BQ24100 Datasheet, PDF (14/26 Pages) Texas Instruments – SYNCHRONOUS SWITCHMODE, LI-ION AND LI-POL CHARGE MANAGEMENT IC WITH INTEGRATED POWERFETS

bq24100, bq24103
bq24105, bq24108
bq24113, bq24115
SLUS606C – JUNE 2004 – REVISED SEPTEMBER 2005
FUNCTIONAL DESCRIPTION FOR STAND-ALONE VERSION (bq2410x) (continued)
V_IREG + R_(SNS) I_OCHARGE
The value of R_(ISET1) is then calculated based on the following equation:
R_SET1 +
K_ISET1
I_OCHARGE
V_ISET1
R_SNS
+
1000 V
V_IREG
where
V_IREG is the voltage regulated across R_SNS
I_OCHARGE is the battery charge current
R_SNS is the external current sense resistor
V_(ISET1) is the output voltage of the ISET1 pin
K_(ISET1) is the V/A gain factor (see Electrical Characteristics table)
The following provide a more detailed design procedure and example for this parameter:
www.ti.com
(3)
(4)
1. Select the charge current.
Example:
• I_OCHARGE = 2 A
• I_OPRECHG = 200 mA
2. Select the sense resistor value. Ensure that the power rating of the sense resistor is not exceeded
Example:
• Let V_IREG = 100 mV (S/B from 100–200 mV
• Solve for
R_(SNS)
+
V_IREG
I_OCHARGE
+
100
2
mV
A
+
50
mW
(5)
• Check availability for R_(SNS). Use value that is equal (next larger value if not available).
• Check for power dissiaption
P_(SNS) + R_(SNS) ^ǒI_OCHARGE^Ǔ2 + 0.05 W (2 A)² + 0.2 W
(6)
• Select 0805 or 1206 size rated at 0.25 W
3. Determine R_(ISET1)
• V_(ISET1) = 1 V
• K_(ISET1) = 1000 V/A
R_(ISET1)
+
K_(ISET1)
R_(SNS)
V_{(ISET1) + 1000 VńA}
I_OCHARGE
0.05 W
2
1V
A
+
10
kW
(7)
4. Determine R_(ISET2)
• V_(ISET2) = 0.1 V
• K_(ISET2) = 1000 V/A
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