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BQ25672: BQ25672 Abnormal operation of ship mode

jiangwf
Prodigy 20 points
Part Number: BQ25672


1、The schematic diagram is shown in the following figure, VBUS=0, Vbat=7.6V

2、 SDRV_ CTRL default value 00。The waveform of VSYS unloaded SDRV is shown in Figure 1, and the voltage of VSYS is normal. VSYS is connected to a 50mA constant current source, and the SDRV waveform is shown in Figure 2. VSYS has been continuously on and off. The waveform of the SDRV connected to the adapter is shown in Figure 3, and the voltage of the VSYS is normal.

3、In the second test, without the adapter, the ship mos cannot function properly. How can I enter ship mode or shutdown mode。

3、

  • 0
    TI__Guru**** 169466 points

    Hi Jiang,

    In battery only mode, SDRV output is pulsed at 50% duty cycle and provides very low output current, so low that even a 10Mohn scope probe loads it.  Also, for ship mode to work, the SFET_PRESENT bit must be set to 1.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 20 points

    It should be like this, our application requires the device to enter ship or shutdown mode. So, in the case of ship FET, VBUS=0, Vbat=7.6V, how to configure the load to work normally through VSYS.

  • 0 in reply to jiangwf
    TI__Guru**** 169466 points

    Hi Jing,

    When in ship mode or shutdown mode, the SFET is off so the battery is no longer connected to SYS pin so V(SYS) = 0V.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 20 points

    My circuit has a ship FET.

    1. When the adapter is not connected, the ship FET opens at a 50% duty cycle, as shown in Figure 1 above.

    2. Connect the adapter and fully open the ship FET, as shown in Figure 3 above. The system can function normally.

    3. Unplug the adapter, and the ship FET returns to the state shown in Figure 1. The system is unable to power and operate from the battery.

    Question: Does the circuit have a ship FET that requires an adapter to be connected in order for the ship MOS to open? How can I configure it to allow the battery to power the system when the adapter is not connected.

  • 0 in reply to jiangwf
    TI__Guru**** 169466 points

    Hi Jiang,

    If the only connection to SDRV is to the shipFET gate (i.e. no scope probes, no resistive load to ground) and BATP is connected on the drain side of the BATFET, then SDRV turns on if the battery is above the UVLO spec below:

    Regards,

    Jeff