L6924D datasheet(22/38 Pages) STMICROELECTRONICS

部品番号	L6924D

部品情報	Battery charger system with integrated power switch for Li-ION/Li-POLYMER

PDF	38 Pages

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メーカー	STMICROELECTRONICS [STMicroelectronics]

ホームページ	http://www.st.com

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22 / 38 page

Applications information: charging process

L6924D

22/38

7.8

Maximum charging time

To avoid the charging of a dead battery for a long time, the L6924D has the possibility can be

set a maximum charging time starting from the beginning of the Fast-Charge Phase. This timer

can be set with a capacitor, connected between the TPRG pin and GND. The CTPRG is the

external capacitor (in nF) and is given by the following formula:

Note:

The maximum recommended CTPRG value must be less than 50 nF.

Figure 16. TPRG pin connection

Where,

VREF = 1.8V,

KT = 279 x 10

VBG = 1.23V, and

TMAXCH is the charging time given in seconds.

If the battery does not reach the End-of-Charge condition before the time expires, a fault is

issued.

Also during the Pre-Charge Phase there is a safety timer, given by:

If this timer expires and the battery voltage is still lower than VPRETH, a fault signal is generated,

and the charge process is terminated.

⎟

⎠

⎞

⎜

⎝

⎛

REF

PRG

MAXCH

TPRG

Eq: 8-6

TPRG

L6924D

CTPRG

MAXCH

MAXPRECH

Eq: 8-7

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