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1 ltc4068-4.2/ltc4068x-4.2 406842fa standalone linear li-ion battery charger with programmable termination programmable charge current up to 950ma complete linear charger in dfn package no mosfet, sense resistor or blocking dioderequired thermal regulation maximizes charge ratewithout risk of overheating* charges directly from a usb port programmable charge current termination preset 4.2v charge voltage with 1% accuracy charge current monitor output for gas gauging* automatic recharge charge status output ?c present?output 2.9v trickle charge threshold (ltc4068) available without trickle charge (ltc4068x) soft-start limits inrush current low profile (3mm 3mm 0.75mm) dfn package cellular telephones, pdas, mp3 players bluetooth applications , ltc and lt are registered trademarks of linear technology corporation. the ltc 4068 is a complete constant-current/constant- voltage linear charger for single cell lithium-ion batteries.its dfn package and low external component count make the ltc4068 ideally suited for portable applications. fur- thermore, the ltc4068 is designed to work within usb power specifications. no external sense resistor or external blocking diode are required due to the internal mosfet architecture. thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature conditions. the charge voltage is fixed at 4.2v and the charge current is programmed with a resis- tor. the ltc4068 terminates the charge cycle when the charge current drops below the programmed termination threshold after the final float voltage is reached. when the input supply (wall adapter or usb supply) is removed, the ltc4068 enters a low current state dropping the battery drain current to less than 2 a. other features include charge current monitor, undervoltage lockout,automatic recharge and status pins to indicate charge termination and the presence of adequate input voltage. bat v cc chrg 1.65k 406842 ta01 1 f v in 4.5v to 6.5v 1-cellli-ion battery ltc4068-4.2 600ma acpr en prog gnd + iterm 825 ? time (hours) 0 charge current (ma) 1.5 406842 ta02 0.5 1.0 2.25 700600 500 400 300 200 100 0 4.754.50 4.25 4.00 3.75 3.50 3.25 3.00 0.25 0.75 1.25 2.0 1.75 constant voltage constant current battery voltage (v) v cc = 5v ja = 40 c/w r prog = 1.65k r term = 825 ? t a = 25 c complete charge cycle (750mah battery) protected by u.s. patents, including 6522118. single cell li-ion battery charger with c/5 termination descriptio u features applicatio s u typical applicatio u downloaded from: http:///
2 ltc4068-4.2/ltc4068x-4.2 406842fa (note 1)input supply voltage (v cc ) ....................... 0.3v to 10v prog, iterm ................................ 0.3v to v cc + 0.3v bat ............................................................. 0.3v to 7v chrg, acpr, en ...................................... 0.3v to 10v bat short-circuit duration .......................... continuous bat pin current ........................................................ 1a prog pin current ................................................... 1ma maximum junction temperature .......................... 125 c operating temperature range (note 2) .. 40 c to 85 c storage temperature range ................. 65 c to 125 c t jmax = 125 c, ja = 40 c/w (note 3) exposed pad is ground (pin 9) must be soldered to pcb order part number dd part marking lbhzlbqb symbol parameter conditions min typ max units v cc input supply voltage 4.25 6.5 v i cc input supply current charge mode (note 4), r prog = 10k 0.4 1 ma standby mode (charge terminated) 200 500 a shutdown mode (en = 5v, v cc < v bat 25 50 a or v cc < v uv ) v float regulated output (float) voltage 0 c t a 85 c, 4.3v < v cc < 6.5v 4.158 4.2 4.242 v i bat bat pin current r prog = 10k, current mode 92 100 105 ma r prog = 2k, current mode 465 500 535 ma standby mode, v bat = 4.2v ?.5 6 a shutdown mode (en = 5v, v cc < v bat or 1 2 a v cc < v uv ) sleep mode, v cc = 0v 1 2 a i trikl trickle charge current v bat < v trikl , r prog = 2k (note 5) 30 45 60 ma v trikl trickle charge threshold voltage r prog = 10k, v bat rising (note 5) 2.8 2.9 3 v v trhys trickle charge hysteresis voltage r prog = 10k (note 5) 80 mv v uv v cc undervoltage lockout voltage from v cc low to high 3.7 3.8 3.92 v v uvhys v cc undervoltage lockout hysteresis 150 200 300 mv v en(il) en pin input low voltage 0.4 