MIC79110
Simple 1.2A Linear Li-ion Battery Charger
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
September 24
, 2013
Revision 2.1
General Description
The Micrel MIC79110 is a simple and accurate lithium-ion
battery charger. The part features a built-in pass transistor,
precision programmable current limiting (±5%), and
precision voltage termination (±0.75% over temperature).
The MIC79110 packs full functionality into a small space.
Other features of the MIC79110 include two independent
indicators: a digital end-of-charge signal that is
programmable with a resistor-to-ground and an analog
current output that is proportional to the output current,
allowing for monitoring of the actual charging current.
Additional features include very low dropout (550mV over
the temperature range), thermal shutdown, and reverse
polarity protection. In the event the input voltage to the
charger is disconnected, the MIC79110 also provides
minimal reverse-current and reversed-battery protection.
Available in both fixed 4.2V and adjustable outputs, the
MIC79110 is offered in the leadless 10-pin 3mm × 3mm
DFN with an operating junction temperature range of
–40˚C to +125˚C.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Features
• Input voltage range: 2.5V to 16V
• High output voltage accuracy of ±0.75% over –5°C to
+60˚C
• Current limit ±5% accurate from –5°C ≤ TJ ≤ + 125°C
• Programmable end-of-charge flag
• Analog output proportional to output current
• Adjustable and fixed 4.2V output
• Low dropout voltage of 550mV at 700mA load, over
temperature
• 1.2A maximum charge current
• Excellent line and load regulation specifications
• Reverse-current protection
• Thermal-shutdown and current-limit protection
• Tiny 10-pin 3mm × 3mm DFN package
• Junction temperature range: –40°C to +125°C
Applications
• Cellular phones and PDAs
• Digital cameras and camcorders
• MP3 players
• Notebook PCs
• Portable Meters
• Cradle/car chargers, and battery packs
Typical Application
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MIC79110
September 23
, 2013 2 Revision 2.1
Ordering Information
Part Number Marking
Code(1) Voltage Junction Temperature Range Package
MIC79110-4.2YML L942 4.2V –40° to +125°C 10-Pin 3mm × 3mm DFN
MIC79110YML L9AA Adjustable –40° to +125°C 10-Pin 3mm × 3mm DFN
1. Pb-Free “Y” indicator is added to the device mark after logo.
Pin Configuration
Fixed Output
10-Pin 3mm × 3mm DFN (ML)
Adjustable Output
10-Pin 3mm × 3mm DFN (ML)
Pin Description
Pin Number
Pin Name
Pin Function
1 SD Shutdown Input. Logic HIGH = Off; Logic LOW = On.
2 RSET Current limit: Sets constant current limit via an external resistor to ground.
IRSET = (0.2V/RSET) × 1000.
3 SNS (Fixed voltage only): Sense output, connect directly to battery.
3 ADJ (Adjustable voltage only): Feedback input.
4 BAT Battery Terminal. Connect to single-cell lithium-ion battery.
5, 6 VIN Input supply pin.
7 ACHG Analog Charge Indicator Output: Current source who’s output current is equal to 1/1000 of the
BAT pin current.
8 DEOC
Digital End-of-Charge Output: N-Channel open-drain output. LOW indicates charging, a current
that is higher than the programmed current set by REOC is charging the battery. When the current
drops to less than the current set by REOC, the output goes high impedance, indicating end-of-
charge.
9 REOC End-of-Charge Set: Sets end-of-charge current threshold via an external resistor to ground.
IEOC = (0.2V/ REOC) × 1000.
