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MIC79110
Simple 1.2A Linear Li-Ion Battery Charger
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 x 3mm MLF(R) with an operating junction temperature range of -40C to +125C. Data sheets and support documentation can be found 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 -5C to +60C * Current limit 5% accurate from -5C TJ + 125C * 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 max charge current * Excellent line and load regulation specifications * Reverse current protection * Thermal shutdown and current limit protection * Tiny 10-Pin 3mm x 3mm MLF(R) package * Junction temperature range: -40C to +125C
Applications
* Cellular phones * PDAs * Digital cameras * Camcorders * MP3 players * Notebook PCs * Portable Meters * Cradle chargers * Car chargers * Battery packs ___________________________________________________________________________________________________________
Typical Application
MIC79110 VIN
SHUTDOWN ENABLE
VIN SD REOC RSET GND
BAT SNS DEOC ACHG
4.2VBAT 4.2V Li-Ion Cell
MIC79110 Typical Application
MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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MIC79110
Ordering Information
Part Number Standard MIC79110-4.2BML MIC79110BML Marking L942 L9AA Pb-Free MIC79110-4.2YML MIC79110YML Marking L942* L9AA* Voltage 4.2V Adj. Junction Temp. Range -40 to +125C -40 to +125C Package 10-pin 3x3 MLF(R) 10-pin 3x3 MLF(R)
* Pb-Free "Y" indicator is added to the device mark after LOGO.
Pin Configuration
SD 1 RSET 2 SNS 3 BAT 4 10 GND 9 REOC 8 DEOC 7 ACHG 6 VIN
SD 1 RSET 2 ADJ 3 BAT 4 10 GND 9 8 7 6 REOC DEOC ACHG VIN
VIN 5
VIN 5
Fixed Output 10-Pin 3mm x 3mm MLF(R) (ML)
Adjustable Output 10-Pin 3mm x 3mm MLF(R) (ML)
Pin Description
Pin Number 1 2 3 3 4 5, 6 7 8 Pin Name SD RSET SNS ADJ BAT VIN ACHG DEOC Pin Function Shutdown Input. Logic High = Off; Logic Low = On. Current limit: Sets constant current limit via an external resistor to ground. IRSET = (0.2V/RSET) x 1000. (Fixed voltage only): Sense output, connect directly to battery. (Adjustable voltage only): Feedback input. Battery Terminal. Connect to single-cell lithium-ion battery. Input supply pin. Analog Charge Indicator Output: Current source who's output current is equal to 1/1000 of the BAT pin current. Digital End-of-Charge Output: N-Ch 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. End-of-Charge Set: Sets end-of-charge current threshold via an external resistor to ground. IEOC = (0.2V/REOC) x 1000. Ground
9 10
REOC GND
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MIC79110
Absolute Maximum Ratings(1)
Input Supply Voltage (VIN).................................... 0V to 18V Shutdown Input Voltage (V) ................................. 0V to 10V Output Voltage (ADJ) .....................................................10V Power Dissipation ...................................Internally Limited Junction Temperature ...............................-40C to +125C
Operating Ratings(2)
Input Supply Voltage ........................................ 2.5V to 16V Shutdown Input Voltage (V) ................................... 0V to 7V Output Voltage (ADJ) ....................................................9.6V Junction Temperature Range (TJ)............. -40C to +125C JA (MLF-10) .......................................................... 60C JC (MLF-10) ............................................................ 2C
Electrical Characteristics(4)
TA = 25C with VIN = VOUT + 1V; ILOAD = 100A; CBATT = 10F; SD = 0V; RSET=1k. Bold values indicate -40C < TJ < +125C; unless otherwise specified. Parameter Output Voltage Accuracy ADJ Pin Voltage Accuracy Line Regulation Load Regulation Dropout Voltage(3) Ground Current VIN Pin Current Shutdown Pin Current Shutdown Input Threshold Shutdown Hysteresis Current Limit Accuracy(4, 5) VIN = VOUT + 1V to 16V @ ILOAD = 50mA ILOAD = 0.1mA to 1A ILOAD = 100mA, RSET = 167 ILOAD = 700mA, RSET = 167 ILOAD = 10mA, RSET = 167 ILOAD = 700mA, RSET = 167 SD = VIN SD = 5.2V, VBAT = 0 Logic High, regulator off Logic Low, regulator on 60 VOUT = 0.9 x VNOM; IOUT = 1.2A, RSET = 167, TJ = -40C to +85C VOUT = 0.9 x VNOM; IOUT = 0.1A, RSET = 2k -5 -20 0.1 RSET shorted to ground, VBAT = 0.9 x VNOM VIN = High impedance or ground 35 30 50 40 1.25 1.65 4.2 50 70 0.74 0.1 150 0.5 37 800 1.0 46 950 190 2.0 55 1150 +5 +20 1.2 2.5 20 65 70 95 100 0.95 1.1 0.9 Condition Variation from VOUT = 4.2V; TJ = -5C to +60C; ILOAD = 50mA Min -0.75 -1.5 0.5955 -0.1 0.3 160 375 2 24 120 0.1 250 550 3 35 300 5 Typ Max +0.75 +1.5 0.6045 +0.1 Units % % V %/V % mV mV mA mA A A V V mV % % A A A mA mA mA mA V A mA A A
0.6
Current Limit Setpoint (5) Range Maximum Current Limit VBAT Reverse Current
Digital End-of-Charge (DEOC) Output IEOC (6, 7) REOC = 4k Current Falling IEOC (6, 7) DEOC Logic-Low Voltage DEOC Leakage Current DEOC On Resistance REOC Maximum Current Limit REOC = 4k Current Rising IDEOC = 5mA, IBAT = 700mA Logic High = VIN = 16V VIN = +5V REOC shorted to ground
Analog Charge Indicator (ACHG) Output (8) ISOURCE IBAT = 50mA IBAT = 1.2A, TJ = -40C to +85C
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Notes: 1. 2. 3. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating.
