MB3836 Datasheet, PDF (10/28 Pages) Fujitsu Component Limited. – Li-Ion Battery Protection IC

MB3836
s FUNCTIONAL DESCRIPTION
(1) Over-charge Detection Block
When the battery is being charged, the over-charge detection block monitors each cell voltage. If any cell voltage
reaches or exceeds the over-charge detection voltage (4.325 V Typ) as in Figure 1 (see "1. Over-charge detection
block and cell voltage input block " in "sOPERATION TIMING CHART"), the COUT terminal (pin 2) goes “H”
level, after a delay time (23 ms Typ) managed by the capacitor (COVT) connected between the COVT terminal
(pin 14) and GND, to turn off the Pch MOS FET for external charge control, thereby stopping charging the battery.
When all the cell voltages in the over-charge detected state become the over-charge release voltage (4.125 V
Typ) or less, the COUT terminal (pin 2) goes “L” level to turn on the Pch MOS FET for external charge control.
Even when a cell voltage reaches or exceeds the over-charge detection voltage as in Figure 2, the cell voltage
does not enter the over-charge detected state if it falls below the over-charge detection voltage within the delay
time (23 ms Typ).
(2) Cell Voltage Input Block
If any cell voltage reaches or exceeds the over-charge detection voltage (4.325 V Typ) as in Figures 1 and 2
(see "1. Over-charge detection block and cell voltage input block" in "sOPERATION TIMING CHART"), the
COUT terminal (pin 2) goes high to turn off the Pch MOS FET for external charge control after a delay time
(23 ms Typ) managed by the capacitor (COVT) connected between the COVT terminal (pin 14) and GND. At the
same time, the cell voltage input block switch for the cell exceeding the over-charge detection value is turned
on to supply the cell voltage input current to that cell so that high-voltage cells are lowered in voltage.
When the cell voltage in the over-charge detected state becomes the over-charge release voltage ( 4.125 V Typ)
or less, the cell voltage input block switch is turned off.
(3) Over-discharge Detection/Power Fail Circuit Block
When the battery is being discharged, the over-discharge detection/power fail circuit block monitors each cell
voltage. If any cell voltage becomes the over-discharge detection voltage (2.75 V Typ) as in Figure 5 (see "3.
Over-discharge detection/power fail circuit" in "sOPERATION TIMING CHART"), the PF terminal (pin 19) outputs
a “L” level PF signal to the notebook PC after a PF output delay time (2 s Typ) managed by the capacitor (CUVT)
connected between the CUVT terminal (pin 12) and GND. At the same time, after a power-down delay time
(20 s Typ) managed by the capacitor (CPDT) connected between the CPDT terminal (pin 11) and GND, the DOUT
terminal (pin 3) goes “H” level to turn off the Pch MOS FET for external discharge control, thereby stopping
discharging the battery.
(4) Over-current Detection Block
The over-current detection block monitors the discharge current from the battery. It detects an over-current if
the potential difference between the VCC and OCV terminals by RON of Pch MOS FET for external charge
control becomes 300 mV or more as in Figure 6 (see "4. Over-current detection block 1" in "sOPERATION
TIMING CHART"). After a delay time (7 ms Typ) managed by the capacitor (COCT) connected between the COCT
terminal (pin 13) and GND, the DOUT terminal (pin 3) goes “H” level to turn off the Pch MOS FET for external
discharge control, thereby stopping discharging the battery.
When the discharge current is large, if the potential difference between the VCC and OCV terminals becomes
600 mV or more as in Figure 7 (see "5. Over-current detection block 2" in "sOPERATION TIMING CHART"),
the DOUT terminal (pin 3) goes “H” level to turn off the Pch MOS FET for external discharge control, thereby
stopping discharging the battery, after a power-down delay time (500 µs Typ) managed by the capacitor (COCT)
connected between the COCT terminal (pin 13) and GND.
Note that, if an over-current is detected, the VS terminal (pin 5) goes “L” level in the same way as when the over-
discharge detection function works. As discharging is stopped, the OCV terminal (pin 1) goes “L” level to
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