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_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 19-5296; rev 0; 6/10 general description the MAX8934G dual-input li+/li-poly linear battery char - ger with smart power selector k safely charges a single li+/li-poly cell in accordance with jeita* recommenda - tions. the MAX8934G monitors the battery temperature (t batt ) while charging, and automatically adjusts the fast-charge current and charge termination voltage as the battery temperature varies. the MAX8934G also monitors the battery temperature while the battery is discharging, and provides a warning flag ( ot ) to the system in the event that the battery is over temperature. safety region 2 is supported (see figure 6 for details). an ultra-low i q , always-on ldo provides an additional 3.3v supply for system power. the MAX8934G operates 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 MAX8934G features a smart power selector to make the best use of limited usb or adapter power. input cur - rent limit and battery charge current limit are indepen - dently set. input power not used by the system charges the battery. charge current limit and dc current limit can be set up to 1.5a and 2a, respectively, while usb input current can be set to 100ma or 500ma. automatic input selection switches the system load from battery to external power. the MAX8934G provides a sys output voltage of 4.35v. other features include overvoltage protection (ovp), open-drain charge status and fault outputs, power-ok monitors, charge timers, and a battery thermistor moni - tor. additionally, on-chip thermal limiting reduces the battery charge-rate to prevent charger overheating. the MAX8934G is available in a 28-pin, 4mm x 4mm, tqfn package. applications pdas, palmtop, and wireless handhelds po rtable me dia, mp3 players, and pnds digital still cameras and digital video cameras handheld game systems features s li+ charger with smart power selector, no external mosfets needed s monitors battery temperature and adjusts charge current and termination voltage automatically per jeita recommendations s ot flags system of a hot battery during discharge s ultra-low i q , always-on 3.3v ldo s common or separate usb and adapter inputs s automatic adapter/usb/battery switchover s load peaks in excess of adapter rating are supported by battery s input ovp to 16v (dc) and 9v (usb) s 40mi sys-to-batt switch s thermal regulation prevents overheating s 4.35v sys regulation voltage + denotes a lead(pb)-free/rohs-compliant package. ** ep = exposed pad. smart power selector is a trademark of maxim integrated products, inc. ordering information * jeita (japan electronics and information technology industries association) standard, a guide to the safe use of secondary lithium ion batteries on notebookCtype personal computers, april 20, 2007. part temp range pin-package MAX8934Geti+ -40n c to +85nc 28 thin qfn-ep** MAX8934G sys ldo gnd charge current load current batt battery system load ac adapter charge and sys load switch usb dc q1 q2 q3 usb 3.3v always-on linear regulator typical operating circuit
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 2 ______________________________________________________________________________________ stresses beyond those listed under absolute 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. dc, pen1 to gnd ................................................. -0.3v to +16v usb to gnd ............................................................ -0.3v to +9v v l to gnd ............................................................... -0.3v to +4v ldo to gnd ......... -0.3v to the lower of +4v and (v sys + 0.3v) thmen, thmsw to gnd ..................... -0.3v to +(v ldo + 0.3v) thm to gnd ....................................... -0.3v to (v thmsw + 0.3v) pset, iset, ct to gnd ............................... -0.3v to (v l + 0.3v) batt, sys, cen, chg, ot, dok, uok, flt, done , usus, pen2 to gnd ............. -0.3v to +6v ep (exposed pad) to gnd ................................... -0.3v to +0.3v dc continuous current (total in two pins) .................... 2.4a rms sys continuous current (total in two pins) ................... 2.4a rms usb continuous current (total in two pins) .................. 2.0a rms batt continuous current (total in two pins) ................. 2.4a rms ldo continuous current ............................................. 50ma rms ldo short-circuit duration ......................................... continuous continuous power dissipation (t a = +70 nc) single-layer board (derate 20.8mw/ n c above +70nc) ...................... 1666.7mw multilayer board (derate 28.6mw/ n c above +70nc) ...................... 2285.7mw operating temperature range .......................... -40n c to +85nc junction temperature ...................................... -40n c to +125nc storage temperature ....................................... -65n c to +150nc lead temperature (soldering, 10s) ................................ +300nc soldering temperature (reflow) ...................................... +260nc electrical characteristics (v dc = v pen1 = v pen2 = 5v, cen = usus = thmen = gnd, v batt = 4v, v thm = 1.65v, usb, thmsw, chg , done , ot , dok , uok , flt are unconnected, c ct = 0.068 f f, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 1) absolute maximum ratings parameter conditions min typ max units dc-to-sys preregulator dc operating voltage range 4.1 6.6 v dc withstand voltage v batt = v sys = 0v 14 v dc undervoltage threshold when v dok goes low, v dc rising, 500mv hysteresis 3.95 4.0 4.05 v dc overvoltage threshold when v dok goes high, v dc rising, 360mv hysteresis 6.8 6.9 7.0 v dc operating supply current i sys = i batt = 0ma, v cen = 0v 1 2 ma i sys = i batt = 0ma, v cen = 5v 0.8 1.5 dc suspend current v dc = v cen = v usus = 5v, v pen1 = 0v 195 340 fa dc-to-sys on-resistance i sys = 400ma, v cen = 5v 0.2 0.35 i dc to batt dropout voltage when sys regulation and charging stops, v dc falling, 150mv hysteresis 10 50 90 mv dc current limit v dc = 5v, v sys = 4v, t a = +25nc r pset = 1.5ki 1800 2000 2200 ma r pset = 3ki 900 1000 1100 r pset = 6.3ki 450 475 500 v pen1 = 0v, v pen2 = 5v (500ma usb mode) 450 475 500 v pen1 = v pen2 = 0v (100ma usb mode) 80 95 100 pset resistance range 1.5 6.3 ki sys regulation voltage v dc = 6v, i sys = 1ma to 1.75a, v cen = 5v 4.29 4.35 4.4 v input current soft-start time connecting dc with usb not present 1.5 ms connecting dc with usb present 50 fs thermal-limit temperature die temperature at when the charging current and input current limits are reduced 100 nc thermal-limit gain i sys reduction with die temperature (above +100nc) 5 %/c v l voltage i vl = 0 to 5ma, usb = unconnected 3 3.3 3.6 v
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dc = v pen1 = v pen2 = 5v, cen = usus = thmen = gnd, v batt = 4v, v thm = 1.65v, usb, thmsw, chg , done , ot , dok , uok , flt are unconnected, c ct = 0.068 f f, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 1) parameter conditions min typ max units usb-to-sys preregulator usb operating voltage range 4.1 6.6 v usb withstand voltage v batt = 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, 360mv hysteresis 6.8 6.9 7.0 v usb operating supply current i sys = i batt = 0ma, v cen = v pen2 = 0v 1 2 ma i sys = i batt = 0ma, v cen = 5v, v pen2 = 0v 0.9 1.5 usb suspend current dc = unconnected, v usb = v cen = v usus = 5v 190 340 fa usb to sys on-resistance dc unconnected, v usb = v cen = 5v, i sys = 400ma 0.22 0.33 i usb-to-batt dropout voltage when sys regulation and charging stops, v usb falling, 150mv hysteresis 10 50 90 mv usb current limit (see table 2) dc unconnected, v usb = 5v, t a = +25nc v pen1 = 0v, v pen2 = 5v 450 475 500 ma v pen1 = v pen2 = 0v 80 95 100 sys regulation voltage dc unconnected, v usb = 6v, v pen2 = 5v, i sys = 1ma to 400ma, v cen = 5v 4.29 4.35 4.4 v input limiter soft-start time input current ramp time 50 fs thermal-limit temperature die temperature at when the charging current and input current limits are reduced 100 nc thermal-limit gain i sys reduction with die temperature (above +100nc) 5 %/nc v l voltage dc unconnected, v usb = 5v, i vl = 0 to 5ma 3 3.3 3.6 v ldo linear regulator ldo output voltage dc unconnected, v usb = 5v, i ldo = 0ma 3.234 3.3 3.366 v v dc = 5v, usb unconnected, i ldo = 0ma 3.234 3.3 3.366 dc and usb unconnected, v batt = 4v, i ldo = 0ma 3.234 3.3 3.366 ldo load regulation i ldo = 0 to 30ma 0.003 %/ma battery charger batt-to-sys on-resistance v dc = 0v, v batt = 4.2v, i sys = 1a 0.04 0.08 i batt-to-sys reverse regulation voltage v pen1 = v pen2 = 0v, i sys = 200ma 50 75 105 mv batt regulation voltagesafety region 2 i batt = 0ma t a = +25nc, v thm_t2 < v thm < v thm_t3 4.175 4.2 4.225 v t a = 0nc to +85nc, v thm_t2 < v thm < v thm_t3 4.158 4.2 4.242 t a = +25nc, v thm_t1 < v thm < v thm_t2 or v thm_t3 < v thm < v thm_t4 4.05 4.075 4.1 t a = 0nc to +85nc, v thm_t1 < v thm < v thm_t2 or v thm_t3 < v thm < v thm_t4 4.034 4.075 4.1
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 4 ______________________________________________________________________________________ electrical characteristics (continued) (v dc = v pen1 = v pen2 = 5v, cen = usus = thmen = gnd, v batt = 4v, v thm = 1.65v, usb, thmsw, chg , done , ot , dok , uok , flt are unconnected, c ct = 0.068 f f, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 1) parameter conditions min typ max units batt recharge threshold safety region 2 change in v batt from done to fast- charge restart v thm_t2 < v thm < v thm_t3 -145 -104 -65 mv v thm_t1 < v thm < v thm_t2 or v thm_t3 < v thm < v thm_t4 -120 -80 -40 batt fast-charge current range r iset = 10ki to 2ki 0.3 1.5 a batt charge current accuracy v sys = 5.5v, v thm_t1 < v thm < v thm_t4 (safety region 2) r iset = 2ki 1350 1500 1650 ma r iset = 4ki 675 750 825 r iset = 10ki 270 300 330 r iset = 2ki, v batt = 2.5v (prequal) 270 300 330 r iset = 4ki, v batt = 2.5v (prequal) 130 150 170 r iset = 10ki, v batt = 2.5v (prequal) 60 iset output voltage r iset = 4ki, i batt = 500ma (v iset = 1.5v at full charge current) v thm_t1 < v thm < v thm_t4 0.9 1 1.1 v charger soft-start time charge-current ramp time 1.5 ms batt prequal threshold v batt rising, 180mv hysteresis 2.9 3 3.1 v batt input current v batt = 4.2v, i ldo = 0 no dc or usb power connected, thmen = low, v cen = 5v 5 12 fa no dc or usb power connected, thmen = high, v cen = 5v 12 25 dc or usb power connected, v cen = 5v 0.003 2 done threshold as a percentage of fast-charge current i batt decreasing 20 % maximum prequal time from cen falling to end of prequal charge, v batt = 2.5v 180 min maximum fast-charge time from cen falling to flt falling 300 min maximum top-off time 15 s timer accuracy -20 +20 % timer extend threshold percentage of fast-charge current below where the timer clock operates at half-speed 50 % timer suspend threshold percentage of fast-charge current below where timer clock pauses 20 %
