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general description the max8845z/max8845y/max8845x/max8845w areintelligent, stand-alone constant-current, constant-volt- age (cccv), thermally regulated linear chargers designed for charging a single-cell lithium-ion (li+) bat- tery. the max8845z/max8845y/max8845x/max8845w integrate a current-sense circuit, mosfet pass element, thermal-regulation circuitry, and eliminate the external reverse-blocking schottky diode to create the simplest and smallest charging solutions for handheld equipment. the ics control the charging sequence from the pre- qualification state through constant current fast-charge, top-off charge, and full-charge indication. proprietary thermal-regulation circuitry limits the die temperature during fast-charging or when the ics are exposed to high ambient temperatures, allowing maximum charg- ing current without damaging the ics. the max8845z/max8845y/max8845x/max8845w achieve high flexibility by providing adjustable fast- charge currents (seti) and an adjustable top-off cur- rent threshold (min) through external resistors. the max8845z/max8845y/max8845x /max8845w feature a booting assistant circuit that distinguishes inputsources and battery connection and provides an enable signal (abo?ax8845z and abo max8845y/max8845x /max8845w) for system booting. the max8845z/max8845y/max8845x/max8845w alsointegrate an overvoltage-protected output (safeout) for low voltage-rated usb or charger inputs in system, and a battery-pack detection circuit (detbat) that disables the charger when the battery pack is absent. other features include an active-low control input ( en ), an active-low input power source detection output ( pok ), and a fully charged top-off threshold detection output ( chg ). the max8845z/max8845y/max8845x/max8845waccept an input supply range from 4.25v (4.4v for max8845w only) to 28v, but disable charging if the supply voltage exceeds +7.5v (+8.0v for max8845x only) to protect against unqualified or faulty ac adapters. the ics operate over the extended tempera- ture range (-40? to +85?) and are available in a com- pact 12-pin, thermally enhanced thin qfn, 3mm x 3mm package (0.8mm max height). applications cellular and cordless phonessmart phones and pdas digital still cameras mp3 players usb appliances charging cradles and docks bluetooth equipment features ? cccv, thermally regulated linear 1-cell li+battery charger ? no external mosfet, reverse blocking diode, orcurrent-sense resistor ? programmable fast-charge currents (1a rms max) ? programmable top-off current threshold (min) ? input overvoltage protected 4.7v output(max8845z/max8845y/max8845w) or 4.85v (max8845x) (safeout) ? proprietary die temperature regulation control(+115?) ? 4.25v (4.4v for max8845w only) to 28v inputvoltage range with input overvoltage protection above +7.5v (+8.0v for max8845x only) ? low-dropout voltage (300mv at 500ma) ? input power-source detection output ( pok ), charge status output ( chg ), charge-enable input ( en ) ? output for autobooting (abo?ax8845z,abo ?ax8845y/max8845x/max8845w) ? tiny, 3mm x 3mm 12-pin thin qfn package,0.8mm height (max) max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output ________________________________________________________________ maxim integrated products 1 19-4340; rev 1; 9/09 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available ordering information part pin-package top mark abo active state max8845z etc+ 12 thin qfn-ep* abl active high max8845y etc+ 12 thin qfn-ep* abm active low max8845x etc+ 12 thin qfn-ep* abq active low max8845w etc+ 12 thin qfn-ep* abr active low note: all devices are specified over the -40? to +85? oper- ating temperature range. + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. bluetooth is a registered trademark of bluetooth sig. typical operating circuit and pin configurations appear at end of data sheet. downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 2 _______________________________________________________________________________________ absolute maximum ratingselectrical characteristics (v in = 5v, v batt = 4v, r pok = 1m ? to batt, en = unconnected, r seti = 2.8k ? to gnd, v detbat = 0, c batt = 2.2?, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in to gnd ...............................................................