DJI MIC wireless microphone teardown

I believe everyone is familiar with the DJI brand, and it has achieved the world’s first in the field of drones. DJI is committed to continuing to advance human progress. Since its establishment in 2006, it has continuously innovated technological products and solutions in the fields of drones, handheld imaging, robotic education and more cutting-edge innovations, reshaping people’s production and lifestyle.

With the rise of short videos, various application scenarios such as shop exploration columns, street interviews, and live broadcast sales have grown rapidly. Coupled with the rise of online classes under the epidemic, wireless microphones have broader application scenarios. DJI has also paid attention to the current market demand for wireless microphones, and recently launched its first wireless microphone – DJI MIC.

DJI MIC wireless microphone has features such as “250m Transmission Range, Dual-Channel Recording, Up to 14 Hours of Onboard Memory, Protable and Compact, Wide Compatibility, 15-hour Battery Life“, which can well meet the needs of various users.

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|1. DJI MIC Charging Case teardown

First, remove the charging case bottom case.

 

 

The four LEDs on the side panel indicate the power information of the charging case, and there is a cable on the right side to connect the Hall element to detect the opening and closing status of the box cover.

The battery indicator board is fixed in the plastic frame with UV glue.

The Hall element is screwed inside the housing.

Detecting the Hall element of the open lid, MagnTek MT8651.

The hinge structure for the opening and closing of the charging case is fixed to the back of the charging cab with 4 screws.

The battery socket, the red and black wires are the positive and negative electrodes, and the yellow wire in the middle is the connection of the battery thermistor.

The magnet that attracts the lid.

The back of the heating chip of the circuit board is coated with blue thermal conductive gel, which cooperates with the heat sink to dissipate heat.

All cables on the motherboard are fixed with UV glue to prevent loosening.

Open the cable and remove the power management circuit board.

Bottom of charging cockpit.

At the bottom of the product cockpit, there is a magnet for adsorption equipment, and the magnet is fixed by UV glue. The four regular holes in the middle are the charging/data contact locations for the microphone.

The battery is from Springpower Technology (Shenzhen) Co., Ltd., the rated capacity is 2600mAh/10Wh, the rated voltage is 3.87V, and the battery model is P13248.

Information on the external label of the battery, manufacturer: Springpower Technology Co., Ltd., manufacturing date: 20210407, made in China, the battery is specially designed for DJI equipment, must use DJI special charging equipment, it is strictly forbidden to disassemble, burn the battery, and prohibit the use of the battery after immersion in water.

The contacts in the charging case for charging the receiver are independently wired and fixed with screws.

The battery is equipped with a circuit protection board, which is wrapped with insulating tape for protection.

The front of the circuit board is coated with three-proof paint for moisture and oxidation resistance. The charging/data contacts for the microphone are integrated on both sides of the motherboard.

There is a heat-dissipating aluminum plate on the back of the circuit board.

The aluminum plate is coated with blue thermal gel and conducts heat between the circuit board.

The back of the charging case circuit board.

The back of the charging case circuit board is also coated with blue heat dissipation gel to increase the heat dissipation capacity.

Front of USB C socket.

On the back of the USB C socket, the data pins are protected by TVS for electrostatic protection.

Pogo Pin connector for device charging/data.

SGMICRO SGM8959-1 Low Noise High Precision Zero Offset Operational Amplifier. Provides excellent performance for driving analog-to-digital converters (ADCs) without degrading differential linearity.

Silkscreen HMAJ IC.

Two YJ YJQ1216A PMOS, withstand voltage -20V, conductance resistance 17mΩ, used for interface protection function.

SMAJ18A TVS diode for input overvoltage protection.

The step-down IC of screen printing OBM provides step-down power supply for the microcontroller.

