BQ24230 Datasheet, PDF (15/33 Pages) Texas Instruments – USB-FRIENDLY LITHIUM-ION BATTERY CHARGER AND POWER-PATH MANAGEMENT IC

bq24230
bq24232
www.ti.com .......................................................................................................................................... SLUS821A – OCTOBER 2008 – REVISED DECEMBER 2008
PGOOD = Hi -Z
CHG = Hi -Z
BATTFET ON
VUVLO<VIN <VOVP No
and
V _IN > V _BAT+ V _{IN (DT)}
Yes
PGOOD = Low
Begin Startup
IIN _(MAX)100 mA
Yes
VOUTshort ?
No
Input Current
Limit set by EN 1
and EN2
Yes
EN 1= EN 2 =1
No
Yes
ILIM or ISET short ?
No
CE = Low
Yes
Begin Charging
No
Figure 25. Start-up Flow Diagram
POWER-PATH MANAGEMENT
The bq2423x features an OUT output that powers the external load connected to the battery. This output is
active whenever a source is connected to IN or BAT. The following sections discuss the behavior of OUT with a
source connected to IN to charge the battery and a battery source only.
INPUT SOURCE CONNECTED – ADAPTER or USB
With a source connected, the power-path management circuitry of the bq2423x monitors the input current
continuously. The OUT output is regulated to a fixed voltage (V_O(REG)). The current into IN is shared between
charging the battery and powering the system load at OUT. The bq2423x has internal selectable current limits of
100 mA (USB100) and 500 mA (USB500) for charging from USB ports, as well as a resistor-programmable input
current limit.
The bq2423x is USB-IF compliant for the inrush current testing. The USB spec allows up to 10µF to be
hard-started, which establishes a 50 µF as the maximum inrush charge value when exceeding 100 mA. The
input current limit for the bq2423x prevents the input current from exceeding this limit, even with system
capacitances greater than 10 µF. Note that the input capacitance to the device must be selected small enough to
prevent a violation (<10 µF), as this current is not limited. Figure 26 demonstrates the startup of the bq2423x and
compares it to the USB-IF specification.
Copyright © 2008, Texas Instruments Incorporated
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