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G _______________________________________________________________________________________ 5 electrical characteristics (continued) (v dc = v pen1 = v pen2 = 5v, cen = usus = thmen = gnd, v batt = 4v, v thm = 1.65v, usb, thmsw, chg , done , ot , dok , uok , flt are unconnected, c ct = 0.068 f f, t a = -40 n c to +85 n c, unless otherwise noted. typical values are at t a = +25 n c.) (note 1) note 1: limits are 100% production tested at t a = +25 n c. limits over the operating temperature range are guaranteed by design. note 2: n c includes external ntc thermistor error. % of thmsw excludes thermistor beta error and external pullup error. ntc thermistor assumed to be 100k i q 1% nominal, part number vishay nths0603n01n1003ff, external pullup resistor = 100ki q1%. parameter conditions min typ max units thermistor monitor (beta = 3964) (note 2) thm cold no-charge threshold (t1) i chg = 0a, when charging is suspended, 2 n c hysteresis -2.1 0 +2.4 nc 76.4 77.2 77.9 % of thmsw thm cold threshold (t2) v batt_reg , reduced, 2nc hysteresis 8.2 10 12 nc 66.2 67 67.6 % of thmsw thm hot threshold (t3) v batt_reg reduced, 2.5nc hysteresis 42.8 45 47.5 nc 29.8 30 30.6 % of thmsw thm hot no-charge threshold (t4) i chg = 0ma, when charging is suspended, 3nc hysteresis 57 60 63.5 nc 19.5 19.8 20.1 % of thmsw thm hot discharge threshold (t ot ) ot asserts low, 5nc hysteresis 71 75 80 nc 12.6 12.9 13.1 % of thmsw thm input leakage thm = gnd or ldo t a = +25nc -1 +0.001 +1 fa t a = +85nc 0.01 thmsw output leakage thmsw = gnd t a = +25nc -0.2 +0.001 +1 fa t a = +85nc 0.01 thmsw output voltage high sourcing 1ma v ldo - 0.05 v logic i/o: pen1, pen2, chg, flt, done, dok, uok, usus, thmen) logic-input thresholds high level 1.3 v low level 0.4 hysteresis 50 mv logic-input leakage current v in = 0 to 5.5v t a = +25nc 0.001 1 fa t a = +85nc 0.01 logic-low output voltage sinking 1ma 25 100 mv logic-high output leakage current v out = 5.5v t a = +25nc 0.001 1 fa t a = +85nc 0.01
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 6 ______________________________________________________________________________________ typical operating characteristics (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) usb operating supply current vs. usb voltage (charger enabled) MAX8934G toc01 usb operatin supply current ( a) 200 400 600 800 1000 1200 0 usb voltage (v) 7 6 4 5 2 3 1 0 8 v batt = 4.2v, v usus = 0v charger in done mode i sys = 0a v usb rising v usb falling entering ovlo usb operating supply current vs. usb voltage (charger disabled) MAX8934G toc02 usb voltage (v) usb operating supply current ( a) 7 6 4 5 2 3 1 100 200 300 400 500 600 700 800 900 0 0 8 v batt = 4.2v, v usus = 0v cen = 1 i sys = 0a pen1 = x, pen2 = 1 v usb rising v usb falling entering ovlo usb suspend current vs. usb voltage MAX8934G toc03 usb voltage (v) usb quiescent current (fa) 7 6 5 4 3 2 1 50 100 150 200 250 0 0 8 v batt = 4.2v, usus = 1 battery input current vs. battery voltage (usb disconnected) MAX8934G toc04 battery voltage (v) battery input current (ua) 4 3 2 1 2 4 6 8 10 12 14 0 0 5 thmen = 1 thmen = 0 charge current (ma) 50 100 150 200 250 300 350 400 450 500 0 charge current vs. battery voltage (500ma usb) MAX8934G toc07 battery voltage (v) 1 2 3 4 0 5 v usb = 5v pen1 = x, pen2 = 1 v batt rising v batt falling charge current vs. battery voltage (1a dc) MAX8934G toc08 battery voltage (v) charge current (ma) 4 3 2 1 200 400 600 800 1000 1200 0 0 5 v dc = 5v pen1 = 1, pen2 = x v batt rising v batt falling battery input current vs. temperature MAX8934G toc05 temperature (c) battery input current ( a) 60 35 10 -15 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 4.0 -40 85 v batt = 4v, thmen = 0, i ldo = 0 usb and dc unconnected charge current vs. battery voltage (100ma usb) MAX8934G toc06 battery voltage (v) charge current (ma) 4 3 2 1 10 20 30 40 50 60 70 80 90 100 0 0 5 v usb = 5v pen1 = x, pen2 = 0 v batt rising v batt falling
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G _______________________________________________________________________________________ 7 typical operating characteristics (continued) (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) sys output voltage vs. sys output current (dc) MAX8934G toc14 sys current (a) sys voltage (v) 2.5 2.0 1.5 1.0 0.5 3.9 4.3 4.7 5.1 5.5 3.5 0.0 3.0 v dc = 6v v dc = 5v v bat = 4v pen1 = 1, pen2 = x cen = 1 battery regulation voltage vs. temperature MAX8934G toc10 battery voltage (v) battery regulation voltage (v) 60 35 10 -15 4.175 4.180 4.185 4.190 4.195 4.200 4.205 4.210 4.215 4.220 4.170 -40 85 sys output voltage vs. dc voltage MAX8934G toc12 dc voltage (v) 12 10 8 6 4 2 0 14 sys voltage (v) 4.2 4.4 4.6 4.8 4.0 v batt = 4.0v no sys load normalized charge current vs. ambient temperature (low ic power dissipation) max8943g toc09 ambient temperature (c) normalized charge current 60 35 -15 10 0.9925 0.9950 0.9975 1.0000 1.0050 1.0025 1.0075 1.0100 0.9900 -40 85 v usb = 5v, v batt = 4v sys output voltage vs. usb voltage MAX8934G toc11 usb voltage (v) sys voltage (v) 7 6 5 4 3 2 1 4.2 4.4 4.6 4.8 4.0 0 8 v batt = 4.0v no sys load sys output voltage vs. sys output current (usb and dc disconnected) MAX8934G toc13 sys output current (a) sys output voltage (v) 1.5 1.0 0.5 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 3.6 0 2.0 v batt = 4.0v the slope of this line shows that the batt-to-sys resistance is 40mi.
