BQ24630 Datasheet, PDF (20/33 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Lithium Phosphate Battery Charger with System Power Selector and Low Iq

bq24630
SLUS894 – JANUARY 2010
Charge
Current
Charge
Suspended
Programmed
Charge Current
(I_CHARGE)
Charge at I_CHG
Charge
Suspended
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1/8 x Programmed
Charge Current
(I_CHARGE/8)
V_LTF V_COOL
V_WARM V_HTF/V_TCO ^Temperature
Figure 19. Typical Charge Current vs Temperature Profile
Assuming a 103AT NTC thermistor on the battery pack as shown in the Typical System Schematic, the value
RT1 and RT2 can be determined by using Equation 7 and Equation 8:
RT2 =
V_VREF
´
RTH_COOL
´
RTH_WARM
´
æ₁
ç
è ^VCOOL
-
1^ö
÷
V_{WARM ø}
RTH_WARM
´
æ
ç
è
V_VREF
V_{W ARM}
-
ö
1_÷
-
RTH_COOL
ø
´
æ
ç
V_VREF
ö
- 1_÷
è ^VCOOL ø
(7)
RT1 =
V_VREF
V_COOL
-1
1
1
+
RT2 RTH_COOL
(8)
VREF
bq24630
TS
RT1
RT2
RTH
103 AT
Figure 20. TS Resistor Network
20
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