Marshall Minor IV continues the family’s classic design and black and gold color scheme, with excellent texture. The earbuds are equipped with 12mm dynamic driver, inheriting Marshall’s iconic sound quality, and provide balanced professional-grade sound effects. The single battery life is up to 7 hours, and the comprehensive battery life is about 30 hours. It also supports fast charging and wireless charging.
We have previously teardown the Marshall products including: Marshall Mode II, Marshall MINOR Ⅲ, Marshall Motif A.N.C., Marshall WOBURN III and Marshall Emberton II. Let’s take a look at the detailed teardown report of Marshall Minor IV.
01/ Marshall Minor IV Charging Case Teardown
Disassemble the charging case shell and take out the charging bin structure.
The front structure of the charging bin, the main board stands upright in the middle and is fixed by screws.
The wireless charging receiving coil is attached to the back of the charging bin, and the battery is fixed in the middle cavity.
Remove all the components fixed on the charging bin.
The bottom structure of the charging bin is equipped with four circular magnets for adsorbing and fixing the earbuds and the charging case lid.
The main circuit inside the charging case includes the battery, the main board, two small boards for charging the earbuds, and the wireless charging receiving coil.
The circuit on one side of the charging case main board.
The circuit on the other side of the charging case main board.
The Injoinic IP5528 TWS charging bin management SoC is a multi-function power management SOC that integrates MCU, boost converter, lithium battery charging management, and battery power indication, providing a complete solution for the TWS charging bin. Thanks to the high integration and rich functions of IP5528, only a few peripheral devices are required when applying it, which effectively reduces the size of the overall solution and reduces the BOM cost.
IP5528 supports follow-up charging function, which can achieve 10mV fine step adjustment of charging voltage in the range of 3.2~5.5V, which can effectively improve the conversion efficiency by 15%~20%, and then improve the comprehensive battery life of TWS earbuds by 15%~20%.
In application, IP5528 only needs one inductor to realize the buck-boost function. Support low-cost inductors and capacitors. The synchronous boost system of IP5528 provides a rated output current of 400mA and a conversion efficiency of up to 93%. When lightly loaded, it automatically enters the sleep state and the quiescent current drops to 15µA.
IP5528 adopts switching charging technology, provides a rated 1A charging current, and a charging efficiency of up to 90%. Built-in chip temperature protection and input voltage intelligent adjustment of charging current. IP5528 has a built-in 12bit ADC, which can accurately measure battery voltage and current. Supports 1/2/3/4 LED power display and digital power display. According to the product manual, IP5528 also supports an output voltage of 3.2V~5.2V and supports fast charging of headphones.
Power management chip peripheral power inductor.
Overvoltage and overcurrent protection IC with screen printing 2601.
Type-C charging interface and bluetooth pairing button.
Injoinic IP6831 is a highly integrated, high-efficiency, WPC Qi-compliant wireless charging receiver chip with a power of 2W. IP6831 integrates high-efficiency synchronous rectification circuit, power output circuit, reverse protection circuit, extremely low heat loss, and good application experience. The internally integrated dynamic rectification voltage control effectively improves the transient response and system efficiency of the chip.
LED indicator for feedback of bluetooth pairing and charging status. The Hall element with screen printing AR3p7 is used to sense the magnetic field changes when the charging case is turned on/off, and then notify the charging case MCU and earbuds to pair or disconnect with the connected device.
The small board circuit for charging earbuds is equipped with two Pogo Pin connectors.
The charging case has a built-in rechargeable lithium-ion battery pack, model: 682134, capacity: 500mAh/1.9Wh, nominal voltage: 3.8V, charging limit voltage: 4.35V, manufacturer: Chongqing VDL Electronics Co., Ltd., made in China.
After tearing off the insulating protective film, the battery protection board circuit.
The lithium battery protection IC with silkscreen UP71AC is responsible for overcharge, over-discharge and overcurrent protection of the battery.
02/ Marshall Minor IV Earbuds Teardown
Disassemble the earbud cavity. The FPC of the components inside the front cavity is connected to the main board at the bottom of the rear cavity through the BTB connector.
