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lt3652hv 1 3652hvfb for more information www.linear.com/lt3652hv typical application description power tracking 2a battery charger the lt ? 3652hv is a complete monolithic step-down bat - tery charger that operates over a 4.95v to 34v input range. the lt3652hv provides a constant-current/constant-voltage charge characteristic, with maximum charge current externally programmable up to 2a. the charger employs a 3.3v loat voltage feedback reference, so any desired battery loat voltage up to 18v can be programmed with a resistor divider. the lt3652hv employs an input voltage regulation loop, which reduces charge current if the input voltage falls below a programmed level, set with a resistor divider. when the lt3652hv is powered by a solar panel, the input regulation loop is used to maintain the panel at peak output power. the lt3652hv can be conigured to terminate charging when charge current falls below 1/10 of the programmed maximum (c/10). once charging is terminated, the lt3652hv enters a low-current (85a) standby mode. an auto-recharge featu re starts a new charging cycle if the battery voltage falls 2.5% below the programmed loat voltage. the lt3652hv also contains a programmable safety timer, used to terminate charging after a desired time is reached. this allows top-off charging at currents less than c/10. features applications n input supply voltage regulation loop for peak power tracking in (mppt) solar applications n wide input voltage range: 4.95v to 34v (40v abs max) n programmable charge rate up to 2a n user selectable termination: c/10 or on-board termination timer n resistor programmable float voltage up to 18v accommodates 4-cell li-ion/polymer, 5-cell lifepo 4 , lead-acid chemistries n parallelable for higher output current n 1mhz fixed frequency n 0.5% float voltage reference accuracy n 5% charge current accuracy n 2.5% c/10 detection accuracy n binary-coded open-collector status pins n thermally enhanced 3mm 3mm dfn and mse packages n solar powered applications n remote monitoring stations n portable handheld instruments n 12v to 24v automotive systems n battery charging from current limited adapter l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks and powerpath is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. v in_reg loop servos maximum charge current to prevent ac adapter output from drooping lower than 24v 5-cell lifepo 4 charger (18v at 1.5a) with c/10 termination powered by inexpensive 24vdc/1a unregulated wall adapter. sw v in ac adapter input 24vdc at 1a v in_reg v fb boost sense bat ntc timer 1f 10v 1n4148 127k 3652 ta01a r110k b = 3380 10f 20h 10f 5-cell lifepo 4 pack (18v float) systemload + lt3652hv 44.2k 750k mbrs340 d3 mbrs340 51.1k shdn chrg fault 150k 665k 0.068 adapter output current (a) 0 0.2 adapter output voltage (v) 12 15 18 3330 27 24 21 0.6 1 1.2 3652 ta01b 36 0.4 0.8 1.6 1.4 2 1.8 1a/24vdc unregulated adapter i vs v characteristic downloaded from: http:///
lt3652hv 2 3652hvfb for more information www.linear.com/lt3652hv pin configuration absolute maximum ratings voltages: v in ........................................................................ 40v v in_reg , shdn , chrg , fault ............ v in + 0.5v, 40v sw ........................................................................ 40v sw-v in .................................................................4.5v boost ................................................... sw+10v, 50v bat, sense ........................................................... 20v (note 1) order information lead free finish tape and reel part marking* package description temperature range lt3652hvedd#pbf lt3652hvedd#trpbf lfrg 12-lead plastic dfn 3mm 3mm C40c to 125c lt3652hvidd#pbf lt3652hvidd#trpbf lfrg 12-lead plastic dfn 3mm 3mm C40c to 125c lt3652hvemse#pbf lt3652hvemse#trpbf 3652hv 12-lead plastic msop C40c to 125c lt3652hvimse#pbf lt3652hvimse#trpbf 3652hv 12-lead plastic msop C40c to 125c consult ltc marketing for parts speciied with wider operating tempera ture ranges. *the temperature grade is identiied by a label on the shipping c ontainer. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speciications, go to: http://www.linear.com/tapeandreel/ . some packages are available in 500 unit reels through designated sales channels with #trmpbf sufix. top view dd package 12-lead (3mm 3mm) plastic dfn 12 11 8 9 10 45 3 2 1 swboost sense bat ntc v fb v in v in_reg shdnchrg fault timer 6 7 13 gnd 12 3 4 5 6 v in v in_reg shdnchrg fault timer 1211 10 9 8 7 swboost sense bat ntc v fb top view 13 gnd mse package 12-lead plastic msop t jmax = 125c, ja = 43c/w, jc = 3c/w exposed pad (pin 13) is gnd, must be soldered to pcb t jmax = 125c, ja = 43c/w, jc = 3c/w exposed pad (pin 13) is gnd, must be soldered to pcb bat-sense ......................................... C0.5v to +0.5v ntc, timer, ........................................................ 2.5v v fb .......................................................................... 5v operating junction temperature range (note 2) ............................................. C40c to 125c storage temperature range ................... C65c to 150c downloaded from: http:///
lt3652hv 3 3652hvfb for more information www.linear.com/lt3652hv symbol parameter conditions min typ max units v in v in operating range v in start voltage v bat = 4.2 (notes 3, 4) v bat = 4.2 (note 4) l l 4.95 7.5 34 v v v in(ovlo) ovlo threshold ovlo hysteresis v in rising l 34 35 1 40 v v v in(uvlo) uvlo threshold uvlo hysteresis v in rising 4.6 0.2 4.95 v v v fb(flt) float voltage reference (note 6) l 3.282 3.26 3.3 3.318 3.34 v v v recharge recharge reference threshold voltage relative to v fb(flt) (note 6) 82.5 mv v fb(pre) reference precondition threshold v fb rising (note 6) 2.3 v v fb(prehyst) reference precondition threshold hysteresis voltage relative to v fb(pre) (note 6) 70 mv v in_reg(th) input regulation reference v fb = 3v; v sense C v bat = 50mv l 2.65 2.7 2.75 v i in_reg input regulation reference bias current v in_reg = v in_reg(th) l 35 100 na i vin operating input supply current cc/cv mode, i sw = 0 standby mode shutdown ( shdn = 0) l 2.5 85 15 3.5 ma a a i boost boost supply current switch on, i sw = 0, 2.5 < v (boost C sw) < 8.5 20 ma i boost/ i sw boost switch drive i sw = 2a 30 ma/a v sw(on) switch-on voltage drop v in C v sw , i sw = 2a 350 mv i sw(max) switch current limit l 2.5 3 a v sense(pre) precondition sense voltage v sense C v bat ; v fb = 2v 15 mv v sense(dc) maximum sense voltage v sense C v bat ; v fb = 3v (note 7) l 95 100 105 mv v sense(c/10) c/10 trigger sense voltage v sense C v bat , falling l 7.5 10 12.5 mv i bat bat input bias current charging terminated 0.1 1 a i sense sense input bias current charging terminated 0.1 1 a i vfb v fb input bias current charging terminated 65 na i vfb v fb input bias current cv operation (note 5) 110 na v ntc(h) ntc range limit (high) v ntc rising l 1.25 1.36 1.45 v v ntc(l) ntc range limit (low) v ntc falling l 0.27 0.29 0.315 v v ntc(hyst) ntc threshold hysteresis % of threshold 20 % r ntc(dis) ntc disable impedance impedance to ground l 250 500 k i ntc ntc bias current v ntc = 0.8v l 47.5 50 52.5 a v shdn shutdown threshold rising l 1.15 1.2 1.25 v v shdn (hyst) shutdown hysteresis 120 mv i shdn shdn input bias current C10 na v chrg , v fault status low voltage 10ma load l 0.4 v i timer charge/discharge current 25 a v timer(dis) timer disable threshold l 0.1 0.25 v the l denotes the speci?cations which apply over the full operating junctio n temperature range, otherwise speci?cations are at t a = 25c (note 2). v in = 20v, boost ? sw = 4v, shdn = 2v, v fb = 3.3v, c timer = 0.6 8 f. electrical characteristics downloaded from: http:///
