Datasheet

C
(DELAY)
+
ƪ
t
d
I
CD
ƫ
1.2 V
t
d
+
ƪ
1.2 V C
(DELAY)
ƫ
I
CD
VC1
VC2
VC4
VC3
GND
VDD
OUT
CD
1.2V(TYP)
R
VD
C
VD
I
CD
=0.2 A(TYP)
C
IN
R
IN
R
IN
R
IN
R
IN
C
IN
C
IN
C
IN
C
(DELAY)
Not Recommended for New Designs
bq29410, bq29411, bq29412
bq29413, bq29414
bq29415, bq29419
www.ti.com SLUS669G –AUGUST 2005–REVISED AUGUST 2008
FUNCTIONAL BLOCK DIAGRAM
OVERVOLTAGE PROTECTION
When one of the cell voltages exceeds V
(PROTECT)
, an internal current source begins to charge the capacitor,
C
(DELAY)
, connected to the CD pin. If the voltage at the CD pin, V
CD,
reaches 1.2 V, the OUT pin is activated and
transitions high. An externally connected NCH FET is activiated and blows the external fuse in the positive
battery rail; see the functional block diagram.
If all cell voltages fall below V
(PROTECT)
before the voltage at pin CD reaches 1.2 V, the delay time does not run
out. An internal switch clamps the CD pin to GND and discharges the capacitor, C
(DELAY)
, and secures the full
delay time for the next occurring overvoltage event.
Once the pin OUT is activated, it transitions back from high to low after all battery cells reach V
(PROTECT)
– V
hys.
DELAY TIME CALCULATION
The delay time is calculated as follows:
Where I
(CD)
= CD current source = 0.18 µA
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