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ltc4075/ltc4075x 1 4075xfa the ltc ? 4075/ltc4075x are standalone linear chargers that are capable of charging a single-cell li-ion 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. internal thermal feedback regulates the battery charge current to maintain a constant die temperature during high power operation or high ambient temperature conditions. the ? oat voltage is ? xed at 4.2v and the charge current is programmed with an external resistor. the ltc4075 terminates the charge cycle when the charge current drops below the programmed termination threshold after the ? nal ? oat voltage is reached. with power applied to both inputs, the ltc4075/ltc4075x can be put into shutdown mode reducing the dcin supply current to 20a, the usbin supply current to 10a, and the battery drain current to less than 2a. other features include automatic recharge, undervoltage lockout, charge status outputs, and power present status outputs to indicate the presence of wall adapter or usb power. dual input battery charger for single-cell li-ion ltc4075 dcin usbin iusb idc bat iterm 1.24k 1% 2k 1% 2k 1% wall adapter usb port 1 f 1 f + 4.2v single cell li-ion battery 800ma (wall) 500ma (usb) 4075 ta01 gnd dual input usb/ac adapter standalone li-ion battery chargers time (hr) 0 charge current (ma) battery voltage (v) dcin voltage (v) 4.2 200 0 400 800 600 1000 1.5 2.5 4075 ta01b 3.6 3.4 5.0 4.0 3.8 2.5 0 ?2.5 0.5 1.0 2.0 3.0 constant voltage usbin = 5v t a = 25 c r idc = 1.25k r iusb = 2k complete charge cycle (1100mah battery) , ltc and lt 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 applicatio s u features descriptio u typical applicatio u charges single-cell li-ion batteries from wall adapter and usb inputs automatic input power detection and selection charge current programmable up to 950ma from wall adapter input no external mosfet, sense resistor or blocking diode needed thermal regulation maximizes charging rate without risk of overheating* preset charge voltage with 0.6% accuracy programmable charge current termination 18a usb suspend current in shutdown independent power present status outputs charge status output automatic recharge available without trickle charge (ltc4075x) available in a thermally enhanced, low pro? le (0.75mm) 10-lead (3mm 3mm) dfn package cellular telephones handheld computers portable mp3 players digital cameras
ltc4075/ltc4075x 2 4075xfa symbol parameter conditions min typ max units v dcin supply voltage 4.3 8 v v usbin supply voltage 4.3 8 v i dcin dcin supply current charge mode (note 4), r idc = 10k 250 800 a standby mode; charge terminated 50 100 a shutdown mode (enable = 5v) 20 40 a i usbin usbin supply current charge mode (note 5), r iusb = 10k, v dcin = 0v 250 800 a standby mode; charge terminated, v dcin = 0v 50 100 a shutdown (v dcin = 0v, enable = 0v) 18 36 a v dcin > v usbin 10 20 a v float regulated output (float) voltage i bat = 1ma 4.175 4.2 4.225 v i bat = 1ma, 0c < t a < 85c 4.158 4.2 4.242 v i bat bat pin current r idc = 1.25k, constant-current mode 760 800 840 ma r iusb = 2.1k, constant-current mode 450 476 500 ma r idc = 10k or r iusb = 10k 93 100 107 ma standby mode, charge terminated C3 C 6 a shutdown mode (charger disabled) C1 C 2 a sleep mode (v dcin = 0v, v usbin = 0v) 1 2 a v idc idc pin regulated voltage constant-current mode 0.95 1 1.05 v v iusb iusb pin regulated voltage constant-current mode 0.95 1 1.05 v i terminate charge current termination threshold r iterm = 1k 90 100 110 ma r iterm = 2k 45 50 55 ma r iterm = 10k 8.5 10 11.5 ma r iterm = 20k 4 5 6 ma input supply voltage (dcin, usbin) ........... C 0.3 to 10v enable, ? c ? h ? r ? g, ? p ? w ? r, usbpwr ................. C 0.3 to 10v bat, idc, iusb, iterm .................................. C 0.3 to 7v dcin pin current (note 7) ..........................................1a usbin pin current (note 7) .................................700ma bat pin current (note 7) ............................................1a bat short-circuit duration ............................ continuous maximum junction temperature .......................... 