L6924U datasheet(14/38 Pages) STMICROELECTRONICS

No de pièce	L6924U

Description	USB compatible battery charger system with integrated power switch for Li-Ion/Li-Polymer

PDF	38 Pages

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Fabricant	STMICROELECTRONICS [STMicroelectronics]

Site Internet	http://www.st.com

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14 / 38 page

Operation description

L6924U

14/38

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, 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.

Figure 7.

Typical charge curves in quasi pulse mode

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

Adapter Voltage

Charge Current

Pow er dissipation

Battery Voltage

End

Charge

Voltage Regulation

Phase

Pre-Charge

Phase

Fast-Charge

Phase

LIM

Ilim x Rdson

PRETH

CHG

PRETH

OPRGTH

AD P

MOS

BAT

ADP

∆

L6924U Fiches technique(PDF) 14 Page - STMicroelectronics