BQ24188_15 Datasheet, PDF (17/52 Pages) Texas Instruments – bq24188 2A, 30V, Host-Controlled Single-Input, Single Cell Switchmode Li-Ion Battery Charger with Power Path Management and USB-OTG Support

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bq24188
SLUSC44A – DECEMBER 2014 – REVISED MAY 2015
Device Functional Modes (continued)
The bq24188 supports a precision Li-Ion or Li-Polymer charging system for single-cell applications. Charging is
done through the internal battery MOSFET. There are 6 loops that influence the charge current; constant current
loop (CC), constant voltage loop (CV), thermal regulation loop, minimum system voltage loop (MINSYS), input
current limit and V_IN-DPM. During the charging process, all six loops are enabled and the one that is dominant
takes control. The minimum system output feature regulates the system voltage to V_SYSREG(LO), so that startup is
enabled even for a missing or deeply discharged battery. Figure 10 shows a typical charge profile including the
minimum system output voltage feature.
Regulation
Voltage
Precharge
Phase
Regulation
Current
V_SYS
(3.6V)
System Voltage
Current Regulation
Phase
Voltage Regulation
Phase
V_BATSHORT
(2.0V)
Battery
Voltage
Termination
I_BATSHORT
Charge Current
Linear Charge
50mA Linear Charge to Maintain
to Close Pack
Minimum
Protector
System
Voltage
Battery FET (Q3) is
ON
Battery
FET
is OFF
Figure 10. Typical Charging Profile of bq24188 with Termination Enabled
9.4.4 Battery Charging Process
When the battery is deeply discharged or shorted, the bq24188 applies a I_BATSHRT current to close the battery
protector switch and bring the battery voltage up to acceptable charging levels. During this time, the battery FET
is off and the system output is regulated to V_SYSREG(LO). Once the battery rises above V_BATSHRT, the charge
current is regulated to the value set in the I²C register. The battery FET is linearly regulated to maintain the
system voltage at V_SYSREG(LO). Under normal conditions, the time spent in this region is a very short percentage
of the total charging time, so the linear regulation of the charge current does not affect the overall charging
efficiency for very long. If the die temperature does heat up, the thermal regulation loop reduces the input current
to maintain a die temperature at 125°C. If the current limit for the SYS output is reached (limited by the input
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