______________________________________ ____________________________________________________ ________ _________ ____________
XB3303G
mS
mS
mS
uS
过充检测延时
过放检测延时
过流检测延时
短路检测延时
t
CU
t
DL
t
IOV
t
SHORT
V
DD
=3.6V
V
DD
=3.6V
130
40
10
75
Figure 3. Functional Block Diagram
FUNCTIONAL DESCRIPTION
The XB3303G monitors the voltage and
current of a battery and protects it from
being damaged due to overcharge voltage,
overdischarge voltage, overdischarge
current, and short circuit conditions by
disconnecting the battery from the load
or charger. These functions are required in
order to operate the battery cell within
specified limits.
The device requires only one external
capacitor. The MOSFET is integrated and
its R
SS(ON)
is as low as 56mΩ typical.
-4-
REV0.1
Normal operating mode
If no exception condition is detected,
charging and discharging can be carried
out freely. This condition is called the
normal operating mode.
Overcharge Condition
When the battery voltage becomes higher
than the overcharge detection voltage (V
CU
)
during charging under normal condition
and the state continues for the overcharge
detection delay time (t
CU
) or longer, the
XB3303G turns the charging control FET
off to stop charging. This condition is called
______________________________________ ____________________________________________________ ________ _________ ____________
XB3303G
the overcharge condition. The overcharge
condition is released in the following two
cases:
1, When the battery voltage drops below
the overcharge release voltage (V
CL
), the
XB3303G turns the charging control FET
on and returns to the normal condition.
2, When a load is connected and
discharging starts, the XB3303G turns the
charging control FET on and returns to the
normal condition. The release mechanism
is as follows: the discharging current flows
through an internal parasitic diode of the
charging FET immediately after a load is
connected and discharging starts, and the
VM pin voltage increases about 0.7 V
(forward voltage of the diode) from the
GND pin voltage momentarily. The
XB3303G detects this voltage and releases
the overcharge condition. Consequently, in
the case that the battery voltage is equal to
or lower than the overcharge detection
voltage (V
CU
), the XB3303returns to the
normal condition immediately, but in the
case the battery voltage is higher than the
overcharge detection voltage (V
CU
),the chip
does not return to the normal condition
until the battery voltage drops below the
overcharge detection voltage (V
CU
) even if
the load is connected. In addition, if the VM
pin voltage is equal to or lower than the
overcurrent 1 detection voltage when a
load is connected and discharging starts,
the chip does not return to the normal
condition.
Remark
If the battery is charged to a voltage higher
than the overcharge detection voltage (V
CU
) and
the battery voltage does not drops below the
overcharge detection voltage (V
CU
) even when a
heavy load, which causes an overcurrent, is
connected, the overcurrent 1 and overcurrent 2 do
not work until the battery voltage drops below the
overcharge detection voltage (V
CU
). Since an actual
battery has, however, an internal impedance of
several dozens of mΩ, and the battery voltage
drops immediately after a heavy load which causes
an overcurrent is connected, the overcurrent 1 and
overcurrent 2 work. Detection of load short-
circuiting works regardless of the battery voltage.
Overdischarge Condition
When the battery voltage drops below the
overdischarge detection voltage (V
DL
)
during discharging under normal condition
and it continues for the overdischarge
detection delay time (t
DL
) or longer, the
XB3303G turns the discharging control
FET off and stops discharging. This
condition is called overdischarge condition.
After the discharging control FET is turned
off, the VM pin is pulled up by the
R
VMD
resistor
between VM and VDD in XB3303G.
Meanwhile when VM is bigger than 1.5
V (typ.) (the load short-circuiting detection
voltage), the current of the chip is reduced
to the power-down current (
I
PDN
). This
condition is called power-down condition.
The VM and VDD pins are shorted by the
R
VMD
resistor in the IC under the
overdischarge and power-down conditions.
The power-down condition is released
when a charger is connected and the
potential difference between VM and VDD
becomes 1.3 V (typ.) or higher (load short-
circuiting detection voltage). At this time,
the FET is still off. When the battery
voltage becomes the overdischarge
detection voltage (V
DL
) or higher (see note),
the XB3303G turns the FET on and
changes to the normal condition from the
overdischarge condition.
Remark
If the VM pin voltage is no less than the
charger detection voltage (V
CHA
), when the battery
under overdischarge condition is connected to a
charger, the overdischarge condition is released
(the discharging control FET is turned on) as usual,
provided that the battery voltage reaches the
overdischarge release voltage (V
DU
) or higher.
Overcurrent Condition
When the discharging current becomes
equal to or higher than a specified value
(the VM pin voltage is equal to or higher
than the overcurrent detection voltage)
-5-
REV0.1
工业自动化与控制
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
