Datasheet

Operation description L6924D
14/38 Doc ID 11908 Rev 9
6.2 Quasi-pulse mode
The quasi-pulse mode can be used when the system can rely on the current limit of the
upstream adapter to charge the battery. In this case, I
CHG
must be set higher than the
current limit of the adapter. In this mode, the L6924D charges the battery with the same
three phases as in linear mode, but the power dissipation is greatly reduced as shown in
Figure 7.
Figure 7. Typical charge curves in quasi pulse mode
The big difference is due to the fact that I
CHG
is higher than the current limit of the adapter.
During the fast-charge phase, the output voltage of the adapter drops and goes down to the
battery voltage plus the voltage drop across the power MOSFET of the charger, as shown in
the following equation:
Equation 2
Where ΔV
MOS
is given by:
Equation 3
Adapter Voltage
Charge Current
Power dissipation
Battery Voltage
End
Charge
Voltage Regulation
Phase
Pre-Charge
Phase
Fast-Charge
Phase
I
LIM
Ilim x Rdson
I
PRETH
I
CHG
V
PRETH
V
OPRGTH
V
ADP
MOSBATADPIN
VVVV
Δ
+
=
=
IR
V
LIMONDS
MOS
×=
Δ
)(