Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Protection for Lithium-Ion Batteries (2-serial cells) Monolithic IC MM1412 October 22, 1998
This IC protects lithium-ion batteries in the event of overcharge, overdischarge and overcurrent. It has the
following two functions: an overcharge detection function that turns the external FET-SW off when a problem
occurs during charging, etc. and excess voltage is impressed on each battery for longer than a certain time,
and an overdischarge detection function that turns the external FET-SW off when battery voltage drops below
a certain voltage during discharge, in order to prevent battery overdischarge. When these functions operate,
the IC enters low current consumption mode. It also has an overcurrent detection function that turns the FET-
SW off when excess current flows due to a short or the like. Since the functions above are provided, the
protection circuitry for lithium-ion batteries can be comprised with fever external components. Temperature conditions A: Ta=-25 ~ 75°C, B: Ta=-20 ~ 70°C, C: Ta=0 ~ 50°C, Series Table D: Ta=0 ~ 40°C, E: Ta=-20 ~ 25°C Overcharge Overcharge Overcharge Overdischarge Overdischarge Overcurrent detection voltage detection detection detection detection temperature hysteresis SOP-8C, E VSOP-8A voltage (V) voltage (V) voltage (V) voltage (mV) conditions voltage (V) Features
1. Consumption current (during overcharge)
VCELL = 4.5 ROC = 270 kΩ 150µA typ.
3. Consumption current (during overdischarge)
4. Consumption current (during overdischarge)
5. Overcharge detection voltage (Ta = 0°C ~ 50°C)
Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Applications Pin Assignment Block Diagram Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Pin Description Pin No. Pin name Functions
Normal mode, overdischarge mode, overcurrent mode: OFF
Discharge control FET (N-ch) control output pin
Monitors discharge current equivalently by the voltage drop between discharge control FET source
and drain. Stops discharge when voltage between CS pin and GND pin goes above overcurrent
detection threshold value, and holds until load is released.
Ground pin, or lower cell load negative pole input pin.
Overcharge detection dead time setting pin
Dead time can be set by adding a capacitor between TD and GND pins.
Connection pin for lower cell positive electrode side and upper cell negative electrode side.
Either upper cell or lower cell battery voltage exceeds overcharge detection voltage. Overcharge
detection operation delay can be set by the dead time setting pin.
Both upper cell and lower cell battery voltages exceed overdischarge detection voltage and are less
Either upper cell or lower cell battery voltage is less than overdischarge detection voltage.
Overdischarge detection dead time is set internally. Overdischarge mode is released when charging
causes voltage to rise above overdischarge detection voltage. Also, when battery voltage goes above
overdischarge release voltage, it resets without charging, but the value is set high. (This function is
included in case charging can not be detected. Also, this release voltage has a temperature coefficient
Voltage between CS and GND exceeds overcurrent detection voltage during discharge. Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Pin Description Pin No. Pin name Equivalent circuit diagram Pin No. Pin name Equivalent circuit diagram Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Absolute Maximum Ratings Storage temperature Operating temperature Power supply voltage OC pin impressed voltage CS pin impressed voltage Allowable loss Recommended Operating Conditions Operating temperature Operating power supply voltage Electrical Characteristics (Except where noted otherwise, Ta=25°C) Models listed MM1412A Measurement conditions Min. Typ. Max. Unit Overcharge detection voltage Overcharge detection hysteresis voltage Overdischarge detection voltage Consumption current 1 Consumption current 2 Consumption current 3 Consumption current 4 VL pin input current Overdischarge release voltage GD pin H output voltage GD pin L output voltage OC pin output current Overcurrent detection threshold value Overcurrent short threshold value Overcurrent release
Load release: Load of 5MEGΩ or more between both battery pack pins
Overcurrent detection delay time 1 Overcurrent detection delay time 2 Overdischarge detection delay time Overcharge detection dead time Start-up voltage
Note 1: Overcurrent short mode delay time (overcurrent delay time 2) is IC response speed.
In actual use, the time for discharging the discharge control FET gate capacity is added.
Also, when voltage change is large due to excess current, the IC internal bias current may turn off
temporarily, causing response time to lengthen. Select the time constant for the capacitor
connected to the power supply pin so that power supply fluctuation is more than 100µs/1V.
Note 2: Calculate overcharge dead time according to the following formula:
Overcharge detection dead time: tALM - 5.55 CTD[s]
Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Measuring Circuit Measuring Circuit 1 (VOC, VOC, VOD, VDF, VST, VCS, IDCH, VGDH, VGDL) Measuring Circuit 2 (tOC, tOD, tOCH) Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Timing Chart Dischage control dead time Keep cirquit GD Over current Description
This IC is a lithium ion battery (2-cell in-series type) protection IC. It has built-in overcharge detection,
overdischarge detection and overcurrent detection circuits, and controls the FET (external N-MOS FET) that
The operation modes can be divided broadly into four, as follows.
The battery voltage of either the upper cell or lower cell goes above overcharge detection voltage.
Detection operation delay for overcharge detection can be set with the dead time setting pin.
The battery voltage of both upper cells and lower cells is above overdischarge detection voltage and below
The battery voltage of either the upper cell or lower cell drops below overdischarge detection voltage. Dead
time for overdischarge detection is set internally. Overdischarge mode is released when charging takes
place and the voltage goes above overdischarge detection voltage. Also, reset will occur even without
charging if battery voltage goes above overdischarge release voltage, but the set value is high. (This
function is provided as a measure for cases when charging can not be detected. Further, this release
voltage has a temperature coefficient of -6mV/°C.)
The voltage between CS-GND goes above overcurrent detection voltage during discharge. Protection for Lithium-Ion Batteries (2-serial cells) MM1412 Application Circuit
Note: Applicable circuits shown are typical examples provided for reference purposes. Mitsumi cannot
assume responsibility for any problems arising out of the use of these circuits or for any infringement of
third party patent and other right due to same. Characteristics Overcharge Detection Time (Dead Time) Overcharge detection time (S) 0.001 External capacitance (CTD)
Note: Dead time can be calculated according to the following formula:
The above specifications are representative, and are not guaranteed values.
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