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general description the MAX8814 intelligent, stand-alone constant-current, constant-voltage (cccv), thermally regulated linear charger is designed for charging a single-cell lithium- ion (li+) battery. the MAX8814 integrates the current- sense circuit, mosfet pass element, thermal- regulation circuitry, and eliminates the reverse-blocking schottky diode to create the simplest and smallest charging solution for handheld equipment. the ic controls the charging sequence from the pre- qualification state through constant-current fast-charge and the final constant voltage charge. proprietary ther- mal-regulation circuitry limits the die temperature dur- ing fast-charging or when the ic is exposed to high ambient temperatures, allowing maximum charging current without damaging the ic. the MAX8814 achieves high flexibility by providing an adjustable fast-charge current through an external resistor. other features include an active-low control input ( en ) and an active-low input power-source detec- tion output ( pok ). the ic also features a booting assis- tant circuit that distinguishes input sources and battery connection and provides an output signal (abo) for system booting. the MAX8814 accepts an input supply range from 4.25v to 28v, but disables charging if the input voltage exceeds +7v to protect against unqualified or faulty ac adapters. the ic operates over the extended tempera- ture range (-40? to +85?) and is available in a com- pact 8-pin thermally enhanced tdfn 2mm x 2mm package (0.8mm max height). applications cellular and cordless phones smartphones and pdas mp3 players digital still cameras usb appliances charging cradles and docks bluetooth equipment features cccv, thermally regulated linear 1-cell li+ battery charger no external mosfet, reverse blocking diode, or current-sense resistor programmable fast-charge current (1a rms max) proprietary die temperature regulation control (+115?) 4.25v to 28v input voltage range with input ovp above +7v charge-current monitor for fuel gauging (iset) low dropout voltage (300mv at 500ma) input power-source detection output ( pok ), charge-enable input ( en ) soft-start limits inrush current output for autobooting (abo) tiny 2mm x 2mm, 8-pin tdfn package, 0.8mm height (max) MAX8814 28v linear li+ battery charger with smart autoboot assistant ________________________________________________________________ maxim integrated products 1 19-0994; rev 0; 10/07 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim's website at www.maxim-ic.com. evaluation kit available ordering information in en abi iset gnd abo batt ep on off pok system supply 2.2 f li+ 4.25v to 28v MAX8814 + typical operating circuit part temp range pin- package pkg code top mark MAX8814eta+ -40? to +85? 8 tdfn 2mm x 2mm t822+2 abi bluetooth is a registered trademark of bluetooth sig. + denotes a lead-free and rohs-compliant package. pin configuration appears at end of data sheet.
MAX8814 28v linear li+ battery charger with smart autoboot assistant 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 5v, v batt = 4v, r pok = 1m to batt, en = 0v, r iset = 2.8k to gnd, c batt = 2.2?, t a = -40? to +85?, unless other- wise 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 rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns 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 to gnd....................................-0.3v to +6v abo to gnd............................................-0.3v to (v batt + 0.3v) iset to gnd .............................................................-0.3v to +4v in to batt continuous current .........................................1a rms continuous power dissipation (t a = +70?) 8-pin tdfn (derate 11.9mw/? above +70?) (multilayer pcb) ........................................................953.5mw 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 voltage range 028v input operating voltage range 4.25 6.50 v v in rising 40 power-ok threshold v in - v batt , 10mv hysteresis (typ) v in falling 30 mv overvoltage-lockout trip threshold v in rising, 100mv hysteresis (typ) 6.5 7 7.5 v constant-current charging mode (i batt = 0a) 0.8 1.35 ic disabled (v en = 5v) 0.23 0.50 t a = +25? 