BM112 Series
BYD Microelectronics Co., Ltd.
One-Cell Li Battery Protectors
General Description
The BM112-XX Series are protectors for lithium-ion and
lithium polymer rechargeable battery with high accuracy
voltage detection. They can be used for protecting single
cell lithium-ion or/and lithium polymer battery packs from
overcharge, over-discharge, excess current and short
circuit. These ICs have suitable protection delay
functions and low power consumption property.
Features
Overcharge Threshold
4.200~ 4.400V
Accuracy
±25mV (25
℃
)
±50mV (-30
℃
~
80℃)
Over-discharge Threshold
Typ. 2.30V
Accuracy
±3.0%
Excess Current Protection Threshold
Typ. 0.150V @ V
DD
= 3.16V
Accuracy
±0.015V
Short Circuit Protection Threshold
Typ. 0.80V @ V
DD
= 3.16V
Accuracy
±0.15V
Low Supply Current
Typ. 4.0uA @ V
DD
= 3.9V
(Standard working current)
Typ. 0.8uA @ V
DD
= 2.0V
(Power-down current)
Output Delay of Overcharge
Typ. 600ms @ V
DD
= 4.4V
Output Delay of Over-discharge
Typ. 72ms @ V
DD
= 2.0V
Small Package
SOT-23-6
GEM2928-6J
DFNWB2*2-6L
Applications
Battery Pack
Protection
Circuit Board
With
BM112
Lithium Ion
Or
Lithium Polymer
Battery Cell
Typical Application Circuits
Notes
R
1
and C
1
are to stabilize the supply voltage of the BM112
series. R
1
C
1
is hence regarded as the time constant for V
DD
pin. C
2
is to stabilize the voltage of V
M
pin. R
1
and R
2
can
also be a part of current limit circuit for the BM112 series.
Recommended values of these elements are as follows:
R
1
＜1kΩ.
A larger value of R1 results in higher
detection voltage, introducing errors.
R
2
＜2.5kΩ.
A larger value of R
2
possibly prevents
resetting from over-discharge even with a charger.
●
R
1
+R
2
＞
1kΩ. Smaller values may lead to power
consumption over the maximum dissipation rating of the
BM112 series.
●
The above diagram and parameters can’t insure the
circuit work well, please choose the suitable parameters
through test.
Datasheet
ES-BYD-WDZCE01D-029 Rev.C/0
Page 1 of 17
BYD Microelectronics Co., Ltd.
BM112 Series
Selection Guide
Type Number
BM112 – XX – YY
Symbol
XX
YY
Meaning
Overcharge detection threshold and accuracy
Different Package
Description
Assigned from AA to WW
ST / JT / CE, etc.
Type Number Option
Through choosing the “XX”, the Overcharge Detection Threshold Voltage (Vdet1) and its accuracy of BM112 can be decided.
And the Over-discharge Detection Threshold Voltage (Vdet2) is determinate accordingly as table 1.
Through choosing the “YY”, the package can be decided. Table 1 also shows part of the corresponding information.
Table 1.
Vdet1 & Vdet2 / Package
Vdet1
4.325 V
4.300 V
4.275 V
4.250 V
SOT-23-6
GEM2928-6J
DFNWB2*2-6L
±25 mV
Vdet1 Accuracy
Vdet2
2.31 V
2.30 V
2.29 V
2.28V
Package
±75mV
( @ 25℃ )
Vdet2 Accuracy
Mark
CHX
CMX
CLX
CRX
Type Number
BM112 – HA
BM112 – MA
BM112 – LA
BM112 – RA
Type Number
ST
JT
CE
Block Diagram
Datasheet
ES-BYD-WDZCE01D-029 Rev.C/0
Page 2 of 17
BYD Microelectronics Co., Ltd.
BM112 Series
Pin Description
Table 2.