0.7 v v en(ih) en pin input high voltage 0.7 1 v r en en pin pull-down resistor 1.2 2 5 m ? v asd v cc ?v bat lockout threshold v cc from low to high 70 100 140 mv v cc from high to low 5 30 50 mv i term charge termination current threshold r term = 1k 90 100 110 ma r term = 5k 17.5 20 22.5 ma v prog prog pin voltage r prog = 10k, current mode 0.93 1 1.07 v v chrg chrg pin output low voltage i chrg = 5ma 0.35 0.6 v v acpr acpr pin output low voltage i acpr = 5ma 0.35 0.6 v ? v rechrg recharge battery threshold voltage v float ?v rechrg , 0 c t a 85 c 60 100 140 mv the denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, unless otherwise noted. absolute axi u rati gs w ww u package/order i for atio uu w electrical characteristics consult ltc marketing for parts specified with wider operating temperature ranges. ltc4068edd-4.2ltc4068xedd-4.2 top view 9 dd package 8-lead (3mm 3mm) plastic dfn 5 6 7 8 4 3 2 1 iterm bat chrg gnd enacpr v cc prog downloaded from: http:///
3 ltc4068-4.2/ltc4068x-4.2 406842fa note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired.note 2: the ltc4068e-4.2/ltc4068xe-4.2 are guaranteed to meet performance specifications from 0 c to 70 c. specifications over the ?0 c to 85 c operating temperature range are assured by design, characterization and correlation with statistical process controls. symbol parameter conditions min typ max units t lim junction temperature in constant 120 c temperature mode r on power fet ?n?resistance 600 m ? (between v cc and bat) t ss soft-start time i bat = 0 to i bat =1000v/r prog 100 s t recharge recharge comparator filter time v bat high to low 0.75 2 4.5 ms t term termination comparator filter time i bat drops below charge termination threshold 400 1000 2500 s the denotes specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, unless otherwise noted. electrical characteristics note 3: failure to solder the exposed backside of the package to the pc board will result in a thermal resistance much higher than 40 c/w. note 4: supply current includes prog pin current and iterm pin current (approximately 100 a each) but does not include any current delivered to the battery through the bat pin (approximately 100ma).note 5: this parameter is not applicable to the ltc4068x. typical perfor a ce characteristics uw prog pin voltage vs supplyvoltage (constant current mode) v cc (v) 4 0.985 v prog (v) 0.990 0.995 1.000 1.005 1.015 4.5 5 5.5 6 405842 g01 6.5 7 1.010 v cc = 5v v bat = 4v t a = 25 c r prog = 10k temperature ( c) ?0 v prog (v) 0.9975 1.0000 1.0025 25 75 405842 g02 0.9950 0.9925 0.9900 ?5 0 50 1.0050 1.0075 1.0100 100 v cc = 5v v bat = 4v r prog = 10k v prog (v) 0 0 i bat (ma) 100 200 300 400 600 0.2 0.4 0.6 0.8 405842 g03 1 1.2 500 v cc = 5v t a = 25 c r prog = 2k r term = 2k prog pin voltagevs temperature charge currentvs prog pin voltage downloaded from: http:///
4 ltc4068-4.2/ltc4068x-4.2 406842fa typical perfor a ce characteristics uw regulated output (float) voltagevs charge current i bat (ma) 0 v float (v) 4.24 300 405842 g04 4.18 4.14 100 200 400 4.124.10 4.264.22 4.20 4.16 500 600 700 v cc = 5v t a = 25 c r prog = 1.25k regulated output (float) voltagevs temperature temperature ( c) ?0 4.185 v float (v) 4.190 4.195 4.200 4.205 4.215 ?5 02 55 0 405842 g05 75 100 4.210 v cc = 5v r prog = 10k regulated output (float) voltagevs supply voltage v cc (v) 4 4.185 v float (v) 4.190 4.195 4.200 4.205 4.215 4.5 5 5.5 6 405842 g06 6.5 7 4.210 t a = 25 c r prog = 10k chrg pin i-v curve(pull-down state) trickle charge currentvs temperature acpr pin i-v curve(pull-down state) v chrg (v) 0 i chrg (ma) 20 25 30 35 405842 g07 15 10 12 46 7 5 0 t a = 40 c t a = 25 c t a = 90 c v cc = 5v v bat = 4v v acpr (v) 0 i acpr (ma) 20 25 30 35 405842 g08 15 10 12 46 7 5 0 t a = 40 c t a = 25 c t a = 90 c v cc = 5v v bat = 4v temperature ( c) ?0 0 i trkl (ma) 10 20 30 40 60 ?5 02 55 0 405842 g09 75 100 50 v cc = 5v v bat = 2.5v r prog = 2k ltc4068 only r prog = 10k trickle charge currentvs supply voltage charge current vs battery voltage v cc (v) 4 0 i trkl (ma) 10 20 30 40 60 4.5 5 5.5 6 405842 g10 6.5 7 50 v bat = 2.5v t a = 25 c r prog = 2k r prog = 10k ltc4068 only trickle charge threshold voltagevs temperature temperature ( c) ?0 v trkl (v) 2.875 2.900 2.925 25 75 405842 g11 2.850 2.825 2.800 ?5 0 50 2.950 2.975 3.000 100 v cc = 5v r prog = 10k ltc4068 only v bat (v) 2.4 i bat (ma) 400 500 600 3.3 3.9 405842 g12 300 200 2.7 3 3.6 4.2 4.5 100 0 v cc = 5v ja = 40 c/w r prog = 2k ltc4068 only downloaded from: http:///
