SLUAAT7 January   2024 BQ25672 , BQ25790 , BQ25792 , BQ25798

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2IRMS Discharge Current
  6. 3External Battery FET
  7. 4Charger With PG and or Host GPIO
  8. 5Buck-only Charger
  9. 6Boosting Charger
  10. 7Summary
  11. 8References

1 Introduction

Integrated FET (I-FET), NVDC switch-mode battery chargers with internal battery FETs between the system (SYS) and battery (BAT) pins are desired for their small PCB footprint. However, unlike battery charger controllers with customizable external FETs, the charger’s internal FETs have fixed max current limitations due primarily to their RDS(ON) and small package. The internal battery FET’s maximum discharge current from BAT to SYS might not be enough to provide the system load when the charger is in battery only mode. To alleviate this issue in some applications, the system load is connected directly to the battery. However, this configuration cannot take advantage of the NVDC's key features of accurate charge and termination current or ability to start up the system from a discharged battery. This application note explains how to make sure that battery charge IC can provide the needed system load.