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BQ25798: BATFET's diode

Yasunori Yanagidate
Prodigy 10 points
Part Number: BQ25798

Tool/software:

I plan to connect a lithium ion battery to the BAT terminal.
In the block diagram of this IC, there is a parasitic diode on the BATFET.
I am assuming that current will continue to flow from BAT through the SYS terminal even when the BATFET is OFF.
Q1. If a load is connected to the SYS terminal, how much current will flow when the BATFET is OFF?
Q2 . If a battery is connected directly to the BAT terminal, is there a possibility that the battery will discharge to below the minimum discharge voltage?

  • +1
    TI__Guru**** 165766 points

    Hi Yasunori,

    Regarding Q1, current flow from BAT to SYS cannot be turned off either to prevent supplement mode when VBUS is applied (charger is in DPM) OR when no VBUS (or EN_HIZ=1).  With no VBUS applied, adding an external shipFET allows for ship or shutdown mode reduces battery Iq through the BATP pin and prevents current flow from the battery to SYS.  Unfortunately, there is no user bit to turn off the external shipFET when VBUS is applied.

    Regarding Q2, yes.  The charger relies on the battery pack protector to prevent battery over discharge.

    Regards,

    Jeff