-0.3v to +30v abi, batt, en , pok , abo, abo , chg , detbat, seti, min, safeout to gnd ................................................-0.3v to +6v in to batt continuous current .........................................1a rms continuous power dissipation (t a = +70?) 12-thin qfn (derate 14.7mw/? above +70?) (multilayer pcb) ......................................................1176.5mw batt short-circuit duration .......................................continuous operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter conditions min typ max units input supply voltage range 0 28 v 4.25 7.00 input supply operating voltage range max8845w only 4.40 7.00 v v in rising, 100mv hysteresis (typ) 7.0 7.5 8.0 overvoltage lockout trip threshold max8845x only 7.5 8.0 8.5 v constant current chargingi in - i batt , i batt = 0 0.22 0.50 constant current chargingi in - i batt, i batt = 500ma 1 ic disabled, v en = 5v 0.20 0.50 t a = +25? 0.02 input current v in = 4v, v batt = 4.2v (4.35v for max8845w only) t a = +85? 0.03 ma batt, chg , pok minimum batt bypass capacitance 2.2 ? v batt prequalification threshold voltage v batt rising, 100mv hysteresis (typ) 2.3 2.5 2.7 v 4.175 4.200 4.225 i batt = 0 t a = -40? to +85? 4.158 4.200 4.242 4.324 4.350 4.376 battery regulation voltage max8845w only 4.306 4.350 4.394 v regulator dropout voltage (v in - v batt )v batt = 4.1v, i batt = 425ma 260 mv v in = 0 to 4v, v batt = 4.2v (4.35v for max8845w only) 51 0 batt input current ic disabled 3 ? current-sense amplifier gain (i batt to i seti )i batt = 500ma 1016 ?/a t a = 0? to +85? 460 500 540 v batt = 3.5v, r seti = 2.8k t a = -40? to +85? 425 500 575 fast-charge current v batt = 3.5v, r seti = 14k t a = 0? to +85? 85 100 115 ma chg top-off threshold i batt falling, battery is charged r min = 1.75k 106 ma downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output _______________________________________________________________________________________ 3 parameter conditions min typ max units chg hysteresis i batt rising after top-off is detected, r min = 1.75k 38 ma chg detection delay i batt falls below top-off threshold 4.0 6.2 10.7 ms prequalification charge current percentage of the fast-charge current, v batt = 2.2v t a = 0? to +85? 5 10 15 % chg , pok output low threshold i pok = 5ma , i chg = 5ma 0.4 v t a = +25? 1 chg , pok output high leakage current v pok = 5.5v, v chg = 5.5v t a = +85? 0.01 ? v in rising 40 pok threshold v in - v batt v in falling 30 mv detbat, safeout detbat logic-input low threshold 0.4 detbat logic-input high threshold 1.3 v detbat pullup resistor detbat to v l = 3v 470 k minimum safeout bypass capacitance 1 f i safeout = 30ma, v in = 5v, t a = 0? to +85? (max8845z/max8845y/max8845w) 4.5 4.7 4.9 safeout regulated output i safeout = 20ma, v in = 5v, t a = 0? to +85? (max8845x) 4.75 4.85 5.0 v safeout current limit 100 ma en , abi, abo, abo en , abi internal pulldown resistor 100 200 400 k en logic-input low threshold 4.25v (4.4v for max8845w only) v in 7v 0.4 v en logic-input high threshold 4.25v (4.4v for max8845w only) v in 7v 1.3 v abi logic-input low threshold v batt = 4v, v in = 0 0.4 v abi logic-input high threshold v batt = 4v, v in = 0 1.3 v abo output low threshold (max8845y/ max8845x/max8845w) open drain, i abo (sink) = 1ma 0.4 v abo output high threshold (max8845y/ max8845x/max8845w) open drain, 100k pullup to batt v batt - 0.4v v abo output low threshold(max8845z) i abo(sink) = 1ma 0.4 v abo output high threshold (max8845z) i abo(source) = 1ma v batt - 0.4v v thermal die temperature regulation threshold 115 ? electrical characteristics (continued)(v in = 5v, v batt = 4v, r pok = 1m ? to batt, en = unconnected, r seti = 2.8k ? to gnd, v detbat = 0, c batt = 2.2?, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) note 1: specifications are 100% production tested at t a = +25?. limits over the operating temperature range are guaranteed by design and characterization. downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 4 _______________________________________________________________________________________ typical operating characteristics (v in = 5v, v batt = 4v, r pok = r chg = 200k ? to 5v, en = unconnected, r seti = 2.8k ? to gnd, r min = 1.74k ? to gnd, r detbat = 4.7k ? to gnd, c batt = 2.2?, t a = +25?, unless otherwise noted.) 0 0.30.2 0.1 0.50.4 0.90.8 0.7 0.6 1.0 0 4 8 12 16 20 24 28 supply current vs. input voltage max8845z/y/x/w toc01 input voltage (v) supply current (ma) v en = 0, i batt = 0 v in rising 0 0.20.1 0.40.3 0.5 0.6 01 0 1 5 5 202530 disabled mode supply current vs. input voltage max8845z/y/x/w toc02 input voltage (v) supply current ( a) v en = 5v 0 200100 400300 600500 700 900800 1000 0 1.0 1.5 2.0 0.5 2.5 3.0 3.5 4.0 4.5 charge current vs. battery voltage max8845z/y/x/w toc03 battery voltage (v) charge current (ma) 0 200100 400300 500 600 01 2 1 6 4 8 20 24 28 charge current vs. input voltage max8845z/y/x/w toc04 input voltage (v) charge current (ma) 0 300200 100 400 500 600 700 800 900 1000 0 200 100 300 400 500 600 charge current vs. input voltage headroom max8845z/y/x/w toc05 v in - v batt (mv) charge current (ma) v batt = 4v, v in rising 0 1.51.0 0.5 2.52.0 4.54.0 3.5 3.0 5.0 0 4 8 1216202428 safeout output voltage vs. input voltage max8845z/y/x/w toc06 input voltage (v) safeout voltage (v) i safeout = 1ma 0 1.51.0 0.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 04 0 20 60 80 100 safeout output voltage vs. load current max8845z/y/x/w toc07 load current (ma) safeout voltage (v) 40 s/div startup into precharge i batt v in 100ma/div 5v/div 5v/div5v/div max8845z/y/x/w toc08 v en v pok 0 00 0 40 s/div shutdown (fast-charge to shutdown) i batt v in 500ma/div 5v/div 5v/div5v/div max8845z/y/x/w toc09 v en v pok 0 00 0 downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output _______________________________________________________________________________________ 5 typical operating characteristics (continued) (v in = 5v, v batt = 4v, r pok = r chg = 200k ? to 5v, en = unconnected, r seti = 2.8k ? to gnd, r min = 1.74k ? to gnd, r detbat = 4.7k ? to gnd, c batt = 2.2?, t a = +25?, unless otherwise noted.) -1.0 -0.4-0.6 -0.8 -0.2 0 0.2 0.4 0.6 0.8 1.0 -40 10 -15 35 60 85 battery regulation accuracy vs. ambient temperature max8845z/y/x/w toc10 ambient temperature ( c) battery regulation accuracy (%) i batt = 0 fast-charge current vs. r seti max8845z/y/x/w toc11 r seti (k ? ) fast-charge current (ma) 1000 100 10 10 100 1000 1 1 10,000 top-off current threshold vs. 1/r min (k ? ) max8845z/y/x/w toc12 1/r min (k ? ) top-off current threshold (ma) 100 150 200 250 300 350 400 450 500 550 600 50 0.4 0.6 0.8 2.0 1.0 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 1.2 1.4 1.6 1.8 top-off current rising top-off current falling 0 200100 400300 600500 700 -40 0 20 -20 40 60 80 100 charge current vs. ambient temperature max8845z/y/x/w toc13 ambient temperature ( c) charge current (ma) v batt = 4v v batt = 3.2v r seti = 2.8k ? 4 s/div autoboot enabled by abi signal (max8845z) v abi v in 5v/div 5v/div 5v/div5v/div max8845z/y/x/w toc14 v batt v abo 0 00 0 20 s/div autoboot enabled by input voltage (max8845z) v abi v in 5v/div 5v/div 5v/div5v/div max8845z/y/x/w toc15 v batt v abo 0 00 0 4 s/div autoboot enabled by abi signal (max8845y/max8845x/max8845w) v abi v in 5v/div 5v/div 5v/div5v/div max8845z/y/x/w toc16 v batt v abo 0 00 0 downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 6 _______________________________________________________________________________________ pin description pin max8845z max8845y/max8845x/ max8845w name function 1 1 seti charge-current program and fast-charge current monitor. output current from seti is1016? per ampere of battery charging current. set the charging current by connecting a resistor (r seti in figure 3) from seti to gnd. i fast-charge = 1400v/r seti . to configure the max8845z/max8845y/max8845x/max8845w as a usb charger, see figure 5. 