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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://w ww.micrel.com september 24 , 2013 revision 2.1 general description the micrel mic79110 i s 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 mic7 9110 packs full functionality into a small space. other features of the mic7 9110 include two independent indicators: a digital end - of - c harge signal that is programmable with a resistor - to - ground and an analog current output that is proportional to the outp ut 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 disconn ected, the mic79110 also provides minimal reverse - current and reversed - battery protection . available in both ?xed 4.2v and adjustable outputs, the mic79110 is offered in the leadless 10 - pin 3mm 3mm dfn with an operatin g junction temperature range of C 40?c to +125?c . datasheets and support documentation are available on micrels web site at : www.micrel.com . features ? input voltage range: 2.5v to 16v ? high output voltage accuracy of 0.75% over C 5c to +60?c ? current limit 5% accurate from C 5c t j + 125c ? programmable end - of - charge flag ? analog output pro portional 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: C 40c to +125c applications ? cellular phones and pdas ? digital cameras and c amcorders ? mp3 players ? notebook pcs ? portable meters ? cradle/car chargers, and b attery packs typical a pplication
micrel, inc. mic79110 september 23 , 201 3 2 revision 2. 1 ordering information part number marking code ( 1 ) voltage junction temperature range package mic79110 - 4.2yml l942 4.2v C 40 to +125c 10- pin 3mm 3mm dfn MIC79110YML l9aa adjustable C 40 to +125c 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 shu tdown input. logic high = off; logic low = on. 2 rset current limit: sets constant current limit via an external resistor to ground. i r set = (0.2v/r set ) 1000. 3 sns (fixed voltage only): sense output, connect directly to battery. 3 adj (adjustab le voltage only): feedback input. 4 bat battery ter minal. connect to single - cell l ithium - ion battery. 5, 6 vin input supply pin. 7 achg analog charge indicator output: current source whos 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 r eoc is charging the battery. when the current drops to less than the current set by r eoc , the output go es high impedance, indicating end - of - charge. 9 reoc end -of - charge set: sets end- of - charge current threshold via an external resistor to ground. i eoc = (0.2v/ r eoc ) 1000. 10 gnd ground
micrel, inc. mic79110 september 23 , 201 3 3 revision 2. 1 absolute maximum ratings ( 2 ) input supply voltage (v in ) .................................... 0v to 18v shutdown input voltage (v sd ) .............................. 0v to 10v output voltage (adj) ..................................................... 10v power dissipation ................................... internally limited junction temperature ............................... C 40c to +125c operating ratings ( 3 ) i nput supply voltage ........................................ 2.5v to 16v shutdown input voltage (v sd ) ................................ 0v to 7v output voltage (adj) .................................................... 9.6v junction temperature range (t j ) ............. C 40c to +125c 3mm 3mm dfn - 10 ( ja ) ..................................... 60c 3mm 3mm dfn - 10 ( jc ) ....................................... 2c electrical characteristics ( 4 ) t a = 25c with v in = v out + 1v; i load = 100a; c bat = 10f; sd = 0v; r set = 1k. bold values indicate C 40oc < t j < +125c; unless otherwise specified. parameter condition min. typ. max. units output voltage accuracy v out = 4.2v; i load = 50ma ; t j = C 5c to +60c - 0.75 +0.75 % v out = 4.2v; i load = 50ma; t j = C 40 c to + 125 c - 1.5 +1.5 adj pin voltage accuracy 0.5955 0.6 0.6045 v line reg ulation v in = v out + 1v to 16v @ i load = 50ma - 0.1 +0.1 %/v load regulation i load = 0.1ma to 1a 0.3 % dropout voltage ( 5 ) i load = 100ma, r set = 167 160 250 mv i load = 700ma, r set = 167 375 550 mv ground current i load = 10ma, r set = 167 2 3 ma i load = 700ma, r set = 167 24 35 ma vin pin current sd = v in 120 300 a shutdown pin current sd = 5.2v, v bat = 0 0.1 5 a shutdown inpu t threshold logic high, regulator off 1.05 v logic low, regulator on 0.93 v shutdown hysteresis 60 mv current limit accuracy ( 6 , 7 ) v out = 0.9 v nom ; i out = 1.2a, r set = 167, t j = C 40c to +85c -5 +5 % v out = 0.9 v nom ; i out = 0.1a, r set = 2k -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 v oltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured a t 1v differen tial. 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. v nom denotes the nominal output voltage . 7. i r set = (0.2v/r set ) 1000 .
micrel, inc. mic79110 september 23 , 201 3 4 revision 2. 1 electrical char acteristics ( 4 ) (continued) t a = 25c with v in = v out + 1v; i load = 100a; c bat = 10f; sd = 0v; r set = 1k. bold values indicate C 40oc < t j < +125c; unless otherwise specified. parameter condition min. typ. max . units maximum current limit r set shorted to ground, v bat = 0.9 v nom 1.25 1.65 2.5 a v bat reverse current v in = high impedance or ground 4.2 20 a digital end C of C charge (deoc) output i eoc ( 8 , 9 ) r eoc = 4k? current falling 35 50 65 ma 30 70 i eoc ( 8 , 9 ) r eoc = 4k? current rising 50 70 95 ma 40 100 d eoc logic C low voltage i eoc = 5ma, i bat = 700ma 0.74 0. 95 v d eoc leakage current logic high = v in = 16v 0.1 a d eoc on resistance v in = +5v 150 190 ? r eoc maximum current limit r eoc shorted to ground 0.5 1.0 2.0 ma analog charge indicator (achg) output i source ( 10) i bat = 50ma 37 46 55 a i bat = 1.2a, t j = C 40c to +85c 800 950 1150 notes: 8. output c urrent i eoc when digital end - of - c harge output goes high impedance. currents greater than i eoc , the d eoc output is low, currents lower than i eoc , d eoc is high i mpedance. 9. i eoc = (0.2v/r eoc ) 1000 . 10. i source is the current output from a chg pin. a resistor to ground from the a chg pin will program a voltage that is proportional to the output current.