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 8 ______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) v l output voltage vs. dc voltage MAX8934G toc16 dc voltage (v) v l output voltage (v) 12 10 8 6 4 2 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 0 14 i vl = 5ma i vl = 0ma charge profile?820mah battery adapter input?1a charge time (min) battery current (ma) 60 40 20 0.2 0.4 0.6 0.8 1.0 1.2 0 0 80 MAX8934G toc18 battery voltage (v) 2.5 3.0 3.5 4.0 4.5 1.5 2.0 v bat i bat dc connect with no usb (r sys = 22i) MAX8934G toc20 3.6v 4.35v 3.6v 0a 1.2a -1a 1a/div 5v/div 5v/div 1a/div v batt v sys i dc i batt 400s/div 160ma 0ma battery charger soft-start c sys charging c dc charging sys output voltage vs. sys output current (usb) MAX8934G toc15 sys output current (a) sys output voltage (v) 2.5 2.0 1.5 1.0 0.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 3.5 0 3.0 v batt = 4.0v, v usb = 5.0v cen = 1 0.1a, pen1 = 0, pen2 = 0 0.5a, pen1 = 0, pen2 = 0 charge profile?820mah battery usb input?500ma charge MAX8934G toc17 time (min) battery current (ma) battery voltage (v) 100 80 60 40 20 0 120 50 100 150 200 250 300 350 400 450 500 0 2.5 3.0 3.5 4.0 4.5 2.0 i bat v bat dc connect with usb connected (r sys = 22i) MAX8934G toc19 4.35v 3.8v 0a 475ma 1.2a -1a 0a 1a/div 5v/div 1a/div 500ma/div v sys i dc i usb i batt 400s/div -303ma battery charger soft-start c dc charging c sys charging
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G _______________________________________________________________________________________ 9 typical operating characteristics (continued) (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) usb connect with no dc (r sys = 22i) MAX8934G toc22 5v 3.3v 3.3v 3.3v -150ma 475ma 3.7v 4.3v -1a 5v/div 5v/div 5v/div 5v/div 500ma/div 500ma/div v usb i usb v sys v uok i batt 200s/div battery charger soft-start c sys charging c dc charging -307ma v chg usb suspend (r sys = 22i) MAX8934G toc24 3.3v 5v/div v usus v sys i usb 200s/div 3.7v -307ma 3.6v 3.3v v chg i batt 475ma 0a 0v 160ma v usb = 5v 5v/div 5v/div 500ma/div 500ma/div ldo output voltage vs. ldo output current (usb disconnected) MAX8934G toc26 ldo output current (ma) ldo output voltage (v) 150 125 25 50 75 100 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.35 2.95 0 175 v dc = 5.0v v batt = 4.0v dc unconnected dc disconnect with no usb (r sys = 22i) MAX8934G toc21 3.6v 3.6v 4v 0a -1a 1a/div 5v/div 5v/div 1a/div v batt v sys i dc i batt 200s/div 160ma -i batt = charging 1.2a usb disconnect with no dc (r sys = 22i) MAX8934G toc23 4.2v 0v 5v/div v usb v sys i usb 200s/div 0ma 3.7v 3.6v 3.3v 3.3v v uok i batt v chg -307ma 475ma 160ma 5v/div 5v/div 5v/div 500ma/div 500ma/div usb resume (r sys = 22i) MAX8934G toc25 5v/div v usus v sys i usb 200s/div 3.7v 3.6v 4.3v 3.3v v chg i batt 3v 0a 160ma 475ma v usb = 5v 5v/div 5v/div 500ma/div 500ma/div 0v -307ma battery charger soft-start
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 10 _____________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) ldo startup waveforms MAX8934G toc27 2v/div 50ma/div 2v/div i batt v ldo v batt 400fs/div 3.6v i ldo = 0 3.3v always-on ldo power-supply rejection ratio vs. frequency MAX8934G toc29 frequency (khz) psrr (db) 10 1 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 -50 0.1 100 v sys = 3.6v i ldo = 10ma resistive load thm normal to thm cold (< t2) transition MAX8934G toc31 1v/div 200mv/div 200ma/div v thm v bat i bat 10ms/div 10i resistor from batt to gnd 4.2v 4.075v 2.2v 420ma ldo output voltage vs. battery voltage MAX8934G toc28 battery voltage (v) ldo output voltage (v) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 0 4.0 v batt rising v batt falling ldo noise density vs. frequency MAX8934G toc30 frequency (khz) output noise (nv / hz) 1000 100 10 1 0.1 100 200 300 400 500 600 700 800 900 0 0.01 10,000 v batt = 3.8v, i ldo = 10ma resistive load
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 11 typical operating characteristics (continued) (t a = +25 n c, circuit o f figure 2 , v dc = 6v, v batt = 3.6v, thermistor beta = 3964, unless otherwise noted. negative battery current indicates charging.) thm normal to thm hot no charge (> t4) transition MAX8934G toc33 500mv/div 2v/div 100ma/div i batt v batt v thm 20ms/div 0.65v 4.2v 0v 0ma 100ma 4.075v hp6060b electronic load set to cc mode thm normal to t2 to t1 (cold, no charge) transition MAX8934G toc35 1v/div 1v/div 200ma/div v thm v batt i batt 10ms/div 10i resistor from batt to gnd 4.2v 0v 0ma 4.075v 2.54v 2.2v 420ma MAX8934G toc34 2v/div 2v/div 2v/div 2v/div v thm v batt v sys 4ms/div thm normal to thm hot threshold discharge t ot v ot 3v 3.6v 3.6v 0.425v thm normal to thm hot (> t3) transition MAX8934G toc32 500mv/div 200mv/div 500ma/div i batt v batt v thm 10ms/div 1.0v 4.2v hp6060b electronic load set to cc mode 4.075v 940ma
