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ltc4078/ltc4078x 1 4078xfb features applications description dual input li-ion battery charger with overvoltage protection the ltc ? 4078/ltc4078x are standalone linear chargers that are capable of charging a single-cell li-ion/polymer battery from both wall adapter and usb inputs. the chargers can detect power at the inputs and automatically select the appropriate power source for charging. no external sense resistor or blocking diode is required for charging due to the internal mosfet architecture. the ltc4078/ltc4078x feature a maximum 22v rating for both wall adapter and usb inputs, although charging stops if the selected power source exceeds the overvoltage limit. internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature con- ditions. the ? oat voltage is ? xed at 4.2v and the charge current is programmed with an external resistor. the ltc4078/ltc4078x terminate the charge cycle when the charge current drops below the programmed termination threshold after the ? nal ? oat voltage is reached. other features include battery present detection, automatic recharge, undervoltage lockout, charge status outputs, and power present status outputs to indicate the presence of wall adapter or usb power. the device is offered in a low pro? le (0.75mm) 3mm 3mm 10-lead dfn package. n 22v maximum voltage for wall adapter and usb inputs n charge single-cell li-ion batteries from wall adapter and usb inputs n automatic input power detection and selection n charge current programmable up to 950ma from wall adapter input n overvoltage lockout for wall adapter and usb inputs n battery detection input disables charger when no battery is present n no external mosfet, sense resistor or blocking diode needed n thermal regulation maximizes charge rate without risk of overheating* n preset charge voltage with 0.6% accuracy n programmable charge current termination n 40a usb suspend current in shutdown n charge status output n automatic recharge n available without trickle charge (ltc4078x) n available in a thermally enhanced, low pro? le (0.75mm) 10-lead (3mm 3mm) dfn package n cellular telephones n handheld computers n portable mp3 players n digital cameras high voltage dual input battery charger for li-ion battery pack charger current vs supply voltage l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. *protected by u.s. patents including 6522118, 6700364. typical application ltc4078 dcinusbin iusb idc bat iterm batdet 1.24k1% 3.9k 2k1% 2k1% wall adapter usb port 1 f 1 f + 4.2vli-ion battery pack 800ma (wall) 500ma (usb) 4078x ta01 gnd supply voltage (v) 2 i bat (ma) 900800 700 600 500 400 300 200 100 0 19 345678 20 4078x ta01b r idc = 1.24k r iusb = 2k v bat = 3.5v v batdet = 0v charge from dcin chargefrom usbin downloaded from: http:///
ltc4078/ltc4078x 2 4078xfb pin configuration absolute maximum ratings input supply voltage (dcin, usbin) ............C0.3 to 22v enable, chrg , pwr , batdet, bat ...............C0.3 to 6v idc, iusb, iterm pin current .................................1ma dcin, usbin, bat pin current ....................................1a bat short-circuit duration ............................ continuous maximum junction temperature........................... 125c operating temperature range (note 2).... C40c to 85c storage temperature range ................... C65c to 125c (note 1) top view dd package 10-lead ( 3mm 3mm ) plastic dfn 10 96 7 8 11 45 3 2 1 dcinbat idc batdet enable usbin iusb iterm pwr chrg t jmax = 125c, ja = 40c/w (note 3) exposed pad (pin 11) is gnd, must be soldered to pcb the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v dcin = 5v, v usbin = 5v unless otherwise noted. symbol parameter conditions min typ max units v dcin operating supply voltage l 4.3 5.5 v v usbin operating supply voltage l 4.3 5.5 v i dcin dcin supply current charge mode (note 4), r idc = 10k standby mode; charge terminated shutdown mode (enable = 5v) overvoltage mode (v dcin = 10v) ll 350 7040 70 800120 80 140 aa a a i usbin usbin supply current charge mode (note 5), r iusb = 10k, v dcin = 2v standby mode; charge terminated, v dcin = 2v shutdown (v dcin = 2v, enable = 0v) overvoltage mode (v usbin = 10v) v dcin > v usbin ll 350 7040 70 23 800120 80 140 40 aa a a a v float regulated output (float) voltage i bat = 1ma i bat = 1ma, 0c < t a < 85c 4.1854.165 4.24.2 4.2154.235 vv i bat bat pin current r idc = 1.25k, constant-current mode r iusb = 2.1k, constant-current mode r idc = 10k or r iusb = 10k standby mode, charge terminated shutdown mode (charger disabled) sleep mode (v dcin = 0v, v usbin = 0v) ll l 770455 93 800476 100 C7.5C7.5 C7.5 830495 107 C12 C12 C12 mama ma aa a lead free finish tape and reel part marking package description temperature range ltc4078xedd#pbf ltc4078xedd#trpbf lcyp 10-lead (3mm 3mm) plastic dfn C40c to 85c ltc4078edd#pbf ltc4078edd#trpbf ldjy 10-lead (3mm 3mm) plastic dfn C40c to 85c consult ltc marketing for parts speci? ed with wider operating temperature ranges. consult ltc marketing for information on non-standard lead based ? nish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/ order informationelectrical characteristics downloaded from: http:///
