Datasheet

L6924D Application information: monitoring and protection
Doc ID 11908 Rev 9 27/38
8.2 Battery absence detection
This feature provides a battery absent detection scheme to detect the removal or the
insertion of the battery. If the battery is removed, the charge current falls below the I
ENDTH
.
At the end of the de-glitch time, a detection current I
DETECT
, equal to 1 mA, is sunk from the
output for a time of T
DETECT
. The device checks the voltage at the output. If it is below the
V
PRETH
, a current equal to I
DETECT
is injected in the output capacitor for a T
DETECT
, and it is
checked to see if the voltage on the output goes higher than V
ABS
(the value is V
OPRGTH
-50
mV). If the battery voltage changes from V
PRETH
to V
ABS
and vice versa in a T
DETECT
time,
it means that no battery is connected to the charger. The T
DETECT
is expressed by:
Equation 26
8.3 Status pins
To indicate various charger status conditions, there are two open-collector output pins, ST1
and ST2. These status pins can be used either to drive status LEDs, connected to an
external power source, by a resistor, or to communicate to a host processor. These pins
must never be connected to the V
IN
when it exceeds their absolute value (6 V).
Figure 22. Battery absent detection flow chart
3
1054×
=
MAXCH
DETECT
T
T
BATTERY
ABSENT
Detect Low Absent
V
BAT
>
V
PRETH
FAST CHARGE
Detect High Absent
V
BAT
>
V
RCH
PRE CHARGE
NO
YES
YES
NO
DETECT LOW ABSENT = a I
SINK
is sunk for a T
DET
from the battery
DETECT HIGH ABSENT = a I
INJ
is injected for a T
DET
in the battery
T
DET
= 100ms (Typ.)
I
SINK
= I
INJ
= 1mA (Typ.)