S-8233B Datasheet, PDF (13/26 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC (FOR A 3-SERIAL-CELL PACK)

Rev.4.2_00
BATTERY PROTECTION IC FOR 3-SERIAl-CELL PACK
S-8233B Series
„ Operation
Remark Refer to “Battery Protection IC Connection Example”.
Normal condition
This IC monitors the voltages of the three serially-connected batteries and the discharge current to control
charging and discharging. If the voltages of all the three batteries are in the range from the over
discharge detection voltage (V_DD) to the over charge detection voltage (V_CU), and the current flowing
through the batteries becomes equal or lower than a specified value (the VMP terminal voltage is equal or
lower than over current detection voltage 1), the charging and discharging FETs turn on. In this condition,
charging and discharging can be carried out freely. This condition is called the normal condition. In this
condition, the VMP and VCC terminals are shorted by the R_VCM resistor.
Over current condition
This IC is provided with the three over current detection levels (V_IOV1,V_IOV2 and V_IOV3) and the three over
current detection delay time (t_IOV1,t_IOV2 and t_IOV3) corresponding to each over current detection level.
If the discharging current becomes equal to or higher than a specified value (the VMP terminal voltage is
equal to or higher than the over current detection voltage) during discharging under normal condition and
it continues for the over current detection delay time (t_IOV) or longer, the discharging FET turns off to stop
discharging. This condition is called an over current condition. The VMP and VCC terminals are shorted
by the R_VCM resistor at this time. The charging FET turns off.
When the discharging FET is off and a load is connected, the VMP terminal voltage equals the V_SS
potential.
The over current condition returns to the normal condition when the load is released and the impedance
between the EB- and EB+ terminals (see Figure 9 for a connection example) is 100 MΩ or higher. When
the load is released, the VMP terminal, which and the VCC terminal are shorted with the R_VCM resistor,
goes back to the V_CC potential. The IC detects that the VMP terminal potential returns to over current
detection voltage 1 (V_IOV1) or lower (or the over current detection voltage 2 (V_IOV2) or lower if the COVT
terminal is fixed at the 'L' level and over current detection 1 is inhibited) and returns to the normal
condition.
Over charge condition
If one of the battery voltages becomes higher than the over charge detection voltage (V_CU) during
charging under normal condition and it continues for the over charge detection delay time (t_CU) or longer,
the charging FET turns off to stop charging. This condition is called the over charge condition. The 'H'
level signal is output to the conditioning terminal corresponding to the battery which exceeds the over
charge detection voltage until the battery becomes equal to lower than the over charge release voltage
(V_CD). The battery can be discharged by connecting an Nch FET externally. The discharging current can
be limited by inserting R11, R12 and R13 resistors (see Figure 9 for a connection example). The VMP
and VCC terminals are shorted by the R_VCM resistor under the over charge condition.
The over charge condition is released in two cases:
1) The battery voltage which exceeded the over charge detection voltage (V_CU) falls below the over
charge release voltage (V_CD), the charging FET turns on and the normal condition returns.
2) If the battery voltage which exceeded the over charge detection voltage (V_CU) is equal or higher than
the over charge release voltage (V_CD), 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 VMP terminal
voltage decreases by about 0.6 V from the VCC terminal voltage momentarily. The IC detects this
voltage (over current detection voltage 1 or higher), releases the over charge condition and returns to
the normal condition.
Seiko Instruments Inc.
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