Datasheet

BatteryPack
VBUS
GND
D+
D-
USBPort
DC+
GND
Adaptor
VDD
D-
D+
GND
TTDM
Host
SystemLoad
DisconnectafterDetection
OR
ISET/100/500 mA
1
2
3
4
5
10
9
8
7
6
IN
ISET
VSS
PRETERM
D + D -
ISET 2
CHG
TS
OUT
bq24050/2
1 Fm
1 Fm
1kW
1.5kW
2kW
+
bq24050
bq24052
bq24055
www.ti.com SLUS940B –SEPTEMBER 2009–REVISED JUNE 2012
bq2405x CHARGER APPLICATION DESIGN EXAMPLE
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 © 2009–2012, Texas Instruments Incorporated 27