Datasheet

bq24230
bq24232
www.ti.com SLUS821E –OCTOBER 2008–REVISED JANUARY 2014
APPLICATIONS INFORMATION
bq24232 Charger Design Example
See Figure 18 for the Design Example Schematic.
Requirements
• Supply voltage = 5 V
• Fast-charge current of approximately 200 mA; ISET - pin 16
• Input Current Limit =500 mA; ILIM - pin 12
• Termination Current = 25 mA - pin 15
• Safety timer duration, Fast charge = 6.25 hours; TMR – pin 14
• TS – Battery Temperature Sense = 10 kΩ NTC (103AT-2)
Calculations
Program the Fast-Charge Current (ISET):
R
ISET
= K
ISET
/ I
CHG
K
ISET
= 870 AΩ from the electrical characteristics table.
R
ISET
= 870 AΩ/0.2 A = 4.35kΩ
Select the closest standard value, which for this case is 4.32 kΩ. Connect this resistor between ISET (pin 16)
and V
SS
.
Program the Input Current Limit (ILIM)
R
ILIM
= K
ILIM
/ I
I_MAX
K
ILIM
= 1530 AΩ from the electrical characteristics table.
R
ISET
= 1530 AΩ / 0.5 A = 3.06 kΩ
Select the closest standard value, which for this case is 3.06 kΩ. Connect this resistor between ILIM (pin 12) and
V
SS
.
Program the Termination Current Threshold (ITERM)
R
ITERM
= R
ISET
× I
TERM
/ K
ITERM
K
ITERM
= 0.03 A from electrical characteristics table
R
ITERM
= 4.32 kΩ × 0.025 A/0.03 A = 3.6 kΩ
Select the closest standard value, which for this case is 3.57 kΩ. Connect this resistor between ITERM (pin 15)
and V
SS
Program 6.25-Hour Fast-Charge Safety Timer (TMR)
R
TMR
= t
MAXCHG
/ (10 × K
TMR
)
K
TMR
= 40 s/kΩ from the electrical characteristics table.
R
TMR
= (6.25 hr × 3600 s/hr) / (10 × 40 s/kΩ) = 56.25 kΩ
Select the closest standard value, which for this case is 56.2 kΩ. Connect this resistor between TMR (pin 2) and
V
SS
.
TS Function
Use a 10-kΩ NTC thermistor in the battery pack (103AT). To disable the temperature sense function, use a fixed
10-kΩ resistor between the TS (pin 1) and V
SS
. Pay close attention to the linearity of the chosen NTC so that it
provides the desired hot and cold turnoff thresholds.
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