BQ24188_15 Datasheet, PDF (15/52 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
9.3 Feature Description
The bq24188 is a highly integrated single cell Li-Ion battery charger and system power path management device
that supports operation from either a USB port or wall adapter supply. The power path feature allows the
bq24188 to power the system from a high efficiency DC to DC converter while simultaneously and independently
charging the battery. The power path also permits the battery to supplement the system current requirements
when the adapter cannot. Many features are programmable using the I2C interface. To support USB OTG
applications, the bq24188 is configurable to boost the battery voltage to 5V and supply up to 1A at the input. The
battery is charged with three phases: precharge, constant current and constant voltage. Thermal regulation
prevents the die temperature from exceeding 125°C. Additionally, a JEITA compatible battery pack thermistor
monitoring input (TS) is included to prevent the battery from charging outside of its safe temperature range
The Device Functional Modes section explains these features in detail.
9.4 Device Functional Modes
9.4.1 High Impedance Mode
High Impedance mode (Hi-Z mode) is the low quiescent current state for the bq24188. During Hi-Z mode, the
buck converter is off, and the battery FET and BGATE are on. SYS is powered by BAT. The bq24188 is in Hi-Z
mode when V_IN < V_UVLO, the HZ_MODE bit in the I²C is '1' or the CD terminal is driven high. Hi-Z mode resets
the safety timer.
The bq24188 contains a CD input that is used to disable the IC and place the bq24188 into high-impedance
mode. Drive CD low to enable the bq24188 and enter normal operation. Drive CD high to disable charge and
place the bq24188 into high-impedance mode. CD is internally pulled down to PGND with a 100kΩ resistor.
When exiting Hi-Z mode, charging resumes in approximately 110ms.
9.4.2 Battery Only Connected
When the battery is connected with no input source, the battery FET is turned on. After the battery rises above
V_BATUVLO and the deglitch time, t_DGL(BAT), the SYS output starts to rise. In this mode, the current is not regulated;
however, there is a short circuit current limit. If the short circuit limit (I_LIM(DISCHG)) is reached for the deglitch time
(t_DGL(SC)), the battery FET is turned off for the recovery time (t_REC(SC)). After the recovery time, the battery FET is
turned on to test and see if the short has been removed. If it has not, the FET turns off and the process repeats
until the short is removed. This process protects the internal FET from over current. If an external FET is used
for discharge, the body diode prevents the load on SYS from being disconnected from the battery and t_DGL(BAT) is
not applicable.
9.4.3 Input Connected
9.4.3.1 Input Voltage Protection in Charge Mode
9.4.3.1.1 Sleep Mode
The bq24188 enters the low-power sleep mode if the voltage on V_IN falls below sleep-mode entry threshold,
V_BAT+V_SLP, and V_IN is higher than the undervoltage lockout threshold, V_UVLO. In sleep mode, the input is isolated
from the battery. This feature prevents draining the battery during the absence of V_IN. When V_IN < V_BAT+ V_SLP,
the bq24188 turns off the PWM converter, turns the battery FET and BGATE on, sends a single 128μs pulse on
the STAT and INT outputs and the STATx and FAULT_x bits of the status registers are updated in the I²C. Once
V_IN > V_BAT+ V_SLP, the STATx bits are cleared and the device initiates a new charge cycle. The FAULT_x bits are
not cleared until they are read in the I²C and the sleep condition no longer exists.
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