The SGMICRO SGM41511 is an I2C controlled 3A single cell battery charger with high input voltage capability and narrow voltage direct current (NVDC) power path management with integrated converters and power switches for single cell Li-Ion or Li-polymer batteries. This highly integrated 3A device enables fast charging and supports a wide input voltage range for smartphones, tablets and portable systems. I2C programming makes it a very flexible power supply and charger design solution. ‎

‎The device includes four main power switches: input reverse blocking FET (RBFET, Q1), high-side switching FET (HSFET, Q2) for buck or boost mode, for buck or boost mode switching The low-side switching FET (LSFET, Q3) and the battery FET (BATFET, Q4) used to control the system and battery interconnect. A bootstrap diode for high-side gate drive is also integrated. The internal power path has very low impedance to reduce charging time and maximize battery discharge efficiency. In addition, input voltage and current regulations provide maximum charging power to the battery through various types of input sources. ‎

HDSC HC32F176 microcontroller, HC32F170/ HC32F176 series is a general-purpose MCU with wide voltage operating range. It integrates a 12-bit 1Msps high-precision SARADC, a 12-bit DAC, and a rich set of communication peripherals such as comparators, op amps, built-in high-performance PWM timers, LCD display, multi-channel UART, SPI, and I2C. Built-in AES, TRNG and other information security modules have the characteristics of high integration, high anti-interference and high reliability. The core of this product adopts Cortex-M0+ core, cooperates with mature Keil & IAR debugging and development software, supports C language, assembly language, and assembly instructions.

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|2. DJI MIC Transmitter teardown

First, disassemble the bottom case of the DJI MIC transmitter along the parting line.

The bottom shell of the transmitter is fixed with the shell of the receiver by snaps and is reinforced by glue.

The internal structure of the DJI MIC transmitter housing.

The battery is connected with a socket and reinforced with glue.

The cable pads of the charging contacts are cushioned with sponge.

The cable pad that connects to the microphone has a cushioning sponge.

Unscrew the screws to separate the receiver board from the receiver housing, which has bluetooth antennas on both sides.

The battery side is covered with buffer foam.

There is a vibration motor at one end of the transmitter. The vibration motor is protected by a special rubber cover to prevent the vibration of the motor from affecting the internal components of the receiver.

Remove the rubber cover of the vibration motor.

Rotor vibration motor for tips.

The pickup microphone is welded on the cable, corresponding to the opening of the microphone on the shell.

Laser engraving 120 BFC MEMS microphone for sound pickup.

The bluetooth antenna inside the casing is made of metal evaporation.

Antenna on the other side of the transmitter.

The charging contacts inside the transmitter are protected by a metal cover, and the metal cover is fixed with UV glue, which is double-fixed to prevent the micro-motion buttons from loosening. On both sides are magnets for adsorption and charging.

On the front of the main board of the receiver, there is a metal protective cover at the position of important components.

On the back of the receiver motherboard, metal protective covers are also provided for important components.

Transmitter lithium battery label information, product name “secondary lithium ion battery”, charging limit voltage “4.4V”, from Springpower Technology (Shenzhen) Co., Ltd.

The battery is provided with a protective plate, and the thermistor is fixed on the battery with glue.

Tear off the lithium battery label, the information on the battery, the battery model SP532125, the battery capacity is 320mAh/1.232Wh, and the rated voltage is 3.85V.

3.5mm female connector, silkscreen 211022.

Multi-color LED indicator to indicate battery level and connection status.

Connect the metal contacts of the antenna.

Patch button.

Inside the smaller shield is the circuit for the bluetooth connection part.

Cellwise CW6305 high-precision lithium battery linear charging chip for internal battery charging management of the transmitter. The CW6305 supports +28V withstand voltage input, supports a maximum 500mA input current limit, integrates the power path management function, and the current provided by the charging adapter can be dynamically distributed between the system load and the battery. For lithium batteries with deep discharge or undervoltage protection, the system can also be turned on immediately after inserting the charger.

The maximum charging current of CW6305 is 470mA, and the minimum charging cut-off current is 1mA. It can be adapted to various products such as TWS headsets, neckband bluetooth headphones, smart bracelet and stylus.

