BQ24100_08 Datasheet, PDF (27/38 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs (bqSWITCHER™)

bq24100, bq24103, bq24103A
bq24104, bq24105, bq24108, bq24109
bq24113, bq24113A, bq24115
www.ti.com .................................................................................................................................................. SLUS606N – JUNE 2004 – REVISED NOVEMBER 2008
Using bq24105 to Charge the LiFePO₄ Battery
The LiFePO₄ battery has many unique features such as a high thermal runaway temperature, discharge current
capability, and charge current. These special features make it attractive in many applications such as power
tools. The recommended charge voltage is 3.6 V and termination current is 50 mA. Figure 19 shows an
application circuit for charging one cell LiFePO4 using bq24105. The charge voltage is 3.6 V and recharge
voltage is 3.516 V. The fast charging current is set to 1.33 A while the termination current is 50 mA. This circuit
can be easily changed to support two or three cell applications. However, only 84 mV difference between
regulation set point and rechargeable threshold makes it frequently enter into recharge mode when small load
current is applied. This can be solved by lower down the recharge voltage threshold to 200 mV to discharge
more energy from the battery before it enters recharge mode again. See the application report, Using the
bq24105/25 to Charge LiFePO₄ Battery (SLUA443), for additional details. The recharge threshold should be
selected according to real application conditions.
V_IN
C_IN
1.5 KW
10 mF
1.5 KW
Adapter
Present
1.5 KW
Done
Charge
BQ24105
3 IN
OUT 1
4 IN
OUT 20
6 VCC PGND 17
2 STAT1 PGND 18
19 STAT2 SNS 15
L_OUT
10 mH
D1
C_OUT
MMBZ18VALT1
R_SNS
0.1W
10 mF
Battery
Pack
Pack+
Pack-
103AT
C_TTC
0.1 mF
0.1 mF
5 PG
7 TTC
16 CE
10 VSS
13 FB
BAT 14
ISET1 8
7.5 KW R_ISET1
20 KW
ISET2 9
R_ISET2
TS 12
VTSB
9.31 KW RT1
VTSB 11
442 KW RT2 _{0.1 mF}
0.1 mF
143 KW
200 KW
Figure 19. 1-Cell LiFePO4 Application
Copyright © 2004–2008, Texas Instruments Incorporated
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