Pin
1
2
3
4
5
6
SOT-23-6
Description
Over-discharge detection, CMOS output
Connected to charger’s negative pin
Overcharge detection, CMOS output
Test Pin
Power supply
Ground
Symbol
D
O
V
M
C
O
D
P
V
DD
V
SS
SOT-23-6 (Top Side)
Table 3.
Pin
1
2
3
4
5
6
GEM2928-6J
GEM2928-6J (Top Side)
Description
Over-discharge detection, CMOS output
Connected to charger’s negative pin
Overcharge detection, CMOS output
Test Pin
Power supply
Ground
Symbol
D
O
V
M
C
O
D
P
V
DD
V
SS
Table 4. DFNWB2*2-6L
DFNWB2*2-6L (Top Side)
Pin
1
2
3
4
5
6
Symbol
C
O
V
M
D
O
V
SS
V
DD
D
P
Description
Over-charge detection, CMOS output
Connected to charger’s negative pin
Over-discharge detection, CMOS output
Ground
PIN 1
6
5
4
Mark
1
2
3
Power supply
Test Pin
Notes: Overcharge delay, excess-current delay and over-discharge delay will all be shorten with the D
P
connected to V
DD
. In
normal condition, D
P
should be connected to Vss or floating.
In the package of DFNWB2*2-6L, Pin1 to pin6 are the lead
connection, but in the middle of the package outline, there is a exposed PAD. In the typical application, this PAD must be floating.
Datasheet
ES-BYD-WDZCE01D-029 Rev.C/0
Page 3 of 17
BYD Microelectronics Co., Ltd.
BM112 Series
Function Description
Normal Condition:
V
DD
is between the Over-discharge Detection Threshold
(Vdet2) and Overcharge Detection Threshold (Vdet1) and the
V
M
pad voltage is between Charger Detection Voltage (Vcha)
and the Excess Current 1 Threshold Voltage (Vdet3),
therefore the outputs of D
O
pad and C
O
pad are high and the
MOSFETs of charge and discharge are all on. Charging and
discharging can be carried out freely.
Overcharge Condition:
When V
DD
increases and passes Vdet1 during charging under
the normal condition, the output of Co pad will change from
high to low after Overcharge Detection Delay Time (Tvdet1),
turning off the charging control FET.
If, within Tvdet1, V
DD
becomes lower than Vdet1 and stays for
duration shorter than Overcharge Reset Delay Time (Treset)
before rising up over Vdet1 again, this type of instantaneous
falling of V
DD
is ignored. Otherwise, if the time V
DD
stays lower
than Vdet1 is longer than Treset, the timing related to Tvdet1
shall be reset.
Abnormal Charge Current Condition:
If the V
M
pin voltage falls below the Charger Detection
Voltage (Vcha) during charging under normal condition and
it continues for the Abnormal Charge Current Delay Time
(Tab) or longer, the charging control FET turns off and
charging stops. This action is called the abnormal charge
current detection.
Abnormal charge current detection works when the D
O
pin
voltage is “H” and the V
M
pin voltage falls below the Charger
Detection Voltage (Vcha). To an over-discharged battery,
only when charging makes the battery voltage higher than
the Over-discharge Detection Threshold (VDT), the
Abnormal Charge Current Detection can act. Abnormal
charge current state is released, once the voltage difference
between VM pin and VSS pin becomes less than the
Abnormal Charge Current Detection Threshold Voltage
(VAB) value.
Overcharge Protection Release Condition:
The charging state can be reset and the output of Co
becomes high when V
DD
becomes lower than the Overcharge
Release Voltage (Vrel1) and stays longer than Overcharge
Release Delay Time (Tvrel1).
When a load is connected to V
DD
after a charger is
disconnected from the battery pack, while the V
DD
level is
lower than Vdet1, the output of Co becomes high.
Over-discharge Condition:
While discharging, after V
DD
lowers below Over-discharge
Detection Threshold (Vdet2), Do pad goes low after
Over-discharge Detection Delay Time (Tvdet2). The Do pad
would switch off the discharging control FET and stop
discharging.
