Honor Magic Watch 2 disassembly: Embracing global chips and achieving bigger dreams

Smartwatch is not a watch, but a portable wearable device in the shape of a watch. Time may be just the most insignificant function of smartwatch. What is the concept of smartwatch now? It can receive information more conveniently and quickly, monitor one's health status all the time, realize more scientific intelligent reminder, etc. These are the most basic communication functions, detection solutions supported by multiple sensors, and considerate UI interaction design, which are the significance of smartwatch.

The Honor MagicWatch 2 smartwatch adopts an integrated 2.5D glass design. The entire screen slides smoothly without any obstruction. The AMOLED screen can ensure that the watch still has outstanding display effects under strong light. The frame of the watch is made of smooth frosted metal, giving people a sporty + business style. There are speaker and microphone openings on the side, supporting Bluetooth connection to the phone to answer calls and the watch to play music alone. On the back of the watch is the heart rate sensor and charging port area, with four screws fixing the metal back cover. The heart rate sensor module is slightly raised. The advantage of this design is that when wearing the watch, the wrist will not feel oppressive but can accurately monitor the heart rate.

When I first bought the Honor Magic Watch 2, Honor still belonged to Huawei. Now, things have changed. Is Honor still competitive without Huawei? Perhaps this issue of the Honor Magic Watch 2 review can tell you the answer.
 

Disassembly

Before disassembly, MagicWatch2 had been used for a while. Compared with many smart watches, the most impressive thing was its battery life of about 2 weeks. However, after disassembly, it was found that the built-in lithium battery was only 455mAh, so the product's power consumption control was a bit amazing. What is the hardware solution?

The disassembled family photo is shown in the picture above. It can be roughly divided into the case, the back cover and two main boards (hereinafter referred to as PCB board 1 and PCB board 2). Although they do not take up much space, the chips on the two PCB boards are really small and numerous.

Case construction

Magicwatch2 uses a 1.39-inch AMOLED color round screen. The ambient light sensor is mounted on the touch screen FPC cable, which can adjust the screen brightness according to the external ambient light. In addition, the two crowns are used for power and function buttons respectively, and there are waterproof rubber rings on the crowns, which support 50 meters of waterproof.

Back cover structure

In the space of smart watches, where every inch of land is valuable, the space of the back cover structure is basically fully utilized, and there are many related components, including speakers, barometers, microphones, vibrators, heart rate sensors, etc.

The heart rate sensor integrates 2 photodiodes and 2 LEDs, and monitors heart rate and blood oxygen saturation through the lens at the bottom. The back cover has a power supply FPC cable and two magnets. It should be noted that this watch does not have wireless charging, and is charged via USB to metal contacts. Therefore, the magnets on the back cover of the watch are not only used to fix it during charging, but also to prevent the circuit from shorting due to reverse connection of positive and negative during charging.

PCB board 1 (small)

In addition to the connector interface, PCB board 1 mainly includes power circuit and audio circuit.

The main components in the power circuit include TI boost converter (TPS61099), TI buck converter (TPS62743), and MPS lithium battery charge management chip (MP2662). 

TPS61099 is a synchronous boost converter with an ultra-low quiescent current of 1 microampere. It is mainly used for boost design of battery-powered circuits in watches. It can operate efficiently under light load conditions, which is very important for extending battery life. In addition, its efficiency is very high. For example, in the 3.3V to 5V circuit output, it can achieve up to 93% efficiency under 200mA load conditions.

The TPS62743 is an ultra-low power DC/DC that supports an input voltage of 2.15V to 5.5V, and the input voltage after startup is as low as 2V. It provides 8 programmable output voltages, which can be selected in the range of 1.2V to 3.3V through three selection pins. At the same time, the output current of this model of buck converter can reach 300mA, and the conversion efficiency of the output current is as high as 90% at 10 microamperes. In particular, the package is super small, which is very suitable for space-sensitive electronic products such as smart watches and wearable devices.

It is worth mentioning that both of these TI materials can be purchased in stock on the Mouser Electronics official website.

Audio function is also a core function of smart watches. The main components in the circuit include X-Powers' two-channel ADC (AC107) and Awin Electronics' audio amplifier (AW8896).
As we all know, one of the most important features of wearable devices is low power consumption. The biggest feature of AC107 is its ultra-low power consumption. With a signal-to-noise ratio of 103dB, the power consumption is only 13mW, which is about 1/6 of similar competing products. Therefore, it is very suitable for wearable device applications such as low-power smart watches. AW8896 is a digital smart K audio amplifier that integrates an adaptive boost converter, sound quality enhancement algorithm and speaker protection, so the sound of the watch in actual calls is still very loud and clear. ADC+amplifier+mike+speaker just form a complete audio call link for smart watches.
 

PCB board 2 (large)

There are more devices on PCB board 2, including Sony's new generation GNSS receiver chip (S4LP173) and Toshiba 4GB NAND FLASH (THGBMNG5D1LBAIL) on the front.

The device on the back is shown in the figure below.

AKM's 3-axis electronic compass (AK09918C) can realize functions such as watch compass.

NXP's NFC controller (PN80T) integrates embedded security elements and short-range wireless communication, and NXP provides a Loader Service solution, which greatly simplifies the development and integration of payment functions for R&D personnel, reducing development difficulty and maintenance costs.

ST's ultra-low power L series microcontroller (STM32L4R9ZI), one of the most important features of this microcontroller is low power consumption, but the special thing about this MCU is that it has quite good performance and rich functions while ensuring low power consumption. For example, it supports up to 120MHz main frequency, 2MB FLASH and 640KB SRAM, but the most important thing is that it has a function that is particularly practical for smart watches. It integrates a proprietary 2D hardware graphics accelerator (Chrom-ART), which can efficiently handle repetitive graphics operations, thus freeing up the main CPU to perform real-time processing or even more advanced graphics operations. So it is very suitable for smart watch applications that have both low power consumption requirements and graphical interface requirements.

Another low-power core chip of Magicwatch2 is Huawei HiSilicon Kirin A1 (Hi1132). The new generation of Kirin A1 chip has passed the dual certification of Bluetooth 5.2 and low-power Bluetooth, supports Huawei's self-developed dual-channel synchronous transmission technology, is equipped with a high-speed audio processing unit, and supports stable and fast wireless connection. In fact, there are already many applications based on Kirin A1 chips on the market, whether it is the currently popular true wireless headphones, smart speakers, or this smart watch.

Other devices on PCB board 2 include ST's 3-axis accelerometer/gyroscope, Winbond's 8M SPI FLASH, etc. For more detailed chip models, please refer to the following BOM table.
 

summary

After disassembling the Honor MagicWatch 2 smartwatch, I was deeply moved. Although the smartwatch and smart bracelet are only one word apart, they are incomparable in terms of function and R&D design. In terms of function, the smartwatch has more sensor collection and a more beautiful UI interface;

In terms of R&D and design, the hardware solution of smart watches is even more outstanding than that of wristbands. In general, the hardware solution of MagicWatch2 includes: the processing core chip Kirin A1 and STM32L4 series microcontroller of smart watches; the core of audio function X-Powers analog-to-digital converter and Awinic audio amplifier; sensors with various functions, ST accelerometer/gyroscope sensor, AKM electronic compass and other manufacturers' optical heart rate sensor, ambient light sensor, pressure sensor; Sony's global satellite navigation system receiving solution, NXP's NFC and other hardware. It can be said that this small smart watch condenses the high-tech hard work of various IC design manufacturers around the world. If you want to know more details, please click to watch the hot product review video exclusively sponsored by Mouser Electronics.