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 12 _____________________________________________________________________________________ pin description pin name function 1 done charge complete output. the done active-low, open-drain output pulls low when the charger enters the done state. the charger current = 0ma when done is low. see figure 7. 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, and r pset . see table 2. both dc pins must be connected together externally. connect a 10 f f ceramic capacitor from dc to gnd. the dc inputs should be grounded if not used. 4 cen active-low charger enable input. connect cen to gnd or drive low with a logic signal to enable battery charging when a valid source is connected at dc or usb. drive high with a logic signal to disable battery charging. 5 pen1 input limit control 1. see table 2 for complete information. 6 pen2 input limit control 2. see table 2 for complete information. 7 pset dc input current-limit setting. connect a resistor from pset to gnd to program the dc current limit up to 2a (3000v/r pset ). 8 v l internal logic ldo output bypass pin. provides 3.3v when dc or usb is present. connect a 0.1ff ceramic capacitor from v l to gnd. v l powers the internal circuitry and provides up to 5ma to an external load. 9, 13 gnd ground. both gnd pins must be connected together externally. 10 ct charge timer program input. a capacitor from ct to gnd sets the maximum prequal and fast-charge timers. connect ct to gnd to disable the timer. 11 iset charge current-limit setting. a resistor (r iset ) from iset to gnd programs the fast-charge charge current up to 1.5a (3000v/r iset ). the prequal charge current is 20% of the set fast-charge charge current. 12 usus usb suspend digital input. as shown in table 2, driving usus high suspends the dc or usb inputs if they are configured as a usb power input. 14 thm thermistor input. connect a negative temperature coefficient (ntc) thermistor with good thermal contact with the battery from thm to gnd. use a thermistor with beta = 3964. connect a resistor of equal resistance to the thermistor resistance at +25c from thm to thmsw so that the battery temperature can be monitored, and the fast-charge current and/or the charge termination voltage is automatically adjusted, in accordance with safety region 2 of the jeita specification. 15 thmen thermistor enable input. thmen controls thmsw by connecting the external thermistor pullup resistor and the thermistor monitoring circuit to ldo. drive thmen high to enable the thermistor circuit in discharge mode and to connect the external thermistor pullup resistor. drive thmen low to disconnect the external thermistor pullup resistor and to disable the thermistor monitoring circuit to conserve battery energy when not charging. 16 thmsw thermistor pullup supply switch. drive thmen high to enable the thmsw, shorting the thmsw output to ldo. drive thmen low to open the thmsw switch. thmsw is always on when a valid input source is present and the battery is being charged. when no input source is present, thmsw is controlled by thmen. thmsw is also active when the battery is being discharged, so that the battery temperature can be monitored for an overtemperature condition.
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 13 pin description (continued) pin name function 17 ldo always-on linear regulator output. ldo is the output of an internal always-on 3.3v ldo that provides power to external circuitry. the ldo output provides up to 30ma of current for indicator leds or other loads. ldo remains active even when only a battery is present, so that the thermistor monitor circuitry can be activated when the battery is being discharged, and other circuitry can remain powered. connect a 1ff ceramic capacitor from ldo to gnd. 18, 19 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. connect a 4.7ff ceramic capacitor from usb to gnd. 20, 21 batt battery connection. connect the positive terminal of a single-cell li+ battery to batt. the battery charges from sys when a valid source is present at dc or usb. batt powers sys when neither dc nor usb power is present, or when the sys load exceeds the input current limit. both batt pins must be connected together externally. 22 chg charger status output. the chg active-low, open-drain output pulls low when the battery is in fast charge or prequal. otherwise, chg is high impedance. 23, 24 sys system supply output. sys is connected to batt through an internal 40mi system load switch when dc or usb are 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 or 4.35v. when the system load (i sys ) exceeds the dc or usb current limit, sys is regulated to 75mv below v batt and both the input and the battery service the sys load. bypass sys to gnd with a 10ff ceramic capacitor. both sys pins must be connected together externally. 25 ot battery overtemperature flag. the ot active-low, open-drain output pulls low when thmen is high and the battery temperature is r +75nc. 26 dok dc power-ok output. the dok active-low, open-drain output pulls low when a valid input is detected at dc. 27 uok usb power-ok output. the uok active-low, open-drain output pulls low when a valid input is detected at usb. 28 flt fault output. the flt active-low, open-drain output pulls low when the battery timer expires before prequal or fast charge complete. ep exposed pad. connect the exposed pad to gnd. connecting the exposed pad does not remove the requirement for proper ground connections to the appropriate pins.
