• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 241 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25723: BATFET's operation in battery fully depleted or battery removal mode

zong xu
Prodigy 130 points
Part Number: BQ25723
Other Parts Discussed in Thread: BQ28Z610, EV2400

Tool/software:

Hi TI expert,

When i did validation about BQ25723's characteristics, found when battery fully depleted(Vcell<2.5V) or remove battery from system, Vsys is regulated @Vsys_min normally, but VBAT=0V because of BATFET's turning off.

Measure the BATDRV pin, found the volatge of BATDRV pin is equal to Vsys(BATFET's VGS=0V). Obviouly charger is intended to turn off BATFET in this mode.

But when battery pack fully depleted(Vcell<2.5V), pack will also turn off the CHG&DSG FET as well, which cause VBAT=0V; and if want to wakeup and charge pack again, we do need a way to turnon BATFET to trigger & wakeup pack's gauge to enable it's charge and discharge MOSFET so as to charge the cell.

Also when it comes to shipping setting, the encountered challenge is same. BATFET's body diode always enable the power path from pack to system even though turn off the BATFET, so currently i'm also inclined to set pack in sleep mode(turn off CHG&DSG FET), which will also cause system side VBAT=0V.(BTW the pack's gauge model is BQ28Z610)

so i want to confirm whether this behavior is expected or not(charger is intended to turn off BATFET when battery fully depleted(Vcell<2.5V) or remove battery from system), if yes, is there any certain register to force turn on BATFET when  VBAT=0V(battery fully depleted(Vcell<2.5V) or remove battery from system).

attach the SCH for reference, appreciated!

  • 0
    TI__Mastermind 32745 points

    Hi, Zong,

    zong xu said:

    so i want to confirm whether this behavior is expected or not(charger is intended to turn off BATFET when battery fully depleted(Vcell<2.5V) or remove battery from system), if yes, is there any certain register to force turn on BATFET when  VBAT=0V(battery fully depleted(Vcell<2.5V) or remove battery from system).

    When charge is disabled, the BATFET is off. 

    When charge is enabled, the BATFET is ON. 

    To enable charge, set charge current() register and CHARGE_INHIBIT=0.

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 130 points

    Hi Tiger,

    Thanks for your timely reply.

    I think the charger is already enabled. please see the captured waveform, disconnected pack from system, apply 15V on charger's VBUS, no system load, charger is enabled and work in PFM mode, and the BATDRV(CH4)=VSYS_MIN(CH2), BATFET is turned off, and VBAT=0V.

    To clarify more clearly, also using EV2400 and battery management studio GUI to capture the register status as below, no abnormal found.

  • +1 in reply to zong xu
    TI__Mastermind 32745 points

    I know, the charger is live. 

    To enable charge, set charge current() register(0x02) >0 and CHARGE_INHIBIT=0.

    Regards

    Tiger