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general description the MAX8677A is an integrated 1-cell li+ charger and smart power selector with dual (dc and usb) power inputs. it can operate with either separate inputs for usb and ac adapter power*, or from a single input that accepts both. all power switches for charging and switching the load between battery and external power are included on-chip. no external mosfets are required. the MAX8677A features a smart power selector to make the best use of limited usb or adapter power. the battery charge current and input current limit are independently set up to 1.5a and 2a, respectively. input power not used by the system charges the bat- tery. usb input current can be set to 100ma or 500ma. automatic input selection switches the system load from battery to external power. other features include overvoltage protection (ovp), charge status and fault outputs, power-ok monitors, charge timer, and battery thermistor monitor. additionally, on-chip thermal limiting reduces the battery charge rate to prevent overheating. the MAX8677A is available in a 4mm x 4mm, 24-pin tqfn-ep package. . applications pdas, palmtops, and wireless handhelds smart cell phones portable media/mp3 players gps navigation digital cameras features complete charger and smart power selector no external mosfets required common or separate usb and adapter inputs system operates with discharged or no battery automatic adapter/usb/battery switchover load peaks over adapter rating are supported by battery input overvoltage protection to 16v 40m ? system-to-battery switch thermal regulation prevents overheating chg , dok , uok , and flt indicators 5.3v (typ) sys regulation voltage MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ________________________________________________________________ maxim integrated products 1 MAX8677A 24 23 22 21 20 19 flt uok dok sys sys chg 18 17 16 15 14 13 12 tqfn (4mm x 4mm x 0.8mm) 3456 7 8 9 10 11 12 pset vl gnd ct iset thm usus tset usb usb bat bat pen2 pen1 cen dc dc done pin configuration ordering information MAX8677A q1 ac adapter charge and sys load switch charge current load current usb usb bat sys gnd dc q2 q3 battery system load typical operating circuit 19-0722; rev 1; 1/07 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. + denotes a lead-free package. part temp range pin- package pkg code MAX8677Aetg+ -40? to +85? 24 tqfn-ep (4mm x 4mm) t2444-4 * protected by us patent #6,507,172. smart power selector is a trademark of maxim integrated products, inc.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dc = 5v, thm = cen = usus = gnd, v bat = 4v, v pen1 = v pen2 = 5v, usb, tset, done , chg , dok , uok , flt are unconnected, 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 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. dc, pen1 to gnd .................................................-0.3v to +16v usb to gnd .............................................................-0.3v to +9v vl to gnd ................................................................-0.3v to +4v bat, sys, cen , usus, pen2, tset to gnd...........-0.3v to +6v thm, pset, iset, ct to gnd .........................-0.3v to vl + 0.3v done , chg , dok , uok , flt to gnd.....................-0.3v to +6v ep (exposed paddle) to gnd ...............................-0.3v to +0.3v dc continuous current (total in 2 pins) ........................2.4 a rms sys continuous current (total in 2 pins) .......................2.4 a rms usb continuous current (total in 2 pins) ......................2.0 a rms bat continuous current (total in 2 pins).......................2.4 a rms continuous power dissipation (t a = +70?) (derate 27.8 mw/? above +70?) .......................... 2222mw operating temperature range ...........................-40? to +85? junction temperature range ............................-40? to +125? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter conditions min typ max units dc-to-sys preregulator dc operating range 4.1 6.6 v dc standoff voltage v bat = v sys = 0v 14 v dc undervoltage threshold w hen v d o k g oes l ow , v d c r i si ng , 500m v typ i cal hyster esi s 3.95 4.0 4.05 v dc overvoltage threshold w hen v dok g oes hi g h, v d c r i si ng , 100m v typ i cal hyster esi s 6.8 6.9 7.0 v i sys = i bat = 0ma, v cen = 0v 1 2 dc supply current i sys = i bat = 0ma, v cen = 5v 0.8 1.5 ma dc shutdown current v dc = v cen = usus = 5v, v pen1 = 0v 195 333 ? dc-to-sys on-resistance i sys = 400ma, v cen = 5v 0.2 0.35 ? dc-to-bat dropout voltage when sys regulation and charging stops, v dc falling, 150mv hysteresis 10 50 90 mv r pset = 1.5k ? 1800 2000 2200 r pset = 3k ? 900 1000 1100 r pset = 6.3k ? 450 475 500 v pen1 = 0v, v pen2 = 5v (500ma usb mode) 450 475 500 dc current limit (see table 2 for input source control) v dc = 6v, v sys = 5v, t a = +25? v pen1 = 0v, v pen2 = 0v (100ma usb mode) 80 95 100 ma pset resistance range 1.5 6.3 k ? sys regulation voltage v dc = 6v, i sys = 1ma to 1.75a, v cen = 5v 5.1 5.3 5.5 v connecting dc when no usb present 1.5 ms input current soft-start time connecting dc with usb present 50 ? thermal-limit temperature die temperature at which charging and input current limits are reduced 100 ? thermal-limit gain i sys reduction/die temperature (above +100?) 5 %/? vl voltage i vl = 0ma to 10ma 3.0 3.3 3.6 v