lt3652hv 4 3652hvfb for more information www.linear.com/lt3652hv symbol parameter conditions min typ max units t timer full charge cycle timeout 3 hr precondition timeout 22.5 min timer accuracy l C10 10 % f o operating frequency 1 mhz dc duty cycle range continuous operation l 15 90 % the l denotes the speci?cations which apply over the full operating junctio n temperature range, otherwise speci?cations are at t a = 25c (note 2). v in = 20v, boost ? sw = 4v, shdn = 2v, v fb = 3.3v, c timer = 0.6 8 f. 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 lt3652hv is tested under pulsed load conditions such that t j ? t a . the lt3652hve is guaranteed to meet performance speciications from 0c to 85c junction temperature. speciications over the C40c to 125c operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. the lt3652hvi speciications are guaranteed over the full C40c to 125c operating junction temperature range. note that the maximum ambient temperature consistent with these speciications is determined by speciic operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. note 3: v in minimum voltages below the start threshold are only supported if (v boost -v sw ) > 2v. note 4: this parameter is valid for programmed output battery loat voltages 4.2v. v in operating range minimum is 0.75v above the programmed output battery loat voltage (v bat(flt) + 0.75v). v in start voltage is 3.3v above the programmed output battery loat voltage (v bat(flt) + 3.3v). note 5: output battery loat voltage (v bat(flt) ) programming resistor divider equivalent resistance = 250k compensates for input bias current. note 6: all v fb voltages measured through 250k series resistance. note 7: v sense(dc) is reduced by thermal foldback as junction temperature approaches 125c. electrical characteristics downloaded from: http:///
lt3652hv 5 3652hvfb for more information www.linear.com/lt3652hv typical performance characteristics switch forward drop (v in ? v sw ) vs temperature cc/cv charging; sense pin bias current vs v sense c/10 threshold (v sense ?v bat ) vs temperature v fb reference voltage vs temperature v in standby mode current vs temperature switch drive (i sw /i boost ) vs switch current t j = 25c, unless otherwise noted. temperature (c) C50 v fb (flt) 3.296 3.298 3.300 3.302 0 50 75 3652 g01a 3.304 C25 25 100 125 temperature (c) C50 65 i vin current (a) 70 75 80 100 90 0 50 75 3652 g02 9585 C25 25 100 switch current (a) 0 i sw /i boost 18 24 30 36 1.6 12 6 0 21 27 33 15 9 3 0.4 0.8 1.2 0.2 1.8 0.6 1.0 1.4 2.0 3652 g03 temperature (c) C50 320 v sw(on) (mv) 340 360 380 480 420 0 50 75 3652 g04 440 460400 C25 25 100 125 i sw = 2a v sense (v) 0 C350 i sense (a) C250 C150 C50 100 1 2 2.5 50 C300 C200 C100 0 0.5 1.5 3652 g05 v bat = v bat(pre) v bat = v bat(flt) temperature (c) C50 8 v sense(c/10) (mv) 9 10 11 12 0 50 75 3652 g06 C25 25 100 125 temperature (c) C50 v in_reg(th) (v) 2.680 2.685 2.690 2.7152.710 2.705 2.700 2.695 0 50 75 3652 g01 2.720 C25 25 100 125 v in_reg threshold vs temperature: i chg at 50% downloaded from: http:///
lt3652hv 6 3652hvfb for more information www.linear.com/lt3652hv typical performance characteristics maximum charge current (v sense ?v bat ) vs temperature thermal foldback ? maximum charge current (v sense ?v bat ) vs temperature cc/cv charging; bat pin bias current vs v bat t a = 25c, unless otherwise noted. temperature (c) C50 99.0 v sense(dc) (mv) 99.2 99.6 99.8 100.0 101.0 100.4 0 50 75 3652 g07 99.4 100.6 100.8100.2 C25 25 100 125 v fb = 3v temperature (c) 0 v sense(dc) (mv) 40 8020 60 100 120 45 65 85 105 125 35 135 25 55 75 95 115 3652 g08 v bat (v) 0 C0.4 i bat (ma) 0.0 0.4 0.8 2.2 1.6 1 2 2.5 2.01.2 C0.2 0.2 0.6 1.0 1.81.4 0.5 1.5 3 3652 g09 v bat(flt) v in_reg (v) 2. 65 v sense(dc) (mv) 0 20 8060 40 2. 67 2. 69 2. 7 3652 g10 100 2. 66 2. 68 2. 72 2. 71 2. 73 2. 74 2. 75 v bat(flt) (v) 0 2 0 i rfb (a) 86 10 12 18 3652 g11 42 6 4 8 10 12 16 14 time (minutes) 0 efficiency (%) charge current (a); power loss (w) 0 0.5 2.0 2.51.5 1.0 40 80 100 3652 g12 3.0 35 45 7565 55 9585 20 60 140 120 160 180 200 chargecurrent efficiency powerloss v in = 20v maximum charge current (v sense ?v bat ) vs v in_reg voltage v float programming resistor current vs v float for 2-resistor network charge current, ef?ciency, and power loss vs time (i chg(max) = 2a; v float = 8.2v) charger ef?ciency vs battery voltage (i chg = 2a) v bat (v) 70 efficiency (%) 76 80 82 84 86 8874 72 78 90 5 7 9 11 13 4 14 15 3 6 8 10 12 3652 g13 v in = 20v with input blocking diode battery bias current with charger disabled (i bat + i sense + i boost + i sw ) v bat (v) 0 0 battery current (a) 2 6 8 10 12 18 3652 f14 4 6 2 14 8 4 16 10 18 12 14 16 v in floating v in = 20v v shdn = 0v downloaded from: http:///
