Analog Devices has released a reference design integrating battery charging, power management, fuel gauging and data communication for true wireless stereo earbuds and their charging cradle.
Analog Devices has released a reference design for a true wireless stereo (TWS) system that combines the power management and communication functions required by wireless earbuds and their charging cradle. The design supports both left and right earbuds and integrates battery charging, voltage regulation, battery monitoring and audio interfacing. It provides a compact platform for evaluating power management in battery-powered audio devices.
On the charging cradle side, the design incorporates a switching charger that supports charging currents of up to 3 A and a fuel gauge for monitoring battery capacity. A power-selection circuit manages energy distribution between USB input, wireless charging, the system supply and the battery. Another power converter generates a regulated 5 V output for charging the earbuds, while a single-inductor multiple-output (SIMO) regulator provides programmable voltage rails for the processor, Bluetooth and sensor modules.
For communication between the cradle and earbuds, the reference design uses bidirectional powerline communication (PLC). This allows the earbuds to send information, such as battery charging status and remaining capacity, through the power connection. A microcontroller configures the charging, voltage regulation and communication circuits while collecting battery status and fuel-gauge information. This approach enables data exchange between the earbuds and their cradle without requiring a separate communication connection for these functions.
Within the earbuds, a SIMO buck-boost regulator generates three independently programmable power rails from a single inductor, reducing the space required for power conversion. A low-dropout (LDO) regulator provides a 150 mA output for noise-sensitive circuits, including the audio codec. The design also includes a configurable linear battery charger with battery-temperature monitoring and a fuel gauge that monitors a single-cell lithium-ion battery. An audio codec provides an Inter-IC Sound (I²S) interface for connecting a host processor, microphone inputs and headphone outputs.
Analog Devices provides supporting resources for the reference design, including schematics, printed circuit board (PCB) layout files, bill of materials (BOM) and test results. The design documentation also describes the implementation of the charging, power management and communication subsystems. These resources can help engineers evaluate the architecture and adapt it for wireless earbuds and other compact battery-powered audio products.
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