BQ24050 Datasheet, PDF (27/37 Pages) Texas Instruments – 800mA Single Cell Li-Ion Battery Charger With Automatic Adaptor/USB Detection

bq24050
bq24052
bq24055
www.ti.com.................................................................................................................................... SLUS940A – SEPTEMBER 2009 – REVISED SEPTEMBER 2009
bq2405x CHARGER APPLICATION DESIGN EXAMPLE
Adaptor
DC+
GND
bq24050/2
1 _IN
2 _ISET
OUT ¹⁰
1.5kW
TS ⁹
1kW
1mF
3 _VSS
CHG ⁸
OR
4 _{PRETERM ISET 2} 7
Battery Pack
+
System Load
1mF
USB Port
VBUS
GND
D+
D-
5 _D+
2kW
D- ⁶
Disconnect after Detection
VDD
TTDM
ISET/100/500 mA
GND
D+
D-
Host
Requirements
• Supply voltage = 5 V
• Fast charge current: I_OUT-FC = 540 mA; ISET-pin 2
• Termination Current Threshold: %_IOUT-FC = 10% of Fast Charge or 54mA
• Pre-Charge Current by default is twice the termination Current or 108mA
• TS – Battery Temperature Sense = 10k NTC (103AT)
Calculations
Program the Fast Charge Current, ISET:
R_ISET = [K_(ISET) / I_(OUT)]
from electrical characteristics table. . . K_(SET) = 540AΩ
R_ISET = [540AΩ/0.54A] = 1.0 kΩ
Selecting the closest standard value, use a 1kΩ resistor between ISET (pin 16) and V_SS.
Program the Termination Current Threshold, ITERM:
R_PRE-TERM = K_(TERM) × %_IOUT-FC
R_PRE-TERM = 200Ω/% × 10% = 2kΩ
Selecting the closest standard value, use a 2kΩ resistor between ITERM (pin 15) and Vss.
One can arrive at the same value by using 20% for a pre-charge value (factor of 2 difference).
R_PRE-TERM = K_(PRE-CHG) × %_IOUT-FC
R_PRE-TERM = 100Ω/% × 20%= 2kΩ
TS Function
Use a 10k NTC thermistor in the battery pack (103AT).
To Disable the temp sense function, use a fixed 10k resistor between the TS (Pin 1) and V_SS.
CHG and PG
LED Status: connect a 1.5k resistor in series with a LED between the OUT pin and the CHG pin. Connect a 1.5k
resistor in series with a LED between the OUT pin and the and PG pin.
Copyright © 2009, Texas Instruments Incorporated
Submit Documentation Feedback
27
Product Folder Link(s): bq24050 bq24052 bq24055