SLUAAG9 September   2021 BQ25170 , BQ25171-Q1 , BQ25175

 

  1.   Trademarks
  2. 1Introduction
  3. 2BQ25171-Q1 Design Decisions
  4. 3700 mA/70 mA Variable Charge Current Li-Ion Fast Charge Design
  5. 4200 mA Time Charge 3S NiMH Design
  6. 545 mA Fast Charge LiFePO4 Design
  7. 6Pin Configuration
  8. 7R-ISET Common Values
  9. 8Common Questions: Tips and Tricks

3 700 mA/70 mA Variable Charge Current Li-Ion Fast Charge Design

Figure 3-1 provides a solution that will charge a Li-Ion battery at 700 mA or 70 mA with charge current selection controlled by a GPIO pin on a host device and termination at 10% of the selected charge current.

  • R-ISET1 will set fast charge current to 70 mA, 4.2 kΩ.
  • R-ISET2 will combine with R-ISET1 in parallel to set fast charge current to 700 mA, 480 Ω.
  • The external NMOS transistor with gate voltage controlled by a host GPIO pin will set fast charge current to 700 mA when turned on.
  • R-CHM_TMR will set chemistry to Li+ with a 10 hour safety timer, 82 kΩ.
  • R-VSET will set the number of cells and regulation voltage to 1 cell Li-Ion 4.2 V, 18 kΩ.
  • Charge enable (/CE) pin is connected to host MCU for external device control.
  • R-TS is required, a 10 kΩ NTC in battery pack is connected to pin.
  • STAT1/STAT2 LEDs are used together to indicate charge status and faults, they are optional.

This application supports enhanced charge current flexibility.

GUID-20210928-SS0I-PL1V-R9QD-DZXD4FGPJZZN-low.pngFigure 3-1 BQ25171-Q1 700-mA/70-mA Fast Charge