2 2 detbat battery pack id resistor detection input. if detbat is pulled low through a pulldown resistor less than 51k ? the charger is enabled. if detbat is left unconnected, the charger is disabled. 3 3 abi autobooting external input. see the autobooting assistant section and table 1 for autobooting conditions. abi is pulled to gnd through an internal 200k ? resistor. 44 en active-low, logic-level enable input. drive en high to disable charger. drive en low or leave unconnected for normal operation. en has an internal 200k ? pulldown resistor. 5 5 gnd ground. connect gnd and the exposed pad to a large copper ground plane formaximum power dissipation. connect gnd to the exposed pad directly under the ic. 66 pok active-low, input voltage status indicator. pok is an open-drain output that asserts low when 2.35v < v in < 7v (7.5v for max8845x only) and (v in - v batt ) > 40mv. if v in > +7.5v (+8.0v for max8845x only) or v batt > v in the ic is shut down and pok becomes high impedance. connect a pullup resistor to the microprocessor? i/o voltage when interfacing with a microprocessor logic input. 7 abo active-high, autobooting logic output. see the autobooting assistant section and table 1 for autobooting conditions. ? abo active-low, open-drain logic output. see the autobooting assistant section and table 1 for autobooting conditions. 8 8 batt li+ battery connection. bypass batt to gnd with a 2.2? ceramic capacitor. 99m i n top - o ff c ur r ent thr eshol d p r og r am m ab l e inp ut. i m in ( m a) fal l i ng = 148v /r m in ( k ? ) + 22 ( m a) . 10 10 chg active-low, charging indicator. chg is an open-drain output that is pulled low once charging begins. chg is high impedance when the battery current drops below min, or when the ic is disabled. connect a pullup resistor to the microprocessor? i/o voltage when interfacing with a microprocessor logic input. 11 11 in input supply voltage. bypass in to gnd with a 1? or larger ceramic capacitor to improve line noise and input transient rejection. 12 12 safeout 4.7v (max8845z/max8845y/max8845w) or 4.85v (max8845x) regulated ldo output with input overvoltage protection. bypass safeout to gnd with a 1? or larger ceramic capacitor. safeout can be used to supply low voltage-rated usb systems. e p exposed pad. connect the exposed pad to a large ground plane for maximum powerdissipation. connect gnd to the exposed pad directly under the ic. downloaded from: http:///
detailed description the max8845z/max8845y/max8845x/max8845wchargers use voltage, current, and thermal-control loops to charge a single li+ cell and protect the battery (figure 1). when a li+ battery with a cell voltage below 2.5v is inserted, the max8845z/max8845y/max8845x/ max8845w chargers enter a prequalification stage where it precharges that cell with 10% of the user-pro- grammed fast-charge current (figure 2). the chg indi- cator is driven low to indicate entry into the prequalifi-cation state. when the battery voltage exceeds 2.5v, the charger soft-starts as it enters the fast-charge stage. the fast-charge current level is programmed through a resistor from seti to gnd. as the battery voltage approaches 4.2v, the charging current is reduced. if the battery current drops to less than the max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output _______________________________________________________________________________________ 7 output driver, current sense, and logic temperature sensor vl regulator ref refok v in ovlo vl uvlo v ref v ref logic battdetbat abi abo (max8845z only) abo (max8845y/max8845x/max8845w) en pok in batt in batt pok 200k ? gnd ep +115 c 4.2v li+ (4.35v for max8845w only) v i/o 200k ? chg max8845z max8845y max8845x max8845w v l v ref i minref detbat linear regulator with ovp seti min safeout figure 1. max8845z/max8845y/max8845x/max8845w functional diagram downloaded from: http:///
