BQ24188_15 Datasheet, PDF (19/52 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

www.ti.com
bq24188
SLUSC44A – DECEMBER 2014 – REVISED MAY 2015
Device Functional Modes (continued)
9.4.7 Battery Overvoltage Protection (BOVP)
If the battery is ever above the battery OVP threshold (V_BOVP), the battery OVP circuit shuts the PWM converter
off and the battery FET is turned on to discharge the battery to safe operating levels. A battery OVP most
commonly occurs when the bq24188 returns to DEFAULT mode after a watchdog timer expiration or RESET bit
written to '1'. In this condition, the V_BATREG is reset and may be below the battery voltage. Other conditions may
be when the input is initially plugged in before I²C communication is established or TS WARM conditions or when
writing the V_BATREG to less than the battery voltage. The battery OVP condition is cleared when the battery
voltage falls below the hysteresis of V_BOVP either by the battery discharging or writing the V_BATREG to a higher
value. When a battery OVP event exists for t_DGL(BOVP), the bq24188 turns the battery FET and BGATE on, sends
a single 128μs pulse on the STAT / INT outputs and the STATx and FAULT_x bits are updated in the I²C. Once
the BOVP fault is removed, the STATx bits are cleared and the device returns to normal operation. The
FAULT_x bits are not cleared until they are read in the I²C after the BOVP condition no longer exists.
9.4.8 Dynamic Power Path Management
The bq24188 features a SYS output that powers the external system load connected to the battery. This output
is active whenever a valid source is connected to IN or BAT. When V_SYS > V_SYSREG(LO), the SYS output is
connected to V_BAT. If the battery voltage falls to V_MINSYS, V_SYS is regulated to the V_SYSREG(LO) threshold to
maintain the system output even with a deeply discharged or absent battery. In this mode, the SYS output
voltage is regulated by the buck converter and the battery FET is linearly regulated to regulate the charge current
into the battery. The current from the supply is shared between charging the battery and powering the system
load at SYS. The dynamic power path management (DPPM) circuitry of the bq24188 monitors the current limits
continuously and if the SYS voltage falls to the V_MINSYS threshold, it adjusts charge current to maintain the
minimum system voltage and supply the load on SYS. If the charge current is reduced to zero and the load
increases further, the bq24188 enters battery supplement mode. During supplement mode, the battery FET is
turned on and V_BAT = V_SYS while the battery supplements the system load.
2000mA
1800mA
I_SYS
800mA
0mA
1500mA
I_{IN ~850mA}
0mA
1A
I_BAT
0mA
–200mA
V_SYS
3.6V
3.5V
~3.1V
DPPM loop active
Supplement
Mode
Figure 11. Example DPPM Response (V_Supply=5V, V_BAT = 3.1V, 1.5A Input Current Limit)
Copyright © 2014–2015, Texas Instruments Incorporated
Product Folder Links: bq24188
Submit Documentation Feedback
19