Datasheet

Operation description L6924U
12/37 Doc ID 14716 Rev 2
Figure 5. Li-Ion charging profile
6.1 Linear mode
When operating in linear mode, the device works in a way similar to a linear regulator with a
constant current limit protection.
It charges the battery in three phases:
● Pre-charging current ("pre-charge" phase).
● Constant current ("fast-charge" phase).
● Constant voltage ("voltage regulation" phase).
V
ADP
is the output voltage of the upstream AC-DC adapter that is, in turn, the input voltage
of the L6924U. If the battery voltage is lower than the default pre-charge voltage (V
PRETH
),
the pre-charge phase takes place. The battery is pre-charged with a low current, internally
set to 10 % of the fast charge current.
When the battery voltage goes higher than V
PRETH
, the battery is charged with the fast
charge current (I
USB
or I
AC
according to the selection of the MODE pin).
Finally, when the battery voltage is close to the regulated output voltage (4.2 V), the voltage
regulation phase takes place and the charging current is reduced. The charging process
ends when the charging current reaches the programmed value (I
ENDTH
) or when the
charging timer expires.
Figure 6 shows the different phases.
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
0.450
0.500
0 200 400 600 800 1000 1200
Charging time (sec)
Ichg (A)
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
4.500
Vbatt (V)
Ichg
Vbatt