BQ24188_15 Datasheet, PDF (25/52 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
The bq24188 will not enter boost mode unless the IN voltage is less than the UVLO. When the boost function is
enabled, the bq24188 enters a linear mode to bring IN up to the battery voltage. Once V_IN > (V_BAT – 1V), the
bq24188 begins switching and regulates IN up to 5V. If V_IN does not rise to within 1V of V_BAT within 8ms, an
over-current event is detected and boost mode is exited and a boost mode over-current event is announced, the
BOOST_EN bit is reset to ‘0’ and the STAT_x and FAULT_x bits in the Status/ Control register are updated.
9.4.18.3 Burst Mode during Light Load
In boost mode, the IC operates using burst mode to improve light load efficiency and reduce power loss. During
boost mode, the PWM converter is turned off when the device reaches minimum duty cycle and the output
voltage rises to V_BURST(ENT) threshold. This corresponds to approximately a 75mA inductor current. The converter
then restarts when V_IN falls to V_BURST(EXT). See Figure 37 in the Typical Operating Characteristics for an example
waveform.
9.4.18.4 Watchdog Timer in Boost Mode
During boost mode, the watchdog timer is active. The watchdog timer works the same as in charge mode. Write
a “1” to the TMR_RST reset bit in the control register. If the watchdog timer expires, the IC resets the
EN_BOOST bit to 0, signals the fault pulse on the STAT and INT terminals. The FAULT_x bits read "Low Supply
Fault" as this is a higher priority fault than the WD timer.
9.4.18.5 STAT/ INT During Boost Mode
During boost mode, the STAT and INT outputs are high impedance. Under fault conditions, a 128µs pulse is sent
out to notify the host of the error condition.
9.4.18.6 Protection in Boost Mode
9.4.18.6.1 Output Over-Voltage Protection
The bq24188 contains integrated over-voltage protection on the IN terminal. During boost mode, if an over-
voltage condition is detected (V_IN > V_BOOSTOVP), after deglitch t_{DGL(BOOST_OVP)}, the IC turns off the PWM converter,
resets EN_BOOST bit to 0, sets fault status bits and sends out a fault pulse on STAT and INT. The converter
does not restart when VIN drops to the normal level until the EN_BOOST bit is reset to 1.
9.4.18.6.2 Output Over-Current Protection
The bq24188 contains over current protection to prevent the device and battery damage when IN is overloaded.
When an over-current condition occurs, the cycle-by-cycle current limit limits the current from the battery to the
load. If the overload condition lasts for 8ms, the overload fault is detected. When an overload condition is
detected, the bq24188 turns off the PWM converter, resets EN_BOOST bit to 0, sets the fault status bits and
sends out the fault pulse on STAT and INT. The boost operation starts only after the fault is cleared and the
EN_BOOST bit is reset to 1 using the I²C.
9.4.18.6.3 Battery Voltage Protection
During boost mode, when the battery voltage is below the minimum battery voltage threshold, V_BATUVLO, the IC
turns off the PWM converter, resets EN_BOOST bit to 0, sets fault status bits and sends out a fault pulse on
STAT and INT. Once the battery voltage returns to the acceptable level, the boost starts only after the
EN_BOOST bit is set to 1. Proper operation below 3.3V down to the V_BATUVLOis not specified.
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