Chargind Ic - LG MG300d Service Manual

3. TECHNICAL BRIEF
3.6 Chargind IC (ISL6299, U704)
CUR_MON
(ABB AUX2)
CHG_EN
(GPIO0)
The ISL6299 is designed for a single-cell Li-ion or Li-polymer battery charging circuit that accepts both
a USB port and a desktop cradle as its power source.
Input Auto Selection
When both input sources are present, the charger selects only one power source to charge the
battery. When the CRDL input is higher than the POR threshold, CRDL is selected as the power
source. Otherwise the USB input is selected. If the CRDL input voltage is below the battery voltage but
the USB input voltage is higher than the battery voltage, then the USB input is used to charge the
battery. The control circuit always breaks both internal power devices before switching from one power
source to the other to avoid a cross conduction of both power MOSFETs.
USB Charge Current
When the USB port is selected as the power source, the charge current enabled by the logic input at
the USBON pin. When the USBON is driven to logic LOW, the charger is disabled. When the USBON
is driven to logic HIGH, the charge current is fixed at a typical value of 380mA. Thus for the USB input,
the USBON pin has a similar function as the EN pin. The following table describes the USB charge
control by both the USBON pin and EN pin The USBON pin is equivalent to a logic LOW when left
floating. Typically the P-channel MOSFET for the USB input has an rDS(ON) of 700mΩ at room
temperature. With a 380mA charge current, the typical head room is 260mV. Thus, if the input voltage
drops to a level that the voltage difference between the USB pin and the BAT pin is less than 260mV,
the rDS(ON) becomes a limiting factor of the charge current; and the charger drops out the constant
current regulation.
VUSBIN VCHARGE
D700
CUS02
C731 R723 R724
NA NA 10K
R728 R731 C738 C739
36K 10K 1u 1u
Figure 3-15. CIRCUIT FOR BATTERY CHARGING
- 46 -
Charging IC
VBAT 2V8_VEXT
U704 ISL6299
1 10
CRDL BAT
R722
2
USB
100K
6 3
IMIN _PPR
4
_CHG
9
ICDL
7 8
USBON GND
5 11
_EN PGND
R729 C740
100K 1u
CHG_STAT
(GPIO1)