Electronic Design - PCB design of smart wearable devices: smart bracelet

Smart wearable devices, especially smart bracelets, as a more popular product form in recent years, have attracted more and more people's attention. Although not everyone can use it, the emergence of smart bracelets does bring new challenges to PCB design and processing.

A smart bracelet usually consists of a radio frequency circuit unit, a clock circuit unit, a memory circuit unit, a sensor circuit unit, and a main control MCU unit. The circuit PCB usually needs to be assembled in a small volume for single-sided or double-sided patching., The circuit board is mainly 4-layer or 6-layer.

Since so many functions are concentrated on a small PCB board, the PCB designer should pay special attention to the layout and wiring of the bracelet. Now Lao Chen has summarized some precautions for everyone.

First, rationally arrange the partitions and pay attention to wiring protection.

From the above PCB circuit board, it can be seen that the various parts of the smart bracelet circuit (marked by different color boxes) are well partitioned: because the smart bracelet is a collection of digital circuit components, you only need to do a good job in the circuit design The matching resistance and capacitance distribution can complete circuit modules with certain functions, thus making the circuit design more concise and easy to find. Although some sensor circuit units use analog circuit technology for data collection, once the module is designed as a module, data communication and information transmission can be completed through the corresponding connection interface.

In the layout of circuit modules, on the one hand, it is necessary to pay attention to the shortest path between the clock circuit and the crystal oscillator circuit to reach the target control. On the other hand, pay attention to avoiding the data line when routing the clock to prevent interference from affecting the stability of the system.

When wiring, it is necessary to protect the key wiring, such as whether the clock generating circuit, crystal oscillator circuit, etc. are covered with copper, whether the ring ground protection is performed, etc., generally will be protected in the design, and the crystal oscillator part needs to be digging copper. .

Second, handle the radio frequency circuit well.

The smart bracelet needs to be linked with the mobile phone when in use. Therefore, the radio frequency part is the key part. In this part of the design, special attention must be paid. Now the smart bracelets on the market are nothing more than wireless data transmission based on Bluetooth, so the focus is on the processing of Bluetooth radio frequency. If the smart bracelet is only used for data transmission and does not require the transmission of sound and music, then Bluetooth Low Energy is the best choice. In the design, the shape of the Bluetooth antenna, the antenna layout, and the material of the smart bracelet casing all affect the intelligence An important factor in the performance of the bracelet. In the smart bracelet PCB design process, an excellent RF antenna engineer is particularly important.

Third, do a good job of ESD protection.

Circuit ESD is a very important part of PCB design and cannot be ignored. Today, the importance of ESD to smart bracelet products is emphasized. Different countries and regions have different standards for different products or the same product ESD requirements. In order to make the product pass the relevant test, the ESD protection design must be carried out during the design, and the ESD test must be carried out after the design is completed to ensure that the product passes the product. Electronic testing adapted to the local market.

Finally, reserve the system upgrade interface.

The function upgrade of a smart bracelet is of great significance to users or fans of smart bracelets. If a product undergoes software upgrades at an appropriate time (maybe the hardware is designed to some functions in the early stage but the software has not kept up in order to catch up with the market, or it may be that some software bugs have been repaired), this means that the product is still non-stop In the development process, this is a good psychological compensation for users. The PCB factory should design the elements of the smart bracelet in the PCB. There are usually two ways to upgrade the software of smart bracelets: through the USB interface and the wireless push method. As for which method to use, it needs to be determined in the preliminary planning and software and hardware planning.