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector _______________________________________________________________________________________ 3 parameter conditions min typ max units usb-to-sys preregulator usb operating range 4.1 6.6 v usb standoff voltage v bat = v sys = 0v 8 v usb undervoltage threshold when v uok goes low, v usb rising, 500mv hysteresis 3.95 4.0 4.05 v usb overvoltage threshold when v uok goes high, v usb rising, 100mv hysteresis 6.8 6.9 7.0 v i sys = i bat = 0ma, v cen = 0v, v pen2 = low 1 2 usb supply current i sys = i bat = 0ma, v cen = 5v, v pen2 = low 0.9 1.5 ma usb shutdown current dc = unconnected, v usb = v cen = v usus = 5v 190 333 ? usb-to-sys on-resistance dc = unconnected, v usb = v cen = 5v, i sys = 400ma 0.2 0.31 ? usb-to-bat drop-out voltage when sys regulation and charging stops, v usb falling, 250mv hysteresis 10 50 90 mv v pen1 = 0v, v pen2 = 5v 450 475 500 usb current limit (see table 2 for input source control) dc = unconnected, v usb = 5v, t a = +25? v pen1 = 0v, v pen2 = 0v 80 95 100 ma sys regulation voltage dc = unconnected, v usb = 6v; i sys = 1ma to 400ma, v cen = 5v 5.1 5.3 5.5 v input limiter soft-start time input current ramp time 50 s thermal-limit start temperature 100 ? thermal-limit gain i sys reduction/die temperature (above +100?) 5 %/? vl voltage dc = unconnected, v usb = 5v; i vl = 0 to 10ma 3.0 3.3 3.6 v charger bat-to-sys on-resistance v dc = 0v, v bat = 4.2v, i sys = 1a 0.04 0.08 ? bat-to-sys reverse regulation voltage v pen1 = v pen2 = 0v, i sys = 200ma 40 68 90 mv t a = +25? 4.179 4.2 4.221 bat regulation voltage i bat = 0ma t a = 0? to +85? 4.158 4.2 4.242 v bat recharge threshold change in v bat from done to fast-charge -135 -95 -45 mv bat charge-current set range r iset = 10k ? to 2k ? (note 2) 0.3 1.5 a r iset = 2.4k ? 1125 1250 1375 r iset = 4k ? 675 750 825 r iset = 10k ? 270 300 330 r iset = 4k ? , v bat = 2.5v (prequal mode) 50 75.0 100 r iset = 6.2k ? , v bat = 2.5v (prequal mode) 23 48 73 bat charge-current accuracy, charger loop in control v sys = 5.5v, t a = 0? to +85? r iset = 10k ? , v bat = 2.5v (prequal mode) 30 ma electrical characteristics (continued) (v dc = 5v, thm = cen = usus = gnd, v bat = 4v, v pen1 = v pen2 = 5v, usb, tset, done , chg , dok , uok , flt are unconnected, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1)
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 4 _______________________________________________________________________________________ electrical characteristics (continued) (v dc = 5v, thm = cen = usus = gnd, v bat = 4v, v pen1 = v pen2 = 5v, usb, tset, done , chg , dok , uok , flt are unconnected, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter conditions min typ max units iset voltage r iset = 4k ? , i bat = 500ma (v iset = 1.5v at full charge current) 0.9 1.0 1.1 v charger soft-start time charge-current ramp time 1.5 ms bat prequal threshold v bat rising, 180mv hysteresis 2.9 3 3.1 v no dc or usb power connected 3 6 ? bat leakage current v bat = 4.2v dc or usb connected, v cen = 5v 3 6 ? v tset = 0 5 v tset = open 10 done threshold as a percentage of fast-charge i bat decreasing v tset = v l 15 % maximum prequal time from v cen falling to end of prequal charge, v bat = 2.5v, c t = 0.068? 30 min maximum fast-charge time from v cen falling to v flt falling, c t = 0.068? 300 min timer accuracy c t = 0.068? -20 +20 % timer extend threshold percentage of fast-charge current below which timer clock operates at half speed 50 % timer suspend threshold percentage of fast-charge current below which timer clock pauses 20 % thm thm threshold, cold when charging is suspended, 2% hysteresis 72 74 76 % of v l thm threshold, hot when charging is suspended, 2% hysteresis 26 28 30 % of v l thm threshold, disabled when thm function is disabled 3 % of v l thm = gnd or v l ; t a = +25? -0.1 0.001 +0.2 thm input leakage thm = gnd or v l ; t a = +85? 0.01 ? logic i/o: chg , flt , done , dok , uok , pen1, pen2, cen , tset, usus high level 1.3 low level 0.4 v logic input thresholds hysteresis 50 mv high level v l - 0.3 midlevel 1.2 v l - 1.2 tset input threshold low level 0.3 v tset = gnd -20 -6 tset input-bias current tset = v l 620 ? t a = +25? 0.001 1 logic input-leakage current v input = 0v to 5.5v t a = +85? 0.01 ? logic output voltage, low sinking 1ma 25 100 mv t a = +25? 0.001 1 logic output-leakage current, high v out = 5.5v t a = +85? 0.01 ? note 1: limits are 100% production tested at t a = +25?. limits over the operating temperature range are guaranteed by design. note 2: guaranteed by design.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector _______________________________________________________________________________________ 5 typical operating characteristics (t a = +25?, unless otherwise noted.) usb quiescent current vs. usb voltage (charger enabled) MAX8677A toc01 usb voltage (v) usb quiescent current (ma) 7 6 4 5 2 3 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 08 v bat = 4.2, v usus = 0v exiting uvlo entering ovlo charger in done mode i sys = 0v pen1 = x, pen2 = 1 v usb rising v usb falling usb quiescent current vs. usb voltage (charger disabled) MAX8677A toc02 usb voltage (v) usb quiescent current (ma) 7 6 45 23 1 0.2 0.4 0.6 0.8 1.0 1.2 0 08 v bat = 4.2, v usus = 0v exiting uvlo entering ovlo cen = 1 i sys = 0v pen1 = x, pen2 = 1 v usb rising v usb falling usb quiescent current vs. usb voltage (suspend) MAX8677A toc03 usb voltage (v) usb quiescent current (ma) 7 6 45 23 1 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0 08 v bat = 4.2, usus = 1 pen1 = x, pen2 = 1 battery leakage current vs. battery voltage (usb disconnected) MAX8677A toc04 battery voltage (v) battery leakage current ( a) 45 23 1 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 0 usb = open battery leakage current vs. temperature MAX8677A toc05 temperature ( c) battery leakage current ( a) 60 85 10 35 -15 3.48 3.50 3.52 3.54 3.56 3.58 3.60 3.46 -40 v bat = 4v battery leakage current vs. battery voltage (usb connected) MAX8677A toc06 battery voltage (v) battery leakage current ( a) 45 23 1 1 2 3 4 5 6 7 0 0 v usb = 5v usus = 1 cen = 1 charge current vs. battery voltage (100ma usb) MAX8677A toc07 battery voltage (v) charge current (ma) 45 23 1 10 20 30 40 50 60 70 80 90 100 0 0 v usb = 5v pen1 = x , pen2 = 1 v bat rising v bat falling charge current vs. battery voltage (500ma usb) MAX8677A toc08 battery voltage (v) charge current (ma) 45 23 1 50 100 150 200 250 300 350 400 450 500 0 0 v usb = 5v pen1 = x, pen2 = 1 v bat rising v bat falling charge current vs. battery voltage (1adc) MAX8677A toc09 battery voltage (v) charge current (a) 45 23 1 0.2 0.4 0.6 0.8 1.0 1.2 0 0 v dc = 5v pen1 = 1 , pen2 = x v bat rising v bat falling