Over-discharge Protection Release Condition:
When IC is in over-discharge condition, if a charger is
connected to the battery pack, and the battery supply voltage
becomes higher than Vdet2, and V
M
is lower than Charger
Detection Voltage (Vcha), Do pad becomes high, allowing
discharging action.
The discharging state also can be reset and the output of Do
becomes high when V
DD
becomes higher than the
Over-discharge Release Voltage (Vrel2), V
M
is between Vdet3
and Vcha, and stays longer than Release Delay Time
(Tvrel1).
When a charger is connected from the battery pack, while the
V
DD
level is lower than Vdet2, the battery pack makes charger
current allowable through the external diode.
Charger Detect Condition:
When a battery in the over-discharge condition is connected to
a charger and provided that the V
M
pin voltage is lower than
the Charger Detection Voltage (Vcha), IC releases the
over-discharge condition and turns on the discharging control
FET
as the battery voltage becomes higher
than the
Over-discharge Detection Voltage (Vdet2) since the charger
detection function works. This action is called charger
detection.
When a battery in the over-discharge condition is connected
to a charger and provided that the V
M
pin voltage is between
the Charger Detection Voltage (Vcha) and Excess Current 1
Page 4 of 17
Datasheet
ES-BYD-WDZCE01D-029 Rev.C/0
BYD Microelectronics Co., Ltd.
BM112 Series
Threshold Voltage (Vdet3), IC releases the over-discharge
condition when the battery voltage reaches the
Over-discharge Release Voltage (Vrel2) or higher.
Excess Current 1 Protection:
During discharging, the current varies with load, and V
M
increases with the rise of the discharging current. Once V
M
rises up to the Excess Current 1 Threshold Voltage (Vdet3) or
higher and stays longer than the Excess Current 1 Delay Time
(Tvdet3), Do pad switches to low, turning off the discharging
control FET. After that excess current state is removed, i.e.
V
M
＜Vdet3,
and the circuit recovers to normal condition.
Excess Current 2 Protection:
During discharging, the current varies with load, and V
M
increases with the rise of the discharging current. Once V
M
rises up to Excess Current 2 Threshold Voltage (Vdet4) or
higher, and stays longer than Excess Current 2 Delay Time
(Tvdet4), Do pad switches to low, turning off the discharging
control FET. After that excess current state is removed, i.e.
V
M
＜Vdet3,
and the circuit recovers to normal condition.
Short Circuit Protection:
This function has the same principle as the excess current
protection. But, the delay time Tshort is far shorter than
Tvdet3 and Tvdet4, and the threshold Vshort is far higher
than Vdet3 and Vdet4. When the circuit is shorted, V
M
increases rapidly. Once V
M
≥Vshort,
Do pad switches to
low, turning off the discharging control FET. After the short
circuit state is removed, i.e. V
M
＜Vdet3,
the circuit recovers
to the normal condition. The short circuit peak current is
related to Vshort and the ON resistance of the two FETs in
series. Output types of Co and Do are CMOS level.
0V battery charge function
This function is used to recharge the connected battery
whose voltage is 0V due to the self-discharge. When the 0 V
battery charge starting charger voltage (V0cha) or higher is
applied between P+ and P− pins (see the Typical
Application Circuits of Page1) by connecting a charger, the
charging control FET gate is fixed to V
DD
pin voltage. When
the voltage between the gate and source of the charging
control FET becomes equal to or higher than the turn-on
voltage by the charger voltage, the charging control FET
turns on to start charging. At this time, the discharging
control FET is off and the charging current flows through the
internal parasitic diode in the discharging control FET. When
the battery voltage becomes equal to or higher than the
Over-discharge Detection Threshold (Vdet2), the IC enters
the normal condition.
Datasheet
ES-BYD-WDZCE01D-029 Rev.C/0
Page 5 of 17
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