BQ24196_17 Datasheet, PDF (13/50 Pages) Texas Instruments – I2C Controlled 2.5-A Single Cell USB/Adapter Charger with Narrow VDC Power Path Management and USB OTG

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bq24196
SLUSB98A – OCTOBER 2012 – REVISED DECEMBER 2014
8.3 Feature Description
8.3.1 Device Power Up
8.3.1.1 Power-On-Reset (POR)
The internal bias circuits are powered from the higher voltage of VBUS and BAT. When VBUS or VBAT rises
above UVLOZ, the sleep comparator, battery depletion comparator and BATFET driver are active. I²C interface
is ready for communication and all the registers are reset to default value. The host can access all the registers
after POR.
8.3.1.2 Power Up from Battery without DC Source
If only battery is present and the voltage is above depletion threshold (V_{BAT_DEPL}), the BATFET turns on and
connects battery to system. The REGN LDO stays off to minimize the quiescent current. The low R_DSON in
BATFET and the low quiescent current on BAT minimize the conduction loss and maximize the battery run time.
The device always monitors the discharge current through BATFET. When the system is overloaded or shorted,
the device will immediately turn off BATFET and keep BATFET off until the input source plugs in again.
8.3.1.2.1 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.
8.3.1.2.2 Shipping Mode
When end equipment is assembled, the system is connected to battery through BATFET. There will be a small
leakage current to discharge the battery even when the system is powered off. In order to extend the battery life
during shipping and storage, the device can turn off BATFET so that the system voltage is zero to minimize the
leakage.
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, the BATFET can be turned on by plugging in adapter.
8.3.1.3 Power Up from DC Source
When the DC source plugs in, the bq24196 checks the input source voltage to turn on REGN LDO and all the
bias circuits. It also checks the input current limit before starts the buck converter.
8.3.1.3.1 REGN LDO
The REGN LDO supplies internal bias circuits as well as the HSFET and LSFET gate drive. The LDO also
provides bias rail to TS1/TS2 external resistors. The pull-up rail of STAT and PG can be connected to REGN as
well.
The REGN is enabled when all the conditions are valid.
1. VBUS above UVLOZ
2. VBUS above battery + V_SLEEPZ in buck mode or VBUS below battery + V_SLEEPZ in boost mode
3. After typical 220ms delay (100ms minimum) is complete
If one of the above conditions is not valid, the device is in high impedance mode (HIZ) with REGN LDO off. The
device draws less than 50 µA from VBUS during HIZ state. The battery powers up the system when the device is
in HIZ.
8.3.1.3.2 Input Source Qualification
After REGN LDO powers up, the bq24196 checks the current capability of the input source. The input source has
to meet the following requirements to start the buck converter.
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