BQ27742-G1 Datasheet, PDF (21/46 Pages) Texas Instruments – Single-Cell Li-Ion Battery Fuel Gauge with Programmable Hardware Protection

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Device Functional Modes (continued)
• SHUTDOWN WAIT Mode
– ANALOG SHUTDOWN State
– LOW VOLTAGE CHARGING State
The relationships among these modes are shown in Figure 15.
bq27742-G1
SLUSBV9C – MARCH 2014 – REVISED FEBRUARY 2016
OCC Fault
CHG FET off
DSG FET on
Fuel Gauge on
LDO on
(V_SRP – V_SRN) > V_OCC
Fault recovery:
Charger removed
Normal
Fuel Gauge in
Normal, SLEEP,
FULLSLEEP Modes
CHG FET on
DSG FET on
Fuel Gauge on
LDO is on
V^{BAT > VUVPREL}
V^{BAT < VUVP}
UVP Fault
(POR State)
CHG FET on
DSG FET off
Fuel Gauge on
LDO is on
FW(ROM) turns
FETs off briefly
POR
(Force UVP set)
(V_SRN – V_SRP) > V_OCD
OR
(V_SRN – V_SRP) > V_SCD
V_BAT > V_OVP
Low Voltage Charging
CHG FET control shorted to
Charger removed
PACKP pin
AND
DSG FET off
Shutdown bit ^{VBAT < Shutdown V}
cleared
Protection off
Fuel Gauge off
LDO is off
OCD/SCD Fault
CHG FET on
DSG FET off
Fuel Gauge on
LDO on
Fault recovery:
load removed
Shutdown Bit
set
V_BAT < V_OVPREL
AND
Charger removed
AND
V_{BAT < Shutdown V Charger attached}
AND
Fault recovery:
V_BAT > V_LVDET
Charger removed
Analog Shutdown
Shutdown Wait
CHG FET off
OVP Fault
CHG FET off
DSG FET on
Fuel Gauge on
CHG FET off
DSG FET off
Fuel Gauge on ^{Charger removed}
DSG FET off
Fuel Gauge off
LDO is off
LDO on
LDO is on
Virtual Shutdown
Figure 15. Operating Modes
7.4.1.1 NORMAL Mode
In this mode, the protector is fully powered and operational. Both CHG and DSG FETs are closed and the
protector continuously checks for fault conditions.
FET enable override capability is available to the fuel gauge to force the CHG or DSG FET open based on
firmware instruction. It is useful for firmware-defined safety features or other special functionality that requires
one or both FETs to be opened based on specific conditions. It cannot, however, be used to enforce FET turn-on
when the hardware protector is one of the protection fault modes, as the latter has ultimate authority over the
FET drive control circuitry.
Firmware can also command the fuel gauge to go into SHUTDOWN mode based on a dedicated Control()
subcommand from the host. In this case, firmware sets the Shutdown bit to indicate intent to go into
SHUTDOWN mode. The fuel gauge then transitions to SHUTDOWN WAIT mode and waits for charger removal
prior to disabling the internal LDO and fully powering down the entire device.
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