MIC79110
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. VNOM denotes the nominal output voltage. IRSET = (0.2V/RSET) x 1000 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. IEOC = (0.2V/REOC) x 1000 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.
4. 5. 6. 7. 8.
Block Diagram
VIN
Current Limit Sense Thermal Protection + VREF End of Charge Detect
BAT SNS Li-Ion DEOC
SD
Shutdown Control RSET Current Limit Set
ACHG
REOC GND
MIC79110 Block Diagram
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MIC79110
Typical Characteristics
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MIC79110
Typical Characteristics (continued)
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MIC79110
Functional Characteristics
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MIC79110 active low, there is reverse battery current protection built in. The current is limited to less than 10A 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.
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 the following equation: IRset = (0.2/Rset) x 1000 Using a 167 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 follows: IREOC = (0.2/REOC) x 1000 Using a 4k REOC resistor will set the end-of-charge current at 50mA. IREOC 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-ofcharge.
MIC79110 V-I Curve
I Current
Standard V-I Curve
0.7V
IMAX = (0.2/R SET )x1000
I Current
500mA
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 October 2007 8
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.
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MIC79110 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 0C or above 45C. Charge current must not be too high, typically below 0.7C 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 100C.
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.
* * *
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Micrel, Inc. Simple Charger - External Trigger to Reset Charge Cycle reset
Reset charge cycle.
MIC79110 External Trigger to Reset Charger 1. VIN steps up to a voltage greater than VBAT. 2. SD held low by CSD until active high DEOC pulls shutdown low. 3. DEOC releases SD, resistor pull-up from SD pin, VIN pulls VSD to VIN. 4. An external signal applied to the gate of the external NCH pulls SD pin-to-ground. 5. IBAT is near zero (2 to 4A) because VIN is below VBAT and the reverse shutoff circuit is turning the charge to the battery off. 6. IBAT is decreased as VBAT approaches VBAT set volt-age. IBAT decreases below the DEOC threshold and DEOC is released high allowing VSD to go high. 7. External NCH turns part on, after a small delay IBAT turns on. 8. Active high DEOC pin goes high because of reverse shutoff. DEOC remains high until IBAT exceeds DEOC threshold, then goes low. 9. IBAT decreases below (see #5) DEOC threshold. 10. Active low DEOC is high because VIN is below VBAT and reverse shutoff holds DEOC comparator off. As VIN increases above VBAT, the reverse volt-age shutoff turns off, DEOC comparator becomes active. While IBAT is below DEOC threshold DEOC active low goes low, when IBAT exceeds DEOC threshold IBAT goes high. 11. Legitimate Activation of active low DEOC until SD shuts down part and DEOC AL (active low) goes high.
SD RSET SNS BAT VIN
GND Reoc DEOC AEOC VIN CDELAY 0.1F
The VIN voltage steps up to a voltage greater than VBAT. When VIN is below VBAT, the IBAT current is near zero and the reverse shutoff circuit is turning the charge to the battery off. The IBAT slowly increases as VIN rises above VBAT. DEOC is pulled low when the IBAT current is above the Ieoc current set by REOC. When the DEOC is low, the shutdown pin is also forced low and helps discharge CSD. When the VBAT reaches the set voltage, the IBAT begins to slowly drop. When the IBAT is less than the IEOC threshold, the DEOC output goes high impedance, indicating end-of-charge. When an external signal is applied to the gate, the external NCH pulls the SD and DEOC pins to ground. This restarts the charging process.
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Vin VSD Vbat set voltage Vbat SD threshold 1 2 2
MIC79110
3 Vgate
6 4 7 5 Ibattery
8 Active high DEOC pin
9 10 Active low DEOC pin
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Micrel, Inc. Auto Top-Off-Charger - Application Circuit
MIC79110 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. Top-Off-Charger with Internal Reset - Application Circuit
Lithium-Ion batteries will begin to lose their charge over time. The MIC79110 can be configured to automatically recharge the battery if the voltage drops below a certain voltage. This minimum voltage is set by a resistor divider at the battery and connected to the SD pin. When the battery voltage falls below the minimum voltage, the SD pin is pulled low to start the normal charging process.
Battery charging Self discharge
SD RSET SNS BAT R1 3M VIN
GND REOC DEOC AEOC VIN
R2
1M LI-ion Battery VIN
4.2 V VBat min VBattery
Deoc trip
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. Auto-Shutdown Using Shutdown Pin
IBattery
Vs
R1 VBat min=0.975V( R2 +1)
R2=1meg
VBat min 1 R1=( 0.975 -1) R 2
Vbat set (4.2V)
Vbat 4 2 3 1 SD Voltage Vbat low set by divider.
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 the following equation to setup the maximum VIN.
VIN (MAX) R1 = +1 VSD R2 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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Package Information
(R) 10-Pin 3mm x 3mm MLF (ML)
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
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. 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. (c) 2004 Micrel, Incorporated.
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