125 c operating temperature range (note 2) .. C 40 c to 85 c storage temperature range .................. C 65 c to 125 c (note 1) the 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. electrical characteristics absolute axi u rati gs w ww u package/order i for atio uu w top view dd package 10-lead (3mm 3mm) plastic dfn exposed pad is gnd (pin 11) must be soldered to pcb 10 9 6 7 8 11 4 5 3 2 1 dcin bat idc usbpwr enable usbin iusb iterm pwr chrg order part number dd part marking ltc4075edd ltc4075xedd lbsc lbrk order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/ consult ltc marketing for parts speci? ed with wider operating temperature ranges. t jmax = 125c, ja = 40c/w (note 3)
ltc4075/ltc4075x 3 4075xfa symbol parameter conditions min typ max units i trikl trickle charge current (note 6) v bat < v trikl ; r idc = 1.25k 60 80 100 ma v bat < v trikl ; r iusb = 2.1k 30 47.5 65 ma v trikl trickle charge threshold (note 6) v bat rising 2.8 2.9 3 v hysteresis 100 mv v uvdc dcin undervoltage lockout voltage from low to high 4 4.15 4.3 v hysteresis 200 mv v uvusb usbin undervoltage lockout voltage from low to high 3.8 3.95 4.1 v hysteresis 200 mv v asd-dc v dcin C v bat lockout threshold v dcin from low to high, v bat = 4.2v 140 180 220 mv v dcin from high to low, v bat = 4.2v 20 50 80 mv v asd-usb v usbin C v bat lockout threshold v usbin from low to high, v bat = 4.2v 140 180 220 mv v usbin from high to low, v bat = 4.2v 20 50 80 mv v enable enable input threshold voltage 0.4 0.7 1 v r enable enable pulldown resistance 1.2 2 5 m v ? c ? h ? r ? g ? c ? h ? r ? g output low voltage i ? c ? h ? r ? g = 5ma 0.35 0.6 v v ? p ? w ? r ? p ? w ? r output low voltage i ? p ? w ? r = 5ma 0.35 0.6 v v usbpwr usbpwr output low voltage i usbpwr = 300a 0.35 0.6 v v rechrg recharge battery threshold v float C v rechrg , 0c < t a < 85c 65 100 135 mv t rechrg recharge comparator filter time v bat from high to low 3 6 9 ms t terminate termination comparator filter time i bat drops below termination threshold 0.8 1.5 2.2 ms t ss soft-start time i bat = 10% to 90% full-scale 175 250 325 s r on-dc power fet on resistance 400 m (between dcin and bat) r on-usb power fet on resistance 550 m (between usbin and bat) t lim junction temperature in 105 c constant-temperature mode the 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. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the ltc4075e/ltc4075xe are guaranteed to meet the performance speci? cations from 0c to 70c. 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 ltc4075x. note 7: guaranteed by long term current density limitations. electrical characteristics
ltc4075/ltc4075x 4 4075xfa charge current (ma) 0 v float (v) 800 500 600 700 400 4075x g01 100 200 300 4.26 4.24 4.22 4.20 4.18 4.16 4.14 4.12 4.10 4075x g04 temperature ( c) ?50 ?25 v float (v) 050 25 75 100 4075x g02 temperature ( c) ?50 ?25 0 50 25 75 100 temperature ( c) ?50 ?25 0 50 25 75 100 4.220 4.215 4.210 4.205 4.200 4.195 4.190 4.185 4.180 v idc (v) 4075x g03 1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 0.992 v iusb (v) 1.008 1.006 1.004 1.002 1.000 0.998 0.996 0.994 0.992 v idc (v) 0 0.2 0.6 1.0 i bat (ma) 0.8 900 800 700 600 500 400 300 200 100 0 i bat (ma) 900 800 700 600 500 400 300 200 100 0 4075x g05 0.4 1.2 v iusb (v) 0 0.2 0.6 1.0 0.8 0.4 1.2 4075x g06 v pwr (v) 0 35 30 25 20 15 10 5 0 35 4075x g07 12 467 i pwr (ma) 4075x g08 r idc = 1.25k r idc = r iusb = 2k v dcin = v usbin = 5v v dcin = v usbin = 5v v dcin = v usbin = 5v v dcin = v usbin = 5v v dcin = 5v v dcin = 8v v dcin = 4.3v v usbin = 8v v usbin = 4.3v r idc = 1.25k v usbin = 5v r iusb = 1.25k r iusb = 2k r iusb = 10k r idc = 2k r idc = 10k 35 30 25 20 15 10 5 0 i chrg (ma) t a = ? 40 c t a = 25 c t a = 90 c t a = ? 40 c t a = ? 40 c t a = 25 c t a = 25 c t a = 90 c t a = 90 c v chrg (v) 035 12 467 v usbpwr (v) 0 i usbpwr (ma) 6 5 4 3 2 1 0 35 4075x g09 12 467 v dcin = 5v v usbin = 0v iusb pin voltage vs temperature (constant-current mode) charge current vs idc pin voltage charge current vs iusb pin voltage ? p ? w ? r pin i-v curve ? c ? h ? r ? g pin i-v curve usbpwr 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) typical perfor a ce characteristics uw