0.021 0.065 in input current v in = 4v, v batt = 4.2v t a = +85? 0.021 ma v in = 0 to 4v, v batt = 4.2v 110 batt input current ic disabled 3 ? t a = 0? to +85? 4.179 4.200 4.221 battery regulation voltage i batt = 0a t a = -40? to +85? 4.158 4.200 4.242 v minimum batt bypass capacitance 2.2 ? t a = 0? to +85? 524 570 616 v batt = 3.5v t a = -40? to +85? 485 570 656 t a = 0? to +85? 89 107 125 fast-charge current v batt = 3.5v, r iset = 14k t a = -40? to +85? 80 107 134 ma prequalification charge current percentage of the fast-charge current, v batt = 2.2v, t a = 0? to +85? 41015% die temperature regulation threshold +115 ? v batt prequalification threshold voltage v batt rising, 100mv hysteresis (typ) 2.3 2.5 2.7 v current-sense amplifier gain (i batt to i iset ) i batt = 570ma 877.2 ?/a
MAX8814 28v linear li+ battery charger with smart autoboot assistant _______________________________________________________________________________________ 3 parameter conditions min typ max units regulator dropout voltage (v in - v batt ) v batt = 4.1v, i batt = 425ma 240 500 mv en logic-input low voltage 4.25v < v in < 6.5v 0.4 v en logic-input high voltage 4.25v < v in < 6.5v 1.3 v en and abi internal pulldown resistance 100 200 400 k abi logic-input low voltage v in = 0v 0.4 v abi logic-input high voltage v in = 0v 1.3 v abo output low voltage i abo (sink) = 1ma 0.4 v abo output high voltage i abo (source) = 1ma v batt - 0.4v v pok output low voltage i pok = 5ma 0.4 v t a = +25? 0.001 1 pok output high leakage current v pok = 5.5v t a = +85? 0.002 ? electrical characteristics (continued) (v in = 5v, v batt = 4v, r pok = 1m to batt, en = 0v, r iset = 2.8k to gnd, c batt = 2.2?, t a = -40? to +85?, unless other- wise 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. typical operating characteristics (v in = 5v, v batt = 4v, r pok = 1m to batt, en = 0v, r iset = 2.8k to gnd, c batt = 2.2?, t a = -40? to +85?, unless other- wise noted. typical values are at t a = +25?.) 0 0.3 0.2 0.1 0.5 0.4 0.9 0.8 0.7 0.6 1.0 0 4 8 1216202428 supply current vs. voltage MAX8814 toc01 input voltage (v) supply current (ma) en = 0v 0 100 200 300 400 500 600 700 800 010 5 15202530 disabled mode supply current vs. input voltage MAX8814 toc02 input voltage (v) supply current ( a) v en = 5v 0 200 100 400 300 600 500 700 900 800 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 MAX8814 toc03 battery voltage (v) charge current (ma)
MAX8814 28v linear li+ battery charger with smart autoboot assistant 4 _______________________________________________________________________________________ 0 300 200 100 500 400 900 800 700 600 1000 0 4 8 12 16 20 24 28 charge current vs. input voltage MAX8814 toc04 input voltage (v) charge current (ma) 0 300 200 100 400 500 600 700 800 900 1000 0 200 100 300 400 500 charge current vs. input voltage headroom MAX8814 toc05 v in - v batt (mv) charge current (ma) v batt = 4v v in rising 40 s/div startup into precharge 100ma/div MAX8814 toc06 0a 5v/div 5v/div 5v/div 0v 0v 0v i batt v in v en v pok v batt = 2v 100 s/div shutdown (fast-charge to shutdown) 500ma/div MAX8814 toc07 0a 0v 5v/div 5v/div 5v/div 0v 0v i batt v in v en v pok -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 voltage accuracy vs. ambient temperature MAX8814 toc08 temperature ( c) battery regulation voltage accuracy (%) i batt = 0a charge current vs. r iset MAX8814 toc09 r iset (k ) charge current (ma) 1000 100 10 10 100 1000 1 1 10,000 0 200 100 400 300 600 500 700 -40 10 -15 356085 charge current vs. ambient temperature MAX8814 toc10 temperature ( c) charge current (ma) r iset = 2.8k v batt = 4v v batt = 3.2v 4 s/div autoboot enabled by abi signal MAX8814 toc11 0v 0v 5v/div 5v/div 5v/div 5v/div 0v 0v v abi v in v batt v abo 4 s/div autoboot enabled by input supply MAX8814 toc12 0v 5v/div 0v 5v/div 5v/div 5v/div 0v 0v v abi v in v batt v abo typical operating characteristics (continued) (v in = 5v, v batt = 4v, r pok = 1m to batt, en = 0v, r iset = 2.8k to gnd, c batt = 2.2?, t a = -40? to +85?, unless other- wise noted. typical values are at t a = +25?.)