lt3652hv 7 3652hvfb for more information www.linear.com/lt3652hv pin functions v in (pin 1): charger input supply. v in operating range is 4.95v to 34v. v in must be 3.3v greater than the pro - grammed output battery loat voltage (v bat(flt) ) for reli - able start-up. (v in C v bat(flt) ) 0.75v is the minimum operating voltage, provided (v boost C v sw ) 2v. i vin ~ 85a after charge termination. this pin is typically con - nected to the cathode of a blocking diode. v in_reg (pin 2): input voltage regulation reference. maxi - mum charge current is reduced when this pin is below 2.7v. connecting a resistor divider from v in to this pin enables programming of minimum operational v in voltage. this is typically used to program the peak power voltage for a solar panel. the lt3652hv servos the maximum charge current required to maintain the programmed operational v in voltage, through maintaining the voltage on v in_reg at or above 2.7v. if the voltage regulation feature is not used, connect the pin to v in . shdn (pin 3): precision threshold shutdown pin. the enable threshold is 1.2v (rising), with 120mv of input hysteresis. when in shutdown mode, all charging functions are disabled. the precision threshold allows use of the shdn pin to incorporate uvlo functions. if the shdn pin is pulled below 0.4v, the ic enters a low current shutdown mode where v in current is reduced to 15a. typical shdn pin input bias current is 10na. if the shutdown function is not desired, connect the pin to v in . chrg (pin 4): open-collector charger status output; typically pulled up through a resistor to a reference volt - age. this status pin can be pulled up to voltages as high as v in when disabled, and can sink currents up to 10ma when enabled. during a battery charging cycle, if required charge current is greater than 1/10 of the programmed maximum current (c/10), chrg is pulled low. a tem - perature fault also causes this pin to be pulled low. after c/10 charge termination or, if the internal timer is used for termination and charge current is less than c/10, the chrg pin remains high-impedance. fau lt (pin 5): open-collector charger status output; typically pulled up through a resistor to a reference volt - age. this status pin can be pulled up to voltages as high as v in when disabled, and can sink currents up to 10ma when enabled. this pin indicates fault conditions during a battery charging cycle. a temperature fault causes this pin to be pulled low. if the internal timer is used for termina - tion, a bad battery fault also causes this pin to be pulled low. if no fault conditions exist, the fa u lt pin remains high-impedance. timer (pin 6): end-of-cycle timer programming pin. if a timer-based charge termination is desired, connect a capacitor from this pin to ground. full charge end-of- cycle time (in hours) is programmed with this capacitor following the equation: t eoc = c timer ? 4.4 ? 10 6 a bad battery fault is generated if the battery does not achieve the precondition threshold voltage within one- eighth of t eoc , or: t pre = c timer ? 5.5 ? 