BQ24085_17 Datasheet, PDF (25/42 Pages) Texas Instruments – 750-mA Single-Chip Li-Ion and Li-Pol Charge Management IC With Thermal Regulation

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9 Application and Implementation
bq24085, bq24086, bq24087, bq24088
SLUS784E – DECEMBER 2007 – REVISED DECEMBER 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The bq24085/6/7/8 series are highly integrated Li-Ion and Li-Pol linear chargers, targeted at space-limited
portable applications. The battery is charged in three phases: conditioning, constant or thermally regulated
current, and constant voltage. An internal programmable charge timer provides a backup protection feature for
charge termination and is dynamically adjusted during the thermal regulation phase.
9.2 Typical Applications
The typical application diagrams shown here are configured for 400 mA fast charge current, 40 mA pre-charge
current, 5 hour safety timer and 30 min pre-charge timer.
9.2.1 bq24086 and bq24088 Typical Application
bq24086
bq24088
Input Power
C3
4.7 mF
R1
R2
1.5 kW 1.5 kW
1
R_{TMR 2}
49.9 kW
RED
3
IN
TMR
STAT 1
OUT ¹⁰
BAT ⁹
TS ⁸
GREEN
4 _{STAT 2}
5
Vss
7
PG
ISET ⁶
R ISET
1.13 kW
R8
C2
2.2 mF
Li-Ion or Li-Pol
Battery Pack
Pack+
+
Pack-
RT1
10 kW
TEMP
RT2
33.2 kW
Power
Good
Figure 18. bq24086 and bq24088 Application Schematic
9.2.1.1 Design Requirements
• Supply voltage = 5 V
• Safety timer duration of 5 hours for fast charge
• Fast charge current of approximately 400 mA
• Battery temp sense is not used
9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Selecting Input and Output Capacitor
In most applications, all that is needed is a high-frequency decoupling capacitor on the input power pin. A 1-μF
ceramic capacitor, placed in close proximity to the IN pin and GND pad, works fine. In some applications,
depending on the power supply characteristics and cable length, it may be necessary to increase the input filter
capacitor to avoid exceeding the IN pin maximum voltage rating during adapter hot plug events.
The bq2408x, at low charge currents, requires a small output capacitor for loop stability. A 0.1-μF ceramic
capacitor placed between the BAT and ISET pad is typically sufficient.
Copyright © 2007–2015, Texas Instruments Incorporated
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