Smart bracelet PCB board design precautions

Smart bracelet, as a more popular product form in the past two years, has attracted more and more attention from people, although it can not be accepted by all, but its production has indeed made some changes in the electronic product market.

A smart bracelet is usually composed of a radio frequency circuit unit, a clock circuit unit, a memory circuit unit, a sensor circuit unit and a main control MCU unit, etc., and the circuit PCB is usually concentrated in a small range, single-sided or double-sided SMT, and the circuit board is based on 4 or 6 layers. The following is the circuit PCB of the 37-degree smart bracelet found on the network.

Since so many functions are concentrated on a smaller PCB board, we should pay special attention to the layout and wiring of the hand ring, and now summarize some precautions for reference.

First, partition layout, pay attention to cable protection.

As can be seen from the above PCB board, the various parts of the smart bracelet circuit (different color box marks) have a good partition: because the smart bracelet is a collection of digital circuit components, as long as the matching resistance and capacitance distribution in the circuit design, you can complete a certain function of the circuit module, which makes the circuit design more concise and easy to find. Although some sensor circuit units use analog circuit technology for data acquisition, once the module is designed as a module, then data communication and information transfer can be completed through the corresponding connection interface.

In the circuit module layout, on the one hand, it is necessary to pay attention to the clock circuit and crystal oscillator circuit to reach the target through the shortest path, on the other hand, it is also necessary to pay attention to avoiding the data line when the clock is running, 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 generation circuit, crystal oscillator circuit, etc. is protected by copper, whether the ring ground protection, etc., generally in the design, protection will be carried out, and copper mining is required for the crystal oscillator part.

Second, deal with the RF circuit.

The smart bracelet needs to be linked with the mobile phone when it is used, therefore, the radio frequency part is the key part, and we must pay special attention to this part of the design. Now the smart bracelets on the market are nothing more than wireless data transmission based on Bluetooth, so the focus is on Bluetooth RF processing. If the smart bracelet is only used for data transmission without the transmission of sound and music, then Bluetooth low power is the best choice, in the design, Bluetooth antenna shape, antenna layout, smart bracelet shell material, etc. are important factors affecting the performance of the smart bracelet. In the PCB design process of smart bracelet, an excellent RF antenna engineer is particularly important.

Third, do a good job of ESD protection.

In the previous article, I also wrote about some circuit ESD technology and knowledge, and today it is important to talk about the importance of ESD for smart bracelet products. Different countries and regions have different standards for different products or the same product ESD requirements, in order to make the product through the relevant testing, ESD protection design should be carried out during the design, and ESD detection should be carried out after the design is completed to ensure that the product is adapted to the local market electronic testing.

Finally, reserve the system upgrade interface.

Whether the function of a smart bracelet is convenient to upgrade is of great significance to users or smart bracelet fans. If a product is upgraded at an appropriate time (it may be that the early hardware design has some functions and the software has not kept up in order to catch up with the market, or it may be that some software bugs have been fixed), which indicates that the product is still in the process of continuous research and development, which is a good psychological compensation for users. 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 adopt, it needs to be determined in the pre-planning and software and hardware planning.