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| BQ24180_1 Datasheet, PDF (33/41 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and Accessory Power Connection | |||
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bq24180
www.ti.com
SLUSA02 A â FEBRUARY 2010 â REVISED FEBRUARY 2010
LOUT
=
5
´
2.5 ´ (5 - 2.5)
(3 ´ 106 ) ´ 1.25
´
0.3
(4)
LOUT = 1.11 mH
Select the output inductor to standard 1 mH. Calculate the total ripple current with using the 1-mH inductor:
DIL
=
VBAT ´ (VBUS - VBAT)
VBUS ´ f ´ LOUT
(5)
DIL
=
5
´
2.5 ´ (5 -
(3 ´ 106 ) ´
2.5)
(1 ´
10-6 )
(6)
ÎIL = 0.42 A
Calculate the maximum output current:
ILPK
= IOUT
+
DIL
2
(7)
0.42
ILPK = 1.25 + 2
(8)
ILPK = 1.46 A
Select 2.5mm by 2.0mm 1-mH 1.5-A surface mount multi-layer inductor. The suggested inductor part
numbers are shown as following.
Table 4. Inductor Part Numbers
PART NUMBER
INDUCTANCE
SIZE
MANUFACTURER
LQM2HPN1R0MJ0
1 mH
2.5 x 2.0 mm
muRata
MIPS2520D1R0
1 mH
2.5 x 2.0 mm
FDK
MDT2520-CN1R0M
1 mH
2.5 x 2.0 mm
TOKO
CP1008
1 mH
2.5 x 2.0 mm
Inter-Technical
2. Determine the output capacitor value COUT using 40 kHz as the resonant frequency:
1
fo =
2p ´ LOUT ´ COUT
(9)
1
COUT = 4p2 ´ f02 ´ LOUT
(10)
COUT
=
1
4p2 ´ (40 ´ 103 )2 ´ (1 ´ 10-6 )
(11)
COUT = 15.8 mF
Select two 0603 X5R 6.3V 10-mF ceramic capacitors in parallel i.e., muRata GRM188R60J106M.
3. Determine the sense resistor using the following equation:
R(SNS)
=
V(RSNS)
I(CHARGE)
(12)
The maximum sense voltage across sense resistor is 85 mV. In order to get a better current regulation
accuracy, V(RSNS) should equal 100mV, and calculate the value for the sense resistor.
R(SNS)
=
85mV
1.25A
(13)
R(SNS) = 68 mâ¦
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq24180
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