Usb Charging Circuit - LG KE820 Service Manual

3.15. USB charging circuit

The USB charging circuit is a fully integrated USB VBUS voltage single-cell Li-ion battery charger
circuit.
The charger uses a CC/CV charge profile required by Li-ion batteries. CC charging current and End of
charging current is programmable I
I resistor between this pin and the GND pin to set the charge current limit determined by the
REF
following equation:
I = 12089/39K = 310mA
CC
The End Of Charging current is set by IMIN That can be programmed by the as following equation:
I = 11000/220K = 50mA
EOC
U108
C168
0.1u
5 COM
R178
CHG_LED_CTRL
1K
Charging indicator LED LD100 controlled by S-GOLD2's GPIO that is CHG_LED_CTRL. When
TA(Travel Adaptor) is plugged in to 18pin MMI connector, SM-POWER detect charger voltage then
inform charger detecting to S-GOLD2. S-GOLD2 maintain low level of CHG_LED_CTRL until get
EOC(End Of Charging) message from SM-POWER. The LD100 controlled by S-GOLD2 both power
off and power on case. When USB cable is connected via MMI connector, indicator LED is controlled
same mechanism with TA inserted case. USB charging EOC is not indicated when the terminal is in off
status. LED just indicates charging status even though USB charging process reached EOC because
S_GOLD2 is in off status.
& I resistors.
REF MIN
VCHG VBUS_USB
D1 KDS121E
2
3
1
VBUS_USB
NO 6 R184 47
NC 4 R131 330
NLAST4599DFT2G
LD100
R180
100K
SML-521MUWT86
Figure 27 USB charging circuit
- 53 -
3. TECHNICAL BRIEF
2V72_IO
R177
10K
U104
1
VIN
2
_PPR
3
_USB_EOC _CHG
4
_EN
9
PGND
C140
0.1u
VBAT
ISL6294
8
BAT
7
IREF
6
IMIN
5
GND
R141 R142 C141
220K 39K 0.1u