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 14 _____________________________________________________________________________________ figure 1. block diagram set input limit v l ldo for ic power current- limited voltage regulator thermistor monitor (see figure 5) charge termination and monitor pwr ok dc dc dok v l usb uok pen1 pen2 usus pset gnd ep dc power management li+ battery charger and sys load switch sys t sys ldo ot iset batt batt thm thmsw thmen ct chg set input limit current- limited voltage regulator input and charger current-limit logic control charger current and voltage control thermal regulation pwr ok usb power management 3.3v always-on low-i q ldo charge timer MAX8934G cen flt done chg
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 15 figure 2. typical application circuit using separate dc and usb connector dc charge done adapter r pu 1mi r pu 4x 1mi c dc 10ff c sys 10ff c batt 4.7ff c usb 4.7ff c ldo 1ff dc pen 1 pen 2 pset v l gnd ct thms w thms w active disabled thm thme n ce n done fl t uo k do k to ldo ldo overtemperature fault output usb pwr ok dc pwr ok to system load charge indicator 1-cell li+ sys sys chg batt batt us b us b ld o usus ep ot 1 2 3 4 off charge on 500ma 100ma 6 7 8 9, 13 10 15 16 14 5 12 17 19 usb suspend 18 21 20 22 24 23 26 27 28 25 r pset 1.5ki 1mi iset 11 r iset 3ki 100ki ntc 100ki 25c c vl 0.1ff c ct 0.068ff MAX8934G vbus d- d+ id gnd 2 1 3 4 5
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 16 _____________________________________________________________________________________ figure 3. typical application circuit using a 5-pin usb connector or other dc/usb common connector dc charge done 5-pin usb connector r pu 1mi r pu 4x 1mi c dc 10ff c sys 10ff c batt 4.7ff c ldo 1ff dc pset v l gnd ct thms w thms w active disabled thm thme n done fl t uo k do k to ldo v ldo overtemperature fault output usb pwr ok dc pwr ok to system load charge indicator 1-cell li+ sy s sy s chg bat t bat t us b us b ld o usus ep ot 1 2 3 ce n 5 off charge on dc vbus d- d+ id gnd usb pen 2 pen 1 500ma 100ma 6 7 8 9, 13 10 15 16 14 4 1 2 3 4 5 12 17 19 usb suspend 18 21 20 22 24 23 26 27 28 25 r pset 1.5ki 1mi iset 11 r iset 3ki 100ki ntc 100ki 25c c vl 0.1ff c ct 0.068ff MAX8934G
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 17 detailed description the MAX8934G is a dual-input linear charger with smart power selector that safely charges a single li+/li-poly cell in accordance with jeita specifications. the MAX8934G integrates 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 sepa - rately connected to an ac adapter output and a usb port, or the dc input could be a single power input that connects to either an adapter or usb. logic inputs, pen1 and pen2, select the correct current limits 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 5-pin usb connector or another dc/usb common connector. in addition to charging the battery, the MAX8934G 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, where total sys current 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 sources are connected, dc takes precedence. in some instances, there may not be enough adapter current or usb current to supply peak system loads. the MAX8934G 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 system load. if a system load peak exceeds the input current limit, supple - mental current is taken from the battery. thermal limiting prevents overheating by reducing power drawn from the input source. the MAX8934G features an overvoltage limiter at sys. if the dc or usb input voltage exceeds the sys regulation voltage, v sys does not follow v dc or v usb , but remains at its regulation voltage. the MAX8934G has numerous other charging and power-management features that are detailed in the following sections. a 3.3v ultra-low quiescent current, always-on ldo pro - vides up to 30ma for indicator leds and for backup power to the system. this ldo powers the thermistor monitor circuitry and provides bias to the external pullup resistor for the thermistor. table 1. external components list for figures 2 and 3 component (figures 2 and 3) function part number c dc dc filter capacitor 10ff 10%, 16v x5r ceramic capacitor (0805) taiyo yuden emk212bj106kg c usb usb filter capacitor 4.7ff 10%, 10v x5r ceramic capacitor (0805) taiyo yuden lmk212bj475kd c vl v l filter capacitor 0.1ff 10%, 10v x5r ceramic capacitor (0402) taiyo yuden lmk105bj104kv c sys sys output bypass capacitors 10ff 10%, 6.3v x5r ceramic capacitor (0805) taiyo yuden jmk212bj106kd c batt battery bypass capacitor 4.7ff 10%, 6.3v x5r ceramic capacitor (0805) taiyo yuden jmk212bj475kd c ct charger timing capacitor 0.068ff 10%, 16v x5r ceramic capacitor (0402) taiyo yuden emk105bj683kv c ldo ldo output capacitor 1ff 1 0%, 6.3v x5r ceramic capacitor (0402) taiyo yuden jmk105bj105kv r pu (x5) logic-output pullup resistors 1mi 5% resistor thm negative tc thermistor vishay ntc thermistor p/n nths0603n01n1003ff r thmsw thm pullup resistor 100ki r pset dc input current-limit programming resistor 1.5ki 1% for 2a limit r iset fast-charge current programming resistor 3ki 1% for 1a charging
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 18 _____________________________________________________________________________________ smart power selector the MAX8934G smart power selector seamlessly dis - tributes power among the external inputs, the battery, and the system load (see the typical operating circuit ). the basic functions performed are: u with both an external power supply (usb or adapter) and battery connected: u when the system load requirements are less than the input current limit, the battery is charged with residual power from the input. u when the system load requirements exceed the input current limit, the battery supplies supplemen - tal current to the load. u when the battery is connected and there is no external power input, the system is powered from the battery. u when an external power input is connected and there is no battery, the system is powered from the external power input. system load switch an internal 40m i mosfet connects sys to batt (q3 in the typical operating circuit ) 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-batt switch also holds up sys when the system load exceeds the input current limit. if that should happen, the sys-batt switch turns on so that the battery supplies additional sys load current. if the system load continu - ously 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 usu - ally occur only in short peaks. during these peaks, battery energy is used, but at all other times the battery charges. input limiter the input voltage limiter is essentially an ldo regula - tor. while in dropout, the regulator dissipates a small i 2 r loss through the 0.2 i mosfet (q1 in the typical operating circuit ) between dc and sys. with an ac adapter or usb source connected, the input limiter distributes power from the external power source to the system load and battery charger. in addition to the input limiters 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 t he overvoltage threshold (6.9v typ), the MAX8934G enters overvoltage lockout (ovlo). ovlo protects the MAX8934G and downstream circuitry from high-voltage stress up to 14v at dc and 8v at usb. in ovlo, v l remains on, the input switch that sees overvoltage (q1, q2, typical operating circuit ) opens, 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, typical operating circuit ) open and the charger turns off. the batt-to-sys switch (q3, typical operating circuit ) closes, allowing the battery to power sys. an input is also invalid if it is less than batt, or less than the dc undervoltage threshold of 3.5v (falling). with an invalid input voltage, sys connects to batt through a 40mi switch (q3, typical ope rating circuit ). input overcurrent protection the current at dc and usb is limited to prevent input overload. this current 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 75mv below batt and the battery supplies supplemental load current. thermal limiting the MAX8934G reduces input limiter current by 5%/ nc when its die temperature exceeds +100 n c. the system load (sys) has priority over the charger current, so low - ering the charge current first reduces the input current. if the junction temperature still reaches +120 n c 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 75mv below batt. 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 current to prevent the sys voltage from collapsing. maintaining a higher sys voltage improves efficiency and reduces power dissipation in the input limiter. the total current through the switch (q1 or q2 in the typical operating circuit ) is the sum of the load current at sys and the bat - tery charging current. the MAX8934G limiter clamps at 4.35v, so input voltages greater than 4.35v can increase power dissipation in the limiter. the MAX8934G input