10 5 a 0.68f capacitor is typically used, which generates a timer eoc at three hours, and a precondition limit time of 22.5 minutes. if a timer-based termination is not desired, the timer function is disabled by connecting the timer pin to ground. with the timer function disabled, charging terminates when the charge current drops below a c/10 threshold, or i chg(max) /10 v fb (pin 7): battery float voltage feedback reference. the charge function operates to achieve a inal loat voltage of 3.3v on this pin. output battery loat voltage (v bat(flt) ) is programmed using a resistor divider. v bat(flt) can be programmed up to 18v. the auto-restart feature initiates a new charging cycle when the voltage at the v fb pin falls 2.5% below the loat voltage reference. the v fb pin input bias current is 110na. using a resistor divider with an equivalent input resistance at the v fb pin of 250k compensates for input bias current error. required resistor values to program desired v bat(flt) follow the equations: r1 = (v bat(flt) ? 2.5 ? 10 5 )/3.3 () r2 = (r1 ? 2.5 ? 10 5 )/(r1 - (2.5 ? 10 5 )) () r1 is connected from bat to v fb , and r2 is connected from v fb to ground. downloaded from: http:///
lt3652hv 8 3652hvfb for more information www.linear.com/lt3652hv ntc (pin 8): battery temperature monitor pin. this pin is the input to the ntc (negative temperature coeficient) thermistor temperature monitoring circuit. this function is enabled by connecting a 10k, b = 3380 ntc thermistor from the ntc pin to ground. the pin sources 50a, and monitors the voltage across the 10k thermistor. when the voltage on this pin is above 1.36 (t < 0c) or below 0.29v (t > 40c), charging is disabled and the chrg and fa u lt pins are both pulled low. if internal timer termina - tion is being used, the timer is paused, suspending the charging cycle. charging resumes when the voltage on ntc returns to within the 0.29v to 1.36v active region. there is approximately 5c of temperature hysteresis associated with each of the temperature thresholds. the temperature monitoring function remains enabled while the thermistor resistance to ground is less than 250k, so if this function is not desired, leave the ntc pin unconnected. bat (pin 9): charger output monitor pin. connect a 10f decoupling capacitance (c bat ) to ground. depend - ing on application requirements, larger value decoupling capacitors may be required. the charge function operates to achieve the programmed output battery loat voltage (v bat(flt) ) at this pin. this pin is also the reference for the current sense voltage. once a charge cycle is termi - nated, the input bias current of the bat pin is reduced to < 0.1a, to minimize battery discharge while the charger remains connected. sense (pin 10): charge current sense pin. connect the inductor sense resistor (r sense ) from the sense pin to the bat pin. the voltage across this resistor sets the average charge current. the maximum charge current (i chg(max) ) corresponds to 100mv across the sense resistor. this resistor can be set to program maximum charge cur - rent as high as 2a. the sense resistor value follows the relation: r sense = 0.1/i chg(max) () once a charge cycle is terminated, the input bias current of the sense pin is reduced to < 0.1a, to minimize battery discharge while the charger remains connected. boost (pin 11): bootstrapped supply rail for switch drive. this pin facilitates saturation of the switch transistor. connect a 1f or greater capacitor from the boost pin to the sw pin. operating range of this pin is 0v to 8.5v, referenced to the sw pin. the voltage on the decoupling capacitor is refreshed through a rectifying diode, with the anode connected to either the battery output voltage or an external source, and the cathode connected to the boost pin. sw (pin 12): switch output pin. this pin is the output of the charger switch, and corresponds to the emitter of the switch transistor. when enabled, the switch shorts the sw pin to the v in supply. the drive circuitry for this switch is bootstrapped above the v in supply using the boost supply pin, allowing saturation of the switch for maximum eficiency. the effective on-resistance of the boosted switch is 0.175. gnd (pin 13): ground reference and backside exposed lead frame thermal connection. solder the exposed lead frame to the pcb ground plane. pin functions downloaded from: http:///