According to 52audio, products such as OnePlus Buds, OPPO Enco M31 and Honor FlyPods 3 true wireless earbuds have already applied Cellwise’s charging management chip.

YJ YJQ1216A PMOS, withstand voltage -20V, conductance resistance 17mΩ, used for interface protection function.

Two screen-printed OBG step-down chips.

SN74AHC1G04 Single-phase inverter for signal level shifting.

NORDIC nRF52810 High-performance entry-level bluetooth 5 SOC, built-in 64MHz main frequency M4 core, built-in 192KB Flash and 24KB RAM. ‎

SKYWORKS SKY66112 RF front-end module, suitable for bluetooth applications, for bluetooth signal amplification, integrated PA and LNA.

The overvoltage protection tube of silk screen B1 is used for overvoltage protection of the data terminal of the USB-C interface.

SGMICRO SGM3715 analog switch for internal and external microphone switching.

NuvoTon NAU85L40YGB four-channel audio ADC with integrated microphone bias circuit for microphone voice signal acquisition and analog-to-digital conversion.

Then remove the larger shield.

Silkscreen SY1KI IC.

External memory to store boot firmware.

SanDisk SDINBDG4-8G e.MMC 5.1 interface industrial-grade i NAND EMMC memory with a capacity of 8GB for recording function storage.

NXP MIMXRT685SFVKB i.MX RT cross-border MCU, built-in dual-core M33 processor, the highest frequency is 300MHz, built-in 4.5MB memory, built-in DSP core. It has the characteristics of high processing performance, low power consumption, high integration and high information security.

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|3. DJI MIC Receiver teardown

Pry open the receiver back cover along the parting line.

There is a thermal pad inside the casing to dissipate heat for the charging chip.

The internal structure of the DJI MIC receiver housing.

The cable connecting the screen and the charging/data interface.

There is a heat-dissipating silicone pad on the metal shield.

Remove the motherboard from the receiver cavity.

The battery side is covered with buffer foam.

Take out the battery inside the receiver bottom case, the internal structure of the receiver bottom case.

The bluetooth antenna inside the casing is made of metal evaporation.

Antenna on the other side of the transmitter.

The charging/communication contacts inside the transmitter are protected by a metal cover, which is fixed with UV glue, and there are magnets on both sides for adsorption and charging.

Receiver lithium battery label information, product name “secondary lithium ion battery”, charging limit voltage “4.4V”, from Springpower Technology (Shenzhen) Co., Ltd.

Tear off the lithium battery label, the information on the battery, the battery model SP532125, the battery capacity is 320mAh/1.232Wh, and the rated voltage is 3.85V.

There is a larger shield on the front of the receiver circuit board.

The back of the receiver circuit board.

Two audio output sockets.

Micro buttons on the motherboard.

YJ YJQ1216A PMOS, withstand voltage -20V, conductance resistance 17mΩ, used for interface protection function.

Cellwise CW6305 high-precision lithium battery linear charging chip, used for the internal battery charging management of the transmitter. CW6305 supports +28V withstand voltage input, supports up to 500mA input current limit, integrates power path management function, the current provided by the charging adapter can be dynamically distributed between the system load and the battery; for lithium batteries with deep discharge or undervoltage protection, plug-in charging After the device is installed, the system can also be turned on immediately. The maximum charging current of CW6305 is 470mA, and the minimum charging cut-off current is 1mA. It can be adapted to various products such as TWS headset, neckband bluetooth headset, smart bracelet and stylus.

According to 52audio, there are already OnePlus Buds, OPPO Enco M31, Honor FlyPods 3 true wireless ANC earbuds and other products using the Cellwise charging management chip.

Nuvoton Stereo Codec Series Model NAU88L25B audio codec designed for smartphones, tablets, Chromebooks, laptops, game consoles, bluetooth headphones and other mobile devices. Ultra-low power, high-performance audio codec, built-in equipment including I2S/PCM interface, high-quality stereo DAC, mono ADC, Class G stereo headset amplifier, industry-leading audio accessories detection.