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 6 _______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25?, unless otherwise noted.) sys output voltage vs. usb voltage MAX8677A toc12 v usb (v) v sys (v) 48 567 23 1 4.2 4.4 4.8 4.6 5.0 5.2 4.0 0 v bat = 4v no sys load sys output voltage vs. dc voltage MAX8677A toc13 v dc (v) v sys (v) 10 414 8 612 2 4.4 4.6 5.0 4.8 5.2 5.4 4.0 4.2 0 v bat = 4v no sys load sys output voltage vs. sys output current (usb and dc disconnected) MAX8677A toc14 v sys (v) 1.5 0.5 2.0 1.0 i sys (a) 3.9 4.0 4.1 4.3 4.2 4.4 4.5 3.6 3.8 3.7 0 v bat = 4v the slope of this line shows that the bat-to-sys resistance is 40m ? sys output voltage vs. sys output current (dc) MAX8677A toc15 v sys (v) 2.0 2.5 1.0 0.5 3.0 1.5 i sys (a) 4.3 4.7 5.1 5.5 3.5 3.9 0 v dc = 6v v dc = 5v v bat = 4v pen1 = 1, pen2 = x cen = 1 sys output voltage vs. sys output current (usb) MAX8677A toc16 v sys (v) 2.0 2.5 1.0 0.5 3.0 1.5 i sys (a) 4.1 4.5 4.3 4.9 4.7 5.1 3.5 3.9 3.7 0 v bat = 4v v usb = 5v pen1 = x, pen2 = 1 cen = 1 100ma 500ma vl output voltage vs. dc voltage MAX8677A toc17 v vl (v) 812 10 4 214 6 v dc (v) 1.5 2.0 3.0 2.5 3.5 0 1.0 0.5 0 i vl = 0ma i vl = 10ma normalized charge current vs. ambient temperature (low ic power dissipation) MAX8677A toc10 ambient temperature ( c) normalized charge current 60 85 10 35 -15 0.9925 0.9975 0.9950 1.0000 1.0050 1.0025 1.0075 1.0100 0.9900 -40 v usb = 5v, v bat = 4v battery regulation voltage vs. temperature MAX8677A toc11 temperature ( c) battery regulation voltage (v) 60 85 10 35 -15 4.185 4.195 4.190 4.200 4.205 4.180 -40 40ppm/ c
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector _______________________________________________________________________________________ 7 charge profile ?400mah battery adapter input?a charge MAX8677A toc18 v bat (v) i bat (a) 100 150 50 time (min) 2.5 3.5 3.0 5.0 5.5 4.5 4.0 6.0 0 2.0 1.5 1.0 0.5 0.6 1.0 0.8 1.2 0.4 0.2 0 0 v bat i bat charge profile ?400mah battery usb input?00ma charge MAX8677A toc19 v bat (v) i bat (a) 120 140 160 180 40 20 100 80 60 time (min) 2.0 3.0 2.5 4.0 4.5 3.5 5.0 0 1.5 1.0 0.5 0.25 0.40 0.45 0.30 0.35 0.50 0.15 0.20 0.05 0.10 0.00 0 v bat i bat typical operating characteristics (continued) (t a = +25?, unless otherwise noted.) dc connect with usb connected (r sys = 25 ? ) MAX8677A toc20 200 s/div v sys i dc i usb i bat 500ma/div c dc charging c sys charging 4.2v 4.6v 0a 0a 0a 5v 500ma 500ma -320ma -310ma negative battery current flows into the battery (charging) battery charger soft-start dc connect with no usb (r sys = 25 ? ) MAX8677A toc21 400 s/div v bat v sys i dc i bat 500ma/div 500ma/div 5v/div 5v/div c dc charging c sys charging 3.6v 3.6v 0a -1a 1.2a 120ma 5v negative battery current flows into the battery (charging) battery charger soft-start dc disconnect with no usb (r sys = 25 ? ) MAX8677A toc22 20 s/div v sys i dc i bat 500ma/div 500ma/div 2v/div 3.6v 0a 0.2a -1a 1.2a 5v negative battery current flows into the battery (charging) usb connect with no dc (r sys = 25 ? ) MAX8677A toc23 200 s/div v usb i usb v sys i bat 500ma/div 500ma/div 5v/div 5v/div 5v/div 10v/div c usb charging c sys charging 0v 4.3v 0a -300ma 500ma 140ma 3v 3v 0v 0v 3.6v 5v 5v battery charger soft-start v uok v chg
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 8 _______________________________________________________________________________________ usb disconnect with no dc (r sys = 25 ? ) MAX8677A toc24 200 s/div v usb i usb v sys i bat 500ma/div 1a/div 5v/div 5v/div 5v/div 10v/div 0a -300ma 475ma 120ma 3v 3v 0v 0v 3.6v 4.3v 5v v uok v chg usb suspend MAX8677A toc25 200 s/div v usus i usb v sys i bat 500ma/div 500ma/div 5v/div 5v/div 2v/div -500ma 0a 0a 3v 0v 0v 4v 4.6v 500ma 5v v chg usb resume MAX8677A toc26 200 s/div v usus i usb v sys i bat 500ma/div 500ma/div 5v/div 5v/div 2v/div 0a 0a 3v 3v 0v 0v 4v 4.6v -500ma 500ma v chg c sys charging battery charger soft-start pin description pin name function 1 done charge done output. active-low, open-drain output pulls low when the charger enters the done state. no charging current flows when done is low. see figure 5. 2, 3 dc dc power input. dc is capable of delivering up to 2a to sys. dc supports both ac adapter and usb inputs. the dc current limit is set with pen1, pen2, usus, and r pset . see table 2. both dc pins must be connected together externally. 4 cen charger enable input. connect cen to gnd to enable battery charging when a valid source is connected at dc or usb. connect to vl or drive high with a logic signal to disable battery charging. 5 pen1 dc input limit control. if pen1 is high, the dc input current limit is 3000/r pset . if pen1 is low, the dc limit is set by pen2 and usus. see table 2. typical operating characteristics (continued) (t a = +25?, unless otherwise noted.)
