BQ24196_17 Datasheet, PDF (17/50 Pages) Texas Instruments – I2C Controlled 2.5-A Single Cell USB/Adapter Charger with Narrow VDC Power Path Management and USB OTG

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bq24196
SLUSB98A – OCTOBER 2012 – REVISED DECEMBER 2014
8.3.2.3 Supplement Mode
When the system voltage falls below the battery voltage, the BATFET turns on and the BATFET gate is
regulated the gate drive of BATFET so that the minimum BATFET V_DS stays at 30 mV when the current is low.
This prevents oscillation from entering and exiting the supplement mode. As the discharge current increases, the
BATFET gate is regulated with a higher voltage to reduce R_DSON until the BATFET is in full conduction. At this
point onwards, the BATFET V_DS linearly increases with discharge current. Figure 12 shows the V-I curve of the
BATFET gate regulation operation. BATFET turns off to exit supplement mode when the battery is below battery
depletion threshold.
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
5 10 15 20 25 30 35 40 45 50 55
V(BAT-SYS) (mV)
Figure 12. BATFET V-I Curve
8.3.3 Battery Charging Management
The bq24196 charges 1-cell Li-Ion battery with up to 2.5A charge current for high capacity tablet battery. The 12-
mΩ BATFET improves charging efficiency and minimizes the voltage drop during discharging.
8.3.3.1 Autonomous Charging Cycle
With battery charging enabled at POR (REG01[5:4] = 01), the bq24196 can complete a charging cycle without
host involvement. The device default charging parameters are listed in .
Table 3. Charging Parameter Default Setting
DEFAULT MODE
Charging voltage
Charging current
Pre-charge current
Termination current
Temperature profile
Safety timer
bq24196
4.208 V
2.048 A
256 mA
256 mA
Hot/Cold
8 hours
A new charge cycle starts when the following conditions are valid:
• Converter starts
• Battery charging is enabled by I²C register bit (REG01[5:4]) = 01 and CE is low
• No thermistor fault on TS1 and TS2
• No safety timer fault
• BATFET is not forced to turn off (REG07[5])
The charger device automatically terminates the charging cycle when the charging current is below termination
threshold and charge voltage is above recharge threshold. When a full battery voltage is discharged below
recharge threshold (REG04[0]), the bq24196 automatically starts another charging cycle.
The STAT output indicates the charging status of charging (LOW), charging complete or charge disable (HIGH)
or charging fault (Blinking). The status register REG08[5:4] indicates the different charging phases: 00-charging
disable, 01-precharge, 10-fast charge (constant current) and constant voltage mode, 11-charging done. Once a
charging cycle is complete, an INT is asserted to notify the host.
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