ltc4078/ltc4078x 3 4078xfb note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the ltc4078/ltc4078x are guaranteed to meet the performance speci? cations from 0c to 85c. speci? cations over the C 40c to 85c operating temperature range are assured by design, characterization and correlation with statistical process controls. note 3: failure to correctly solder the exposed backside of the package to the pc board will result in a thermal resistance much higher than 40c/w. see thermal considerations. note 4: supply current includes idc and iterm pin current (approximately 100a each) but does not include any current delivered to the battery through the bat pin. note 5: supply current includes iusb and iterm pin current (approximately 100a each) but does not include any current delivered to the battery through the bat pin. note 6: this parameter is not applicable to the ltc4078x. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v dcin = 5v, v usbin = 5v unless otherwise noted. symbol parameter conditions min typ max units v idc idc pin regulated voltage constant-current mode 1 v v iusb iusb pin regulated voltage constant-current mode 1 v i terminate charge current termination threshold r iterm = 1k r iterm = 2k r iterm = 10k r iterm = 20k ll l l 9042 8 3.5 100 5010 5 110 5812 6.5 mama ma ma i trikl trickle charge current (note 6) v bat < v trikl ; r idc = 1.25k v bat < v trikl ; r iusb = 2.1k 6030 80 47.5 100 65 mama v trikl trickle charge threshold (note 6) v bat rising hysteresis 2.8 2.9 100 3v mv v uvdc dcin undervoltage lockout voltage from low to high hysteresis 4 4.15 190 4.3 v mv v uvusb usbin undervoltage lockout voltage from low to high hysteresis 3.8 3.95 170 4.1 v mv v ovdc dcin overvoltage lockout voltage from low to high hysteresis 5.8 6 185 6.2 v mv v ovusb usbin overvoltage lockout voltage from low to high hysteresis 5.8 6 185 6.2 v mv v asd-dc v dcin C v bat lockout threshold v dcin from low to high, v bat = 4.2v v dcin from high to low, v bat = 4.2v 7010 120 40 170 70 mvmv v asd-usb v usbin C v bat lockout threshold v usbin from low to high v usbin from high to low 7010 120 40 170 70 mvmv v enable enable input threshold voltage 0.6 0.9 1.2 v r enable enable pulldown resistance l 1 2 3.5 m v bdet batdet input threshold voltage from low to high 1.25 1.75 2 v i batdet batdet pull-up current v batdet = 0v 2 4 6 a v boc batdet open circuit voltage 4 4.2 4.4 v v ol output low voltage ( chrg , pwr ) i sink = 5ma 0.12 0.35 v v rechrg recharge battery threshold voltage v float C v rechrg , 0c < t a < 85c 90 125 160 mv t rechrg recharge comparator filter time v bat from high to low 2.25 4.1 6.75 ms t terminate termination comparator filter time i bat drops below termination threshold 1 1.6 2.4 ms r on-dc power fet on resistance (between dcin and bat) 600 m r on-usb power fet on resistance (between usbin and bat) 700 m t lim junction temperature in constant- temperature mode 120 c downloaded from: http:///
ltc4078/ltc4078x 4 4078xfb typical performance characteristics iusb pin voltage vs temperature (constant-current mode) charge current vs idc pin voltage charge current vs iusb pin voltage pwr pin i-v curve chrg pin i-v curve regulated output (float) voltage vs charge current regulated output (float) voltage vs temperature idc pin voltage vs temperature (constant-current mode) t a = 25c, unless otherwise speci? ed. i bat (ma) 0 v float (v) 4.20 4.22 900 800 700 600 500 400 300 200 100 4078x g01 4.184.16 4.10 4.12 4.14 4.264.24 v dcin = v usbin = 5v r idc = 1.24k r idc = r iusb = 2k temperature ( c) C10 v float (v) 4.210 90 70 50 30 10 4078x g02 4.180 4.2204.215 4.200 4.2054.190 4.1954.185 v dcin = v usbin = 5v temperature ( c) C10 v idc (v) 1.004 90 70 50 30 10 4078x g03 0.992 1.0081.006 1.000 1.0020.996 0.9980.994 v dcin = 5v temperature ( c) C10 v iusb (v) 1.004 90 70 50 30 10 4078x g04 0.992 1.0081.006 1.000 1.0020.996 0.9980.994 v usbin = 5v v idc (v) 0 i bat (ma) 1.2 0.8 1.0 0.6 0.4 0.2 4078x g05 0 900800 700 600 500 400 300 200 100 v dcin = 5v r idc = 1.24k r idc = 2k r idc = 10k v iusb (v) 0 i bat (ma) 1.2 0.8 1.0 0.6 0.4 0.2 4078x g06 0 900800 700 600 500 400 300 200 100 v usbin = 5v r iusb = 1.24k r iusb = 2k r iusb = 10k v pwr (v) 0 i pwr (ma) 6 5 14 3 2 4078x g07 0 6050 40 30 20 10 v dcin = v usbin = 5v v chrg (v) 0 i chrg (ma) 6 5 14 3 2 4078x g08 0 6050 40 30 20 10 v dcin = v usbin = 5v downloaded from: http:///