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 19 limiter power loss is (v dc C v sys ) x i dc , where v sys may be as high as 4.35v. the input limiter power loss is not less than 0.2 i x i dc 2 . also note that the MAX8934G turns off when any input exceeds 6.9v (typ). 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 current limit as the input power source is changed. the MAX8934G facilitates this by allowing different input cur - rent limits for dc and usb as shown in table 2. when the input current limit is reached, the first action taken by the MAX8934G is to reduce the battery charge current. this allows the regulator to stay in dropout dur - ing heavy loads, thus reducing power dissipation. if, after the charge current is reduced to 0ma, the load at sys still exceeds the input current limit, sys voltage begins to fall. when the sys voltage drops to batt, the sys- to-batt switch turns on, using battery power to support the system load during the load peak. the MAX8934G 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: sepa - rate 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 connected high (to dc or v l ). 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 common connector is used for both ac adapter and usb sources, the dc input is used for both input sources. the unused usb inputs should be grounded 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 suspend (further selected by pen2 and usus). pen1 can be pulled up by the ac adapter power to implement hard - ware adapter/usb selection . usb suspend driving usus high when pen1 is low turns off the char - ger and reduces input current to 190 f a to accommodate usb suspend mode. the input limiter is disabled and sys is supported by batt. 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 has 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 is valid. table 2. input limiter control logic * charge current cannot exceed the input current limit. actual charge current may be less than the maximum charge current if the total sys load exceeds the input current limit. 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 3000v/r pset usb input off; dc input has priority 3000v/r iset usb power at dc input l x l h l 475ma 475ma l x l l l 95ma 95ma l x l x h usb suspend 0 usb power at usb input; dc unconnected h l x h l no dc input 475ma 3000v/r iset h l x l l 95ma h l x x h usb suspend 0 dc and usb unconnected h h x x x no usb input 0
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 20 _____________________________________________________________________________________ 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 con - nected with usb already present, input current ramps in 50fs . when usb is connected with no dc present, input current also ramps in 50 f s. 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 is below the sys load current, the battery 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 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 7. 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 battery voltage is less than the batt prequal threshold (3.0v), the charger enters prequal mode and charges the battery at 20% of the maximum fast-charge current. this reduced charge rate ensures that the maximum fast-charge current set - ting does not damage a deeply discharged battery. once the battery voltage rises to 3.0v, the charger tran - sitions to fast-charge mode and applies the maximum charge current. as charging continues, the battery volt - age rises until it approaches the battery regulation volt - age where charge current starts tapering down. when charge current decreases to 20% of the fast-charge current, the charger enters a brief 15s top-off state, then done pulls low and charging stops. if the battery volt- age subsequently drops below the recharge threshold, charging restarts and the timers reset. 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 MAX8934G 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 = 3000v/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 MAX8934G automati - cally 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. see figure 4. 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 filtering of the charge-current monitor is necessary, add a resistor of 100k i or more between iset and the filter capacitor to preserve charger stability. note that the actual charge current can be less than the set fast-charge current when the charger enters voltage mode or when the input current limiter or thermal limiter reduces charge current. this prevents the charger from overloading the input source or overheating the system. charge termination when the charge current falls to the termination threshold and the charger is in voltage mode, charging is com - plete. charging continues for a brief 15s top-off period and then enters the done state where charging stops. the done current threshold (i done ) is set to 20% of the
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 21 fast-charge current setting. note that if charge current falls to i done as a result of the input or thermal limiter, the charger does not enter the done state. for the char - ger to enter the done state, the charge current must be less than i done , the charger must be in voltage mode, and the input or thermal limiter must not be reducing the charge current. the charger exits the done state, and fast-charge resumes if the battery voltage subsequently drops 104mv or if cen is cycled. charge status outputs charge output (chg) 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 ( i done ) 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 MAX8934G is used with a microprocessor ( fp), connect a pullup resistor between chg and the logic i/o voltage to indicate charge status to the f p. alternatively, chg can sink up to 20ma for an led indicator. charge done output (done) done is an open-drain, active-low output that goes low when charging is complete. the charger enters its done state 15s after the charge current falls to the charge-termination threshold (i done ) and the charger is in voltage mode. the charger exits the done state, and fast-charge resumes, if the battery voltage subsequently drops 104mv, or if input power or cen is cycled. when the MAX8934G is used in conjunction with a f p, con- nect a pullup resistor between done and the logic i/o voltage to indicate charge status to the f p. alternatively, done can sink up to 20ma for an led indicator. fault output ( flt ) 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 : ct pq c prequal: t 180min 0.068 f = f ct fc c fast charge: t 300min 0.068 f = f to top off:t 15s ? = while in fast-charge mode, a large system load or device self-heating can cause the MAX8934G 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 pro - grammed 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 