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MM1248 Schematic ( PDF Datasheet ) - MITSUMI

Teilenummer MM1248
Beschreibung Control of Lithium Ion Battery Charging and Discharging
Hersteller MITSUMI
Logo MITSUMI Logo 




Gesamt 8 Seiten
MM1248 Datasheet, Funktion
MITSUMI
Control of Lithium Ion Battery Charging and Discharging MM1248
Control of Lithium Ion Battery Charging and Discharging
Monolithic IC MM1248
Outline
This IC was developed for use in controlling charging and discharging of lithium ion batteries (battery modules
with three cells connected in series). In charging control, the voltage of the battery module as a whole is
controlled in constant-voltage control. Discharge control and monitoring of overvoltage rely on monitoring of
the voltages of individual cells.
Features
1. Charging control voltage
VBATH=12.465V±1.5% (Ta=-20°C~70°C)
2. Overcharge detection voltage
VCELL=4.335V±1.5% (Ta=-20°C~70°C)
3. Internal circuit for setting dead time (for overvoltage detection, discharge control)
4. Low consumption current on overdischarge IBATH3=1µA typ.
5. High-precision internal overvoltage detection startup circuit (cell voltage 4.2V or higher at end of charging)
Package
SOP-16B (MM1248XF)
Absolute Maximun Ratings (Except where noted otherwise, Ta=25°C)
Item
Storage temperature
Operating temperature
Input voltage
Charge voltage
Power supply voltage
Voltage applied to OV2 pin
Allowable loss
Symbol
TSTG
TOPR
VIN max.
VBAT max.
VCC max.
VO2 max.
Pd
Ratings
-40~+125
-20~+70
18
15
15
10
350
Units
°C
°C
V
V
V
V
mW






MM1248 Datasheet, Funktion
MITSUMI
Control of Lithium Ion Battery Charging and Discharging MM1248
2.2. Charging signal off
When the charging signal is off (CON pin "H"), the high-precision overvoltage sensing unit is in standby
state. A rough overcharging sensing unit is provided internally to sense the overvoltage in this state.
The rough overcharging sensing unit monitors the voltages of each cell, and if the voltage of any cell rises
to or exceeds 4.2V, triggering overvoltage sensing (rough), the high-precision overcharging sensing unit
enters the operating state.
Thereafter operation is the same as in "(2-1) Charging signal on" above.
2-3. Discharge off
In an overdischarge state, if the rough overvoltage detection voltage for any cell reaches or exceeds 4.2V,
an overvoltage signal is output.
Hence in this case a dead time is not set. Further, reset depends on the hysteresis voltage at the time of
rough overvoltage detection.
3. Discharge control
Voltage monitoring for discharge control is performed for each cell; if the voltage of any cell falls to 2.4V or
less, the dead time setting pin (CDC pin 8) is discharged, and if the voltage drops to the discharge-off
threshold voltage, an overdischarge state is detected and the discharge switch gate pin (pin 1) is set "H"
and the battery module monitor unit input gate (pin 10) is also set "H"; the battery module monitor output
impedance goes high.
At this time the monitoring circuit switches to a low consumption current (1µA typ. when all cell voltages
are 2.4V), and the state switches from overdischarge to the reset monitoring state (with reset occurring
when all cell voltages reach 2.65V).
Reset from the overdischarge state occurs when the CDC pin is charged under constant current after all
cell voltages have reached 2.65V; when this pin reaches the threshold voltage for overdischarge reset,
discharge is again turned on.
The dead time setting block of the discharge control unit has a circuit configuration such that if either the
overdischarge or the reset state continues for longer than the set time, the state is switched. Hence when
the state changes within the set time, the CDC pin undergoes rapid charging or discharging.
4. Battery module voltage monitor output
This block outputs a voltage equal to 1/3 the voltage of the battery module; within the IC, it is used as the
charge control input. One-third the battery module voltage is supplied by a bleeder resistance, but in order
to reduce the consumption current on overdischarge, a switch is provided such that current does not flow
through this resistance when overdischarge occurs. The charging voltage and overvoltage detection are
both highly precise, and so this switch is designed to use an external FET.
When battery voltage information is to be input to a microcomputer, this feature may be used, but with the
following caveats regarding use.
1. The output upon overdischarge is at high impedance.
2. The output sink current is small.
In order to reduce the consumption current, the output sink current is held low; but depending on the
external components used, response may be slow, affecting charging control and resulting in oscillation
under constant-voltage control. In such cases, a resistance (of about 300k) should be inserted between
the monitor output and GND, to boost the sink capacity.
Pin Assignment
16 15 14 13 12 11 10 9
Discharge control cell
voltage monitoring
Overcharge
detection unit
(high-precision)
12345678
1 DCHG 9
GND
2
CHG
10 FET (G)
3 VIN 11 BATL
4
CON
12
OV2
5 OV1 13 BATM
6
VBAT
14 FET (D)
7
CCC
15 BATH
8
CDC
16
VCC

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