BQ24100_10 Datasheet, PDF (23/40 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POLYMER CHARGE-MANAGEMENT IC WITH INTEGRATED POWER FETs ( bqSWITCHER™)

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bq24100, bq24103, bq24103A
bq24104, bq24105, bq24108, bq24109
bq24113, bq24113A, bq24115
SLUS606O – JUNE 2004 – REVISED MARCH 2010
bqSWITCHER SYSTEM DESIGN EXAMPLE
The following section provides a detailed system design example for the bq24100.
System Design Specifications:
• V_IN = 16V
• V_BAT = 4.2V (1-Cell)
• I_CHARGE = 1.33 A
• I_PRECHARGE = I_TERM = 133 mA
• Safety Timer = 5 hours
• Inductor Ripple Current = 30% of Fast Charge Current
• Initiate Charge Temperature = 0°C to 45°C
1. Determine the inductor value (L_OUT) for the specified charge current ripple:
DI_L + I_CHARGE I_CHARGERipple
L_OUT
+
V_BAT ^ǒV_INMAX
V_INMAX ƒ
* V_BAT^Ǔ
DI_L
L_OUT + ₁₆
4.2 (16 * 4.2)
(1.1 10⁶) (1.33
0.3)
L_OUT + 7.06 mH
(13)
Set the output inductor to standard 10 mH. Calculate the total ripple current with using the 10 mH inductor:
DI_L
+
V_BAT ^ǒV_INMAX
V_INMAX ƒ
* V_BAT^Ǔ
L_OUT
DI_L + ₁₆
4.2 (16 * 4.2)
(1.1 10⁶) (10 10^*6)
DI_L + 0.282 A
(14)
Calculate the maximum output current (peak current):
I
LPK
+
I_OUT
)
DI_L
2
I_LPK
+
1.33
)
0.282
2
I_LPK + 1.471 A
(15)
Use standard 10 mH inductor with a saturation current higher than 1.471A. (i.e., Sumida CDRH74-100)
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Product Folder Link(s): bq24100 bq24103 bq24103A bq24104 bq24105 bq24108 bq24109 bq24113 bq24113A
bq24115