prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 1 of 10 general description the lp 28012 is a complete constant - current/ constant voltage linear charger for single cell lithium - ion batteries. its esop8 package and low external component count make the lp 28012 ideally suited for portable applications. no external sense resistor is needed, and no blocking diode is required due to the internal mosfet architecture. thermal feedback regulates the charge current to limit the die temperature during high power op eration or high ambient temperature. the charge voltage is fixed at 4.2v, and the charge current can be iset rammed externally with a single resistor. the lp 28012 automatically terminates the charge cycle when the charge current drops to 1/10th the iset ra mmed value after the final float voltage is reached. when the input supply is removed, the lp 28012 automatically enters a low current state, dropping the battery drain current to less than 4 a. other features include charge current monitor, under voltage lockout, automatic recharge and a status pin to indicate charge termination and the presence of an input voltage. order information 1 . 2 a single - chip li - ion and li - pol charge lp 28012 f: pb - free package type qv : tdfn - 10 applications ? portable media players/ game ? power bank ? pda/ mid ? bluetooth applications features ? very low power dissipatio n ? short - circuit protection ? programmable charge current up to 1 2 00ma ? no mosfet, sense resistor or blocking diode required ? cons tant - current/constant - voltage op eration with thermal regulation to maximize charge rate without risk of overheating ? 8 a supply current in shutdown ? drainage charge current thermal regulation status outp uts for led or system interface ? indica tes charge and fa ult conditions ? consumption available in tdfn - 10 package ? rohs compliant and 100% lead (pb) - free typical application circuit i charg =1000/rset marking information device marking package shipping lp 28012 lps lp 2 8012 xxxx qv : tdfn - 10 3k/reel 2k battery vin 1 0uf 1uf rset lp280 12 stat1 2 gnd 5 stat2 3 vin 1 batt 10 en 8 iset 6
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 2 of 10 functional pin description package type pin configurations tdfn - 10 pin description pin pin n o. description 4 ,7, 9 nc no connector. 6 iset charge current program, charge current monitor and shutdown pin. the charge current is pro grammed by connecting a 1% resistor (r prog )t o ground. when charging in constant - current mode, this pin servos to 1v. in all modes, the vo ltage on this pin can be used to measure the charge current using the following formula . iset= 1000 /r iset . 5 , 11 gnd vss is the connection to system ground. 1 vin vin is the input power source. connect to a wall adapter. 10 batt bat is the connection to the battery. typically a 1 0 f tantalum capacitor is needed for stability when there is no battery attached. when a battery is attached, only a 0.1f ceramic capacitor is required. 3 stat 2 open - drain charge status output. when the battery is charging, the sta t pin is pulled high by an internal n - channel mosfet. when the charge cycle is completed, the pin is pulled low. 2 stat 1 open - drain charge status output. when the battery is charging, the stat pin is pulled low by an internal n - channel mosfet. when the c harge cycle is completed, the pin is pulled high. 8 en chip enable pin. charging when the pin voltage is floating and high, discharge when the pin in low voltage.
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 3 of 10 function block diagram 8 2 3 6 5 10 1 schmitt ce ca ma va c 1 c 2 c 3 ref 1 .22v stat 1 stat 2 shdn to bat 2 .9 v vcc 3 a r 3 1 v r 4 0 .1 v r 5 set set gnd r 2 r 1 bat vcc 5 a 1200x 1 x + + + + + + - - - - - - absolute maximum ratings ? input voltage to gnd (v in ) ------------------------------------------- -- ---------------------------------- 3.9 v to 7 v ? bat, iset, stat (v x ) -------------------------------------------- - -------------------------------- 0.3v to v in +0.3v ? bat short - circ uit duration ------------------------------------- - ------ -- -------------------------------- continuous ? bat pin current ------------------------------------------------ - -- --- ---------------------------------------- 1 2 00ma ? maximum junction temperature ----- -------------------------- ----------------------------------------------- 125c ? operating junction temperature range (t j ) ----------------------------------------------------- - 40 to 85c ? maximum sold ering temperature (at leads, 10 sec) ----------- ------- ----------------------------------- 260c thermal information ? maximum power dissipation (p d ,ta<40 c ) ------------------ --- -------------------------------------------- 1.5 w ? thermal resistance (ja) ------------------------------------------ -- ---------------- ----------------------------- 46 /w lp 28012