5 ltc4068-4.2/ltc4068x-4.2 406842fa typical perfor a ce characteristics uw charge current vs supply voltage charge currentvs ambient temperature recharge threshold voltagevs temperature power fet ?n?resistancevs temperature v cc (v) 4 0 i bat (ma) 100 200 300 400 600 4.5 5 5.5 6 405842 g13 6.5 7 500 v bat = 4v t a = 25 c ja = 40 c/w r prog = 2k r prog = 10k temperature ( c) ?0 i bat (ma) 400 500 600 25 75 405842 g14 300 200 ?5 0 50 100 125 100 0 v cc = 5v v bat = 4v ja = 40 c/w r prog = 2k onset of thermal regulation r prog = 10k temperature ( c) ?0 4.04 v rechrg (v) 4.06 4.08 4.10 4.12 4.16 ?5 02 55 0 405842 g15 75 100 4.14 v cc = 5v r prog = 10k temperature ( c) ?0 r ds(on) (m ? ) 700650 600 550 500 450 400 350 ?5 02550 405842 g17 75 125 100 v cc = 4.2v i bat = 100ma r prog = 2k uu u pi fu ctio s iterm (pin 1): charge termination program. the charge termination current threshold current is programmed byconnecting a 1% resistor, r term , to ground. the current threshold i term , is set by the following formula: i v r r v i term term term term == 100 100 , bat (pin 2): charge current output. provides charge current to the battery from the internal p-channel mosfet,and regulates the final float voltage to 4.2v. an internal precision resistor divider from this pin sets the float voltage. this divider is disconnected in shutdown mode tominimize current drain from the battery. chrg (pin 3): charge status open-drain output. when the battery is charging, the chrg pin is pulled low by aninternal n-channel mosfet. when the charge cycle is completed, chrg becomes high impedance. gnd (pins 4, 9): ground/exposed pad. the exposed backside package pad (pin 9) is electrical ground andmust be soldered to the pc board for maximum heat transfer. downloaded from: http:///
6 ltc4068-4.2/ltc4068x-4.2 406842fa when v cc is within 100mv of the bat pin voltage, the ltc4068 enters shutdown mode dropping the batterydrain current to less than 2 a. acpr (pin 7): power supply status open-drain output. when v cc is greater than the undervoltage lockout thresh- old and at least 100mv above v bat , the acpr pin is pulled to ground; otherwise, the pin is high impedance.en (pin 8): enable input . a logic high on the en pin will put the ltc4068 into shutdown mode where the battery draincurrent is reduced to less than 2 a and the supply current is reduced to less than 50 a. a logic low or floating the en pin (allowing an internal 2m ? pull-down resistor to pull this pin low) enables charging. uu u pi fu ctio s prog (pin 5): charge current program and charge cur- rent monitor. charge current is programmed by connect-ing a 1% resistor, r prog , to ground. when charging in constant-current mode, this pin servos to 1v. in all modes,the voltage on this pin can be used to measure the charge current using the following formula: i bat = (v prog /r prog ) ?1000 this pin is clamped to approximately 2.4v. driving this pinto voltages beyond the clamp voltage can draw large currents and should be avoided. v cc (pin 6): positive input supply voltage. provides power to the charger. v cc can range from 4.25v to 6.5v. this pin should be bypassed with at least a 1 f capacitor. block diagra w + + + 2 6 + 120 c t die t a ma ca c1 * 1 1000 va r1 bat r2 r3 1v0.1v r4 r5 prog 5 a r prog ref 1.211v v cc chrg 3 en 8 gnd 4, 9 406842 bd + c2* 2.9v to bat *trickle chargedisabled on the ltc4068x term acpr charge shdn en logic acpr 7 5 1 iterm r term 1 downloaded from: http:///
7 ltc4068-4.2/ltc4068x-4.2 406842fa operatio u the ltc4068 is a single cell lithium-ion battery chargerusing a constant-current/constant-voltage algorithm. it can deliver up to 950ma of charge current (using a good thermal pcb layout) with a final float voltage accuracy of 1%. the ltc4068 includes an internal p-channel power mosfet and thermal regulation circuitry. no blockingdiode or external current sense resistor is required; thus, the basic charger circuit requires only two external com- ponents. furthermore, the ltc4068 is capable of operat- ing from a usb power source. normal charge cycle a charge cycle begins when the voltage at the v cc pin rises above the uvlo threshold level and a 1% program resistoris connected from the prog pin to