BQ24072T_1 Datasheet, PDF (15/34 Pages) Texas Instruments – 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC

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bq24072T
bq24075T, bq24079T
SLUS937A – DECEMBER 2009 – REVISED APRIL 2010
R4
1.5 kW
R5
1.5 kW
SYSTEM
Adaptor
DC+
GND
R6
10 kW
R7
13.2 kW
C1
1 mF
R8
100 kW
TEMP
PACK+
C3
4.7 mF
IN
OUT
VSS
bq24072T
EN2
EN1
TS
TD
CE
BAT
C2
4.7 mF
PACK-
R1
46.4 kW
R2
1.18 kW
R3
1.13 kW
HOST
Figure 26. Using bq24072T in a Host Controlled Charger Application
DETAILED FUNCTIONAL DESCRIPTION
The bq2407x devices are integrated Li-Ion linear chargers and system power path management devices targeted
at space-limited portable applications. The device powers the system while simultaneously and independently
charging the battery. This feature reduces the number of charge and discharge cycles on the battery, allows for
proper charge termination and enables the system to run with a defective or absent battery pack. It also allows
instant system turn-on even with a totally discharged battery. The input power source for charging the battery
and running the system can be an AC adapter or a USB port. The devices feature Dynamic Power Path
Management (DPPM), which shares the source current between the system and battery charging, and
automatically reduces the charging current if the system load increases. When charging from a USB port, the
input dynamic power management (V_IN-DPM) circuit reduces the input current if the input voltage falls below a
threshold, preventing the USB port from crashing. The power-path architecture also permits the battery to
supplement the system current requirements when the adapter cannot deliver the peak system currents.
UNDERVOLTAGE LOCKOUT (UVLO)
The bq2407X family remains in power down mode when the input voltage at the IN pin is below the undervoltage
threshold (UVLO). During the power down mode the host commands at the control inputs (CE, EN1 and EN2)
are ignored. The Q1 FET connected between IN and OUT pins is off, and the status outputs, CHG and PGOOD,
are high impedance. The Q2 FET that connects BAT to OUT is ON. (If SYSOFF is high, Q2 is off). During power
down mode, the VOUT(SC2) circuitry is active and monitors for overload conditions on OUT.
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