L6924D_07 datasheet(15/38 Pages) STMICROELECTRONICS

Part #	L6924D

Description	Battery charger system with integrated power switch for Li-ION/Li-POLYMER

PDF	38 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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15 / 38 page

L6924D

Operation description

15/38

The big difference is due to the fact that ICHG 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:

Where

∆V

MOS is given by:

Where,

ILIM = current limit of the wall adapter, and RDS(on) = resistance of the power MOSFET.

The difference between the set charge current and the adapter limit should be high enough to

minimize the RDS(on) value (and the power dissipation). This makes the control loop completely

unbalanced and the power element is fully turned on.

Figure 8 shows the RDS(on) values for different output voltage and charging currents for an

adapter current limit of 500mA.

Figure 8.

rDS(on) curves vs charging current and output voltage

MOS

BAT

ADP

∆

Eq. 7-2

LIM

MOS

∆

)

(

Eq. 7-3

L6924D Datasheet(PDF) 15 Page - STMicroelectronics