L6924D datasheet(18/38 Pages) STMICROELECTRONICS

Part #	L6924D

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

PDF	38 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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18 / 38 page

Applications information: charging process

L6924D

18/38

7.2

Pre-charge current

The L6924D allows pre-charging the battery with a low current when the battery voltage is

lower than a specified threshold (VPRETH). The Pre-charge current has a default value equal to

10% of the fast-charge current (see Chapter 7.2: Pre-charge current on page 18). However it

can be adjusted by connecting a resistor from the IPRE pin to GND or VREF Figure 10. When the

resistor is connected from IPRE pin and GND, the current is higher than the default value. The

RPRE value is given by:

Figure 10. IPRE pin connection

When RPRE is connected to VREF, the current is lower than the default value. VREF is the

external reference equal to 1.8V, VBG is the internal reference equal to 1.23V and KPRE is a

constant equal to 950.Figure 11

The relationship is shown in the equation 8.2:

Figure 11. IPRE pin connection

PRG

PRE

PRECH

PRE

−

Eq: 8-1

L6924D

PRE

L6924D

PRE

PRECH

PRG

REF

PRE

−

Eq: 8-2

REF

L6924D

PRE

REF

L6924D

PRE

L6924D Datasheet(PDF) 18 Page - STMicroelectronics