Nuvoton includes a dynamic range compressor (DRC), programmable biquad filter, sidetone and digital mixer, high-end built-in signal processor, not only improves the sound quality to the highest level, while eliminating unwanted signal frequencies . The integrated frequency-locked loop (FLL) design supports multiple frequencies with fewer external components.

SGMICRO SGM3715 analog switch for audio signal switching.

Two YJ YJQ1216A PMOS, withstand voltage -20V, conductance resistance 17mΩ, used for interface protection function.

Silkscreen SY1KI IC.

Silkscreen BKHM power chip.

Silkscreen the IC of B1.

Screen printing 72P switch.

SKYWORKS SKY66112 RF front-end module, suitable for bluetooth applications, for bluetooth signal amplification, integrated PA and LNA.

NORDIC nRF52810 High-performance entry-level bluetooth 5 SOC, built-in 64MHz main frequency M4 core, built-in 192KB Flash and 24KB RAM.

Silkscreen MN GK bluetooth filter.

Nuvoton NAU88L21YG audio codec, built-in ADC and DAC, supports stereo headphone driver output. Supports single stereo differential microphone input, supports two single-ended microphone inputs, and supports stereo digital microphone input.

GigaDevice GD25Q128E 16MB SPI interface memory for storing receiver firmware information.

The step-down IC of the silk-screen OBM has a total of three channels of step-down power supply for the main control.

NXP MIMXRT685SFVKB i.MX RT cross-border MCU, built-in dual-core M33 processor, the highest frequency is 300MHz, built-in 4.5MB memory, built-in DSP core. It has the characteristics of high processing performance, low power consumption, high integration and high information security.

All components of DJI MIC wireless microphone.

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|4. Summary

Charging case size: 102.87mm*41.55mm*61.51mm, easy to carry in daily use. The built-in metal fittings of the charging case increase the overall feel.

In terms of battery life, all devices use lithium batteries produced by Springpower Technology (Shenzhen) Co., Ltd. to provide stable and long-lasting battery life. Among them, the charging case has a built-in 2600mAh battery, which can provide 15 hours of battery life. The transmitter and receiver use a 320mAh battery, taking into account the two characteristics of small size and high energy.

The charging case uses a power supply IC for the SGMICRO SGM41511 in the internal configuration, which is used to charge the battery, while charging the receiver and transmitter through reverse boosting. The built-in HDSC HC32F176 microcontroller is used for power display and machine control functions.

The launcher has a 2-sided twill design to enhance friction. Many parts inside the transmitter are fixed with glue to enhance the firmness of the internal parts during use. In terms of charging IC, the CellWise CW6305 500mA lithium battery linear charging chip is used, which supports high-precision linear charging, +28V maximum input withstand voltage, and ±0.5% charging modulation voltage accuracy. The constant current charging current is up to 470mA, and the charging current is as low as 1mA. Supports low-voltage or over-discharged batteries, and the system starts up immediately.

The transmission adopts nRF52810 bluetooth SOC with SKY66112 front-end for long-distance transmission. Built-in NAU85L40YGB audio ADC for analog audio acquisition, NXP MIMXRT685SFVKB for complete machine control, and SanDisk 8GB EMMC for recording function.

The outside of the receiver adopts a twill design to support the installation of the back clip, and a display screen that can understand the device information is designed on the top of the receiver. In terms of compatibility, the interface of the DJI MIC wireless microphone receiver can be replaced, so as to achieve switching between Android phones and Apple phones.

In the internal configuration of the receiver, the DJI MIC receiver has a built-in Nuvoton stereo codec series model NAU88L25B audio codec for digital conversion of analog input signals, and the bluetooth signal transmission uses the same nRF52810 as the transmitter with SKY66112. In terms of charging IC, the receiver also adopts CellWise CW6305 500mA linear lithium battery charging chip. There is also a built-in NAU88L21YG audio codec inside the receiver for playback. The whole machine control and screen status display are carried out by NXP MIMXRT685SFVKB.

Source: 52audio

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