voltage mode where charge current reduces due to current tapering under normal charging. to exit a fault state, toggle cen or remove and reconnect the input source(s). note also that thermistor out of range or on-chip thermal-limit conditions are not considered faults. when the MAX8934G is used in conjunction with a f p, connect a pullup resistor between flt and the logic i/o voltage to indicate fault status to the f p. alternatively, flt can sink up to 20ma for an led indicator. thermistor monitor the MAX8934G thermistor monitor is configured to execute jeita recommendations regarding li+/li-poly battery charging by adjusting the fast charge current and/or the charge termination voltage accordingly (see figure 6 ). connect the thm input to an external negative temperature coefficient (ntc) thermistor to monitor bat - tery or system temperature. since the thermistor monitor - ing circuit employs an external bias resistor from thm to thmsw, the thermistor is not limited only to 10k i (at figure 4. monitoring the battery charge current with v iset 1.5 v iset 0 0 2000 (1.5v/r iset ) battery charging current (a) monitoring the battery charge current with v iset discharging v iset (v)
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 22 _____________________________________________________________________________________ +25n c). any thermistor resistance can be used as long as the value of r thmsw is equivalent to the thermistors +25n c resistance. the MAX8934G thm thresholds are optimized for a thermistor beta of 3964. the general rela - tion of thermistor resistance to temperature is defined by the following equation: 1 1 - t 273 c 298 c t 25 r r e ? ? ? ? ? ? ? ? + ? ? ? ? = where: r t = the resistance in ohms of the thermistor at temperature t in nc r 25 = the resistance in ohms of the thermistor at +25 nc a = the material constant of the thermistor t = the temperature of the thermistor in nc charging is suspended when the thermistor temperature is out of range (v thm_t1 < v thm or v thm < v thm_t4 ). the charge timers are also suspended and hold their state but no fault is indicated. when the thermistor comes back into range, charging resumes and the charge timer continues from where it left off. the thmen input controls thmsw and the thermistor monitor circuitry when the battery charger is disabled, providing the user with the means to minimize the bat - tery current drain caused by the thermistor monitor. the thmen input is ignored while the battery is charging, since the thermistor must be monitored at all times. while charging, the thermistor monitor is used to auto - matically adjust the charge termination voltage and/or the fast-charge current, depending on the sensed bat - tery temperature. if the battery temperature exceeds the thm hot overtemperature threshold and thmen is high, the ot flag pulls low. typical systems connect ot to a f p input so that the system can safely shut down. always-on ldo the ultra-low quiescent current ldo is always on and is preset to an output voltage of 3.3v. the ldo provides up to 30ma output current. when dc and usb are invalid and the battery is discharging, the ldo output volt - age tracks v sys as it drops below 3.3v. a 1 f f ceramic capacitor connected from ldo to gnd is recommended for most applications. power dissipation pcb layout and routing good design minimizes ground bounce and voltage gradients in the ground plane. 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 pad directly under the ic. use mul - tiple tightly spaced vias to the ground plane under the exposed pad to help cool the ic. position input capaci - tors from dc, sys, batt, 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 batt as short and wide as possible. refer to the max8934a evaluation kit for a suitable pcb layout example. table 3. package thermal characteristics 28-pin 4mm x 4mm thin qfn single-layer pcb multilayer pcb continuous power dissipation 1666.7mw (derate 20.8mw/nc above +70nc) 2285.7mw (derate 28.6mw/nc above +70nc) b ja 48nc/w 35nc/w b jc 3nc/w 3nc/w
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 23 figure 5. thermistor monitor details t chg sys ldo vint chg vint thermistor monitor charger control chg ot t4 (60nc) t3 (45nc) t2 (10nc) t ot (75nc) t1 (0nc) - + vint chg - + vint vint thm thmsw thmen r thmsw vint chg chg + - vint vint thmen not charging - + vint vint + - chg low-i q , always-on 3.3v ldo tr ac ks sys wh en dc and us b ar e no t present, the battery is being discharged, and v batt p 3.3v.
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 24 _____________________________________________________________________________________ figure 6. safety region 2: fast-charge currents and charge termination voltages temperature (nc) temperature (nc) 0 4.2 t1 t2 t3 t4 t1 t2 t3 t4 4.1 4.075 4.0 0.5c c 10 25 45 60 0 10 25 45 60 85 85 batt regulation voltage (v) (v batt_reg ) fast-charge current (i chg )
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 25 figure 7. charger state diagram state diagram is for 10nc < temp < +45nc, outside of this range see figure 6 v batt < 2.82v reset timer i chg > i done reset timer v batt < 4.1v reset timer i chg < i done and v batt = 4.2v and thermal or output limit not exceeded reset timer any state timer > t pq timer > 15s v batt < 2.82v, reset timer v batt > 3v, reset timer v thm > v thm_ot v thm < v thm_ot v thm_t1 < v thm < v thm_t4 timer resume v thm_t1 < v thm or v thm < v thm_t4 timer suspend (pq, fc, top-off) any charging state overtemp ot = low uok or dok = low cen = 0 reset timer not ready uok and dok = high-z chg = high-z flt = high-z done = high-z i chg = 0ma prequal uok or dok = low chg = low flt = high-z done = high-z 0v p v batt p 3v i chg = i chgmax 10 fast-charge uok or dok = low chg = low flt = high-z done = high-z 3v p v batt p 4.2v i chg = i chgmax top-off uok or dok = low chg = high-z flt = high-z done = high-z batt = 4.2v i chg = i done done uok or dok = low chg = high-z flt = high-z done = low 4.1v < v batt < 4.2v i chg = 0ma temperature suspend i chg = 0ma uok or dok = previous state chg = high-z flt = high-z done = high-z cen = high or remove and reconnect the input source(s) toggle cen or remove and reconnect the input source(s) fault uok and dok = lo w chg = high-z flt = low done = high-z i chg = 0ma timer > t fc (timer slowed by 2x if i chg < i chgmax /2, and paused if i chg < i chgmax /5 while batt < 4.2v)
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 26 _____________________________________________________________________________________ chip information process: bicmos pin configuration MAX8934G thin qfn top view 26 27 25 24 10 9 11 dc cen pen1 pen2 pset 12 done batt usb ldo batt thmsw thmen 1 *ep *exposed pad 2 ot 4 5 6 7 20 21 19 17 16 15 dok uok usus iset ct gnd dc usb 3 18 28 8 flt v l sys 23 13 gnd sys 22 14 thm chg
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G ______________________________________________________________________________________ 27 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages. note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline n o. land pattern no. 28 tqfn-ep t2844+1 21-0139 90-0068 24l qfn thin.eps
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 28 _____________________________________________________________________________________ package information (continued) for the latest package outline information and land patterns, go to www.maxim-ic.com/packages. note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. 24l qfn thin.eps
dual-input linear charger, smart power selector with advanced battery temperature monitoring MAX8934G 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 29 ? 2010 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description date pages changed 0 6/10 initial release

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