ltc4078/ltc4078x 5 4078xfb typical performance characteristics charge current vs ambient temperature charge current vs supply voltage charge current vs battery voltage dcin power fet on-resistance vs temperature usbin power fet on-resistance vs temperature enable pin threshold voltage (on-to-off) vs temperature usbin shutdown current vs temperature dcin shutdown current vs temperature enable pin pulldown resistance vs temperature t a = 25c, unless otherwise speci? ed. temperature ( c) C10 0 i bat (ma) 100 300 400 500 1000 700 30 70 90 200 800 900600 10 50 110 130 4078x g10 r idc = r iusb = 2k r idc = 1.24k v dcin = v usbin = 5v v bat = 4v ja = 30 c/w v dcin (v) 4.0 i bat (ma) 500 600 700 7.5 8.0 4078x g11 400 300 0 100 4.5 5.5 6.5 7.0 5.0 6.0 200 900 800 r idc = 1.24k v bat = 4v ja = 30 c/w v bat (v) 2.4 i bat (ma) 600 4.5 4.2 4078x g12 400 0 3.9 2.7 3.3 3.0 3.6 200 1000 800 v dcin = v usbin = 5v r idc = 1.24k ja = 30 c/w temperature ( c) C10 r ds(on) (m ) 90 70 50 30 10 4078x g13 500 800750 700 650 600 550 v bat = 4v i bat = 200ma temperature ( c) C10 r ds(on) (m ) 90 70 50 30 10 4078x g14 800750 700 900850 650 600 v bat = 4v i bat = 200ma temperature ( c) v enable (v) 940 960 980 4078x g15 920900 860 880 1000 C10 90 70 50 30 10 v dcin = v usbin = 5v temperature ( c) C50 i usbin ( a) 40 50 100 4078x g16 3020 45 5535 25 C25 25 75 05 0 60 v enable = 0v v usbin = 4.3v v usbin = 5v temperature ( c) C50 i dcin ( a) 40 50 100 4078x g17 3020 45 5535 25 C25 25 75 05 0 60 v enable = 5v v dcin = 4.3v v dcin = 5v temperature ( c) C50 r enable (m ) 2.3 100 4078x g18 2.1 2.21.9 1.6 C25 25 75 05 0 1.7 2.01.8 2.4 downloaded from: http:///
ltc4078/ltc4078x 6 4078xfb undervoltage lockout threshold vs temperature overvoltage lockout threshold vs temperature battery drain current vs temperature recharge threshold voltage vs temperature batdet voltage/current vs temperature batdet pin threshold voltage (on-to-off) vs temperature typical performance characteristics t a = 25c, unless otherwise speci? ed. C10 90 70 50 30 10 temperature ( c) v uv (v) 4.10 4.15 4078x g19 4.05 4.00 3.85 3.90 3.95 4.254.20 dcin uvlo usbin uvlo C10 90 70 50 30 10 temperature ( c) v ov (v) 4078x g20 5.80 5.90 6.10 5.95 6.00 6.055.85 dcin ovlo usbin ovlo temperature ( c) v rechrg (v) 4.07 4078x g21 4.03 4.114.05 4.09 v dcin = v usbin = 5v C10 90 70 50 30 10 temperature ( c) C50 i bat ( a) 8.0 100 4078x g22 7.06.0 C25 25 75 05 0 9.07.5 8.56.5 v dcin = v usbin = not connected v bat = 4.2v C10 90 70 50 30 10 temperature ( c) v bdet (v) 4078x g23 1.4 1.6 2.0 1.7 1.8 1.91.5 v dcin = v usbin = 5v C10 90 70 50 30 10 temperature ( c) v boc (v) i batdet ( a) 4078x g24 4.0 4.2 4.4 4.34.1 3.00 4.50 6.005.25 3.75 v dcin = v usbin = 5v v boc i batdet downloaded from: http:///
ltc4078/ltc4078x 7 4078xfb pin functions usbin (pin 1): usb input supply pin. this input provides power to the battery charger assuming a voltage greater than v uvusb and less than v ovusb is present (typically 3.95v to 6v respectively). however, the dcin input will take priority if a voltage greater than v uvdc is present at dcin (typically 4.15v). the usbin input allows charge currents up to 850ma. this pin should be bypassed with a 1f capacitor. iusb (pin 2): charge current program for usb power. the charge current is set by connecting a resistor, r iusb , to ground. when charging in constant-current mode, this pin servos to 1v. the voltage on this pin can be used to measure the battery current delivered from the usb input using the following formula: i bat = v iusb r ius b 1000 iterm (pin 3): termination current threshold program. the termination current threshold, i terminate , is set by connecting a resistor, r iterm , to ground. i terminate is set by the following formula: i terminate = 100v r iter m when the battery current, i bat , falls below the termination threshold, charging stops and the chrg output becomes high impedance. this pin is internally clamped to approxi- mately 1.5v. driving this pin to voltages beyond the clamp voltage should be avoided. pwr (pin 4): open-drain power supply status output. when the dcin or usbin pin voltage is valid to begin charg- ing (i.e. when the supply is greater than the undervoltage lockout threshold, less than the overvoltage lockout thresh- old and at least 120mv above the battery terminal), the pwr pin is pulled low by an internal n-channel mosfet. otherwise pwr is high impedance. this output is capable of driving an led.chrg (pin 5): open-drain charge status output. when the ltc4078/ltc4078x are charging, the chrg pin is pulled low by an internal n-channel mosfet. when the charge cycle is completed, chrg becomes high impedance. this output is capable of driving an led.enable (pin 6): enable input. when the ltc4078/ltc4078x are charging from the dcin source, a logic low on this pin enables the charger. when the ltc4078/ltc4078x are charging from the usbin source, a logic high on this pin enables the charger. if this input is left ? oating, an internal 2m pulldown resistor defaults the ltc4078/ltc4078x to charge when a wall adapter is applied and to shut down if only the usb source is applied. batdet (pin 7): battery detection input. when the volt- age on this pin falls below v bdet (typically 1.75v), the charger is on and ready for charging a battery. if this input is left ? oating, an internal pull-up resistor will dis- able charging. idc (pin 8): charge current program for wall adapter power. the charge current is set by connecting a resis- tor, r idc , to ground. when charging in constant-current mode, this pin servos to 1v. the voltage on this pin can be used to measure the battery current delivered from the dc input using the following formula: i bat = v idc r id c 1000 bat (pin 9): battery charger output. this pin provides charge current to the battery and regulates the ? nal ? oat voltage to 4.2v. dcin (pin 10): wall adapter input supply pin. this input provides power to the battery charger assuming a voltage greater than v uvdc and less than v ovdc is present (typi- cally 4.15v to 6v respectively). a valid voltage on the dcin input will always take priority over the usbin input. the dcin input allows charge currents up to 950ma. this pin should be bypassed with a 1f capacitor. exposed pad (pin 11): gnd. the exposed backside of the package is ground and must be soldered to pc board ground for electrical connection and maximum heat transfer. downloaded from: http:///
ltc4078/ltc4078x 8 4078xfb block diagram C + C + C + + C C + C + C + C + 4.15v bat 2.9v bat 3.95v 1.75vbat C + 6v 0.1v i bat /1000 i bat /1000 i bat /1000 4 5 3 8 2 11 dc_enable usb_enable disable trickle charger control cc/cv regulator cc/cv regulator 9 10 1 r iterm r iusb r idc iterm iusb idc gnd 120 c t die usbin uvlousbin ovlo dcin ovlorecharge dcin uvlo dcin bat usbin pwr chrg termination thermal regulation 7 batdet 4078x bd C + 0.9v C + C + bat 4.075v 6v 6 enable 2m v boc tricklecharge* *trickle charge disabled on the ltc4078x downloaded from: http:///
ltc4078/ltc4078x 9 4078xfb operation the ltc4078/ltc4078x are designed to ef? ciently man- age charging of a single-cell lithium-ion battery from two separate power sources: a wall adapter and usb power bus. using the constant-current/constant-voltage algorithm, the charger can deliver up to 950ma of charge current from the wall adapter supply or up to 850ma of charge current from the usb supply with a ? nal ? oat voltage accuracy of 0.6%. the ltc4078/ltc4078x have two internal p-chan- nel power mosfets and thermal regulation circuitry. no blocking diodes or external sense resistors are required. power source selection the ltc4078/ltc4078x can charge a battery from ei- ther the wall adapter input or the usb port input. the ltc4078/ltc4078x automatically sense the presence of voltage at each input. if both power sources are present, the ltc4078/ltc4078x default to the wall adapter source provided a valid voltage is present at the dcin input. valid voltage is de? ned as: ? supply voltage is greater than the uvlo threshold and less than the ovlo threshold. ? supply voltage is greater than the battery voltage by 40mv. the open-drain power status output ( pwr ) indicates which power source has been selected. table 1 describes the behavior of this status output. programming and monitoring charge current the charge current delivered to the battery from the wall adapter or usb supply is programmed using a single re- sistor from the idc or iusb pin to ground. both program resistors and charge currents (i chrg ) are calculated using the following equations: r idc = 1000v i chrg d c ,i