max8845z/max8845y/max8845x/max8845w top-off current threshold set by r min , the charger enters top-off mode and the chg indicator goes high impedance signaling that the battery is fully charged. overvoltage-protected output (safeout) safeout is a linear regulator that provides an outputvoltage of 4.7v (max8845z/max8845y/max8845w) or 4.85v (max8845x) and can be used to supply low volt- age- rated usb systems. the safeout linear regulator turns on when v in 4.25v regardless of en and is dis- abled when v in is greater than the overvoltage thresh- old (7.5v typ) (8.0v typ for max8845x only). battery-pack detection input (detbat) detbat is a battery-pack id resistor detector thatenables the battery charger if pulled low through a resistor that is less than 51k ? . if detbat is left uncon- nected or the pulldown resistor is 51k ? or greater the battery charger is disabled. if detbat is not used con-nect detbat to gnd for normal operation. pok output the open-drain pok output asserts low when 2.35v v in 7v (7.5v for max8845x only) and (v in - v batt ) 40mv (typ v in rising). pok is high impedance during shutdown. when interfacing with a microprocessorlogic input, a pullup resistor to the microprocessor? i/o voltage may be required. autobooting assistant the max8845z/max8845y/max8845x/max8845w con-tain autobooting assistant circuits that generate an enable signal for system booting (abo?ax8845z, abo ?ax8845y/max8845x/max8845w). for the max8845z, the booting assistant functions as an internalor gate (figure 1). the first input is dependant on the input voltage (v in ) and detbat while the second input is an external signal applied to abi. the first input ( pok ) is driven high once detbat is pulled low through aresistor less than 51k ? , 2.35v v in 7v (7.5v for only max8845x), and (v in - v batt ) 40mv (typ v in rising). the second input signal (abi) is driven by an externalsource (table 1). abi enables an autoboot signal when a battery is connected at batt and is independent of pok . if pok is pulled low, the booting assistant always drives abo high regardless of abi. abi is pulled to gndthrough an internal 200k ? resistor. if abi is supplied from an outside exposed pin, a rc filter (figure 4) isrequired for esd protection and noise filtering. if abi is supplied by a system? internal gpio, or logic, the rc filter is not required. for the max8845y/max8845x/ max8845w, the output abo is only dependent on the state of abi (table 1). chg charge indicator output chg is an open-drain output that indicates charge sta- tus. table 2 describes the state of chg during different stages of operation. chg is suitable for driving a charge indication led. if the max8845z/max8845y/max8845x/ 28v linear li+ battery chargers with battery detection and overvoltage protected output 8 _______________________________________________________________________________________ v batt < 2.5v precharge 10% of ifast-charge chg = low fast-charge constant-current charge 100% of i fast-charge chg = low top-off 4.2 voltage regulation chg = high-z (max8845z/max8845y/max8845x) 4.35 voltage regulation (max8845w) (v in - v batt ) < 30mv v batt < 2.4v v batt 2.5v v in < ovp, and (v in - v batt ) 40mv, and ic enabled shutdown charger = disabled chg = high-z v in > ovp, or (v in - v batt ) < 30mv, or ic disabled asynchronous from anywhere v in > ovp, or (v in - v batt ) < 30mv, or thermal shutdown, or ic disabled i batt > 295v/r min (k ? ) - 24ma i batt i min for 6.2ms (typ) or longer charging current reduction charging current is reduced as necessary die temperature > +115 c any charging state return to charging state die temperature +115 c figure 2. charge-state diagram downloaded from: http:///
