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| BQ24075T Datasheet, PDF (12/29 Pages) Texas Instruments – 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC | |||
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bq24075T
bq24079T
SLUS937 â DECEMBER 2009
APPLICATION CIRCUITS
www.ti.com
R4
1.5 kW
R5
1.5 kW
SYSTEM
Adaptor
DC+
GND
R6
10 kW
R7
13.2 kW
C1
1µF
R8
100 kW
TEMP
PACK +
C3
4.7 µF
IN
OUT
VSS
bq24075T EN2
bq24079T
EN1
TS
SYSOFF
CE
BAT
C2
4.7µF
PACK -
R1
R2
R3
46.8 kW
1.18 kW 1.13 kW
HOST
NOTE: VIN = UVLO to VOVP, IFASTCHG = 800mA, IIN(MAX) = 1.35A, Battery Temperature Charge Range = 0°C to 50°C, 6.25
hour Fastcharge Safety Timer
Figure 22. Using the bq24075T/bq24079T to Disconnect the Battery from the System
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 (VIN-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.
12
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Product Folder Link(s): bq24075T bq24079T
Copyright © 2009, Texas Instruments Incorporated
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