Pick up the connector, and the bottom structure of the rear cavity is sealed by gluing.
Take out the battery, the speaker structure inside the front cavity. Fix it with glue, and weld the wire to the FPC.
Take out the speaker, the main component circuit inside the cavity.
BTB connector connecting the FPC to the main board.
The front diaphragm of the earbud speaker.
The magnet on the back of the earbud speaker, and the edge tuning hole are protected by silk screen.
After actual measurement, the speaker size is about 12.25mm.
The earbuds have a built-in soft-pack button battery, model: 1054PF4C, nominal voltage: 3.85V, rated energy: 0.173Wh.
The metal copper column connected to the charging case on the FPC.
The optical in-ear detection sensor is used to automatically pause music playback when the earbuds are removed, and automatically resume playback after wearing.
Remove the tail plug and take out the motherboard inside the earbud stem.
The touch detection patch on the wall of the internal cavity of the earbud stem.
The circuit on one side of the motherboard, the FPC at the end of the motherboard is equipped with a call microphone.
A bracket is fixed on the other side of the motherboard, and a bluetooth antenna is attached to the top.
Remove the bracket, the circuit on the other side of the motherboard. There is a QR code label on the main control.
There are two metal domes connected to the bluetooth antenna.
Tear off the label, the main control chip uses AIROHA AB1565M bluetooth audio SoC, which supports Bluetooth 5.3.
Touch detection IC with silk screen 2E.
Sunlord SDCL0603Q series multilayer ceramic inductors. The multilayer structure of this series of inductors ensures high reliability and production efficiency of the product. In addition, through the carefully designed coils and electrodes, high Q value and high self-resonant frequency (SRF) are achieved. Plus, it is made by dry process, which can provide high-precision and high-consistency products to meet the stringent requirements of precision electronic components.
Metal dome connected to the touch detection sensor.
BTB connector for connecting the cable.
WINSEMI WSDF3316C lithium battery protection IC. The WSDF3316 series is a highly integrated solution for single-cell lithium-ion/lithium polymer rechargeable battery pack protection. It integrates advanced power MOSFET, high-precision voltage detection circuit and delay circuit, and has overcharge, over-discharge, overcurrent and short-circuit protection functions. And the power consumption is very low during operation, and it also supports CTL shipping mode settings.
WSDF3316c mainly adopts multi-pulse shipping mode (low power mode) and reset function (power-off restart hard reset function), which can prevent false triggering of shipping and effectively solve the problem of product system crash.
The crystal oscillator of laser engraving 26 WHc provides clock for bluetooth chip.
Two power inductors outside the bluetooth chip provide power for its internal circuit.
MEMS microphone of laser engraving 3646 is used for voice call function pickup.
All components of Marshall Minor IV true wireless earphones.
03/ Summary
Marshall Minor IV continues the brand’s characteristic family design. The charging case is a rounded square design with lychee leather texture decoration. The earbuds adopt a long stem in-ear design, and the weight of a single earbud is only 4.2g, which is comfortable to wear.
The charging case has a built-in 500mAh rechargeable lithium-ion battery pack and supports wired/wireless charging modes, both of which use the Injoinic power management solution. The wired mode is managed by the IP5528 TWS charging bin management SoC, which is highly integrated and has rich functions. It supports follow-up charging and can improve the conversion efficiency by 15%~20%. The wireless mode uses the IP6831 wireless charging receiver chip, which complies with the WPC Qi standard and has an output power of 2W.
The earbud cavity is equipped with a 12mm dynamic driver and a 0.173Wh soft-pack button battery. The wires are welded to the FPC and then connected to the motherboard through a BTB connector. The FPC is equipped with an optical in-ear detection sensor and charging contacts. The earbud stem is equipped with a motherboard, microphone, bluetooth antenna and touch detection sensor. The motherboard is equipped with a WINSEMI WSDF3316C lithium battery protection IC and a Sunlord SDCL0603Q series multilayer ceramic inductor.
PS: Translated from 52audio
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