The charger provides an N-FET driving
pin (SDRV) to control an external ship FET. The SDRV pin is the output of a
charge pump that provides 100 nA typical drive current to drive the ship FET
gate to typically 5-V above the battery voltage. 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 is valid with
adapter present, during forward charging, in OTG mode or in the battery only
- Shutdown Mode when SDRV_CTRL[1:0] = 01. The ship
FET turns off. The I2C is
disabled. The charger is totally shutdown and can only be woken up by an
adapter plug-in. This mode can only be entered when no adapter is present.
If SDRV_CTRL[1:0] is written to 01 with an adapter present, the write is
- Ship Mode when SDRV_CTRL[1:0] = 10. The ship FET
The ship FET turns 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 can only be entered when no adapter is present. If SDRV_CTRL[1:0] is
written to 01 with an adapter present, the write is ignored.
- 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 8-15 The Application Diagram for
the External Ship FET