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 4 of 10 electrical characteristics (t he specifications which apply over the full operating temperature range, otherwise specifications are at ta = 25 c. vcc = 5v, unless otherwise noted. ) symbol parameter conditions min typ. max units vin adapter /usb volt age range 2.65 5 7 v icc input supply current charge mode, r iset = 10k 300 2000 ua standby mode (charge terminated) 200 500 shutdown mode (riset not connected, vcc < vbat, or vcc < vuv) 25 50 vfloat regulated output (float) voltage 0c ta 85c, ibat = 40ma 4.158 4.2 4.242 v ibat bat pin current r iset = 1 k, current mode 100 0 ma r iset = 2k, current mode 500 standby mode, vbat = 4.2v shutdown mode (r iset not connected) sleep mode, vcc = 0v 0 - 2.5 1 1 -6 2 2 ua itri kl trickle charge current vbat < vtrikl, r iset = 2k 60 m a vtrikl trickle charge threshold voltage r iset = 10k, vbat rising 2.8 2.9 3.0 v vtrhys trickle charge hysteresis voltage r iset = 10k 120 mv vuv vcc under voltage lockout threshold from v cc low to high 3. 9 v vuvhys vcc under voltage lockout hysteresis 150 200 300 mv vmsd manual shutdown threshold voltage iset pin rising 2 v iset pin falling 2.2 v vasd vcc C vbat lockout threshold voltage vcc from low to high 70 100 140 mv vcc from high to low 5 30 50 mv iterm c/10 termination current threshold r iset = 10k 0.085 0.10 0.115 ma/ma r iset = 2k 0.085 0.10 0.115 ma/ma v iset iset pin voltage r iset = 10k, current mode 2 v i stat stat pin weak pull - down current v stat = 5v 5 ua v stat stat pin output low voltage i stat = 5ma 0.35 0.6 v vre stat recharge battery threshold voltage vfloat - vre stat 100 150 200 mv tlim junction temperature in constant temperature mode 120 c ron power fet on resistance (between vcc and bat) 600 m tss soft - start time ibat = 0 to ibat = 8 5 0 v/r iset 1 00 us i iset iset pin pull - up current 150 ua
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 5 of 10
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 6 of 10 application information the lp 28012 is a single cell lithium - ion battery charger using a constant - current/constant - voltage algorithm. it can deliver up to 12 00ma of charge cu rrent (using a good thermal pcb layout) with a final float voltage accuracy of 1%. the lp 28012 includes an internal p - channel power mosfet and thermal regulation circuitry. no blocking diode or external current sense resistor is required; thus, the basic charger circuit requires only two external com ponents. furthermore, the lp 28012 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% is et ram resistor is connected from the iset pin to ground or when a battery is connected to the charger output. if the bat pin is less than 2.9v, the charger enters trickle charge mode. in this mode, the lp 28012 supplies approximately 1/10 the iset rammed c harge current to bring the battery volt age up to a safe level for full current charging. (note: the lp 28012 does not include this trickle charge feature). when the bat pin voltage rises above 2.9v, the charger enters constant - current mode, where the iset rammed charge current is supplied to the battery. when the bat pin approaches the final float voltage (4.2v), the lp 28012 enters constant - voltage mode and the charge current begins to decrease. when the charge current drops to 1/10 of the iset rammed valu e, the charge cycle ends. iset ramming charge current the charge current is iset rammed using a single resistor from the iset pin to ground. the battery charge current is 6 00 times the current out of the iset pin. the iset ram resistor and the charge cu rrent are calculated using the following equations: rset= 1 0 00 v/ichg ichg= 1 0 00 v/rset the charge current out of the bat pin can be determined at any time by monitoring the iset pin voltage using the following equation: ibat= vset x 5 0 0/rset note: vset is 2v olts . charge termination a charge cycle is termi nated when the charge current falls to 1/10th the iset rammed value after the final float voltage is reached. this condition is detected by using an internal, filtered comparator to monitor the iset pin. when the iset pin voltage falls below 100mv 1 for lon ger than t term (typically 1ms), charging is terminated. the charge current is latched off and the lp 28012 enters standby mode, where the input supply current drops to 200a. (note: c/10 termination is disabled in trickle charging and thermal limiting modes ). when charging, transient loads on the bat pin can cause the iset pin to fall below 2 00mv for short periods of time before the dc charge current has dropped to 1/10th the iset rammed value. the 1ms filter time (t term ) on the termination comparator ensur es that transient loads of this nature do not result in premature charge cycle termi nation. once the average charge current drops below 1/10th the iset rammed value, the lp 28012 terminates the charge cycle and ceases to provide any current through the bat pin. in this state, all loads on the bat pin must be supplied by the battery. the lp 28012 constantly monitors the bat pin voltage in standby mode. if this voltage drops below the 4.05v recharge threshold (v re stat ), another charge cycle be gins and curren t is once again supplied to the battery. to manually 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 iset pin. figure 1 shows the state diagram of a typi cal charge cycle. charge status indicator ( stat ) the charge status output has three different states: strong pull - down (~10ma), weak pull - down (~20a) and high impedance. the strong pull - down state indicates that the lp 28012 is in a charge cycle. once th e charge cycle has terminated, the pin state is determined by under voltage lockout conditions. a weak pull - down indicates that v cc meets the uvlo conditions and the lp 28012 is ready to charge. high impedance indicates that the lp 28012 is in under voltage lockout mode: either v cc is less than 100mv above the bat pin voltage or insufficient voltage is applied to the v cc pin. a microprocessor can be used to distin guish between these three
