L6924UTR datasheet(20/37 Pages) STMICROELECTRONICS

Part #	L6924UTR

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

PDF	37 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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20 / 37 page

Applications information: charging process

L6924U

20/37

Doc ID 14716 Rev 2

7.4

End-of-charge current

When the charge voltage approaches the battery regulated voltage (internally set to 4.2 V),

the voltage regulation phase takes place. The charge current starts to decrease until it goes

below a programmable termination current, IENDTH. This current can be selected by an

external resistor connected between the IEND pin and GND Figure 13, whose value can be

calculated as:

Equation 8

Figure 13.

IEND pin connection

Where KEND is 1050 and VMIN is 50 mV.

When the charge current goes below IENDTH, after a deglitch time, the status pins notify the

end of charge and the charge process ends.

This de-glitch time is expressed as:

Equation 9

where TMAXCH is the maximum charging time. (Chapter 7.7 on page 21)

IEND pin is also used to monitor the charge current, because the current injected in REND is

proportional to the charge current. The voltage across REND can be used by a

microcontroller to check the charge status like a gas gauge.

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

ENDTH

END

MIN

END

220

MAXCH

DEGLITCH

L6924UTR Datasheet(PDF) 20 Page - STMicroelectronics