ground. if the bat pin is less than 2.9v, the charger enters trickle charge mode. in this mode, the ltc4068 supplies approximately 1/10th the programmed charge current to bring the battery volt- age up to a safe level for full current charging. (note: the ltc4068x does not include this trickle charge feature.) when the bat pin voltage rises above 2.9v, the charger enters constant-current mode where the programmed charge current is supplied to the battery. when the bat pin approaches the final float voltage (4.2v), the ltc4068 enters constant-voltage mode and the charge current begins to decrease. when the charge current drops to the programmed termination threshold (set by the external resistor r term ), the charge cycle ends. programming charge currentthe charge current is programmed using a single resistor from the prog pin to ground. the charge current out of the bat pin is 1000 times the current out of the prog pin. the program resistor and the charge current are calcu- lated using the following equations: r v i i v r prog chg chg prog == 1000 1000 , charge current out of the bat pin can be determined at anytime by monitoring the prog pin voltage and using the following equation: i v r bat prog prog = 1000 programming charge terminationthe charge cycle terminates when the charge current falls below the programmed termination threshold. this threshold is set by connecting an external resistor, r term , from the iterm pin to ground. the charge terminationcurrent threshold (i term) is set by the following equation: i v r ir r r v i term term chg prog term term term == = 100 10 100 ? the termination condition is detected by using an internalfiltered comparator to monitor the iterm pin. when the iterm pin voltage drops below 100mv * for longer than t term (typically 1ms), charging is terminated. the charge current is latched off and the ltc4068 enters standbymode where the input supply current drops to 200 a. (note: termination is disabled in trickle charging andthermal limiting modes.) i term can be set to be 1/10th of i chg by shorting the iterm pin to the prog pin, thus eliminating the need for externalresistor r term . when configured in this way, i term is always set to i chg /10, and the programmed charge current is set by the equation: i v r r v i chg prog prog chg == 500 500 , ** when charging, transient loads on the bat pin can causethe iterm pin to fall below 100mv for short periods of time before the dc charge current has dropped to 10% of the programmed value. the 1ms filter time (t term ) on the termination comparator ensures that transient loads ofthis nature do not result in premature charge cycle termi- nation. once the average charge current drops below the programmed termination threshold, the ltc4068 termi-nates the charge cycle and ceases to provide any current out of the bat pin. in this state, any load on the bat pin must be supplied by the battery. the ltc4068 constantly monitors the bat pin voltage in standby mode. if this voltage drops below the 4.1v recharge any external sources that hold the iterm pin above 100mv will prevent the ltc4068 fromterminating a charge cycle. these equations apply only when the iterm pin is shorted to the prog pin. * ** downloaded from: http:///
8 ltc4068-4.2/ltc4068x-4.2 406842fa operatio u threshold (v rechrg ), another charge cycle begins and charge current is once again supplied to the battery. tomanually restart a charge cycle when in standby mode, the input voltage must be removed and reapplied or the charger must be shut down and restarted using the en pin. figure 1 shows the state diagram of a typical charge cycle. thermal limitingan internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 120 c. this feature protects the ltc4068 from excessive temperature and allows theuser to push the limits of the power handling capability of a given circuit board without risk of damaging the ltc4068. the charge current can be set according to typical (not worst case) ambient temperature with the assurance that the charger will automatically reduce the current in worst-case conditions. dfn power considerations are discussed fur- ther in the applications information section. undervoltage lockout (uvlo) an internal undervoltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until v cc rises above the undervoltage lockout threshold. the uvlocircuit has a built-in