S-8253A Datasheet, PDF (23/32 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 2-SERIAL OR 3-SERIAL-CELL PACK

Rev.3.7_00
BATTERY PROTECTION IC FOR 2-SERIAL OR 3-SERIAL-CELL PACK
S-8253A/B Series
„ Precautions
• In case of designing a circuit by using the CTL pin, as seen in Figure 15, note that discharging may stop during connecting a battery
pack and the device.
【Cause】
This is because the overcurrent detection voltage 3 (V_IOV3) is detected due to the rush current which flows into the device while a
battery pack is in the delay time-shortening status.
【Mechanism】
As seen in Figure 15, before a battery pack is connected to the device, the battery pack may be in the charge / discharge inhibited
status in which the CTL pin is internally pulled-up. From this status, if connecting the battery pack to the device, the CTL pin will be
pulled-down in a time-constant C1 × (R1 + R_PD) by a pull-down resistor in the device. If the CTL’s potential reaches
V_CTLL<V_CTL<V_CTLH, the battery pack goes in the delay time-shortening status so that it releases charging and discharging, hence it
starts charging a parasitic capacitor in the device. In this case, if the rush current, which makes the S-8253A/B Series to detect the
overcurrent detection voltage 3 (V_IOV3), flows into the device, the overcurrent detection delay time 3 (t_IOV3 = 300 µs typ.) will be
shortened. So that the battery pack goes in the overcurrent status in several 10 µs. However, the battery pack goes in the normal
status by connecting the device to the charger.
Battery pack
Device
EB+
S-8253A/B
VDD
DOP
COP
Rush current
Parasitic
capacitor
VMP
200 nA
CTL
C1
R1
CTL
Discharging
EB−
Pull-down
resistor
R_PD
CTL ^{CTL = H}
Figure 15
CTL = L
CTLM
DOP
OFF
VMP
<3>
ON
OFF
ON
tIOV3
Rush current
<4>
Connect battery pack to device
Connect charger
<2>
<1>
Figure 16
Seiko Instruments Inc.
Mode
<1> : Normal mode
<2> : Overcurrent mode
<3> : Charge / discharge inhibit mode
<4> : Delay time-shortening mode
(enable to charge / discharge)
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