Datasheet

Operation description L6924D
12/38 Doc ID 11908 Rev 9
When the V
PRE
pin is not used to program the Pre-Charge voltage threshold, it has two
different functions:
● If the voltage across V
PRE
pin is lower than 0.8 V, when I < I
ENDTH
, the end of charge is
notified by the status pin, but the charging process is not disabled. The charge process
ends when the maximum charging time expires.
● If the voltage at V
PRE
pin false under 0.5 V the timer is reset on the falling edge.
Battery disconnection control is provided thanks to the differentiated sensing and forcing
output pins. A small current is sunk and forced through V
OUT
. If V
OSNS
doesn’t detect the
battery, the IC goes into a standby mode.
Figure 5 shows the real charging profile of a Li-Ion battery, with a fast charge current of 450
mA (R
PRG
= 26 kΩ),
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 L6924D. If the battery voltage is lower than a set pre-charge voltage (V
PRETH
), the
pre-charge phase takes place. The battery is pre-charged with a low current I
PRE
(Chapter 7.2 on page 17).
When the battery voltage goes higher than V
PRETH
, the battery is charged with the fast
charge current I
CHG
, set through an external resistor (Chapter 7.4 on page 18).
Finally, when the battery voltage is close to the regulated output voltage V
OPRGTH
(4.1 V or
4.2 V), the voltage regulation phase takes place and the charging current is reduced. The
Charging profile
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
Vb att