chrg dc = 1000v r id c r iusb = 1000v i chrg us b ,i chrg usb = 1000v r ius b *any external sources that hold the iterm pin above 100mv will prevent the ltc4078x from terminating a charge cycle. charge current out of the bat pin can be determined at any time by monitoring the idc or iusb pin voltage and applying the following equations: i bat = v idc r id c 1000, (charging from wall adapter) i bat = v iusb r ius b 1000, (charging from usbsupply) battery detection by default, the batdet pin is pulled high with an internal resistor, disabling the charger. to enable the charger, the batdet pin must be pulled below the v bdet threshold (typically 1.75v). an external resistor to ground less than 100k (typically 3.9k) located in the battery pack is used to detect battery presence. programming charge termination the charge cycle terminates when the charge current falls below the programmed termination threshold level during constant-voltage mode. this threshold is set by connecting an external resistor, r iterm , from the iterm pin to ground. the charge termination current threshold (i terminate ) is set by the following equation: r iterm = 100v i terminat e ,i terminate = 100v r iter m the termination condition is detected using an internal ? ltered comparator to monitor the iterm pin. when the iterm pin voltage drops below 100mv* for longer than t terminate (typically 1.6ms), charging is terminated. the charge current is latched off and the ltc4078/ltc4078x enter standby mode. when charging, transient loads on the bat pin can cause the iterm pin to fall below 100mv for short periods of time before the dc charge current has dropped below the downloaded from: http:///
ltc4078/ltc4078x 10 4078xfb operation programmed termination current. the 1.6ms ? lter time (t terminate ) on the termination comparator ensures that transient loads of this nature do not result in premature charge cycle termination. once the average charge current drops below the programmed termination threshold, the ltc4078/ltc4078x terminate the charge cycle and stops providing current out of the bat pin. in this state, any load on the bat pin must be supplied by the battery. low-battery charge conditioning (trickle charge) this feature ensures that near-dead batteries are gradually charged before applying full charge current. if the bat pin voltage is below 2.9v, the ltc4078 supply 1/10th of the full charge current to the battery until the bat pin rises above 2.9v. for example, if the charger is programmed to charge at 800ma from the wall adapter input and 500ma from the usb input, the charge current during trickle charge mode would be 80ma and 50ma, respectively. the ltc4078x does not include the trickle charge feature; it outputs full charge current to the battery when the bat pin voltage is below 2.9v. the ltc4078x are useful in applications where the trickle charge current may be insuf? cient to supply a load during low-battery voltage conditions. automatic recharge in standby mode, the charger sits idle and monitors the battery voltage using a comparator with a 4.1ms ? lter time (t rechrg ). a charge cycle automatically restarts when the battery voltage falls below 4.075v (which corresponds to approximately 80% to 90% battery capacity). this ensures that the battery is kept at, or near, a fully charged condi- tion and eliminates the need for periodic charge cycle initiations. manual shutdown the enable pin has a 2m pulldown resistor to gnd. the de? nition of this pin depends on which source is supplying power. when the wall adapter input is supplying power, logic low enables the charger and logic high disables it (the pulldown defaults the charger to the charging state). the opposite is true when the usb input is supplying power; logic low disables the charger and logic high enables it (the default is the shutdown state). the dcin input draws 40a when the charger is in shutdown mode. the usbin input draws 40a during shutdown if no voltage is applied to dcin, but draws only 23a when v dcin provides valid voltage (see table 1). status indicatorsthe charge status open-drain output ( chrg ) has two states: pulldown and high impedance. the pulldown state indicates that the ltc4078/ltc4078x are in a charge cycle. once the charge cycle has terminated or the ltc4078/ltc4078x are disabled, the pin state becomes high impedance. the power supply status open-drain output ( pwr ) has two states: pulldown and high impedance. the pulldown state indicates that power is present at either dcin or usbin. table 1. power source selection (v batdet < 1.75v) v usbin < 3.95v or v usbin < bat + 50mv 6v > v usbin > 3.95v and v usbin > bat + 50mv 22v > v usbin > 6v enable high low or no connect high low or no connect high low or no connect v dcin < 4.15v or v dcin < bat + 50mv no charging. pwr : hi-z chrg : hi-z no charging. pwr : hi-z chrg : hi-z charging from usbin source. pwr : low chrg : low no charging. pwr : low chrg : hi-z no charging. pwr : hi-z chrg : hi-z no charging. pwr : hi-z chrg : hi-z 6v > v dcin > 4.15v and v dcin > bat + 50mv no charging. pwr : low chrg : hi-z charging from dcin source. pwr : low chrg : low no charging. pwr : low chrg : hi-z charging from dcin source. pwr : low chrg : low no charging. pwr : low chrg : hi-z charging from dcin source. pwr : low chrg : low 22v > v dcin > 6v no charging. pwr : hi-z chrg : hi-z no charging. pwr : hi-z chrg : hi-z no charging. pwr : low chrg : hi-z no charging. pwr : low chrg : hi-z no charging. pwr : hi-z chrg : hi-z no charging. pwr : hi-z chrg : hi-z downloaded from: http:///
ltc4078/ltc4078x 11 4078xfb this output is strong enough to drive an led. if no valid voltage is applied at either pin, the pwr pin is high im- pedance, indicating that the ltc4078/ltc4078x lack valid input voltage (see table 1) to charge the battery. thermal limiting an internal thermal feedback loop reduces the programmed charge current if the die temperature attempts to rise above a preset value of approximately 120c. this feature protects operation figure 1. ltc4078 state diagram of a charge cycle the ltc4078/ltc4078x from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damag- ing the device. 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 package power considerations are discussed further in the applications information section. shutdown mode (usbin) chrg state: hi-z full current (bat > 2.9v) 1/10th full current (bat < 2.9v)* chrg state: pulldown full current (bat > 2.9v) 1/10th full current (bat < 2.9v)* chrg state: pulldown standby mode (dcin) no charge current chrg state: hi-z shutdown mode (dcin) chrg state: hi-z yes no bat < 4.075v bat < 4.075v i bat < i terminate in voltage mode i bat < i terminate in voltage mode no power standby mode (usbin) no charge current chrg state: hi-z yes nono yes batdet < 1.75v batdet < 1.75v no yes no 6v > usbin > 3.95v and usbin > bat yes dcin > 4.15v and dcin > bat 6v > dcin > 4.15v and dcin > bat enable = low enable = high power applied dcin power removed usb power removed 4078x f01 *ltc4078 only downloaded from: http:///
ltc4078/ltc4078x 12 4078xfb applications information using a single charge current program resistor the ltc4078/ltc4078x can program the wall adapter charge current and usb charge current independently using two program resistors, r idc and r iusb . figure 2 shows a charger circuit that sets the wall adapter charge current to 800ma and the usb charge current to 500ma. in applications where the programmed wall adapter charge current and usb charge current are the same, a single program resistor can be used to set both charge currents. figure 3 shows a charger circuit that uses one charge current program resistor. stability considerationsthe constant-voltage mode feedback loop is stable without any compensation provided a battery is connected to the charger output. however, a 1f capacitor with a 1 series resistor is recommended at the bat pin to keep the ripple voltage low when the battery is disconnected. when the charger is in constant-current mode, the charge current program pin (idc or iusb) is in the feedback loop, not the battery. the constant-current mode stability is af- fected by the impedance at the charge current program pin. with no additional capacitance on this pin, the charger is stable with program resistor values as high as 20k (i chrg = 50ma); however, additional capacitance on these nodes reduces the maximum allowed program resistor. power dissipation when designing the battery charger circuit, it is not necessary to design for worst-case power dissipation scenarios because the ltc4078/ltc4078x automatically reduce the charge current during high power conditions. the conditions that cause the ltc4078/ltc4078x to reduce charge current through thermal feedback can be approximated by considering the power dissipated in the ic. most of the power dissipation is generated from the internal charger mosfet. thus, the power dissipation is calculated to be: p d = (v in C v bat ) ? i bat p d is the dissipated power, v in is the input supply volt- age (either dcin or usbin), v bat is the battery voltage and i bat