Datasheet

L6924U Application information: monitoring and protection
Doc ID 14716 Rev 2 27/37
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
RCH
(4.05 V). If the battery
voltage changes from V
PRETH
to V
RCH
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 24
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 with an
external power source, by a resistor, or to communicate to a host processor.
Figure 20. Battery absence 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.)