hysteresis of 200mv. furthermore, to protect against reverse current in the power mosfet, the uvlo circuit keeps the charger in shutdown mode if v cc falls to within 30mv of the bat voltage. if the uvlo com-parator is tripped, the charger will not come out of shut- down mode until v cc rises 100mv above the bat voltage. manual shutdownat any point in the charge cycle, the ltc4068 can be put into shutdown mode by driving the en pin high. this reduces the battery drain current to less than 2 a and the supply current to less than 50 a. when in shutdown mode, the chrg pin is in the high impedance state. a newcharge cycle can be initiated by driving the en pin low. an internal resistor pull-down on this pin forces the ltc4068 to be enabled if the pin is allowed to float. automatic recharge once the charge cycle is terminated, the ltc4068 continu- ously monitors the voltage on the bat pin using a com- parator with a 2ms filter time (t recharge ). a charge cycle restarts when the battery voltage falls below 4.10v (whichcorresponds to approximately 80% to 90% battery capac- ity). this ensures that the battery is kept at, or near, a fully figure 1. state diagram of a typical charge cycle trickle charge mode 1/10th full current bat > 2.9v bat < 2.9v bat > 2.9v ltc4068only chrg: strong pull-down charge mode full current chrg: strong pull-down shutdown mode chrg: hi-z en driven low or uvlo condition stops en driven high or uvlo condition i cc drops to <25 a power on iterm < 100mv standby mode no charge current chrg: hi-z 2.9v < bat < 4.1v 406842 f01 charge status indicator (chrg)the charge status output has two states: pull-down and high impedance. the pull-down state indicates that the ltc4068 is in a charge cycle. once the charge cycle has terminated or the ltc4068 is disabled, the pin state becomes high impedance. power supply status indicator (acpr) the power supply status output has two states: pull-down and high impedance. the pull-down state indicates that v cc is above the uvlo threshold (3.8v) and is also 100mv above the battery voltage. if these conditions are not met,the acpr pin is high impedance indicating that the ltc4068 is unable to charge the battery. downloaded from: http:///
9 ltc4068-4.2/ltc4068x-4.2 406842fa applicatio s i for atio wu uu stability considerationsthe constant-voltage mode feedback loop is stable with- out an output capacitor, provided a battery is connected to the charger output. with no battery present, an output capacitor on the bat pin is recommended to reduce ripple voltage. when using high value, low esr ceramic capaci- tors, it is recommended to add a 1 ? resistor in series with the capacitor. no series resistor is needed if tantalumcapacitors are used. in constant-current mode, the prog pin is in the feedback loop, not the battery. the constant-current mode stability is affected by the impedance at the prog pin. with no additional capacitance on the prog pin, the charger is stable with program resistor values as high as 20k; how- ever, additional capacitance on this node reduces the maximum allowed program resistor. the pole frequency at the prog pin should be kept above 100khz. therefore, if the prog pin is loaded with a capacitance, c prog , the following equation can be used to calculate the maximumresistance value for r prog : r c prog prog 1 210 5 average, rather than instantaneous charge current may beof interest to the user. for example, if a switching power supply operating in low current mode is connected in parallel with the battery, the average current being pulled out of the bat pin is typically of more interest than the instantaneous current pulses. in such a case, a simple rc ltc4068-4.2 gnd prog r prog 10k c filter 406842 f02 chargecurrent monitor circuitry figure 2. isolating capacitive load on prog pin and filtering power dissipation it is not necessary to design for worst-case power dissi-pation scenarios because the ltc4068 automatically reduces the charge current during high power conditions. the conditions that cause the ltc4068 to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the ic. nearly all of this power dissipation is generated by the internal mosfet?his is calculated to be approximately: p d = (v cc ?v bat ) ?i bat where p d is the power dissipated, v cc is the input supply voltage, v bat is the battery voltage and i bat is the charge current. the approximate ambient temperature at whichthe thermal feedback begins to protect the ic is: t a = 120 c ?p d ja t a = 120 c ?