SLUAA04A june   2020  – may 2023 BQ25150 , BQ25155 , BQ25618 , BQ25619 , TS5A12301E , TS5A3157 , TS5A3159A , TS5A6542

 

  1.   1
  2.   High-Efficiency Charging for TWS Using a 2-Pin Interface
  3.   Trademarks
  4. 1 Introduction
  5. 2 System Overview
    1. 2.1 Charging Case
      1. 2.1.1 BQ25619
      2. 2.1.2 TLV62568P
      3. 2.1.3 TPS22910A
      4. 2.1.4 TS5A12301E
      5. 2.1.5 MCU
    2. 2.2 Earbuds
      1. 2.2.1 BQ25155
      2. 2.2.2 TPS22910A
      3. 2.2.3 TS5A12301E
      4. 2.2.4 BT/SOC
  6. 3 Charging Case Algorithm Implementation
    1. 3.1 Initialization and Main Code
    2. 3.2 UART Interrupt and Output Voltage Adjustment
  7. 4 Earbud Algorithm Implementation
    1. 4.1 Initialization and Main Code
    2. 4.2 Interrupt and Transmission
  8. 5 Test Procedure
  9. 6 Test Results
    1. 6.1 Dynamic Voltage Adjustment
    2. 6.2 BQ25619 with 4.6-V Output
    3. 6.3 Standard Boost with 5V Output
  10. 7 Summary
  11. 8 Schematics
  12. 9 PCB Layout
  13. 10Software
    1. 10.1 Charging Case main.c
    2. 10.2 Earbuds main.c
  14. 11Revision History

6.1 Dynamic Voltage Adjustment

The first system shown is the one discussed in this paper. This design offers the best performance as a result of the 2-pin communication-enabled, efficient charging scheme. By reducing the difference between the case output voltage and the earbud battery voltage, the power dissipated by the linear battery charger is reduced. This allows for optimal thermal performance and increased case battery life.

Below is a scope capture of a charging cycle using the proposed solution. The maximum current at the input of the case was 265 mA, while providing 200 mA to the earbud battery. Each pulse that can be seen is a communication cycle.

GUID-8CA4C6E6-A278-4F7C-99B3-119460124047-low.png Figure 6-1 Charge Cycle of the Dynamic Voltage Adjustment Design

Figure 6-2 shows an image taken by a FLIR thermal camera. This image shows the system at its maximum temperature during the charging process. The temperature of 27.7°C is only 2.7°C above the ambient room temperature of 25°C.

GUID-C01281CB-5B61-4DD8-AF67-87A89DD8E244-low.png Figure 6-2 Thermal Performance of the Dynamic Voltage Adjustment Design