PCB design considerations for smart bracelets

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Posted by summer77 from the Self Improvement category at 29 Sep 2019 08:56:16 am.
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As a popular product form in the past two years, smart bracelets have attracted the attention of more and more people. Although it is not acceptable to everyone, its production has indeed led to some changes in the electronics market.

The smart wristband usually consists of a radio frequency circuit unit, a clock circuit unit, a memory circuit unit, a sensor circuit unit and a main MCU unit. The circuit PCB is usually concentrated in a small range to realize a single-sided or double-sided patch. The board is mainly 4 or 6 layers.

Since versatility is concentrated on a small PCB, we must pay special attention to the layout and wiring of the bracelet.

First, the partition layout, pay attention to the line protection.
As can be seen from the PCB board above, the various parts of the smart bracelet (different color box marks) have good partitioning: since the smart bracelet is a collection of digital circuit components, as long as the matching resistor and capacitor distribution are used, Some functional circuit blocks make the circuit design simpler and easier to find. Although some sensors circuit units use analog circuit technology for data acquisition, once the module is designed as a module, data communication and information transfer can be accomplished through the corresponding connection interface.

On the one hand, in the layout of the circuit module, it is necessary to pay attention to the clock circuit and the crystal oscillator circuit to achieve the goal through the shortest path. On the other hand, when routing clocks, care should be taken to avoid using data lines to prevent interference from affecting system stability.

When wiring, it is necessary to protect key traces, such as clock generation circuits, crystal oscillator circuits, etc., whether copper protection, ring protection, etc., is usually protected in the design, because the crystal part needs to be dig copper.

Second, the RF circuit is processed.

When used, the smart bracelet needs to be linked to the phone. Therefore, the RF section is a key part. Care must be taken in this part of the design. Today, smart bracelets on the market are nothing more than Bluetooth-based wireless data transmission, so the focus is on the processing of Bluetooth radios. Bluetooth low-power is the best choice if the smart bracelet is only used for data transmission without the need to transmit sound and music. At the time of design, the shape of the Bluetooth antenna, the antenna layout, the material of the smart bracelet, etc. all affect intelligence. An important factor in the performance of the bracelet. Excellent RF antenna engineers are especially important in the smart bracelet PCB design process.

Again, perform ESD protection.

Different countries and regions have different standards for different products or the same product ESD requirements. To pass the relevant tests, the ESD protection design should be carried out during the design process. Once the design is complete, an ESD test should be performed to ensure that the product passes. Adapt to local market electronic testing.

Finally, keep the system upgrade interface.

Whether the function upgrade of the smart bracelet is convenient for the user or the smart bracelet powder is of great significance. If the product is upgraded at the appropriate time, it indicates that the product is still in the process of continuous development, which is a good psychological compensation for the user. There are usually two ways to upgrade your smart bracelet software: via USB interface and wireless push. As for which method to use, it needs to be determined in the early planning and hardware and software plans.
The above is the PCB design considerations for the smart bracelet I have organized.
June 2023
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