BQ24295 Datasheet, PDF (21/45 Pages) Texas Instruments – I2C Controlled 3A Single Cell USB Charger

bq24295
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SLUSBC1 – SEPTEMBER 2013
BATFET Turn Off
The BATFET can be forced off by the host through I²C REG07[5]. This bit allows the user to independently turn
off the BATFET when the battery condition becomes abnormal during charging. When BATFET is off, there is no
path to charge or discharge the battery. When battery is not attached, the BATFET should be turned off by
setting REG07[5] to 1 to disable charging and supplement mode.
Shipping Mode
To extend battery life and minimize power when system is powered off during system idle, shipping, or storage,
the device can turn off BATFET so that the system voltage is zero to minimize the leakage. The BATFET can be
turned off by setting REG07[5] (BATFET_DISABLE) bit.
In order to keep BATFET off during shipping mode, the host has to disable the watchdog timer (REG05[5:4]=00)
and disable BATFET (REG07[5]=1) at the same time. Once the BATFET is disabled, one of the following events
can turn on BATFET and clear REG07[5] (BATFET_DISABLE) bit.
1. Plug in adapter
2. Write REG07[5]=0
3. watchdog timer expiration
4. Register reset (REG01[7]=1)
5. A logic low to high transition on QON pin (refer to Figure 22 for detail timing)
QON
Min. 2ms
BATFET Status
Turn off by i2c command
REG07[5]=1
Turn on by QON
REG07[5]=0
Figure 22. QON Timing
Boost Mode Operation from Battery
The device supports boost converter operation to deliver power from the battery to other portable devices
through PMID pin. The boost mode output current rating meets the 1.5A charging requirements for smartphone
and tablet. The boost operation is enabled by default if the conditions are valid:
1. BAT above BATLOWV threshold (V_BATLOWV set by REG04[1])
2. VBUS less than BAT+V_SLEEP (in sleep mode)
3. Boost mode operation is enabled (OTG pin HIGH and REG01[5:4]=10)
4. After 30ms delay from boost mode enable
In battery boost mode, the device employs a 1.5MHz step-up switching regulator. During boost mode, the status
register REG08[7:6] is set to 11, the PMID output voltage is 5.1V. In addition, the device provides adjustable
boost voltage from 4.55V to 5.5V by changing BOOSTV bits in REG06[7:4]. Any fault during boost operation,
including PMID over-voltage, sets the fault register REG09[6] to 1 and an INT is asserted.
For power bank applications, the boost current is supported from PMID pin as in the application diagram. It is
recommended to use the minimum PMID cap value 20uF for boost current. Please note that there is no boost
current limit setting when the boost current is sourced from PMID pin, hence it is important not to overload the
boost current under this condition.
Copyright © 2013, Texas Instruments Incorporated
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