is the charge current. the approximate ambient temperature at which the thermal feedback begins to protect the ic is: t a = 120c C p d ? ja t a = 120c C (v in C v bat ) ? i bat ? ja example: an ltc4078/ltc4078x operating from a 5v wall adapter (on the dcin input) is programmed to supply 800ma full-scale current to a discharged li-ion battery with a voltage of 3.3v. figure 3. dual input charger circuit. the wall adapter charge current and usb charge current are both programmed to be 500ma figure 2. dual input charger with independent charge currents in this circuit, the programmed charge current from both the wall adapter supply is the same value as the programmed charge current from the usb supply: i chrg dc = i chrg usb = 1000v r ise t ltc4078 dcinusbin iusb idc bat iterm batdet r21.24k 1% r43.9k r12k 1% r32k 1% wall adapter usb port c2, 1 f c1 1 f + 4.2vli-ion battery pack 800ma (wall) 500ma (usb) 4078x f02 gnd ltc4078 dcinusbin iusb idc bat iterm batdet r43.9k r12k 1% r32k 1% wall adapter usb port c2, 1 f c1 1 f + 4.2vli-ion battery pack 500ma 4078x f03 gnd downloaded from: http:///
ltc4078/ltc4078x 13 4078xfb applications information assuming ja is 40c/w (see thermal considerations), the ambient temperature at which the ltc4078/ltc4078x will begin to reduce the charge current is approximately: t a = 120c C (5v C 3.3v) ? (800ma) ? 40c/w t a = 120c C 1.36w ? 40c/w = 120c C 54.4c t a = 65.6c the ltc4078/ltc4078x can be used above 70.6c ambi- ent, but the charge current will be reduced from 800ma. the approximate current at a given ambient temperature can be approximated by: i bat = 120 cCt a (v in Cv bat ) j a using the previous example with an ambient temperature of 75c, the charge current will be reduced to approxi- mately: i bat = 120 cC75 c (5v C 3.3v) 40 c/ w = 45 c 68 c/ a i bat = 662ma it is important to remember that ltc4078/ltc4078x 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 120c. thermal considerations in order to deliver maximum charge current under all conditions, it is critical that the exposed metal pad on the backside of the ltc4078/ltc4078x dfn package is properly soldered to the pc board ground. when cor- rectly soldered to a 2500mm 2 double sided 1oz copper board, the ltc4078/ltc4078x has a thermal resistance of approximately 40c/w. failure to make thermal contact between the exposed pad on the backside of the package and the copper board will result in thermal resistances far greater than 40c/w. as an example, a correctly soldered figure 4. input soft connect circuit ltc4078/ltc4078x can deliver over 800ma to a battery from a 5v supply at room temperature. without a good backside thermal connection, this number would drop to much less than 500ma. input capacitor selection when an input supply is connected to a portable product, the inductance of the cable and the high-q ceramic input capacitor form an l-c resonant circuit. while the ltc4078/ ltc4078x are capable of withstanding input voltages as high as 22v, if the input cable does not have adequate mutual coupling or if there is not much impedance in the cable, it is possible for the voltage at the input of the product to reach as high as 2x the input voltage before it settles out. to prevent excessive voltage from damaging the ltc4078/ltc4078x during a hot insertion, it is best to have a low voltage coef? cient capacitor at the input pins to the ltc4078/ltc4078x. this is achievable by select- ing an x5r or x7r ceramic capacitor that has a higher voltage rating than that required for the application. for example, if the maximum expected input voltage is 15v, a 25v x5r 1f capacitor would be a better choice than the smaller 16v x5r capacitor. note that no charging will occur with 15v in. using a tantalum capacitor or an aluminum electrolytic capacitor for input bypassing, or paralleling with a ceramic capacitor will also reduce voltage overshoot during a hot insertion. ceramic capacitors with y5v or z5u dielectrics are not recommeded. alternatively, the following soft connect circuit can be employed (as shown in figure 4). ltc4078 dcin/usbin input cable +15v input c1 1 f c2 100nf mn1 4078x f04 gnd r1 40k downloaded from: http:///