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector _______________________________________________________________________________________ 9 pin description (continued) pin name function 6 pen2 usb high/low control. pen2 sets the dc or usb current limit to 100ma (pen2 low) or 500ma (pen2 high). pen2 controls both dc and usb current limits when pen1 is low. see table 2. 7 pset dc input current-limit set. connect a resistor to ground to program the dc current limit to 3000/r pset . 8vl logic ldo output. vl is the output of an ldo that powers the max8667a internal circuitry. vl also provides 3.3v at up to 10ma to power external circuitry. connect a 0.1? capacitor from vl to gnd. 9 gnd ground 10 ct charge timer program pin. a capacitor from ct to gnd sets the fast-charge (t fstchg ) and prequal (t prequal ) fault timers. connect to gnd to disable the timer. 11 iset charge current set input. a resistor (r iset ) from iset to gnd programs the maximum charge current up to 1.5a. the prequal charge current is 10% of the set maximum charge current. 12 thm thermistor input. connect a negative temperature coefficient (ntc) thermistor that has good thermal contact with the battery from thm to gnd. connect a resistor equal to the thermistor +25? resistance from thm to vl. charging is suspended when the thermistor is outside the hot and cold limits. connect thm to gnd to disable the thermistor temperature sensor. 13 usus usb suspend input. with pen1 low, driving usus high turns off both the usb and dc inputs. with pen1 high, driving usus high turns off only the usb input. see table 2. 14 tset termination current set pin. connect to gnd, leave open, or connect to vl for a 5%, 10%, or 15% (of i chgmax ) termination current (i term ) threshold. 15, 16 usb usb power input. usb is capable of delivering up to 0.5a to sys. the usb current limit is set with pen2 and usus. see table 2. both usb pins must be connected together externally. 17, 18 bat battery connection. connect to a single-cell li+ battery. the battery charges from sys when a valid source is present at dc or usb. bat powers sys when neither dc nor usb power is present, or when the sys load exceeds the input current limit. both bat pins must be connected together externally. 19 chg charger status output. active-low, open-drain output pulls low when the battery is in fast-charge or prequal. otherwise, chg is high impedance. 20, 21 sys system supply output. sys is connected to bat through an internal 40m ? system load switch when dc or usb is invalid, or when the sys load is greater than the input current limit. when a valid voltage is present at dc or usb, sys is limited to 5.3v. when the system load (i sys ) exceeds the d c or u s b cur r ent l i m i t, s y s i s r eg ul ated to 68m v b el ow bat, and b oth the u s b i np ut and the b atter y ser vi ce s y s . bypass sys to gnd with a 10? x5r or x7r ceramic capacitor. both sys pins must be connected together externally. 22 dok dc power-ok output. active-low, open-drain output pulls low when a valid input is detected at dc. 23 uok usb power-ok output. active-low, open-drain output pulls low when a valid input is detected at usb. 24 flt fault output. active-low, open-drain output pulls low when the battery timer expires before prequal or fast-charge complete. ?p exposed paddle. connect the exposed paddle to gnd. connecting the exposed paddle does not remove the requirement for proper ground connections to the appropriate pins.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 10 ______________________________________________________________________________________ MAX8677A dc power management current- limited voltage regulator set input limit thermistor monitor (see figure 7) charge termination and monitor charge timer pwr ok usb power management current- limited voltage regulator charger current- voltage control bat+ bat- t ntc input and charger current limit set logic ic thermal regulation set input limit ep pset usus pen2 pen1 usb usb uok dc mode 500ma 100ma usb limit usb suspend dc limit pwr ok li+ battery charger and sys load switch sys iset bat thm vl chg done vl = 15% to system load n.c. = 10% 5% tset flt ct cen gnd dok dc ac adapter figure 1. block diagram circuit description the MAX8677A contains an li+ battery charger, as well as power mosfets and control circuitry to manage power flow in portable devices. see figure 1. the charger has two power inputs, dc and usb. these can be separately connected to an ac adapter output and a usb port, or the dc input can be a single power input that connects to either an adapter or usb. logic inputs, pen1 and pen2, select the correct current limits
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ______________________________________________________________________________________ 11 MAX8677A done 1 flt r pu 560k ? charge done c dc 4.7 f adapter 24 to vl r pu 3x 560k ? fault output usb pwr ok dc pwr ok to system load charge indicator 1-cell li+ vbus to vl 560k ? usb dc 2 uok 23 dc 3 dok 22 cen 4 off charge on sys 21 pen1 5 sys 20 pen2 6 chg 19 pset r pset r iset 10k ? 7 bat 18 vl 8 bat 17 gnd 9 usb 16 ct 10 usb 15 iset 11 tset 14 thm 12 usus 13 c sys 10 f c bat 4.7 f c usb 4.7 f gnd usb suspend to vl: i term = 15% open: i term = 10% gnd: i term = 5% 500ma c l 0.1 f c t 0.068 f ntc 10k ? +25 c 100ma figure 2. typical application circuit using separate dc and usb connectors for two-input or single-input operation. figure 2 is the typical application circuit using separate dc and usb connectors. figure 3 is the typical application circuit using a mini 5-style connector or other dc/usb com- mon connector. in addition to charging the battery, the MAX8677A also supplies power to the system through the sys output. the charging current is also provided from sys so that the set input current limit controls the total sys current, which is the sum of the system load current and the battery-charging current. sys is powered from either the dc input pin or the usb input pin. if both the dc and usb are connected, dc takes precedence.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 12 ______________________________________________________________________________________ MAX8677A done 1 flt 560k ? charge done c dc 4.7 f 24 to vl 3x 560k ? fault output usb pwr ok dc pwr ok to system load charge indicator 1-cell li+ to vl 560k ? dc 2 vbus d- d+ id gnd 1 2 3 4 5 uok 23 dc 3 dok 22 cen 4 off on charge dc-usb id sys 21 pen1 5 sys 20 pen2 6 chg 19 pset r pset r iset 10k ? 