MAX8814 28v linear li+ battery charger with smart autoboot assistant _______________________________________________________________________________________ 5 pin description pin name function 1in input supply voltage. bypass in to gnd with a 1? or larger ceramic capacitor to minimize line noise and maximize input transient rejection. 2 gnd ground. connect gnd and the exposed paddle to a large copper ground plane for maximum power dissipation. connect gnd to the exposed paddle directly under the ic. 3 iset charge-current program and fast-charge current monitor. output current from iset is 877.2? per ampere of battery charging current. set the charging current by connecting a resistor (r2 in figure 3) from iset to gnd. i fast-charge = 1596v / r iset . to configure the MAX8814 as a usb charger, see figure 4. 4 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. 5 abo autobooting logic output. see the autobooting assistant section and table 1 for autobooting conditions. 6 en 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. 7 pok input-voltage status indicator. connect a 1m pullup resistor from pok to an external system supply. pok is an open-drain output that asserts low when v in > 4.25v and (v in - v batt ) 40mv. if v batt (v in - 40mv), the ic is shut down and pok becomes high impedance. 8 batt battery connection. bypass batt to gnd with a minimum of 2.2? of capacitor. ?p exposed paddle. connect the exposed paddle to a large ground plane for maximum power dissipation. connect gnd to the exposed paddle directly under the ic.
MAX8814 28v linear li+ battery charger with smart autoboot assistant 6 _______________________________________________________________________________________ detailed description the MAX8814 charger uses voltage, current, and ther- mal-control loops to charge a single li+ cell and pro- tect the battery (figure 1). when a li+ battery with a cell voltage below 2.5v is inserted, the MAX8814 charger enters the prequalification stage where it precharges that cell with 10% of the user-programmed fast-charge current (figure 2). when the battery voltage exceeds 2.5v, the charger soft-starts as it enters the fast-charge stage. in the MAX8814, the fast-charge current level is programmed through a resistor from iset to gnd. as the battery voltage approaches 4.2v, the charging current is reduced. once the battery volt- age reaches 4.2v, the ic then enters a constant voltage regulation mode to maintain the battery at full charge. thermal regulation the thermal-regulation loop limits the MAX8814 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 ic. 6 _______________________________________________________________________________________ output driver, current sense, and logic temperature sensor vl regulator ref refok v in ovlo vl uvlo v ref v ref logic batt iset abi abo en pok in batt in batt pok 200k gnd ep +115 c li+ c3 2.2 f v i/o 200k c1 1 f r2 2.8k 4.25v to 28v r3 1m MAX8814 v l v ref figure 1. functional diagram
MAX8814 28v linear li+ battery charger with smart autoboot assistant _______________________________________________________________________________________ 7 charger enable input the MAX8814 contains an active-low logic input ( en ) used to enable the charger. drive en low, leave uncon- nected, or connect to gnd to enable the charger- control circuitry. drive en high to disable the charger- control circuitry. en has an internal 200k pull-down resistor. pok output the open-drain pok output asserts low when v in 4.25v and (v in - v batt ) 40mv (typ, v in rising). pok requires an external pullup resistor (1m typ) to an external power supply. pok is high impedance when v batt (v in - 40mv). autobooting assistant the MAX8814 contains an autobooting assistant circuit that generates an enable signal for system booting (abo). the booting assistant functions as an internal ?r?gate (figure 1). the first input is dependent on the input voltage (v in ), and the second input is an external signal applied to abi. the first input (pok) is driven high once v in 4.25v and (v in - v batt ) 40mv (typ, v in rising). the second input signal (abi) is driven by an external source. abi enables an autoboot signal (abo high) 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 (see table 1). abi is pulled to gnd through an internal 200k resistor. if abi is driven externally, a rc filter (r1 and c2 of figure 3) is required for esd protection and noise filter- ing. if abi is supplied by a system? internal gpio, or logic, the rc filter is not required. soft-start the soft-start algorithm activates when entering fast- charge mode. in the MAX8814, when the prequalifica- tion state is complete (v batt 2.5v), the charging current ramps up in 250? to the full charging current. this reduces the inrush current on the input supply. _______________________________________________________________________________________ 7 v batt < 2.5v precharge 10% charge current fast-charge constant-current charge 100% charge current voltage regulation constant voltage charge regulated 4.2v at batt (v in - v batt ) < 30mv v batt < 2.4v v batt 2.5v v in < 7v, and (v in - v batt ) 40mv, and ic enabled shutdown charger = disabled v in > 7v, or (v in - v batt ) < 30mv, or ic disabled asynchronous from anywhere v in > 7v, or (v in - v batt ) < 30mv, or ic disabled v batt 4.2v v batt < 4.2v figure 2. charge-state diagram abi batt pok charger state abo low present hi-z shutdown low high present hi-z shutdown high x not present low fast-charge/voltage regulation high x present low fast-charge/voltage regulation high table 1. abo and pok states x = don? care.