10 GND Ground
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MIC79110
September 23
, 2013 3 Revision 2.1
Absolute Maximum Ratings(2)
Input Supply Voltage (VIN) .................................... 0V to 18V
Shutdown Input Voltage (VSD) .............................. 0V to 10V
Output Voltage (ADJ) ..................................................... 10V
Power Dissipation ................................... Internally Limited
Junction Temperature ............................... –40°C to +125°C
Operating Ratings(3)
Input Supply Voltage ........................................ 2.5V to 16V
Shutdown Input Voltage (VSD) ................................ 0V to 7V
Output Voltage (ADJ) .................................................... 9.6V
Junction Temperature Range (TJ) ............. –40°C to +125°C
3mm × 3mm DFN-10 (θJA) ..................................... 60°C
3mm × 3mm DFN-10 (θJC) ....................................... 2°C
Electrical Characteristics(4)
TA = 25°C with VIN = VOUT + 1V; ILOAD = 100µA; CBAT = 10µF; SD = 0V; RSET = 1kΩ. Bold values indicate –40ºC < TJ < +125°C; unless
otherwise specified.
Parameter
Condition
Min.
Typ.
Max.
Units
Output Voltage Accuracy VOUT = 4.2V; ILOAD = 50mA; TJ = –5°C to +60°C -0.75 +0.75 %
VOUT = 4.2V; ILOAD = 50mA; TJ = –40°C to +125°C -1.5 +1.5
ADJ Pin Voltage Accuracy 0.5955 0.6 0.6045 V
Line Regulation VIN = VOUT + 1V to 16V @ ILOAD = 50mA -0.1 +0.1 %/V
Load Regulation ILOAD = 0.1mA to 1A 0.3 %
Dropout Voltage(5) ILOAD = 100mA, RSET = 167Ω 160 250 mV
ILOAD = 700mA, RSET = 167Ω 375 550 mV
Ground Current ILOAD = 10mA, RSET = 167Ω 2 3 mA
ILOAD = 700mA, RSET = 167Ω 24 35 mA
VIN Pin Current SD = VIN 120 300 µA
Shutdown Pin Current SD = 5.2V, VBAT = 0 0.1 5 µA
Shutdown Input Threshold Logic High, regulator off 1.05 V
Logic Low, regulator on
0.93
V
Shutdown Hysteresis 60 mV
Current Limit Accuracy(6, 7)
VOUT = 0.9 × VNOM; IOUT = 1.2A, RSET = 167Ω,
TJ = –40°C to +85°C -5 +5 %
VOUT = 0.9 × VNOM; IOUT = 0.1A, RSET = 2kΩ -20 +20 %
Current-Limit Setpoint Range(7) 0.1 1.2 A
Notes:
2. Exceeding the absolute maximum rating may damage the device.
3. The device is not guaranteed to function outside its operating rating.
4. Specification for packaged product only.
5. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V
differential. For outputs below 2.5V, dropout voltage is the input-to-output voltage differential with the minimum input voltage 2.5V. Minimum input
operating voltage is 2.5V.
6. VNOM denotes the nominal output voltage.
7. IRSET = (0.2V/RSET) × 1000.
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MIC79110
September 23
, 2013 4 Revision 2.1
Electrical Characteristics(4) (Continued)
TA = 25°C with VIN = VOUT + 1V; ILOAD = 100µA; CBAT = 10µF; SD = 0V; RSET = 1kΩ. Bold values indicate –40ºC < TJ < +125°C; unless
otherwise specified.
Parameter Condition Min. Typ. Max. Units
Maximum Current Limit RSET shorted to ground, VBAT = 0.9 × VNOM 1.25 1.65 2.5 A
VBAT Reverse Current VIN = High impedance or ground 4.2 20 µA
Digital End–of–Charge (DEOC) Output
IEOC(8, 9) REOC = 4kΩ Current Falling 35 50 65 mA
30 70
IEOC(8, 9) REOC = 4kΩ Current Rising 50 70 95 mA
40 100
DEOC Logic–Low Voltage IEOC = 5mA, IBAT = 700mA 0.74 0.95 V
DEOC Leakage Current Logic HIGH = VIN = 16V 0.1 µA
DEOC On Resistance VIN = +5V 150 190 Ω
REOC Maximum Current Limit REOC shorted to ground 0.5 1.0 2.0 mA
Analog Charge Indicator (ACHG) Output
ISOURCE(10) IBAT = 50mA 37 46 55 µA
IBAT = 1.2A, TJ = –40°C to +85°C 800 950 1150
Notes:
8. Output current IEOC when digital end-of-charge output goes high impedance. Currents greater than IEOC, the DEOC output is low, currents lower than
IEOC, DEOC is high impedance.