max8845w are used in conjunction with a microproces-sor, a pullup resistor to the logic i/o voltage allows chg to indicate charge status to the microprocessor insteadof driving an led. thermal regulation the thermal-regulation loop limits the max8845z/max8845y/max8845x/max8845w die temperature to +115? by reducing the charge current as necessary. this feature not only protects the ic from overheating, but also allows a higher charge current without risking damage to the system. charger enable input the max8845z/max8845y/max8845x/max8845wcontain active-low logic input ( en ) used to enable the chargers. drive en low, leave unconnected, or connect to gnd to enable the charge-control circuitry. drive en high to disable the charger-control circuitry. en has an internal 200k ? pulldown resistor. soft-start the soft-start algorithm activates when entering fast-charge mode. when the prequalification state is com- plete (v batt exceeds +2.5v), the charging current ramps up in 250? to the full charging current. thisreduces the inrush current demand on the input supply. applications information fast charge-current setting the maximum charging current is programmed by anexternal resistor connected from seti to gnd (r seti ). use the following equation to determine the fast-chargecurrent (i fast_charge ): where i fast_charge is in amps and r seti is in ohms. r seti must always be 1.4k ? or higher due to the con- tinuous charging current limit of 1a rms . top-off current threshold setting the top-off current threshold is programmed by anexternal resistor connected from min to gnd (r min ). use the following equation to determine the top-off cur-rent (i min ): i min (falling) = 148v/r min (k ? ) + 22ma i min (rising) = 295v/r min (k ? ) - 24ma where i min is in ma and r min is in k ? . use r min 2.2k ? . i v r fast charge seti _ = 1400 max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output _______________________________________________________________________________________ 9 abi batt pok charger state abo (max8845z) abo (max8845y/ max8845x/max8845w) low present high-z shutdown low high-z high present high-z shutdown high low low not present low cc/cv mode high high-z low present low fast-charge/top-off high high-z high present low fast-charge/top-off high low table 1. autobooting output states en v in v batt i batt chg state high x x 0 high-z disabled > 7.5v x low x> v in - 30mv 0 high-z shutdown low 4.25v (4.4v for max8845w only) v in 7.5v < 2.4v 10% of i fast-charge * low precharge low 4.25v (4.4v for max8845w only) v in 7.5v 2.5v 100% of i fast-charge * low fast-charge low 4.25v (4.4v for max8845w only) v in 7.5v 4.2v (4.35v for max8845w only) < i min high-z top-off table 2. chg states x = don? care. * i fast-charge is reduced as necessary to prevent the die temperature from exceeding +115?. note: present indicates that v batt 2v and not present indicates that the battery is not connected. downloaded from: http:///
max8845z/max8845y/max8845x/max8845w capacitor selection connect a ceramic capacitor from batt to gnd forproper stability. use a 2.2? ceramic capacitor for most applications. connect a 1? ceramic capacitor from in to gnd. a larger input capacitor can be used for high charging current to reduce input voltage ripple. connect a 1? ceramic capacitor from safeout to gnd. a larger bypass capacitor for safeout can be used for optimum noise immunity. ceramic capacitors with x5r or x7r dielectric are highly recommended due to their small size, low esr, and small temperature coefficients. thermal considerations the max8845z/max8845y/max8845x/max8845w areavailable in thermally enhanced thin qfn packages with exposed pads. connect the exposed pad to a large copper ground plane to provide a thermal contact between the device and the circuit board for increased power dissipation. the exposed pad transfers heat away from the device, allowing the ic to charge the battery with maximum current, while minimizing the increase in die temperature. dc input sources the max8845z/max8845y/max8845x/max8845woperate from well-regulated dc sources. the full charg- ing input voltage range is 4.25v (4.4v for max8845w only) to 7.5v (8v for max8845x only). the device can withstand up to 28v on the input without damage