micrel, inc. mic79110 september 23 , 201 3 5 revision 2. 1 block diagram
micrel, inc. mic79110 september 23 , 201 3 6 revision 2. 1 typical characteristics
micrel, inc. mic79110 september 23 , 201 3 7 revision 2. 1 typical characteristics (continued)
micrel, inc. mic79110 september 23 , 201 3 8 revision 2. 1 typical characteristics (continued)
micrel, inc. mic79110 september 23 , 201 3 9 revision 2. 1 functional characteristics
micrel, inc. mic79110 september 23 , 201 3 10 revision 2. 1 flow chart
micrel, inc. mic79110 september 23 , 201 3 11 revision 2. 1 application information detailed description the m ic79110 forms a complete charger for 1 - cell l ithium - 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 l ithium - ion chemistries. voltages other than 4.2v can be obtained with the adjustable version. other features include current limit, end - of - charge ?ag , and end - of - charge current limit using an external resistor. the shutdown pin enables low quiescent current when not charging . current - limit mod e mic79110 features an internal current limit that is set by the r set pin with a resistor - to - ground. the maximum current is calculated by equation 1: i rset = (0.2/r set ) 1000 eq. 1 using a 167 r set resistor will achieve the maximum current limit for t he mic79110 at 1.2 amperes. end - of - charge r eoc 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: i eoc = (0.2/r eoc ) 1000 eq. 2 using a 4k r eoc resistor will set the end - of - charge current at 50ma. i eoc should be set at 10% of the batterys rated current. digital end - of - charge output t his pin is the output of an open drain. when tied high to the supply using a resistor, the output will toggle high or low depend ing on the output current of i bat . ? low state indicates that the i bat current is higher than the programmed current set by r eoc . ? high state indicates that the i bat current is lower than the programmed current set by r eoc . the output goes high impedance in dicating end - of - charge. analog end - of - charge output the a chg 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 v bat > v in and the shutdown pin is active low, there is reverse battery current protection built in. the current is limited to les s than 10a over temperature. constant output voltage/current charging t he mic79110 features constant voltage and constant current output to correctly charge l ithium - ion batteries. the constant voltage is either 4.2v or adjustable. the constant current is set by the r set pin and is constant down to around 300mv. since r set 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 l ithium - ion batteries. if the outp ut current is too low, the battery will not begin charge . figure 1 . mic79110 constant output voltage
micrel, inc. mic79110 september 23 , 201 3 12 revision 2. 1 lithium - i on batteries lithium - ion batteries are charged in two stages to reach full capacity. the ?rst stage charges the bat tery with maximum charge current until 90% of the battery cells 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% o f the rated current. a third stage will occasionally top off with charge with constant voltage charge if the battery voltag e drops below a certain threshold . figure 2 . typical two - stage lithium charge profile all l ithium - ion ba tteries 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 charg es 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 l ithium - ion loses charge due to aging wheth er 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 - i on 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 0.7 c . ? discharge current protection to prevent damage due to short circuits. ? protection circuitry for over voltage applie d 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 shutd own protection for the battery if the ambient temperature is above 100c. auto top - off charger application circuit figure 3 . auto top - off charger ? application circuit lithium - i on 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 v bat 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 c harging process .
micrel, inc. mic79110 september 23 , 201 3 13 revision 2. 1 figure 4 . aut o top - off charger application figure 5 . char ging description 1. sd not held low by active high d eoc because d eoc comparators 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 d eoc . 4. divider voltage above sd threshold and d e oc open. 5. divider voltage drops below sd threshold and charging begins again. figure 6 . top - off charger with internal reset ? application circuit this cir cuit is similar to the auto top - off charger circuit mentioned above excep t that the d eoc pin is externally triggered to restart the charging cycle. it still uses the same resistor divider to set the mini mum battery voltage before the l ithium - ion needs to be recharged. figure 7 . auto - shutdown using sh utdown 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 v in using a resistor divider. use e quation 3 to setup the maximum v in : ( ) 1 2 r 1 r v max vin 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.
micrel, inc. mic79110 september 23 , 201 3 14 revision 2. 1 package information ( 11) and recommended landing pattern 10- pin 3mm 3mm dfn (mm ) note: 11. package information is correct as of the publication date. for updates and most current information, go to www.micrel.com .
micrel, inc. mic79110 september 23 , 201 3 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 mic rel 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 micr els 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 mal function 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 purchasers use or sale of micrel products for use in life support appliances, devices or systems is a purchasers own risk a nd purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 20 13 micrel, incorporated.
micrel, inc. mic79110 september 23 , 201 3 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

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