EUP9261
Description of Operation
Normal condition
Overcharge condition
When the battery voltage becomes higher than the
overcharge detection voltage (VCU) during charging
under the normal condition and the detection
continues for the overcharge detection delay time (tCU)
or longer, the EUP9261 turns the charging control
FET off to stop charging. This condition is called the
overcharge condition. The overcharge condition is
released by the following two cases ((1) and (2)):
(1) When the battery voltage falls below the
overcharge release voltage, which is equal to the
overcharge detection voltage (VCU) overcharge
detection hysteresis voltage (VHC), the EUP9261 turns
the charging control FET on and turns to the normal
condition.
The EUP9261 monitors the voltage of the battery
connected between VDD and VSS pin and the voltage
difference between VM and VSS pin to control charging
and discharging. When the battery voltage is in the
range from the overdischarge detection voltage (VDL) to
the overcharge detection voltage (VCU), and the VM pin
voltage is in the range from the charger detection
voltage (VCHA) to the overcurrent 1 detection voltage
(VIOV1), the IC turns both the charging and discharging
control FETs on. This condition is called the normal
condition, and in this condition charging and
discharging can be carried out freely.
Note: When a battery is connected to the IC for the first
time, the battery may not enter dischargeable state. In
this case, set the VM pin voltage equal to the VSS
voltage or connect a charger to enter the normal
condition.
(2) When a load is connected and discharging starts,
the EUP9261 turns the charging control FET on and
returns to the normal condition. Just after the load is
connected and discharging starts, the discharging
current flows through the parasitic diode in the
charging control FET. At this moment the VM pin
potential becomes Vf -volt, the voltage for the parasitic
diode, higher than VSS level. When the battery
voltage goes under the overcharge detection voltage
(VCU) and provided that the VM pin voltage is higher
Overcurrent condition (Detection of Overcurrent 1,
Overcurrent 2 and Load short-circuiting)
When the condition in which VM pin voltage is equal to
or higher than the overcurrent detection voltage,
condition that caused by the excess of discharging
current over a specified value, continues longer than
the overcharge detection delay time in a battery under
the normal condition, the EUP9261 turns the
discharging control FET off to stop discharging. This
condition is called the overcurrent condition. Though
the VM and VSS pins are shorted by the RVMS resistor
in the IC under the overcurrent condition, the VM pin
voltage is pulled to the VDD level by the load as long
as the load is connected. The VM pin voltage returns to
VSS level when the load is released. The overcurrent
condition returns to the normal condition when the
impedance between the EB+ and EB- pin (see Figure 2)
becomes higher than the automatic recoverable
impedance, and the IC detects that the VM pin
potential is lower than the overcurrent 1 detection
voltage (VIOV1).
than the overcurrent
1
detection voltage, the
EUP9261 releases the overcharge condition.
Note1:
If the battery is charged to a voltage higher than the
overcharge detection voltage (VCU) and the battery
voltage does not fall below the overcharge detection
voltage (VCU) even when a heavy load is connected,
the detection of overcurrent 1, overcurrent 2 and load
short-circuiting does not work. Since an actual battery
has the internal impedance of several dozens of mΩ,
the battery voltage drops immediately after a heavy
load which causes overcurrent is connected, and the
detection of overcurrent 1, overcurrent 2 and load
short-circuiting then works.
Note2:
Note: The automatic recoverable impedance changes
depending on the battery voltage and overcurrent 1
detection voltage settings.
When a charger is connected after the overcharge
detection, the overcharge condition is not released
even if the battery voltage is below the overcharge
release voltage (VCL (＝Vcu －VHC)). The overcharge
condition is released when the VM pin voltage goes
over the charger detection voltage (VCHA) by removing
the charger.
DS9261 Ver2.4 Jan. 2007
17
EUTECH [ EUTECH MICROELECTRONICS INC ]
