BQ24100_08 Datasheet, PDF (24/38 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
SLUS606N – JUNE 2004 – REVISED NOVEMBER 2008 .................................................................................................................................................. www.ti.com
2. Determine the output capacitor value (_OUT) using 16 kHz as the resonant frequency:
ƒ_o
+
2p
1
Ǹ_LOUT
C_OUT
C_OUT + _4p2
1
ƒ_o ²
L_OUT
C_OUT + _4p2
(16
1
10³)²
(10
10^*6)
C_OUT + 9.89 mF
(16)
Use standard value 10 µF, 25V, X5R, ±20% ceramic capacitor (i.e., Panasonic 1206 ECJ-3YB1E106M
3. Determine the sense resistor using the following equation:
R_SNS
+
V_RSNS
I_CHARGE
(17)
In order to get better current regulation accuracy (±10%), let V_RSNS be between 100 mV and 200 mV. Use
V_RSNS = 100 mV and calculate the value for the sense resistor.
R_SNS
+
100 mV
1.33 A
R_SNS + 0.075 W
(18)
This value is not standard in resistors. If this happens, then choose the next larger value which in this case is
0.1Ω. Using the same equation (15) the actual V_RSNS will be 133mV. Calculate the power dissipation on the
sense resistor:
P_RSNS + I_CHARGE² R_SNS
P_RSNS + 1.33² 0.1
P_RSNS + 176.9 mW
(19)
Select standard value 100 mΩ, 0.25W 0805, 1206 or 2010 size, high precision sensing resistor. (i.e., Vishay
CRCW1210-0R10F)
4. Determine ISET 1 resistor using the following equation:
R_ISET1
+
K_ISET1
R_SNS
V_ISET1
I_CHARGE
R_ISET1
+
1000
0.1
1.0
1.33
R_ISET1 + 7.5 kW
(20)
Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)
5. Determine ISET 2 resistor using the following equation:
R_ISET2
+
K_ISET2 V_ISET2
R_SNS I_PRECHARGE
R_ISET2 +
1000
0.1
0.1
0.133
R_ISET2 + 7.5 kW
(21)
Select standard value 7.5 kΩ, 1/16W ±1% resistor (i.e., Vishay CRCWD0603-7501-F)
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