Datasheet

V
REF
250mV
25mV
+
+
V
REF
Voltage
Reference
1
23 4
5
6
8
9
10
11
12
13
14
1516
7
Q1
Q2
Q3
Q4
Q5
Q6
Q7
Q8
Q9
COMP
VFB
STAT1
IN
DRVE
DRVC
IFBISNSMISNSP
ISNS
GND
CE
D
EXT
0.90V
REF
0.95V
REF
V
IN
V
REF
V
VFB
ChargingState Logic
Q
EXT
External
Supply
R
ISNS
VRLA
Battery
R
A
R
B
R
C
BSTOP
R
D
PRE-CHG
R
T
I
CHG
V
BAT
23 4
5
16
DRVC
IFBISNSMISNSP
IN
R
ISNS2
43 2
5
16
Q
EXT
Q
EXT
DRVC
IFB ISNSMISNSP
IN
Figure8a Figure8b
R
ISNS1
R
ISNS2
R
ISNS1
)
MAX-CHG ILIM ISNS1
TAPER ISNS ISNS1 ISNS2
I = V R
I = V (R + R
¸
¸
MAX-CHG ILIM ISNS1 ISNS2
TAPER ISNS ISNS2
I = V (R + R )
I = V R
¸
¸
bq24450
SLUS929C –APRIL 2009– REVISED FEBRUARY 2012 www.ti.com
Figure 8.
Changing the value of I
TAPER
for a given I
MAX-CHG
In the examples above, I
TAPER
is 10% of I
MAX-CHG
, because V
ILIM
is 250mV and V
ISNS
is 25mV (typical values),
and the same resistor is used for both, the taper comparator and the current-loop amplifier. In most applications,
setting I
TAPER
to 10% of I
MAX-CHG
is perfectly fine. But if, for some reason, a different value of I
TAPER
is required, it
can be achieved, as shown in Figure 9(a) and Figure 9(b).
Figure 9.
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