ltc4078/ltc4078x 14 4078xfb applications information figure 5. low loss reverse polarity protection in this circuit, capacitor c2 holds mn1 off when the cable is ? rst connected. eventually c2 begins to charge up to the usb input voltage applying increasing gate drive to mn1. the long time constant of r1 and c1 prevent the current from rapidly building up in the cable, thus dampening out any resonant overshoot. reverse polarity input voltage protection in some applications, protection from reverse polarity voltage on the input supply pins is desired. with suf? cient supply voltage, a series blocking diode can be used. in other cases where the voltage drop must be kept low, a p-channel mosfet can be used (as shown in figure 5). wall adapter dcin ltc4078 drain-bulk diode of fet 4078x f05 downloaded from: http:///
ltc4078/ltc4078x 15 4078xfb 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 representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description 3.00 0.10 (4 sides) note:1. drawing to be made a jedec package outline m0-229 variation of (weed-2). check the ltc website data sheet for current status of variation assignment 2. drawing not to scale 3. all dimensions are in millimeters 4. 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 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.38 0.10 bottom viewexposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.115 typ 2.38 0.10 (2 sides) 1 5 10 6 pin 1 top mark (see note 6) 0.200 ref 0.00 C 0.05 (dd) dfn 1103 0.25 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 3.50 0.05 packageoutline 0.25 0.05 0.50 bsc dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699) downloaded from: http:///
ltc4078/ltc4078x 16 4078xfb linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2007 lt 0308 rev b printed in usa typical application part number description comments ltc3455 dual dc/dc converter with usb power management and li-ion battery charger ef? ciency >96%, accurate usb current limiting (500ma/100ma), 4mm 4mm qfn-24 package ltc4053 usb compatible monolithic li-ion battery charger standalone charger with programmable timer, up to 1.25a charge current ltc4054/ltc4054x standalone linear li-ion battery charger with integrated pass transistor in thinsot? thermal regulation prevents overheating, c/10 termination, c/10 indicator, up to 800ma charge current ltc4055 usb power controller and battery charger charges single-cell li-ion batteries directly from usb port, thermal regulation, 4mm 4mm qfn-16 package ltc4058/ltc4058x standalone 950ma lithium-ion charger in dfn c/10 charge termination, battery kelvin sensing, 7% charge accuracy ltc4061 standalone li-ion charger with thermistor interface 4.2v, 0.35% float voltage, up to 1a charge current ltc4066 usb power controller and li-ion linear battery charger with low-loss ideal diode seamless transition between input power sources: li-ion battery, usb and wall adapter, low loss (50m) ideal diode, 4mm 4mm qfn-24 package ltc4068/ltc4068x standalone linear li-ion battery charger with programmable termination charge current up to 950ma, thermal regulation, 3mm 3mm dfn-8 package ltc4075/ ltc4075hvx dual input standalone li-ion battery charger 950ma charger current, thermal regulation, c/x charge termination, usb charge current set via resistor, 3mm 3mm dfn package; ltc4075hvx has 22v input protection. ltc4076 dual input standalone li-ion battery charger 950ma charger current, thermal regulation, c/x charge termination, fixed c or c/5 usb charge current for low power usb operation, 3mm 3mm dfn package ltc4077 dual input standalone li-ion battery charger 950ma charger current, thermal regulation, c/x charge termination, programmable c or c/x usb charge current for low power usb operation, fixed c/10 wall adapter and c/10 or c/2 charge current termination, 3mm 3mm dfn package ltc4085 usb power manager with ideal diode controller and li-ion charger charges single-cell li-ion batteries directly from usb port, thermal regulation, 200m ideal diode with <50m option, 4mm 3mm dfn-14 package ltc4089/ ltc4089-5 usb power manager with ideal diode controller and high ef? ciency li-ion battery charger high ef? ciency 1.2a charger from 6v to 36v (40v max) input charges single-cell li-ion batteries directly from usb port, thermal regulation, 200m ideal diode with <50m option, bat-track adaptive output control (ltc4089), fixed 5v output (ltc4089-5), 4mm 3mm dfn-14 package ltc4411/ltc4412 low loss powerpath? controller in thinsot automatic switching between dc sources, load sharing, replaces oring diodes thinsot and powerpath are trademarks of linear technology corporation. full featured li-ion charger 1.24k1% wall adapter usb power 1 f 1 f 800ma (wall) 475ma (usb) 4078x ta02 2.1k1% 1k1% 1k 1k ltc4078 idc iusb dcinusbin bat pwr iterm chrg gnd batdet 3.9k + 4.2v li-ion battery pack related parts downloaded from: http:///

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