BQ24075T Datasheet, PDF (22/29 Pages) Texas Instruments – 1.5A USB-Friendly Li-Ion Battery Charger and Power-Path Management IC

bq24075T
bq24079T
SLUS937 – DECEMBER 2009
www.ti.com
R7
=
V_IN
´
RCOLD
´
RHOT
´
é
ê
1
ë^VCOLD
é
RHOT ´ _ê
V_IN
ù
é
- 1_ú - RCOLD ´ _ê
-
1
ù
ú
V_{HOT û}
V_IN
ù
- 1_ú
ë^VHOT û
ë^VCOLD û
(2)
Where:
V_COLD = 0.25 X V_IN
V_HOT = 0.125 X V_IN
RHOT is the expected thermistor resistance at the programmed hot threshold, RCOLD is the expected thermistor
resistance at the programmed cold threshold. If the value of R6 is less than 100kΩ, R3 must be added to protect
the IC from 28V inputs. If R6 is greater than 100kΩ, R8 does not need to be used.
Adapter
V COLD
+
V_HOT
+
IN
TS ^{R 8}
R61
TEMP
PACK+
Not necessary
in all
applications
R7
PACK-
bq240xT
Figure 30. NTC Monitoring Function
For applications that do not require the TS monitoring function, set R6 = 200kΩ and R7 = 49.9kΩ to set the TS
voltage at a valid level and maintain charging.
APPLICATION INFORMATION
bq2407xT CHARGER DESIGN EXAMPLE
Refer to Typical Application Circuits for Schematics of the Design Example.
Supply voltage = 5V
Fast charge current of approximately 800 mA; ISET – pin 16
Input Current Limit =1.35A; ILIM – pin 12
Safety timer duration, Fast-Charge = 6.25 hours; TMR – pin 14
Battery Temperature Sense = 10kΩ; NTC (103AT-2), 0°C to 50°C Operation
Program the Fast Charge Current (ISET):
22
Submit Documentation Feedback
Product Folder Link(s): bq24075T bq24079T
Copyright © 2009, Texas Instruments Incorporated