ltc4075/ltc4075x 5 4075xfa i bat (ma) 1000 800 600 400 200 0 4075x g10 v dcin (v) i bat (ma) 4075x g11 900 800 700 600 500 400 300 4.0 5.0 6.0 6.5 4.5 5.5 7.0 7.5 8.0 temperature ( c) ?50 r ds(on) (m ? ) 550 500 450 400 350 300 250 25 75 4075x g13 ?25 0 50 100 125 temperature ( c) ?50 25 75 ?25 0 50 100 125 temperature ( c) ?50 25 75 ?25 0 50 100 125 temperature ( c) ?50 25 75 ?25 0 50 100 temperature ( c) ?50 25 75 ?25 0 50 100 temperature ( c) ?50 25 75 ?25 0 50 100 temperature ( c) ?50 25 75 ?25 0 50 100 r ds(on) (m ? ) 800 750 700 650 600 550 500 450 400 350 4075x g14 v enable (mv) 900 850 800 750 700 650 600 i dcin ( a) 4075x g16 50 45 40 35 30 25 20 15 10 5 0 i usbin ( a) 45 40 35 30 25 20 15 10 5 0 4075x g17 4075x g18 r enable (m ? ) 2.8 2.6 2.4 2.2 2.0 1.8 1.6 4075x g15 v dcin = 8v v dcin = 5v v dcin = 4.3v v usbin = 8v v usbin = 5v v usbin = 4.3v enable = 5v enable = 0v v dcin = v usbin = 5v v bat = 4v ja = 40 c/w v bat = 4v i bat = 200ma v bat = 4v i bat = 200ma r idc = 1.25k v bat = 4v ja = 35 c/w r idc = 1.25k r idc = r iusb = 2k onset of thermal regulation onset of thermal regulation v dcin = v usbin = 5v v bat (v) 2.4 i bat (ma) 1000 800 600 400 200 0 3.0 3.6 3.9 4075x g12 2.7 3.3 4.2 4.5 ltc4075 ltc4075x v dcin = v usbin = 5v ja = 40 c/w r idc = 1.25k charge current vs ambient temperature charge current vs supply voltage charge current vs battery voltage dcin power fet on resistance vs temperature usbin power on resistance vs temperature enable pin threshold (on-to-off) vs temperature dcin shutdown current vs temperature usbin shutdown current vs temperature enable pin pulldown resistance vs temperature typical perfor a ce characteristics uw
ltc4075/ltc4075x 6 4075xfa temperature ( c) ?50 ?25 v uv (v) 050 25 75 100 4075x g19 4.30 4.25 4.20 4.15 4.10 4.05 4.00 3.95 3.90 temperature ( c) ?50 ?25 0 50 25 75 100 v rechrg (v) 4.16 4.14 4.12 4.10 4.08 4.06 4.04 4075x g20 4075x g22 dcin uvlo usbin uvlo v dcin = v usbin = 4.3v v dcin = 5v r idc = 1.25k v dcin = v usbin = 8v 100 s/div i bat 500ma/div enable 5v/div temperature ( c) ?50 i bat ( a) 5 4 3 2 1 0 ?1 ?25 02550 4075x g21 75 100 v bat = 4.2v v dcin , v usbin (not connected) undervoltage lockout threshold vs temperature recharge threshold vs temperature charge current during turn-on and turn-off battery drain current vs temperature typical perfor a ce characteristics uw
ltc4075/ltc4075x 7 4075xfa usbin (pin 1): usb input supply pin. provides power to the battery charger. the maximum supply current is 650ma. 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 v r bat iusb iusb = 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 v r terminate iterm = 100 when the battery current, i bat , falls below the termination threshold, charging stops and the ? c ? h ? r ? g output becomes high impedance. this pin is internally clamped to approximately 1.5v. driving this pin to voltages beyond the clamp voltage can draw large currents and should be avoided. ? p ? w ? r (pin 4): open-drain power supply status output. when the dcin or usbin pin voltage is suf? cient to begin charging (i.e. when the supply is greater than the under- voltage lockout threshold and at least 180mv above the battery terminal), the ? p ? w ? r pin is pulled low by an internal n-channel mosfet. otherwise ? p ? w ? r is high impedance. this output is capable of sinking up to 10ma, making it suitable for driving an led. ? c ? h ? r ? g (pin 5): open-drain charge status output. when the ltc4075 is charging, the ? c ? h ? r ? g pin is pulled low by an internal n-channel mosfet. when the charge cycle is completed, ? c ? h ? r ? g becomes high impedance. this output is capable of sinking up to 10ma, making it suitable for driving an led. enable (pin 6): enable input. when the ltc4075 is charging from the dcin source, a logic low on this pin enables the charger. when the ltc4075 is 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 ltc4075 to charge when a wall adapter is applied and to shut down if only the usb source is applied. usbpwr (pin 7): open-drain usb power status output. when the voltage on the usbin pin is suf? cient to begin charging and there is insuf? cient power at dcin, the usb- pwr pin is high impedance. in all other cases, this pin is pulled low by an internal n-channel mosfet, provided that there is power present at the dcin, usbin, or bat inputs. this output is capable of sinking up to 1ma, making it suitable for driving high impedance logic inputs. 