to the ic. if v in is greater than 7.5v (8v for max8845x only), the internal overvoltage-protection circuitry disablescharging until the input falls below 7.5v (8v for max8845x only). an appropriate power supply must provide at least 4.25v at the desired peak charging current and stay below 7v when unloaded. typical application circuits ac adapter application figure 3 shows the max8845z as a li+ battery chargerwith an ac adapter. the max8845z detects the presence of an input supply and detbet, resulting in pok pulled low. once pok is pulled low, the autobooting assistant drives abo high (max8845z) and enables the power supplies of the system to boot up. the max8845z beginscharging the battery when en is low or unconnected. by monitoring chg , the system can detect the top-off thresh- old and terminate the charge through en . the max8845z/max8845y/max8845x/max8845w also pro-vide an overvoltage-protected safeout to the system. factory system interface connector application figure 4 shows the max8845z as an autoboot assistorwith the factory system interface connector. the max8845z detects the abi input even though there is no input voltage available and generates an abo signal to turn on power supplies to boot up the system. the con- figuration in figure 4 is used for system development, testing, and calibrations in production or design stage. usb-powered li-ion charger the universal serial bus (usb) provides a high-speedserial communication port as well as power for the remote device. the max8845z/max8845y/max8845x/ max8845w can be configured to charge batteries at the highest current possible from the host port. figure 5 shows the max8845z as a usb battery charger. to make the circuit compatible with either 100ma or 500ma usb ports, the circuit initializes at 100ma charg- ing current. the microprocessor then enumerates the host to determine its current capability. if the host port is capable, the charging current is increased to 450ma to avoid exceeding the 500ma usb specification through gpio control. the max8845z/max8845y/max8845x/ max8845w also provide an overvoltage-protected safeout to the system. recommended pcb layout and routing place all bypass capacitors for in, batt, andsafeout as close as possible to the device. connect the battery to batt as close as possible to the device to provide accurate battery voltage sensing. provide a large copper ground plane to allow the exposed pad to sink heat away from the device. make all high-current traces short and wide to minimize voltage drops. a sample layout is available in the max8845z evaluation kit to speed designs. 28v linear li+ battery chargers with battery detection and overvoltage protected output 10 ______________________________________________________________________________________ downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output ______________________________________________________________________________________ 11 vbus gpio gpio gpio power supply on system 4.2v li+ pok v i/o chg ac adapter r seti 2.8k ? c batt 2.2 f c safeout 1 f r chg 1m ? r pok 1m ? en ep gnd min r min 1.75k ? batt detbat safeout in abi abo seti max8845z c in 1 f gnd figure 3. ac adapter application downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 12 ______________________________________________________________________________________ vbus gpio gpio gpio power supply on system pok v i/o chg interface connector r seti 2.8k ? c batt 2.2 f c safeout 1 f r chg 1m ? r pok 1m ? en ep gnd min r min 1.75k ? batt safeout in abi abo seti max8845z c in 1 f gnd 4.2v c abi 1 f r abi 10k ? detbat if the power supplyis active-low enabled, use the max8845y. figure 4. factory system interface connector application downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output ______________________________________________________________________________________ 13 vbus gpiogpio gpio gpio power supply on system 4.2v li+ pok v i/o chg mini-usb connector r setia 15.4k ? r seti 3.42k ? c batt 2.2 f c safeout 1 f r chg 1m ? r pok 1m ? en ep gnd min r min 3.09k ? batt detbat safeout in abi abo seti max8845z c in 1 f gnd figure 5. mini usb battery charger downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 14 ______________________________________________________________________________________ v in v safeout pok ovp ovp time v chg v en v safeout = 4.7v (4.85v for max8845x only) v pok figure 6. timing diagram downloaded from: http:///