7 bat 18 vl 8 bat 17 gnd 9 usb 16 ct 10 usb 15 iset 11 tset 14 thm 12 usus 13 c sys 10 f c bat 4.7 f usb suspend to vl: i term = 15% open: i term = 10% gnd: i term = 5% 500ma c l 0.1 f c t 0.068 f ntc 10k ? +25 c 100ma hi = dc lo = usb mini 5-style connector figure 3. typical application circuit using mini 5-style connector or other dc/usb common connector in some instances, there may not be enough adapter current or usb current to supply peak system loads. the MAX8677A smart power selector circuitry offers flexible power distribution from an ac adapter or usb source to the battery and system load. the battery is charged with any available power not used by the sys- tem load. if a system load peak exceeds the input current limit, supplemental current is taken from the bat- tery. thermal limiting prevents overheating by reducing power drawn from the input source. in the past, it might have been necessary to reduce system functionality to limit current drain when a usb source is connected. however, in the MAX8677A, this is no longer the case. when the dc or usb source hits its limit, the battery supplies supplemental current to maintain the load.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ______________________________________________________________________________________ 13 table 1. external components list for figures 2 and 3 component (figures 2, 3) function part c in input filter capacitor 4.7? ceramic capacitor cl vl filter capacitor 0.1? ceramic capacitor c sys sys output bypass capacitors 10? ceramic capacitor c bat battery bypass capacitor 4.7? ceramic capacitor ct charger timing capacitor 0.068? low tc ceramic capacitor r pu (x 4) logic output pullup resistors 560k ? thm negative tc thermistor phillips ntc thermistor, p/n 2322-640-63103, 10k ? ?% at +25? rt thm pullup resistor 10k ? ?% r pset input current-limit programming resistor 1.5k ? ?% for 2a limit r iset fast-charge current programming resistor 3k ? ?% for 1a charging the MAX8677A features ovp. part of this protection is a 5.3v voltage limiter at sys. if the dc or usb input exceeds 5.3v, sys still limits at 5.3v. it is expected that the sys limiter will not need to operate, and will be in dropout in most cases. a typical 5vac adapter oper- ates below the limit level, so both dc and sys would be at 5v in that case. the MAX8677A has numerous other charging and power-management features, which are detailed in the following sections. smart power selector the MAX8677A smart power selector seamlessly dis- tributes power between the external inputs, the battery, and the system load (figure 4). the basic functions performed are: with both an external power supply (usb or adapter) and battery connected: when the system load requirements are less than the input current limit, the battery is charged with residual power from the input. when the system load requirements exceed the input current limit, the battery supplies supple- mental current to the load. when the battery is connected and there is no external power input, the system is powered from the battery. when an external power input is connected and there is no battery, the system is powered from the external power input. a thermal-limiting circuit reduces the battery charge rate and external power-source current to prevent the MAX8677A from overheating. system load switch an internal 40m ? mosfet connects sys to bat (q3, figure 4) when no voltage source is available at dc or usb. when an external source is detected at dc or usb, this switch is opened and sys is powered from the valid input source through the input limiter. the sys-bat switch also holds up sys when the sys- tem load exceeds the input current limit. if that should happen, the sys-bat switch turns on so that the bat- tery supplies additional sys load current. if the system load continuously exceeds the input current limit, the battery does not charge, even though external power is connected. this is not expected to occur in most cases, since high loads usually occur only in short peaks. during these peaks, battery energy is used, but at all other times the battery charges. MAX8677A q1 ac adapter charge and sys load switch charge current load current usb usb bat sys gnd dc q2 q3 battery system load figure 4. smart power selector block diagram
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 14 ______________________________________________________________________________________ input limiter the input voltage limiter is essentially an ldo regulator designed to run in dropout. while in dropout, the regu- lator dissipates a small i 2 r loss through the 0.2 ? mos- fet (q1, figure 4) between dc and sys. with an ac adapter or usb source connected, the input limiter dis- tributes power from the external power source to the system load and battery charger. in addition to the input limiter? primary function of passing power to the system and charger loads at sys, it performs several additional functions to optimize use of available power: input voltage limiting. if an input voltage is above the overvoltage threshold (6.9v typ), the MAX8677A enters overvoltage lockout (ovlo). ovlo protects the MAX8677A and downstream circuitry from high- voltage stress up to 14v at dc and 8v at usb. in ovlo, vl remains on, the input switch that sees overvoltage (q1, q3, figure 4) opens, and the appropriate power-monitor output ( dok , uok ) is high impedance, and chg is high impedance. if both dc and usb see overvoltage, both input switches (q1 and q2, figure 4) open and the charger turns off. the bat-sys switch (q3, figure 4) closes, allowing the battery to power sys. an input is also invalid if it is less than bat, or less than the dc undervoltage threshold of 3.5v (falling). with an invalid input voltage, sys connects to bat through a 40m ? switch (q3, figure 4). input overcurrent protection. the current at dc and usb is limited to prevent input overload. this cur- rent limit can be selected to match the capabilities of the source, whether it is a 100ma or 500ma usb source, or an ac adapter. when the load exceeds the input current limit, sys drops to 68mv below bat and the battery supplies supplemental load current. thermal limiting. the MAX8677A reduces input lim- iter current by 5%/? when its die temperature exceeds +100?. the system load (sys) has priority over the charger current, so input current is first reduced by lowering charge current. if the junction temperature still reaches +120? in spite of charge- current reduction, no input (dc or usb) current is drawn, the battery supplies the entire system load, and sys is regulated at 68mv below bat. note that this on-chip thermal-limiting circuitry is not related to and operates independently from the thermistor input. adaptive battery charging. while the system is powered from dc, the