L6924U STMicroelectronics, L6924U Datasheet - Page 14

• Manufacturer Part Number: L6924U
• Description: Battery Management USB Battery Charger System w/integra
• Manufacturer: STMicroelectronics

Specifications of L6924U

• Product: Charge Management
• Battery Type: Li-Ion
• Output Voltage: 4.2 V
• Output Current: 30 mA
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Package / Case: VFQFPN
• Mounting Style: SMD/SMT
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Operation description
6.2
14/37
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, the fast charge current must be set
higher than the current limit of the adapter. In this mode, the L6924U charges the battery
with the same three phases as in Linear Mode, but the power dissipation is greatly reduced
as shown in
Figure 7.
The big difference is due to the fact that the charge current 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
V
V
O PRGTH
I
PRETH
V
PRETH
I
I
CHG
ADP
LIM
Pre-Charge
Figure
Typical charge curves in quasi pulse mode
Phase
7.
Doc ID 14716 Rev 2
Fast-Charge
V
IN
Phase
=
V
ADP
Ilim x Rdson
=
V
BAT
+
Δ
V
Voltage Regulation
MOS
Adapter Voltage
Power dissipation
Charge Current
Phase
Battery Voltage
Charge
End
L6924U