9. IEOC = (0.2V/REOC) × 1000.
10. ISOURCE is the current output from ACHG pin. A resistor to ground from the ACHG pin will program a voltage that is proportional to the output current.
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Block Diagram
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Typical Characteristics
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Typical Characteristics (Continued)
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Typical Characteristics (Continued)
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Functional Characteristics
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Flow Chart
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Application Information
Detailed Description
The MIC79110 forms a complete charger for 1-cell
lithium-ion batteries. It includes precision voltage control
(0.75% over temperature) to optimize both cell
performance and cycle life. All are compatible with
common 4.2V lithium-ion chemistries. Voltages other
than 4.2V can be obtained with the adjustable version.
Other features include current limit, end-of-charge flag,
and end-of-charge current limit using an external resistor.
The shutdown pin enables low quiescent current when
not charging.
Current-Limit Mode
MIC79110 features an internal current limit that is set by
the RSET pin with a resistor-to-ground. The maximum
current is calculated by Equation 1:
IRSET = (0.2/RSET) × 1000 Eq. 1
Using a 167Ω RSET resistor will achieve the maximum
current limit for the MIC79110 at 1.2 amperes.
End-of-Charge
REOC pin is connected to a resistor-to-ground. This
resistor is used to set the end of charge current for the
lithium-ion battery as in Equation 2:
IEOC = (0.2/REOC) × 1000 Eq. 2
Using a 4kΩ REOC resistor will set the end-of-charge
current at 50mA.
IEOC should be set at 10% of the battery’s rated current.
Digital End-of-Charge Output
This pin is the output of an open drain. When tied high to
the supply using a resistor, the output will toggle high or
low depending on the output current of IBAT.
• Low state indicates that the IBAT current is higher than
the programmed current set by REOC.
• High state indicates that the IBAT current is lower than
the programmed current set by REOC. The output goes
high impedance indicating end-of-charge.
Analog End-Of-Charge Output
The ACHG pin provides a small current that is
proportional to the charge current. The ratio is set at
1/1000th of the output current.
Shutdown
The SD pin serves as a logic input (active low) to enable
the charger.
Built-in hysteresis for the shutdown pin is 50mV over
temperature.
Reverse Polarity Protection
In the event that VBAT > VIN and the shutdown pin is active
low, there is reverse battery current protection built in.
The current is limited to less than 10µA over temperature.
Constant Output Voltage/Current Charging
The MIC79110 features constant voltage and constant
current output to correctly charge lithium-ion batteries.
The constant voltage is either 4.2V or adjustable. The
constant current is set by the RSET pin and is constant
down to around 300mV. Since RSET can be set below
500mA, the minimum output current is set at 500mA for
output voltages below 100mV. This minimum voltage
starts the charging process in lithium-ion batteries. If the
output current is too low, the battery will not begin
charge.
Figure 1. MIC79110 Constant Output Voltage
Micrel, Inc.
MIC79110
September 23
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Lithium-ion Batteries
Lithium-ion batteries are charged in two stages to reach
full capacity. The first stage charges the battery with
maximum charge current until 90% of the battery cell’s
voltage limit is reached. The second stage tops off the
charge with constant voltage charge as the charge
current slowly decreases. End of charge is reached when
the current is less than 3% of the rated current. A third
stage will occasionally top off with charge with constant
voltage charge if the battery voltage drops below a
certain threshold.
