to the main board. Multiple KRCONN metal shrapnel are used on the motherboard to connect the bluetooth antenna and the touch detection sensor. Modular design improves the convenience of assembly and production.
In terms of configuration, the earbud is equipped with a coaxial dual dynamic driver, and three MEMS microphones cooperate to pick up sound. Built-in MIC-POWER 0.212Wh/3.85V high voltage steel shell button battery, Xysemi lithium battery protection IC. The main control chip is AIROHA AB1565AM bluetooth audio SoC, supports Bluetooth 5.3, has the ability to support LE audio, has stable bluetooth connection, clear sound quality and hybrid active noise cancelling function.
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