MAXREFDES1263: True Wireless Stereo Stand and Earbuds

The MAXREFDES1263 is a reference design for the TWS (True Wireless Stereo) application base. This reference design is a power management platform for TWS cradle and earbuds (left and right). It also supplies data communication between the cradle and earbuds, which includes the MAX77651,MAX17270,MAX32660, MAX77818, MAX77813, MAX20340, MAX17260, and MAX98090. This solution demonstrates a small-size, low-power, highly effective, high-accuracy power management system.

On the cradle side, the MAX77818 integrates a high-performance 3A switching charger and proprietary ModelGauge™ m5 fuel gauge, which provides fast charging and industry-leading battery fuel-gauge accuracy. The Smart Power Selector™ architecture includes a network of internal switches and control loops that distributes energy among USB, wireless charging, BYP, SYS, and BATT. The MAX77813 is used to produce stable 5V output from a Li+ battery or VSYS from the earbud charger. The MAX17270 SIMO regulator provides 3.3V outputs with 0.8V to 5.175V programmable voltage range to support a Bluetooth®/sensor module or processor power supply. The MAX20340 is a universal bidirectional powerline communication (PLC) management IC. It features a slave detection circuit that flags an interrupt to the system when the PLC master detects the presence of a PLC slave on the power line. The slave MAX20340 on the earbuds can transmit data to the master MAX20340 on cradle, like battery charging status or information such as remaining capacity (mAH), etc. The MAX32660 is used to configure the SIMO, charger and fuel gauge, and PLC (MAX20340). It also is used to read the battery status and fuel gauge data.

On the earbuds, the MAX20340 is configured in slave mode and transfers to the master detection state. The MAX77651B features a SIMO buck-boost regulator that provides three independently programmable power rails from a single inductor to minimize total solution size and to support the MCU, Bluetooth/sensor module, and other devices’ power supplies. A 150mA LDO provides ripple rejection for audio (audio CODEC) and other noise-sensitive applications. A highly configurable linear charger supports a wide range of Li+ battery capacities and includes battery temperature monitoring for additional safety (JEITA). The MAX17260 ultra-low-power fuel-gauge IC monitors a single-cell battery pack and supports internal current sensing. The MAX32660 is used to configure the MAX77651B, MAX17260, MAX20340, and MAX98090. The MAX98090 provides I2S interface pins to connect customer processor and microphone inputs along with headphone outputs for audio function evaluation.