Figure 2. Typical Two-Stage Lithium Charge Profile
All lithium-ion batteries take approximately 3 hours to
charge with the second stage taking twice as long as the
first stage. Some chargers claim to be fast chargers by
skipping the second stage and just charges the battery
until the cell voltage is reached. This only charges the
battery to 70% capacity.
An increase in the charge current during stage 1 does not
shorten the total charge time. It will only shorten the time
for stage 1 to complete and lengthen the time in stage 2.
The lithium-ion loses charge due to aging whether it is
used or not. Do not store the batteries at full charge and
high heat because it will accelerate the aging process.
Try and store with 40% charge and in a cool
environment.
Lithium-ion Safety Precautions
Every lithium-ion battery pack should have a safety circuit
which monitors the charge and discharge of the pack and
prevents dangerous occurrences.
The specifications of these safety circuits are dictated by
the cell manufacturer and may include the following:
• Reverse polarity protection.
• Charge temperature must not be charged when
temperature is lower than 0°C or above 45°C.
• Charge current must not be too high, typically below
0.7°C.
• Discharge current protection to prevent damage due to
short circuits.
• Protection circuitry for over voltage applied to the
battery terminals.
• Overcharge protection circuitry to stop charge when
the voltage per cell rises above 4.3V.
• Over discharge protection circuitry to stop discharge
when the battery voltage falls below 2.3V (varies with
manufacturer).
• Thermal shutdown protection for the battery if the
ambient temperature is above 100°C.
Auto Top-Off Charger Application Circuit
Figure 3. Auto Top-Off Charger
−
Application Circuit
Lithium-ion batteries will begin to lose their charge over
time. The MIC79110 can be configured to automatically
recharge the battery when the voltage drops below the
minimum battery voltage. This minimum voltage is set by
a resistor divider at the battery and is connected to the
SD pin. For instance, if VBAT is 4.2V and the battery
voltage falls to 3.72V, SD pin gets divided down by R1
and R2 to 0.93V and starts the normal charging process.
While charging the DEOC indictor is turned on, pulling
the SD pin to GND, keeping the MIC79110 on. When the
end of charge is reached, the DEOC pin opens. The
divided down BAT voltage is now 1.05V at the SD pin,
ending the charging process.
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MIC79110
September 23
, 2013 13 Revision 2.1
Figure 4. Auto Top-Off Charger Application
Figure 5. Charging Description
1. SD not held low by active high DEOC because
DEOC Comparator’s inputs do not common-mode to
ground. Divider holds SD low so part can start.
2. SD held low by divider.
3. SD held low by active high DEOC.
4. Divider voltage above SD threshold and DEOC open.
5. Divider voltage drops below SD threshold and
charging begins again.
Figure 6. Top-Off Charger with Internal Reset
−
Application Circuit
This circuit is similar to the auto top-off charger circuit
mentioned above except that the DEOC pin is externally
triggered to restart the charging cycle. It still uses the
same resistor divider to set the minimum battery voltage
before the lithium-ion needs to be recharged.
Figure 7. Auto-Shutdown using Shutdown Pin
The shutdown pin on the MIC79110 can be used to
automatically shutdown the battery charger when the
input voltage rises above a safe operating voltage. To
keep the part from heating up and entering thermal
shutdown, we can connect the shutdown pin to VIN using
a resistor divider. Use Equation 3 to setup the maximum
VIN:
( )
1
2R
1R
V
MAXVIN
SD
+=
Eq. 3
The MIC79110 can be connected to a wall wart with a
rectified DC voltage and protected from over voltages at
the input.
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MIC79110
September 23
, 2013 15 Revision 2.1
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably
expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2013 Micrel, Incorporated.
Micrel, Inc.
MIC79110
September 23
, 2013 16 Revision 2.1
Revision History
Date Change Description/Edits by: Rev.
05/21/13 Original DS edited and reflowed with applied edits − S. Thompson 2.0