(v cc ?v bat ) ?i bat ? ja example: an ltc4068 operating from a 5v supply isprogrammed to supply 800ma full-scale current to a discharged li-ion battery with a voltage of 3.3v. assuming ja is 50 c/w (see thermal considerations), the ambient temperature at which the ltc4068 will begin to reduce thecharge current is approximately: t a = 120 c ?(5v ?3.3v) ?(800ma) ?50 c/w t a = 120 c ?1.36w ?50 c/w = 120 c ?68 c t a = 52 c charged condition and eliminates the need for periodiccharge cycle initiations. the chrg output enters a pull- down state during recharge cycles. if the battery is removed from the charger, a sawtooth waveform of approximately 100mv appears at the charger output. this is caused by the repeated cycling between termination and recharge events. this cycling results in pulsing at the chrg output; an led connected to this pin will exhibit a blinking pattern, indicating to the user that a battery is not present. the frequency of the sawtooth is dependent on the amount of output capacitance. filter can be used on the prog pin to measure the averagebattery current, as shown in figure 2. a 10k resistor has been added between the prog pin and the filter capacitor to ensure stability. downloaded from: http:///
10 ltc4068-4.2/ltc4068x-4.2 406842fa the ltc4068 can be used above 52 c ambient but the charge current will be reduced from the programmed800ma. the approximate current at a given ambient temperature can be approximated by: i ct vv bat a cc bat ja = () 120 using the previous example with an ambient temperatureof 60 c, the charge current will be reduced to approximately: i cc vv c w c ca im a batbat = () = = 120 60 533 5 0 60 85 706 ? / / moreover, when thermal feedback reduces the charge cur-rent the voltage at the prog pin is also reduced proportion- ally as discussed in the operation section. it is important to remember that ltc4068 applications do not need to be designed for worst-case thermal conditions since the ic will automatically reduce power dissipation when the junction temperature reaches approximately 120 c. thermal considerationsi n order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on thebackside of the ltc4068 package is soldered to the pc board ground. correctly soldered to a 2500mm 2 double- sided 1oz copper board, the ltc4068 has a thermalresistance of approximately 40 c/w. failure to make thermal contact between the exposed pad on the back-side of the package and the copper board will result in thermal resistances far greater than 40 c/w. as an example, a correctly soldered ltc4068 can deliver over800ma to a battery from a 5v supply at room tempera- ture. without a good backside thermal connection, this number will drop considerably. v cc bypass capacitor many types of capacitors can be used for input bypassing;however, caution must be exercised when using multilayer applicatio s i for atio wu uu ceramic capacitors. because of the self-resonant and highq characteristics of some types of ceramic capacitors, high voltage transients can be generated under some start-up conditions such as connecting the charger input to a live power source. adding a 1.5 ? resistor in series with an x5r ceramic capacitor will minimize start-upvoltage transients. for more information, see application note 88. charge current soft-start the ltc4068 includes a soft-start circuit to minimize the inrush current at the start of a charge cycle. when a charge cycle is initiated, the charge current ramps from zero to full-scale current over a period of approximately 100 s. this has the effect of minimizing the transient current loadon the power supply during start-up. usb and wall adapter power the ltc4068 allows charging from both a wall adapter and a usb port. figure 3 shows how to combine wall adapter and usb power inputs. a p-channel mosfet, mp1, is used to prevent back conducting into the usb port when a wall adapter is present and a schottky diode, d1, is used to prevent usb power loss through the 1k pull- down resistor. typically a wall adapter can supply more current thanthe 500ma-limited usb port. therefore, an n-channel mosfet, mn1, and an extra 3.3k program resistor are used to increase the charge current to 800ma when the wall adapter is present. the charge termination threshold remains fixed at 80ma. + ltc4068-4.2 bat iterm prog v cc gnd d1 5v wall adapter 800ma i chg usb power 500ma i chg i chg systemload li-ionbattery mp1 1k 3.3k 2k mn1 6 4, 9 21 5 406842 f03 1.25k figure 3. combining wall adapter and usb power downloaded from: http:///