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 v r bat idc idc = 1000 bat (pin 9): charger output and regulator input. 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. provides power to the battery charger. the maximum supply current is 950ma. this should be bypassed with a 1 f 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. pi fu ctio s uuu
ltc4075/ltc4075x 8 4075xfa ? + 7 ? + ? + ? + ? + ? + ? + ? + rechrg trickle term logic 4.1v bat 4.15v bat 3.95v bat 2.9v 100mv i bat /1000 i bat /1000 i bat /1000 4 5 6 3 8 2 11 dc_enable usb_enable charger control cc/cv regulator cc/cv regulator 9 10 1 r iterm r iusb r idc iterm iusb idc gnd 105 c t die usb soft-start dc soft-start usbin uvlo dcin uvlo dcin bat usbin usbpwr enable r enable pwr chrg termination *trickle charge recharge thermal regulation *trickle charge disabled on the ltc4075x 1ma max 10ma max 10ma max 4075 bd block diagra w
ltc4075/ltc4075x 9 4075xfa the ltc4075 is designed to ef? ciently manage 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 650ma of charge current from the usb supply with a ? nal ? oat voltage accuracy of 0.6%. the ltc4075 has two internal p-channel power mosfets and thermal regulation circuitry. no blocking diodes or external sense resistors are required. power source selection the ltc4075 can charge a battery from either the wall adapter input or the usb port input. the ltc4075 automati- cally senses the presence of voltage at each input. if both power sources are present, the ltc4075 defaults to the wall adapter source provided suf? cient power is present at the dcin input. suf? cient power is de? ned as: ? supply voltage is greater than the uvlo threshold. ? supply voltage is greater than the battery voltage by 50mv (180mv rising, 50mv falling). the open drain power status outputs ( ? p ? w ? r and usbpwr) indicate which power source has been selected. table 1 describes the behavior of these status outputs. table 1. power source selection v usbin > 3.95v and v usbin < 3.95v or v usbin > bat + 50mv v usbin < bat + 50mv v dcin > 4.15v and device powered from device powered from v dcin > bat + 50mv wall adapter source; wall adapter source usbin current < 25a ? p ? w ? r: low ? p ? w ? r: low usbpwr: low usbpwr: low v dcin < 4.15v or device powered from no charging v dcin < bat + 50mv usb source; ? p ? w ? r: low ? p ? w ? r: hi-z usbpwr: hi-z usbpwr: low programming and monitoring charge current the charge current delivered to the battery from the wall adapter supply is programmed using a single resistor from the idc pin to ground. likewise, the charge current from the usb supply is programmed using a single resis- tor from the iusb pin to ground. the program resistor and the charge current (i chrg ) are calculated using the following equations: r v i i v r r v i i v r idc chrg dc chrg dc idc iusb chrg usb chrg usb iusb == == ? ? ? ? 1000 1000 1000 1000 , , charge current out of the bat pin can be determined at any time by monitoring the idc or iusb pin voltage and using the following equations: i v r ch ing fromwall adapter i v r ch ing fromusb ply bat idc idc bat iusb iusb = = , ( arg ) , ( arg sup ) 1000 1000 programming charge termination the charge cycle terminates when the charge current falls below the programmed termination threshold during con- stant-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 v i i v r iterm terminate terminate iterm == 100 100 , operatio u
