Datasheet

V
(APG)
+ V
CC
R2
(R1 ) R2)
where V
(APG)
is the voltage at the APG/THM pin.
bq24005PWP
RT1 +
V
B
V
C
* 1
1
RT2
)
1
R
C
RT2 +
V
B
R
H
R
C
ƪ
1
V
C
*
1
V
H
ƫ
R
H
ǒ
V
B
V
H
* 1
Ǔ
* R
C
ǒ
V
B
V
C
* 1
Ǔ
bq24004
bq24005
bq24006
SLUS476F –DECEMBER 2000–REVISED MAY 2012 www.ti.com
If the charger designs incorporate a thermistor, the
resistor divider RT1 and RT2 is calculated by using
the following two equations.
First, calculate RT2.
then use the resistor value to find RT1.
Where:
V
B
= V
CR
(bias voltage)
R
H
= Resistance of the thermistor at the desired
hot trip threshold
R
C
= Resistance of the thermistor at the desired
Figure 18. APG Sensing Circuit
cold trip threshold
V
H
= VP2 or the lower APG trip threshold
Values of resistors R1 and R2 can be calculated
V
C
= VP2 or the upper APG trip threshold
using the following equation:
RT1 = Top resistor in the divider string
RT2 = Bottom resistor in the divider string
Current Regulation
The bq2400x provides current regulation while the
battery-pack voltage is less than the regulation
voltage. The current regulation loop effectively
amplifies the error between a reference signal, Vilim,
and the drop across the external sense resistor,
R
SNS
.
Figure 17. Temperature Threshold
14 Submit Documentation Feedback Copyright © 2000–2012, Texas Instruments Incorporated
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