11 ltc4068-4.2/ltc4068x-4.2 406842fa dd package 8-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1698) u package descriptio 3.00 0.10 (4 sides) note:1. drawing to be made a jedec package outline m0-229 variation of (weed-1) 2. all dimensions are in millimeters 3. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 4. exposed pad shall be solder plated 0.38 0.10 bottom view?xposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.115 typ 2.38 0.10 (2 sides) 1 4 8 5 pin 1 top mark 0.200 ref 0.00 ?0.05 (dd8) dfn 0203 0.28 0.05 2.38 0.05 (2 sides) recommended solder pad pitch and dimensions 1.65 0.05 (2 sides) 2.15 0.05 0.50bsc 0.675 0.05 3.5 0.05 packageoutline 0.28 0.05 0.50 bsc information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no represen-tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. applicatio s i for atio wu uu v in v cc ltc4068 drain-bulk diode of fet 405842 f04 figure 4. low loss input reverse polarity protection reverse polarity input voltage protectionin some applications, protection from reverse polarity voltage on v cc is desired. if the supply voltage is high enough, a series blocking diode can be used. in othercases, where the voltage drop must be kept low, a p-channel mosfet can be used (as shown in figure 4). downloaded from: http:///
12 ltc4068-4.2/ltc4068x-4.2 406842fa part number description comments ltc1732 lithium-ion linear battery charger controller simple charger uses external fet, features preset voltages, c/10 charger detection and programmable timer, input power good indication ltc1733 monolithic lithium-ion linear battery charger standalone charger with programmable timer, up to 1.5a charge current ltc1734 lithium-ion linear battery charger in thinsot tm simple thinsot charger, no blocking diode, no sense resistor needed ltc1734l lithium-ion linear battery charger in thinsot low current version of ltc1734; 50ma i chrg 180ma ltc1998 lithium-ion low battery detector 1% accurate 2.5 a quiescent current, sot-23 ltc4007 4a multicell li-ion battery charger standalone charger, 6v v in 28v, up to 96% efficiency, 0.8% charging voltage accuracy ltc4050 lithium-ion linear battery charger controller c/10 charger detection and programmable timer, thermistor interface ltc4052 monolithic lithium-ion battery pulse charger no blocking diode or external power fet required, 1.5a charge current ltc4053 usb compatible monolithic li-ion battery charger standalone charger with programmable timer, up to 1.25a charge current ltc4054 standalone linear li-ion battery charger thermal regulation prevents overheating, c/10 termination, in thinsot c/10 indicator, up to 800ma charge current ltc4057 li-ion linear battery charger up to 800ma charge current, thermal regulation, thinsot package ltc4058 standalone li-ion linear charger in dfn up to 950ma charge current, kelvin sense for high accuracy, ltc4058x c/10 charge termination ltc4410 usb power manager for simultaneous operation of usb peripheral and battery charging from usb port, keeps current drawn from usb port constant, keeps battery fresh, usewith the ltc4053, ltc1733, or ltc4054 ltc4411 low loss powerpath tm controller in thinsot automatic switching between dc sources, load sharing, ltc4412 replaces oring diodes thinsot and powerpath are trademarks of linear technology corporation. related parts typical applicatio s u full featured single cell li-ion charger bat v cc chrg 2k 5 8 3 7 4, 9 1 2 6 405642 ta03 1 f 1 f v in 5v 1-cellli-ion battery ltc4068-4.2 500ma acpr en prog gnd 1k 1k 1k + iterm li-ion battery charger with reverse polarity input protection bat v cc iterm 1k 5 8 4, 9 21 6 406842 ta04 1 f 5v wall adapter ltc4068-4.2 500ma en prog gnd 1-cellli-ion battery + lt/tp 0904 1k rev a ?printed in usa ? linear technology corporation 2004 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com usb/wall adapter power li-ion charger + ltc4068-4.2 prog v cc 5v wall adapter usb power 1-cellli-ion battery 1k 5k 1.25k 6 21 5 4, 9 406842 ta05 gnd 1 f 100ma/500ma c bat iterm i bat downloaded from: http:///

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