BQ24150A Datasheet, PDF (33/41 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger With Full USB Compliance and USB-OTG Support

bq24150A
bq24151A
www.ti.com ..................................................................................................................................................................................................... SLUS931 – APRIL 2009
L_OUT
=
VBAT ´ (VBUS - VBAT)
VBUS ´ f ´ DI_L
, the worst case is when battery voltage is as close as to half of the input
voltage.
L_OUT
=
5
´
(3
2.5 ´ (5 - 2.5)
´ 10⁶ ) ´ 1.25
´
0.3
L_OUT = 1.11 µH
Select the output inductor to standard 1 µH. Calculate the total ripple current with using the 1-µH inductor:
DI_L
=
VBAT ´ (VBUS - VBAT)
VBUS ´ f ´ L_OUT
DI_L
=
5
´
2.5 ´ (5 -
(3 ´ 106 ) ´
2.5)
(1 ´
10^-6 )
ΔI_L = 0.42 A
Calculate the maximum output current:
I_LPK
= I_OUT
+
DI_L
2
0.42
I_LPK = 1.25 + ₂
I_LPK = 1.46 A
Select 2.5mm by 2.0mm 1-µH 1.5-A surface mount multi-layer inductor. The suggested inductor part
numbers are shown as following.
Table 12. Inductor Part Numbers
PART NUMBER
INDUCTANCE
SIZE
MANUFACTURER
LQM2HPN1R0MJ0
1 µH
2.5 x 2.0 mm
muRata
MIPS2520D1R0
1 µH
2.5 x 2.0 mm
FDK
MDT2520-CN1R0M
1 µH
2.5 x 2.0 mm
TOKO
CP1008
1 µH
2.5 x 2.0 mm
Inter-Technical
2. Determine the output capacitor value C_OUT using 40 kHz as the resonant frequency:
1
f_o =
2p ´ L_OUT ´ C_OUT
1
C_OUT = _{4p2 ´ f02 ´ LOUT}
C_OUT
=
1
4p² ´ (40 ´ 10³ )² ´ (1 ´ 10^-6 )
C_OUT = 15.8 µF
Select two 0603 X5R 6.3V 10-µF ceramic capacitors in parallel i.e., muRata GRM188R60J106M.
3. Determine the sense resistor using the following equation:
R_(SNS)
=
V_(RSNS)
I_(CHARGE)
The maximum sense voltage across sense resistor is 85 mV. In order to get a better current regulation
accuracy, V_(RSNS) should equal 85mV, and calculate the value for the sense resistor.
Copyright © 2009, Texas Instruments Incorporated
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