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BQ24703

LGiuseppe
Prodigy 20 points
Other Parts Discussed in Thread: BQ24703

I have to make a portable system powered by li-ion rechargeable batteries. BQ24703 I used to charge the battery. In the documentation is not indicated following condition ACPRES = low, ACSEL = high (fixed), Battery < BATDEP. In this condition I have to disconnect VSYS.
Also in Table 1 of the data sheet does not show the pinout of BQ24703PW.

Thanks.

  • 0
    TI__Guru 56650 points

    On datasheet page 23rd, "The bq24703, however, automatically reverts over to adapter power, provided the adapter is present, during a deep discharge state. The battery is considered as being in a deep discharge state when the battery voltage is less than (0.8 ´ depleted level). "

    So, wehn battery<BATDEP, the BATDRV of bq24703 is off (BATFET is off). At this condition, do you want to disconnect Vsys from battery or Vin?

    Yes. Table 1 doesn't show the pinout of bq24703PW. We only can use the page one "The top view of PW PACKAGE" to find out the pinout.

  • 0 in reply to Wang5577
    Prodigy 20 points

    So, wehn battery<BATDEP, the BATDRV of bq24703 is off (BATFET is off). At this condition, do you want to disconnect Vsys from battery or Vin?

    Yes, I would disconnect Vsys from  Vbat when the battery is low and the adapter is not present.  On page 10, if BATDRV is high, the mofset U4 through the internal diode continues to supply Vsys ?  To disconnect Vsys  from  Vbat, need two mosfet  back-to-back fashion.

    Thanks

  • 0 in reply to LGiuseppe
    TI__Guru 56650 points

    Yes. The body diode of BATFET is still there. To totally disconnect Vsys from Vbat, it need a back-to-back fashion.

    Generally, changer IC doesn't  drive a back-to-back BATFETs. The battery pack has a back-to-back FET at the input. Please use a gas gauge EVM as reference. I can give a link here: http://focus.ti.com/lit/ug/sluu242a/sluu242a.pdf

  • 0 in reply to Wang5577
    Prodigy 130 points

    Hi, I found this topic thread while looking for information about the exact functioning of BQ703 when the BATDEP condition is active.

    The datasheet tells "The bq24703, however, automatically reverts over to adapter power, provided the adapter is present, during a deep discharge state."

    What does it mean "Provided the adapter is present" ? My problem is to understand which is the behaviour of the controller when: (battery is depleted) AND (ACPRES is low). In other words, if the battery goes depleted while the AC adapter is not present the battery is disconnected to preserve its life or is it left connect giving priority to load supply ?

    Best regards

    Enrico