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 7 of 10 states this method is dis cussed in the applications information secti on. function stat1(p in 2 ) stat2(p in 3 ) charging low high charge end high low thermal limiting an internal thermal feedback loop reduces the iset rammed charge current if the die temperature attempts to rise above a preset value of approximately 120c. this feature protects the lp 28012 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 lp 28012 . the charge current can be set according to typical (not wors t - case) ambient temperature with the assurance that the charger will automatically reduce the current in worst - case conditions. tdfn power consid erations are discussed further in the applications informa tion section. under voltage lockout (uvlo) an int ernal under voltage lockout circuit monitors the input voltage and keeps the charger in shutdown mode until v cc rises above the under voltage lockout threshold. the uvlo circuit has a built - in hysteresis of 200mv. furthermore, to protect against reverse cu rrent in the power mosfet, the uvlo circuit keeps the charger in shutdown mode if v cc falls to within 30mv of the battery voltage. if the uvlo comparator is tripped, the charger will not come out of shutdown mode until v cc rises 100mv above the battery vol tage. manual shutdown at any point in the charge cycle, the lp 28012 can be put into shutdown mode by removing r iset thus floating the iset pin. this reduces the battery drain current to less than 2a and the supply current to less than 50a. a new charge cycle can be initiated by reconnecting the iset ram resistor. in manual shutdown, the stat pin is in a weak pull - down state as long as v cc is high enough to exceed the uvlo conditions. the stat pin is in a high impedance state if the lp 28012 is in under v oltage lockout mode: either v cc is within 100mv of the bat pin voltage or insufficient voltage is applied to the v cc pin. automatic recharge once the charge cycle is terminated, the lp 28012 continu ously monitors the voltage on the bat pin using a com p arator with a 2ms filter time (t recharge ). a charge cycle restarts when the battery voltage falls below 4.05v (which corresponds to approximately 80% to 90% battery capac ity). this ensures that the battery is kept at or near a fully charged condition and eliminates the need for periodic charge cycle initiations. stat output enters a strong pull - down state during recharge cycles. power dissipation the conditions that cause the lp 28012 battery charger to reduce charge current through thermal feedback can be approximated by considering the total power dissipated in the ic. for high charge currents, the lp 28012 power dissipation is approximately: where p d is the total power dissipated within the ic, adp is the input supply voltage, vbat is the battery volta ge, ibat is the charge current and pd_buck is the power dissipation due to the regulator. pd_ buck can be calculated as: where voutb is the regulated output of the switching regulator, ioutb is the regulator load and is the regulator efficiency at that particular load. it is not necessary to perform worst - case power dissipation scenarios because the lp 28012 will automatically reduce the charge current to maintain the die temperature at approximately 125 c. however, the approximate ambient temperature at which the thermal feedback begins to p rotect the ic is:
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 8 of 10 example: consider the extreme case when an lp 28012 is operating from a 6v supply providing 250ma to a 3v li - ion battery, the switching regulator and the ldo are off. the ambient temperature above which the lp 28012 will begin to reduce the 250ma charge current is approximately: (correctly soldered to a 2500mm 2 double - sided 1 oz. copper board, the lp 28012 has a thermal resistance of approximately 43c /w.) t = if there is more power dissipation due to the switching regulator or the ldo, the thermal regulation will kick in at a somewhat lower temperature than this. in the above circumstances, the lp 28012 can be used above 82.75c, but the charge current will be reduced from 250ma . the approximate current at a given ambient temperature can be calculated: o o o note: 1v = 1j/c = 1w/a furthermore, the voltage at the iset pin will change proportionally with the charge current as discussed in the iset ramming charge current secti on.
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 9 of 10 pcb layout considerations it is important to pay special attention to the pcb layout. the following provides some guidelines: ? to obtain optimal performance, the decoupling capacitor from vcc to v(in) a nd the output filter capacit ors from out to vss should be placed as close as possible to the bq24080, with short trace runs to both signal a nd vss pins. the vss pin should have short trace runs to the gnd pin. ? all low - current vss connections should be kept separate from the high - cu rren t charge or discharge paths from the battery. use a single - point ground technique incorporating both t he small - signal ground path and the power ground path. ? the high - current charge paths into in and from the out pins must be sized appropriately for t he maximum charge current in order to avoid voltage drops in these traces. ? the lp 28012 is packaged in a thermally enhanced mlp package. the pa ckage includes a thermal pad to provide an effective thermal contact between the device and the printed circuit boar d (pcb). full pcb design guidelines for this package are provided in the application note entitled, qfn/son pcb attachment
prelimin ary datasheet lp 28 0 12 lp 28012 C 0 0 feb . - 201 4 email: marketing@lowpowersemi.com www.lowpowersemi.com page 10 of 10 packag ing information
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