ltc4075/ltc4075x 10 4075xfa *any external sources that hold the iterm pin above 100mv will prevent the ltc4075 from terminating a charge cycle. the termination condition is detected by using an internal ? ltered comparator to monitor the iterm pin. when the iterm pin voltage drops below 100mv * for longer than t terminate (typically 1.5ms), charging is terminated. the charge current is latched off and the ltc4075 enters 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 programmed termination current. the 1.5ms ? 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 ltc4075 terminates 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. low battery charge conditioning (trickle charge) this feature ensures that near-dead batteries are gradually charged before reapplying full charge current . if the bat pin voltage is below 2.9v, the ltc4075 supplies 1/10th of the full charge current to the battery until the bat pin rises back 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 ltc4075x 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 ltc4075x is useful in applications where the trickle charge current may be insuf? cient to supply the 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 6ms ? lter time (t rechrg ). a charge cycle automatically restarts when the battery voltage falls below 4.1v (which corresponds to approximately 80%-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. if the battery is removed from the charger, a sawtooth waveform of approximately 100mv appears at the battery output. this is caused by the repeated cycling between termination and recharge events. this cycling results in pulsing at the ? c ? h ? r ? g 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. 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 20a when the charger is in shut- down. the usbin input draws 18a during shutdown if no power is applied to dcin, but draws only 10a when v dcin > v usbin . charge current soft-start and soft-stop the ltc4075 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 250s. likewise, internal circuitry slowly ramps the charge current from full-scale to zero in a period of approximately 30s when the charger shuts down or self terminates. this minimizes the transient current load on the power supply during start-up and shut-off. status indicators the charge status output ( ? c ? h ? r ? g) has two states: pull-down and high impedance. the pull-down state indicates that the ltc4075 is in a charge cycle. once the charge cycle has terminated or the ltc4075 is disabled, the pin state becomes high impedance. the pull-down state is capable of sinking up to 10ma. operatio u
ltc4075/ltc4075x 11 4075xfa the power supply status output ( ? p ? w ? r) has two states: pull- down and high impedance. the pull-down state indicates that power is present at either dcin or usbin. this output is strong enough to drive an led. if no power is applied at either pin, the ? p ? w ? r pin is high impedance, indicating that the ltc4075 lacks suf? cient power to charge the battery. the pull-down state is capable of sinking up to 10ma. the usb power status output (usbpwr) has two states: pull-down and high impedance. the high impedance state indicates that the ltc4075 is being powered from the usbin input. the pull-down state indicates that the charger is either powered from dcin or is in a uvlo condition (see table 1). the pull-down state is capable of sinking up to 1ma. 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 105c. this feature protects the ltc4075 from excessive temperature and allows the user to push the limits of the power handling capability of a given circuit board without risk of damaging 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 power considerations are discussed further in the applications information section. trickle charge mode* 1/10th full current chrg state: pulldown shutdown mode i usbin drops to 18 a chrg state: hi-z charge mode full current chrg state: pulldown charge mode full current chrg state: pulldown standby mode no charge current chrg state: hi-z shutdown mode i dcin drops to 20 a chrg state: hi-z bat > 2.9v bat < 2.9v bat < 2.9v 2.9v < bat 2.9v < bat bat > 2.9v bat < 4.1v bat < 4.1v i bat < i terminate in voltage mode i bat < i terminate in voltage mode power selection standby mode no charge current chrg state: hi-z trickle charge mode* 1/10th full current chrg state: pulldown enable driven low enable driven low enable driven high dcin power removed dcin power removed usbin power removed or dcin power applied usbin power removed or dcin power applied dcin power applied only usb power applied startup 4075 f01 enable driven high *ltc4075 only figure 1. ltc4075 state diagram of a charge cycle operatio u