max8845z/max8845y/max8845x/max8845w in batt (max8845z, abo) (max8845y/max8845x/max8845w, abo) detbat safeout pok chg ep c batt 2.2 f system supply gnd min r min 1.75k ? abi en on off seti v safeout 1 f 4.25v (4.4v for max8845w only) to 28v c in 1 f r set 2.80k ? 4.2v (4.35v for max8845w only)li+ max8845z max8845ymax8845x max8845w typical operating circuit 28v linear li+ battery chargers with battery detection and overvoltage protected output ______________________________________________________________________________________ 15 downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 16 ______________________________________________________________________________________ chg 123 987 12 11 10 4 5 6 safeout in min batt abo detbat abi en gnd pok seti max8845z top view *exposed pad + chg 123 987 12 11 10 4 5 6 safeout in min batt abo detbat abi en gnd pok seti max8845ymax8845x max8845w top view *exposed pad + pin configurations chip information process: bicmos downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output ______________________________________________________________________________________ 17 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . thin qfn.eps 0.10 c 0.08 c 0.10 m c a b d d/2 e/2 e a1 a2 a e2 e2/2 l k e (nd - 1) x e (ne - 1) x e d2 d2/2 b l e l c l e c l l c l c marking aaaa package outline, 12l thin qfn, 3x3x0.75mm 21-0136 custom eng 1 2 package type package code document no. 12 thin qfn-ep (3mm x 3mm) t1233-4 downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output 18 ______________________________________________________________________________________ exposed pad variations codes pkg. t1233-1 min. 0.95 nom. 1.10 d2 nom. 1.10 max. 1.25 min. 0.95 max. 1.25 e2 12 n k a2 0.25 ne a1 nd 0 0.20 ref - - 3 0.02 3 0.05 l e e 0.45 2.90 b d a 0.20 2.90 0.70 0.50 bsc. 0.55 3.00 0.65 3.10 0.25 3.00 0.75 0.30 3.10 0.80 pkg ref. min. 12l 3x3 nom. max. 0.35 x 45 pin id jedec weed-1 t1233-3 1.10 1.25 0.95 1.10 0.35 x 45 1.25 weed-1 0.95 weed-1 1.25 1.10 0.95 0.35 x 45 1.25 1.10 0.95 t1233-4 notes: 1. dimensioning & tolerancing conform to asme y14.5m-1994. 2. all dimensions are in millimeters. angles are in degrees. 3. n is the total number of terminals. 4. the terminal #1 identifier and terminal numbering convention shall conform to jesd 95-1 spp-012. details of terminal #1 identifier are optio nal, but must be located within the zone indicated. the terminal #1 identifier may be either a mold or marked feature. 5. dimension b applies to metallized terminal and is measured between 0.20 mm and 0.25 mm from terminal tip. 6. nd and ne refer to the number of terminals on each d and e sid e respectively. 7. depopulation is possible in a symmetrical fashion. 8. coplanarity applies to the exposed heat sink slug as well as the terminals. 9. drawing conforms to jedec mo220 revision c. 10. marking is for package orientation reference only. 11. number of leads shown are for reference only. 12. warpage not to exceed 0.10mm. package outline, 12l thin qfn, 3x3x0.75mm 21-0136 custom eng 2 2 package information (continued) for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . downloaded from: http:///
max8845z/max8845y/max8845x/max8845w 28v linear li+ battery chargers with battery detection and overvoltage protected output maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 19 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 3/09 initial release 1 9/09 corrected the pok output section description and added max8845x and max8845w to data sheet 1?9 downloaded from: http:///

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