Explore the technical secrets of TWS Bluetooth headsets

TWS Bluetooth headsets do not require wired connections. The left and right earphones form a stereo system through Bluetooth, which improves listening to music, talking and wearing. The outside of the true wireless Bluetooth headset completely abandons the wire connection method, and the host can work alone and make hands-free calls. True wireless headphones can be worn in one or both ears. TWS headphones mainly include two wireless earphones and a charging box. From the perspective of component composition, wireless headphones mainly include a main control Bluetooth chip, a storage chip, an audio decoder, various sensors, a flexible circuit board FPC and a battery; the charging box part mainly includes a microcontroller, a power management IC, an overcurrent protection IC and a lithium battery.

Main control Bluetooth chip

The key to solving the transmission and sound quality problems of TWS headphones lies in the development of Bluetooth technology and audio codec technology, which are usually integrated in the main control Bluetooth chip SoC of TWS headphones. Therefore, the Bluetooth SOC chip is crucial to the signal transmission and sound quality performance of TWS headphones. According to industry research, TWS SoC chips usually account for 10%-20% of the cost, while the price of some mid- and low-end Bluetooth chips has dropped to 1.6 yuan. As the number of chip suppliers increases, chip prices are also falling, which will drive the rapid development of the entire TWS headset industry, but competition for main control chips will also intensify.

Memory Chip

It is a general trend for TWS earphones to be equipped with large-capacity NOR Flash. NOR Flash is a non-volatile flash memory technology with high transmission efficiency. Its advantage is that the code can be executed in the chip (XIP), so there is no need to read the code into the system RAM. In order to store more firmware and code programs, TWS earphones must expand an external serial Nor Flash memory. At the beginning, Flash was mostly 8Mbit or 16Mbit, but later manufacturers added functions such as OTA, so 32Mbit, 64Mbit and 128Mbit norflash storage chips are adopted by more and more TWS manufacturers.

Currently, Apple AirPods uses two 128M Nor Flashes, while other TWS earphones have storage capacities between 4M and 128M. The noise reduction, sound quality and intelligence of TWS earphones will increase the complexity of functions, and the demand for algorithm code storage will also increase. It is expected that the capacity of Nor Flash will continue to expand and is expected to be further upgraded to 256M in the future.

Charging and power management chips

Although the power management chip accounts for a relatively low proportion of the cost of the headset, it accounts for nearly 50% of the cost of the charging box that comes with the headset, and mainly includes charging chips, synchronous rectification boost converters, low-dropout regulators, load switches, input overvoltage and overcurrent protection chips, etc. Whether it is battery life or charging, the power management chip needs to ensure TWS fast charging while reducing damage to the headset battery.