ltc4075/ltc4075x 12 4075xfa r iset 2k 1% r iterm 1k 1% wall adapter usb port 1 f 1 f + 500ma 4075 f03 ltc4075 dcin usbin iusb idc bat iterm gnd figure 2. full featured dual input charger circuit r idc 1.24k 1% r iusb 2k 1% r iterm 1k 1% wall adapter usb port 1 f 1 f + 800ma (wall) 500ma (usb) 4075 f02 ltc4075 dcin usbin iusb idc bat iterm gnd figure 3. dual input charger circuit. the wall adapter charge current and usb charge current are both programmed to be 500ma using a single charge current program resistor the ltc4075 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. 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: ii v r chrg dc chrg usb iset ?? == 1000 stability considerations the 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 affected by the impedance at the charge current program pin. with no additional capacitance on this pin, the char- ger 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 neces- sary to design for worst-case power dissipation scenarios because the ltc4075 automatically reduces the charge current during high power conditions. the conditions that cause the ltc4075 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 applicatio s i for atio wu u u
ltc4075/ltc4075x 13 4075xfa p d is the power dissipated, 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 = 105c C p d ? ja t a = 105c C (v in C v bat ) ? i bat ? ja example: an ltc4075 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. assuming ja is 40c/w (see thermal considerations), the ambient temperature at which the ltc4075 will begin to reduce the charge current is approximately: t a = 105c C (5v C 3.3v) ? (800ma) ? 40c/w t a = 105c C 1.36w ? 40c/w = 105c C 54.4c t a = 50.6c the ltc4075 can be used above 50.6c ambient, but the charge current will be reduced from 800ma. the ap- proximate current at a given ambient temperature can be approximated by: i ct vv bat a in bat ja = 105 ? (? ) using the previous example with an ambient temperature of 60c, the charge current will be reduced to approxi- mately: i cc vvcw c ca ima bat bat = = = 105 60 53340 45 68 662 ? (?.) / / it is important to remember that ltc4075 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 105c. 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 ltc4075 package is properly soldered to the pc board ground. when correctly soldered to a 2500mm 2 double sided 1oz copper board, the ltc4075 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 ltc4075 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. protecting the usb pin and wall adapter input from overvoltage transients caution must be exercised when using ceramic capacitors to bypass the usbin pin or the wall adapter inputs. high voltage transients can be generated when the usb or wall adapter is hot plugged. when power is supplied via the usb bus or wall adapter, the cable inductance along with the self resonant and high q characteristics of ceramic capacitors can cause substantial ringing which could exceed the maximum voltage pin ratings and damage the ltc4075. refer to linear technology application note 88, entitled ceramic input capacitors can cause overvoltage transients for a detailed discussion of this problem. the long cable lengths of most wall adapters and usb cables applicatio s i for atio wu u u
