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| BQ24140_14 Datasheet, PDF (34/39 Pages) Texas Instruments – Integrated Dual-Input Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and USB-OTG Support | |||
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bq24140
SLUSAO5 â OCTOBER 2011
www.ti.com
Table 4. 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 (COUT) using 40 kHz as the resonant frequency:
1
fo =
2p ´ LOUT ´ COUT
(9)
COUT
=
1
4p2 ´ f02 ´ LOUT
(10)
COUT
=
1
4p2 ´ (40 ´ 103 )2 ´ (1 ´ 10-6 )
(11)
COUT = 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)
(12)
The maximum sense voltage across the 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.
85mV
R(SNS) = 1.25A
(13)
R(SNS) = 68 mâ¦
This is a standard value. If it is not a standard value, then choose the next close value and calculate the real
charge current. Calculate the power dissipation on the sense resistor:
P(RSNS) = I(CHARGE) 2 Ã R(SNS)
P(RSNS) = 1.252 Ã 0.068
P(RSNS) = 0.106 W
Select 0402 0.125-W 68-m⦠2% sense resistor, i.e. Panasonic ERJ2BWGR068.
34
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