MIC79050-4.2BMM Micrel Inc, MIC79050-4.2BMM Datasheet - Page 7

• Manufacturer Part Number: MIC79050-4.2BMM
• Description: IC BATTERY CHARGER LI-ION 8-MSOP
• Manufacturer: Micrel Inc

Specifications of MIC79050-4.2BMM

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 2.5 V ~ 16 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Applications Information
Simple Lithium-Ion Battery Charger.
Figure 1A shows a simple, complete lithium-ion battery char-
ger. The charging circuit comprises of a cheap wall adapter,
with a load-line characteristic. This characteristic is always
present with cheap adapters due to the internal impedance
of the transformer windings. The load-line of the unregulated
output should be < 4.4V to 4.6V at somewhere between 0.5C
to 1C of the battery under charge. This 4.4 to 4.6V value is
an approximate number based on the headroom needed
above 4.2V for the MIC79050 to operate correctly e.g. For
August 2005
MIC79050
V
V
EOC
REF
= 1.225V
Figure 1A. Load-Line Charger With End-Of-Charge Termination Circuit.
= V
AC Load-line Wall Adapter
REF
Impedence
(1+
R1
R2
)
Figure 1B. Load-Line Characteristics
V
8
6
4
2
0
0
S
of AC Wall Adapter
MIC79050-4.2BM
SOURCE CURRENT (A)
Load-Line Source
IN
EN
0.2
Characteristics
GND
BAT
FB
7
0.4
End of Charge
a 500mAhr battery, the output of the semi- regulated supply
should be between 225mA to 500mA ( 0.5C to 1C ). If it is
below 225mA no damage will occur but the battery will take
longer to charge. Figure 1B shows a typical wall adapter
characteristic with an output current of 350mA at 4.5V. This
natural impedance of the wall adapter will limit the max cur-
rent into the battery, so no external circuitry is needed to
accomplish this.
If extra impedance is needed to achieve the desired load-
line, extra resistance can easily be added in series with the
MIC79050 IN pin.
0.6
1k
0.8
MIC6270
CIM3-1.2
LM4041
10k
R1
R2
4.7µF
Micrel, Inc.
MIC79050