charger draws power from sys to charge the battery. if the charger load plus system load exceeds the input current limit, an adaptive charger control loop reduces charge cur- rent to prevent the sys voltage from collapsing. maintaining a higher sys voltage improves efficien- cy and reduces power dissipation in the input limiter. the total current through the switch (q1 or q2 in figure 4) is the sum of the load current at sys and the battery charging current. the limiter clamps at 5.3v, so input voltages greater than 5.3v can increase power dissipation in the limiter. the limiter power loss is (v dc - 5.3) x i, but not less than i 2 x 0.2 ? . also note that the MAX8677A turns off any input that exceeds 6.9v (nominal). dc and usb connections and current-limit options input current limit the input and charger current limits are set as shown in table 2. it is often preferable to change the input cur- rent limit as the input power source is changed. the MAX8677A facilitates this by allowing different input current limits for dc and usb as shown in table 2. power source dok uok pen1 pen2 usus dc input current limit usb input current limit maximum charge current* ac adapter at dc input l x h x x 3000/r pset 3000/r iset l x l l l 100ma 100ma l x l h l 500ma 500ma usb power at dc input lx l x h usb suspend usb input off; dc input has priority 0 h l x l l 100ma h l x h l 500ma 3000/r iset usb power at usb input; dc unconnected hl x x h usb suspend 0 dc and usb unconnected h h x x x no dc input no usb input 0 table 2. input limiter control logic * charge current cannot exceed the input current limit. charge may be less than the maximum charge current if the total sys load exceeds the input current limit.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ______________________________________________________________________________________ 15 when the input current limit is reached, the first action taken by the MAX8677A is to reduce the battery charge current. this allows the regulator to stay in dropout, or at 5.3v, during heavy loads, thus reducing power dissi- pation. if, after the charge current is reduced to 0ma, the load at sys still exceeds the input current limit, sys begins to fall. when the sys voltage drops to bat, the sys-bat switch turns on, using battery power to sup- port the system load during the load peak. the MAX8677A features flexible input connections (at the dc and usb input pins) and current-limit settings (set by pen1, pen2, pset, and iset) to accommodate nearly any input power configuration. however, it is expected that most systems use one of two external power schemes: separate connections for usb and an ac adapter, or a single connector that accepts either usb or ac adapter output. input and charger current limit are controlled by pen1, pen2, r pset , and r iset , as shown in table 2. separate adapter and usb connectors when the ac adapter and usb have separate connec- tors, the adapter output connects to dc and the usb source connects to usb. pen1 is permanently tied high (to dc or vl). the dc current limit is set by r pset , while the usb current limit is set by pen2 and usus. single common connector for usb or adapter when a single connector is used for both ac adapter and usb sources, the dc input is used for both input sources. when an ac adapter is connected at dc, pen1 should be pulled high to select the current limit set by r pset . when a usb source is connected, pen1 should be low to select 500ma, 100ma, or usb sus- pend (further selected by pen2 and usus). pen1 can be pulled up by the ac adapter power to implement hardware adapter/usb selection. usb suspend driving usus high when pen1 is low turns off charging, as well as the sys output and reduces input current to 190? to accommodate usb suspend mode. power monitor outputs ( uok , dok ) dok is an open-drain output that pulls low when the dc input has valid power. uok is an open-drain output that pulls low when the usb input sees valid power. a valid input for dc or usb is between 4.1v and 6.6v. if a single power-ok output is preferred, dok and uok can be wire-ored together. the combined output then pulls low if either usb or dc sees a valid input. soft-start to prevent input transients that can cause instability in the usb or ac adapter power source, the rate of change of input current and charge current is limited. when a valid dc or usb input is connected, the input current limit is ramped from zero to the set current-limit value (as shown in table 2). if dc is connected with no usb power present, input current ramps in 1.5ms. if dc is connected with usb already present, input cur- rent ramps in 50?. when usb is connected with no dc present, input current ramps also ramps in 50?. if usb is connected with dc already present, the usb input is ignored. if an adapter is plugged into dc while usb is already powered, the input current limit reramps from zero back up to the dc current limit so that the ac adapter does not see a load step. during this transition, if the input current limit falls below the sys load current, the bat- tery supplies the additional current needed to support the load. additionally, capacitance can be added to sys to support the load during input power transitions. when the charger is turned on, charge current ramps from zero to the iset current value in typically 1.5ms. charge current also ramps when transitioning to fast- charge from prequal and when changing the usb charge current from 100ma to 500ma with pen2. there is no di/dt limiting, however, if iset is changed suddenly using a switch at r iset . battery charger the battery charger state diagram is illustrated in figure 5. with a valid dc or usb input, the battery charger initiates a charge cycle when the charger is enabled. it first detects the battery voltage. if the bat- tery voltage is less than the bat prequal threshold (3.0v), the charger enters prequal mode in which the battery charges at 10% of the maximum fast-charge current. this reduced charge rate ensures that the bat- tery is not damaged by the fast-charge current while deeply discharged. once the battery voltage rises to 3.0v, the charger transitions to fast-charge mode and applies the maximum charge current. as charging con- tinues, the battery voltage rises until it approaches the battery regulation voltage (4.2v) where charge current starts tapering down. when charge current decreases to 5%, 10%, or 15% (as set by tset) of the fast-charge current, the charger enters a brief 15s top-off, and then charging stops. if the battery voltage subsequently drops below the 4.1v recharge threshold, charging restarts and the timers reset.
