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4. Circuit Description
Constant Current Charging Mode
Once the battery voltage has exceeded the UVLO threshold the charger will switch to the constant
current charging mode. The MT6305 allows 160mV (typically) across the external current sense resistor.
This constant current can be calculated.
If the voltage of Li-ion battery is below 4.2V (5.1V for NiMH battery), the battery will be in the constant
current charging mode.
Constant Voltage Charging Mode
This mode is only applied to Li-ion battery charging. If the battery has reached the final charge voltage, a
constant voltage is applied to the battery and keeps it at 4.2V. The charge termination is determined by
the baseband chip internally, which will pull the CHRCNTL low to stop the charger. Once the battery
voltage exceeds 4.3V of Li-ion battery (5.1V of NiMH battery), a hardware over voltage protection (OV)
should be activated and turn off the charger block of MT6305.
Pulsed Charging Algorithm
MT6305 is available to pulsed top-off charging algorithm by the CHRCNTL pin. The control signal is from
baseband chipset to limit the charging duty cycle. This charging algorithm combines the efficiency of
switch-mode chargers with the simplicity and low cost of linear chargers.
Battery Voltage Monitor
As the Table 2 shown, the relations of battery voltage and charger control signals are listed. When Vbat <
3.2V, an UVLO signal is active low. When Vbat >= 4.3, an OV signal is active and terminates charging.
The disconnection of battery could be detected by BATDET pin. BATDET is pulled high internally when
battery disconnected and terminates charging immediately.
Vbat
CHRON
Any Vbat
Vbat > 3.2V
Vbat < UVLO
3.2V<Vbat<4.2V
ADC5_USB
ADC6_ASS_ID
Notes: OV terminates charging at 4.3V for Li-ion battery or 5.1V for NiMH battery.
LGE Internal Use Only
CHRCNTL
CHRDET
L
X
X
L
H
X
H
H
H
H
H
H
-UVLO
L
X
X
X
L
L
H
H
H
H
H
H
Copyright © 2007 LG Electronics. Inc. All right reserved.
- 38 -
Charger
BATUSE
Condition
X
No-Charging
X
No-Charging
X
Pre-Charging
L
CC mode
L
CV mode
H
CC mode
Only for training and service purposes
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