EUP9232
Description of Operation
Normal Condition *1
The overcharge condition is release in two cases:
This IC monitors the voltages of the two serially
connected batteries and the discharge current to
control charging and discharging. When the
voltages of two batteries are in the range from the
overdischarge detection voltage (VDD1,2) to the
overcharge detection voltage (VCU1,2), and the
current flowing through the batteries becomes
equal or lower than a specified value (the VM pin
voltage is equal or lower than overcurrent
detection voltage 1) , the charging and discharging
FETs are turned on. In this condition, charging and
discharging can be carried out freely. This
condition is called normal condition.
(1)The battery voltage which exceeded the
overcharge detection voltage (VCU1,2) falls below
the overcharge release voltage (VCD1, 2), the
charging FET turns on and the normal condition
returns.
(2)If the battery voltage which exceeded the
overcharge detection voltage (VCU1, 2) is equal or
higher than the overcharge release voltage
(VCD1,2), but the charger is removed, a load is
placed, and discharging starts, the charging FET
turns on and the normal condition returns.
The release mechanism is as follows: the discharge
current flows through an internal parasitic diode of
the charging FET immediately after a load is
installed and discharging starts, and the VM pin
voltage increases by about 0.6 V from the VSS pin
voltage momentarily. The IC detects this voltage
(overcurrent detection voltage 1 or higher), releases
the overcharge condition and returns to the normal
condition.
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) during discharging under normal condition
and it continues for the overcurrent detection delay
time (tIOV) or longer, the discharging FET is turned
off to stop discharging. This condition is called
overcurrent condition. When the discharging FET is
off and a load is connected, the VM pin voltage
equals the VCC potential.
The overcurrent condition returns to the normal
condition when the load is released and the
impedance between the EB- and EB+ pins (refer to
the Figure 2 for a connection example) is 400 kΩor
higher. When the load is released, the VM pin, which
is shorted to the VSS pin with the Rvsm resistor,
goes back to the VSS potential. The IC detects that
the VM pin potential returns to overcurrent detection
voltage 1 (VIOV1) or lower and returns to the normal
condition.
Overdischarge Condition
If any one of the battery voltages falls below the
overdischarge detection voltage (VDD1,2) during
discharging under normal condition and it continues
for the overdischarge detection delay time (tDD1, 2) or
longer, the discharging FET turns off and
discharging stops. This condition is called the
overdischarge condition. When the discharging FET
turns off, the VM pin voltage becomes equal to the
VCC voltage and the IC’s current consumption falls
below the power-down current consumption (IPDN).
This condition is called the power-down condition.
The VM and VCC pins are shorted by the Rvcm
resistor under the overdischarge and power-down
conditions.
The power-down condition is canceled when the
charger is connected and the voltage between VM
and VCC is overcurrent detection voltage 2 or
higher. When all the battery voltages becomes
equal to or higher than the overdischarge release
voltage (VDU1,2) in this condition, the overdischarge
condition changes to the normal condition.
Overcharge Condition
Following two cases are detected as overcharge
conditions:
(1) If one of the battery voltages becomes higher
than the overcharge detection voltage (VCU1,2
)
during charging under normal condition and it
continues for the overcharge detection delay time
(tCU1,2) or longer, the charging FET turns off to
stop charging.
(2) If one of the battery voltages becomes higher
than the auxiliary overcharge detection voltage
(VCUaux1, 2) the charging FET turns off immediately
to stop charging.
The auxiliary overcharge detection voltages
(VCUaux1,2) are correlated with the overcharge
detection voltages (VCU1,2) and are defined by
following equation:
VCUaux1,2 [V]=1.25×VCU1,2
DS9232 Ver1.1 Feb. 2007
16
EUTECH [ EUTECH MICROELECTRONICS INC ]