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 16 ______________________________________________________________________________________ any state timer > t fstchg (timer slowed by 2x if i chg < i chgmax /2, and paused if i chg < i chgmax /5 while bat < 4.2v) timer > 15s uok or dok = low cen = 0 reset timer timer > t prequal not ready uok and dok = high impedance chg = high impedance flt = high impedance done = high impedance i chg = 0ma prequal uok or dok = low chg = low flt = high impedance done = high impedance 0v v batt 3v i chg = i chgmax /10 fast charge uok or dok = low chg = low flt = high impedance done = high impedance 3v < v batt < 4.2v i chg i chgmax fault uok or dok = low chg = high impedance flt = low done = high impedance i chg = 0ma top-off uok or dok = low chg = high impedance flt = high impedance done = high impedance batt = 4.2v i chg < i term done uok or dok = 0v chg = high impedance flt = high impedance done = low 4.1 < v batt < 4.2v i chg = 0ma cen = hi or remove and reconnect the input source(s). v batt > 3v, reset timer v bat < 4.1v reset timer v batt < 2.82v, reset timer any charging state thm not ok timer suspend thm ok timer resume temperature suspend i chg = 0ma uok or dok = previous state chg = high impedance flt = high impedance done = high impedance i chg < i term and v bat = 4.2v and thermal or input limit not exceeded. reset timer. i chg > i term reset timer v batt < 2.8v reset timer toggle cen or remove and reconnect the input source(s). figure 5. MAX8677A charger state flowchart
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ______________________________________________________________________________________ 17 charge enable ( cen ) when cen is low, the charger is on. when cen is high, the charger turns off. cen does not affect the sys out- put. in many systems, there is no need for the system controller (typically a microprocessor) to disable the charger, because the MAX8677A smart power selector circuitry independently manages charging and adapter/battery power hand-off. in these situations, cen can be connected to ground. setting the charge current iset adjusts charge current to match the capacity of the battery. a resistor from iset to ground sets the maximum fast-charge current: i chgmax = 2000 x 1.5v/r iset = 3000/r iset determine the i chgmax value by considering the char- acteristics of the battery. it is not necessary to limit the charge current based on the capabilities of the expected ac adapter/usb charging input, the system load, or thermal limitations of the pcb. the MAX8677A automat- ically adjusts the charging algorithm to accommodate these factors. monitoring the charge current in addition to setting the charge current, iset can also be used to monitor the actual current charging the bat- tery. the iset output voltage is: v iset = i chg x 1.5v/i chgmax = i chg x r iset /2000 where i chgmax is the set fast-charge current and i chg is the actual battery charge current. a 1.5v output indi- cates the battery is being charged at the maximum set fast-charge current; 0v indicates no charging. this volt- age is also used by the charger control circuitry to set and monitor the battery current. avoid adding more than 10pf capacitance directly to the iset pin. if filter- ing of the charge-current monitor is necessary, add a resistor of 100k ? or more between iset and the filter capacitor to preserve charger stability. see figure 6. note that the actual charge current can be less than the set fast-charge current when the charger enters voltage mode or when charge current is reduced by the input current limiter or thermal limiter. this prevents the charger from overloading the input source or over- heating the system. charge termination when the charge current falls to the termination thresh- old and the charger is in voltage mode, charging is complete. charging continues for a brief 15s top-off period and then enters the done state in which charg- ing stops. the termination current threshold (i term ) is set by tset to a percentage of the fast-charge current: connect tset to gnd for i term = i chgmax x 5% leave tset open for i term = i chgmax x 10% connect tset to vl for i term = i chgmax x 15% when the charger enters done 15s later, the done output goes low. note that if charge current falls to i term as a result of the input or thermal limiter, the charger does not enter done. for the charger to enter done, the charge current must be less than i term , the charger must be in voltage mode, and the input or ther- mal limiter must not be reducing the charge current. charge status outputs charge output ( c c h h g g ) chg is an open-drain, active-low output that is low dur- ing charging. chg is low when the battery charger is in its prequalification and fast-charge states. when charge current falls to the charge termination threshold and the charger is in voltage mode, chg goes high impedance. chg goes high impedance if the thermistor causes the charger to enter temperature suspend mode. when the MAX8677A is used with a microprocessor (?), connect a pullup resistor between chg and the logic i/o voltage to indicate charge status to the ?. alternatively, chg can sink up to 20ma for an led indicator. charge done output ( d d o o n n e e ) done is an open-drain, active-low output that goes low when charging is complete. the charger enters its done state 15s after charge current falls to the 1.5 0 v iset = r iset 2000 x i chg monitoring the battery charge current with v iset 0 2000 (1.5v / r iset ) battery charging current (a) discharging v iset (v) figure 6. monitoring the charge current with the iset voltage
