8.3.11 Ship FET Control
The charger provides an N-FET driving pin (SDRV) to control an external ship FET. When this ship FET is off, it removes leakage current from the battery to the system. The ship FET is controlled by the SDRV_CTRL[1:0] register bits, to support the shutdown mode, ship mode and the system power reset.
- IDLE Mode when SDRV_CTRL[1:0] = 00, POR default. The external ship FET is fully on, I2C is enabled. The internal BATFET status is determined by the charging status. This mode could be for adapter present forward mode, OTG mode or battery only condition.
- Shutdown Mode when SDRV_CTRL[1:0] = 01. The ship FET and the internal BATFET are both off. The I2C is disabled. The charger is totally shutdown and can only be woken up by an adapter plug-in. This mode is only for the battery only condition.
- Ship Mode when SDRV_CTRL[1:0] = 10. The ship FET and the internal BATFET are both off. The I2C is still enabled. The charger can be woken up by setting SDRV_CTRL[1:0] back to 00, or pulling the QON pin low, or an adapter plug-in. This mode is only for the battery only condition.
- System Power Reset when SDRV_CTRL[1:0] = 11. The ship FET is turned off for typical 350ms to reset the system power (converter goes to HIZ mode if VBUS is high), then the ship FET is fully turned on again. The BATFET keeps the status unchanged during the system power reset. After the reset is done, SDRV_CTRL[1:0] goes back to 00.
When the host changes SDRV_CTRL[1:0] from 00 to the other values, the charger turns off the ship FET immediately or delays by tSM_DLY as configured by SDRV_DLY bit. The application diagram when the battery is connected to the charger through an external ship FET is illustrated in the figure below.
Figure 28. The Application Diagram for the External Ship FET