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

5 Buck-only Charger

If no PG pin is available, the charger is always bucking (for example. input voltage > battery voltage + PFET’s VGSth) and the maximum system (battery) voltage is below VGSmax-Q1, the input voltage can be used to directly drive the PFET’s gate, as shown in Figure 5-3.

GUID-20231211-SS0I-FZSZ-7W6H-DNV2FWSXDMDZ-low.svg Figure 5-1 Implementation Using a Buck-only Charger

The Zener diode clamp, D1, from the PFET’s source to gate is only necessary if the charger's input voltage is higher than the VSGmax-Q1. If this configuration, RPD provides current limiting for D1 in forward mode, for example, when no VBUS is applied.