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 18 ______________________________________________________________________________________ charge-termination threshold and the charger is in volt- age mode. the charger exits the done state, and fast- charge resumes, if the battery voltage subsequently drops 100mv, or if input power or cen is cycled. when the MAX8677A is used in conjunction with a ?, connect a pullup resistor between done and the logic i/o voltage to indicate charge status to the ?. alternatively, done can sink up to 20ma for an led indicator. fault output ( f f l l t t ) and charge timer flt is an open-drain, active-low output that goes low during a battery fault. the fault state occurs when either the prequal or fast-charge timer expires. the prequal and fast-charge fault timers are set by c ct : while in fast-charge mode, a large system load or device self-heating can cause the MAX8677A to reduce charge current. under these circumstances, the fast-charge timer adjusts to ensure that adequate charge time is still allowed. consequently, the fast- charge timer is slowed by 2x if charge current is reduced below 50% of the programmed fast-charge level. if charge current is reduced to below 20% of the programmed level, the fast-charge timer is paused. the fast-charge timer is not adjusted if the charger is in volt- age mode where charge current reduces due to cur- rent tapering under normal charging. to exit a fault state, toggle cen or remove and recon- nect the input source(s). note also that thermistor out- of-range or on-chip thermal-limit conditions are not considered faults. when the MAX8677A is used in conjunction with a ?, connect a pullup resistor between flt and the logic i/o voltage to indicate fault status to the ?. alternatively, flt can sink up to 20ma for an led indicator. thermistor input (thm) the thm input connects to an external negative tem- perature coefficient (ntc) thermistor to monitor battery or system temperature. charging is suspended when the thermistor temperature is out of range. the charge timers are suspended and hold their state but no fault is indicated. when the thermistor comes back into range, charging resumes and the charge timer contin- ues from where it left off. connecting thm to gnd dis- ables the thermistor monitoring function. table 3 lists fault temperatures for different thermistors. since the thermistor monitoring circuit employs an exter- nal bias resistor from thm to vl (r tb , figure 7), the thermistor is not limited only to 10k ? (at +25?). t c f fstchg ct = 300 0 068 min . t c f prequal ct = 30 0 068 min . r t thm gnd thm ok disable charger vl vl 0.74 vl 0.28 vl 0.03 vl all comparators 60mv hysteresis cold hot r tb thermistor circuitry bypass thm r tp r ts alternate thermistor connection MAX8677A cen r t figure 7. thermistor monitor circuitry
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector ______________________________________________________________________________________ 19 any resistance thermistor can be used as long as the value of r tb is equivalent to the thermistor? +25? resistance. for example, with a 10k ? at +25? thermis- tor, use 10k ? at r tb , and with a 100k ? at +25? ther- mistor, use 100k ? . for a typical 10k ? (at +25?) thermistor and a 10k ? r tb resistor, the charger enters a temperature suspend state when the thermistor resistance falls below 3.97k ? (too hot) or rises above 28.7k ? (too cold). this corre- sponds to a 0? to +50? range when using a 10k ? ntc thermistor with a beta of 3500. the general rela- tion of thermistor resistance to temperature is defined by the following equation: where: r t = the resistance in ? of the thermistor at tempe- rature t in celsius r 25 = the resistance in ? of the thermistor at +25? = the material constant of the thermistor, which typically ranges from 3000k to 5000k t = the temperature of the thermistor in ? table 3 shows the MAX8677A thm temperature limits for different thermistor material constants. some designs might prefer other thermistor tempera- ture limits. threshold adjustment can be accommodat- ed by changing r tb , connecting a resistor in series and/or in parallel with the thermistor, or using a thermis- tor with different . for example, a +45? hot threshold and 0? cold threshold can be realized by using a ther- mistor with a of 4250 and connecting 120k ? in paral- lel. since the thermistor resistance near 0? is much higher than it is near +50?, a large parallel resistance lowers the cold threshold, while only slightly lowering the hot threshold. conversely, a small series resistance raises the cold threshold, while only slightly raising the hot threshold. raising r tb lowers both the hot and cold thresholds, while lowering r tb raises both thresholds. power dissipation it is important to ensure that the heat generated by the MAX8677A is dissipated into the pcb. the package? exposed paddle must be soldered to the pcb with mul- tiple vias tightly packed under the exposed paddle to ensure optimum thermal contact to the ground plane. this minimizes heat rise in the ic and ensures that maximum charging current is maintained over the widest range of external conditions. table 4 shows the thermal characteristics of the MAX8677A package. pcb layout and routing good design minimizes ground bounce and voltage gradients in the ground plane, which can result in insta- bility or regulation errors. gnd should connect to the power-ground plane at only one point to minimize the effects of power-ground currents. battery ground should connect directly to the power-ground plane. connect gnd to the exposed paddle directly under the ic. use multiple tightly spaced vias to the ground plane under the exposed paddle to help cool the ic. position input capacitors from dc, sys, bat, and usb to the power- ground plane as close as possible to the ic. keep high- current traces, such as those to dc, sys, and bat, as short and wide as possible. refer to the MAX8677A evaluation kit for a suitable pcb layout example. rr e t t = + ? ? ? ? ? ? ? ? ? ? ? ? ? 25 1 273 1 298 thermistor (k) 3000 3250 3500 3750 4250 r tb (k ? ) (figure 7) 10 10 10 10 10 resistance at +25? (k ? ) 1010101010 resistance at +50? (k ? ) 4.59 4.30 4.03 3.78 3.32 resistance at 0? (k ? ) 25.14 27.15 29.32 31.66 36.91 nominal hot-trip temperature (?) 55 53 51 49 46 nominal cold-trip temperature (?) -3 -1 0 2 4.5 table 3. fault temperatures for different thermistors single-layer pcb multilayer pcb continuous power dissipation 1666.7mw derate 20.8mw/? above +70? 2222.2mw derate 27.8mw/? above +70? ja 48?/w 36?/w jc 2.7?/w 2.7?/w table 4. package thermal characteristics chip information process: bicmos
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 20 ______________________________________________________________________________________ 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 .) 24l qfn thin.eps package outline, 21-0139 2 1 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm
MAX8677A 1.5a dual-input usb/ac adapter charger and smart power selector 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 21 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. 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 .) package outline, 21-0139 2 2 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm revision history pages changed at rev 1: 1, 3, 21

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