MAX8814 applications information charge-current selection the maximum charging current is programmed by an external resistor connected from iset to gnd (r iset ). calculate r iset as follows: where i fast-charge is in amperes and r iset is in ohms. iset can be used to monitor the fast-charge cur- rent level. the output current from iset is 877.2? per ampere of charging current. the output voltage at iset is proportional to the charging current: the voltage at iset is nominally 1.4v at the selected fast-charge current and falls with charging current as the cell becomes fully charged or as the thermal-regu- lation circuitry activates. capacitor selection connect a ceramic capacitor from batt to gnd for proper stability. use a 2.2? x5r ceramic capacitor for most applications. connect a 1? ceramic capacitor from in to gnd. use a larger input bypass capacitor for high charging currents to reduce supply noise. thermal considerations the MAX8814 is available in a thermally enhanced tdfn package with an exposed paddle. connect the exposed paddle to a large copper ground plane to pro- vide a thermal contact between the device and the cir- cuit board for increased power dissipation. the exposed paddle 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 MAX8814 operates from a well-regulated dc source. the full charging input voltage range is 4.25v to 7v. the device can withstand up to 28v on the input without damage to the ic. if v in is greater than 7v, the internal overvoltage-protection circuitry disables charg- ing until the input falls below 7v. an appropriate power supply must provide at least 4.25v at the desired peak charging current. v ir iset charge iset = 1140 r v i iset fast charge = ? 1596 28v linear li+ battery charger with smart autoboot assistant 8 _______________________________________________________________________________________ in abi iset abo batt gnd ep vi/o en gpio gpio adc power supply on system pok gnd factory test fixture or ac adapter c3 2.2 f li+ r3 1m r4 10k c4 0.1 f r2 2.8k c1 1 f r1 10k c2 0.1 f MAX8814 figure 3. microprocessor-interfaced li+ battery charger
application circuits microprocessor-interfaced charger figure 3 shows the MAX8814 as a microprocessor- cooperated li+ battery charger. the MAX8814 begins charging the battery when en is low. the microproces- sor can drive en high to disable the charger. the MAX8814 generates a pok signal to indicate the pres- ence of an input supply. by monitoring v iset , the sys- tem can measure the charging current and decide when to terminate the charge. usb-powered li-ion charger the universal serial bus (usb) provides a high-speed serial communication port as well as power for the remote device. the MAX8814 can be configured to charge a battery at the highest current possible from the host port. figure 4 shows the MAX8814 as a usb battery charger. to make the circuit compatible with either 100ma or 500ma usb ports, the circuit initializes at 100ma charging current. the microprocessor then enumerates the host to determine its current capability. if the host port is capable, the charging current is increased to 425ma to avoid exceeding the 500ma usb specification. layout and bypassing place the input and output capacitors as close as pos- sible to the ic. provide a large copper ground plane to allow the exposed paddle to sink heat away from the ic. connect the battery to batt as close as possible to the ic to provide accurate battery voltage sensing. make all high-current traces short and wide to minimize voltage drops. a sample layout is available in the MAX8814 evaluation kit to speed designs. chip information process: bicmos MAX8814 28v linear li+ battery charger with smart autoboot assistant _______________________________________________________________________________________ 9 in abi iset abo batt gnd ep v i/o en gpio gpio gpio adc power supply on system pok gnd usb port c3 2.2 f li+ r3 1m r4 10k c4 0.1 f r2 15.8k c1 1 f MAX8814 vbus + r5 4.99k n figure 4. usb battery charger
MAX8814 28v linear li+ battery charger with smart autoboot assistant 10 ______________________________________________________________________________________ 134 865 batt en abo MAX8814 2 7 pok in iset abi gnd tdfn 2mm x 2mm top view + exposed paddle pin configuration
MAX8814 28v linear li+ battery charger with smart autoboot assistant ______________________________________________________________________________________ 11 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) package outline 21-0168 2 1 d 6 & 8l tdfn exposed pad, 2x2x0.80mm 8l tdfn exposed pads.eps
MAX8814 28v linear li+ battery charger with smart autoboot assistant maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. symbol common dimensions 2.10 1.90 0.80 max. 0.70 min. 0.20 ref. 0.40 0.05 2.10 0.20 0.00 1.90 d a l a1 e a2 k 1.600.10 1.30 ref [(n/2)-1] x e 0.300.05 b 0.65 typ. e package variations pkg. code 0.900.10 e2 d2 6 n t622-1 0.25 min. package outline 21-0168 2 2 d 6 & 8l tdfn exposed pad, 2x2x0.80mm 1.300.10 1.50 ref 0.250.05 0.50 typ. 0.700.10 8 t822-1 0.150 r 0.125 1.200.10 1.50 ref 0.250.05 0.50 typ. 0.800.10 8 t822-2 0.125 package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .)

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