ltc4075/ltc4075x 14 4075xfa figure 5. low loss input reverse polarity protection wall adapter dcin ltc4075 drain-bulk diode of fet 4075 f05 makes them especially susceptible to this problem. to bypass the usb pin and the wall adapter input, add a 1 resistor in series with a ceramic capacitor to lower the effective q of the network and greatly reduce the ringing. a tantalum, os-con, or electrolytic capacitor can be used in place of the ceramic and resistor, as their higher esr reduces the q, thus reducing the voltage ringing. the oscilloscope photograph in figure 4 shows how serious the overvoltage transient can be for the usb and wall adapter inputs. for both traces, a 5v supply is hot-plugged using a three foot long cable. for the top trace, only a 4.7f capacitor (without the recommended 1 series resistor) is used to locally bypass the input. this trace shows excessive ringing when the 5v cable is inserted, with the overvoltage spike reaching 10v. for the bottom trace, a 1 resistor is added in series with the 4.7f capacitor to locally bypass the 5v input. this trace shows the clean response resulting from the addition of the 1 resistor. even with the additional 1 resistor, bad design techniques and poor board layout can often make the overvoltage problem even worse. system designers often add extra inductance in series with input lines in an attempt to mini- mize the noise fed back to those inputs by the application. in reality, adding these extra inductances only makes the overvoltage transients worse. since cable inductance is one of the fundamental causes of the excessive ringing, adding a series ferrite bead or inductor increases the ef- fective cable inductance, making the problem even worse. for this reason, do not add additional inductance (ferrite beads or inductors) in series with the usb or wall adapter inputs. for the most robust solution, 6v transorbs or zener diodes may also be added to further protect the usb and wall adapter inputs. two possible protection devices are the sm2t from stmicroelectronics and the edz series devices from rohm. always use an oscilloscope to check the voltage wave- forms at the usbin and dcin pins during usb and wall adapter hot-plug events to ensure that overvoltage transients have been adequately removed. reverse polarity input voltage protection in some applications, protection from reverse polarity voltage on the input supply pins is desired. if the sup- ply voltage is high enough, 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). applicatio s i for atio wu u u figure 4. waveforms resulting from hot-plugging a 5v input supply 4.7f only 2v/div 4.7f + 1 2v/div 20s/div 3455 f04
ltc4075/ltc4075x 15 4075xfa dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699) 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. package descriptio u 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 view?exposed 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 ? 0.05 (dd10) 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 0.50 bsc 0.675 0.05 3.50 0.05 package outline 0.25 0.05 0.50 bsc
ltc4075/ltc4075x 16 4075xfa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2005 lt 1105 rev a ? printed in usa part number description comments ltc3455 dual dc/dc converter with usb power ef? ciency >96%, accurate usb current limiting (500ma/100ma), management and li-ion battery charger 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 thermal regulation prevents overheating, c/10 termination, with integrated pass transistor in thinsot 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 accura cy 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 seamless transition between input power sources: li-ion battery, usb a nd charger with low-loss ideal diode wall adapter, low-loss (50 ) ideal diode, 4mm 4mm qfn-24 package ltc4068/ltc4068x standalone linear li-ion battery charger with charge current up to 950ma, thermal regulation, programmable termination 3mm 3mm dfn-8 package ltc4410 usb power manager and battery charger manages total power between a usb peripheral and battery charger, ultralow battery drain: 1a, thinsot tm package ltc4411/ltc4412 low loss powerpath tm controller in thinsot automatic switching between dc sources, load sharing, replaces oring diodes full featured li-ion charger 1.24k 1% wall adapter usb power 1 f 1 f + 800ma (wall) 475ma (usb) 4075 ta03 2.1k 1% 1k 1% 1k 1k 1-cell li-ion battery ltc4075 dcin usbin iusb idc bat pwr chrg iterm gnd thinsot and powerpath are trademarks of linear technology corporation typical applicatio u related parts

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