lt3652hv 9 3652hvfb for more information www.linear.com/lt3652hv block diagram 3652 bd +C + C +C C + + C + C + C + C timer 10m 35v 0.1v offset 2.3v 4.6v resetenable countreset c/10 precondition 1.36v0.29v 46 a v in_reg boost v in sw sense bat v fb ntc v int 2.7v 1.3v 1v 0.15v 1.2v 3.3v 3.218v terminate 50 a 0.7v control logic ripple counter status timer osc. ntc 0.2v 125c count count osc 1mhz latch r s r s c-ea 30mv x2.25 10 r s 0.3v v c t die i th mode (timer or c/10) terminate rq s 2.7v uvlo ovlo C + fault chrg standby shdn v-ea + C + C + C + C standby standby + C + C + C + C downloaded from: http:///
lt3652hv 10 3652hvfb for more information www.linear.com/lt3652hv applications information overview lt3652hv is a complete monolithic, mid-power, multi- chemistry buck battery charger, addressing high input voltage applications with solutions that require a minimum of external components. the ic uses a 1mhz constant fre - quency, average-current mode step-down architecture. the lt3652hv incorporates a 2a switch that is driven by a bootstrapped supply to maximize efficiency during charging cycles. wide input range allows operation to full charge from voltages as high as 34v. a precision threshold shutdown pin allows incorporation of uvlo functionality using a simple resistor divider. the ic can also be put into a low-current shutdown mode, in which the input supply bias is reduced to only 15a. the lt3652hv employs an input voltage regulation loop, which reduces charge current if a monitored input voltage falls below a programmed level. when the lt3652hv is powered by a solar panel, the input regulation loop is used to maintain the panel at peak output power. the lt3652hv automatically enters a battery precondition mode if the sensed battery voltage is very low. in this mode, the charge current is reduced to 15% of the programmed maximum, as set by the inductor sense resistor, r sense . once the battery voltage reaches 70% of the fully charged float voltage, the ic automatically increases maximum charge current to the full programmed value. the lt3652hv can use a charge-current based c/10 termination scheme, which ends a charge cycle when the battery charge current falls to one tenth of the pro - grammed maximum charge current. the lt3652hv also contains an internal charge cycle control timer, for timer- based termination. when using the internal timer, the ic combines c/10 detection with a programmable time constraint, during which the charging cycle can continue beyond the c/10 level to top-off a battery. the charge cycle terminates when a specific time elapses, typically 3 hours. when the timer-based scheme is used, the ic also supports bad battery detection, which triggers a system fault if a battery stays in precondition mode for more than one eighth of the total charge cycle time. once charging is terminated, the lt3652hv automati - cally enters a low-current standby mode where supply bias currents are reduced to 85a. the ic continues to monitor the battery voltage while in standby, and if that voltage falls 2.5% from the full-charge float voltage, the lt3652hv engages an automatic charge cycle restart. the ic also automatically restarts a new charge cycle after a bad battery fault once the failed battery is removed and replaced with another battery. the lt3652hv contains provisions for a battery tem - perature monitoring circuit. this feature monitors battery temperature using a thermistor during the charging cycle. if the battery temperature moves outside a safe charg - ing range of 0c to 40c, the ic suspends charging and signals a fault condition until the temperature returns to the safe charging range. the lt3652hv contains two digital open-collector outputs, which provide charger status and signal fault conditions. these binary-coded pins signal battery charging, standby or shutdown modes, battery temperature faults, and bad battery faults. general operation (see block diagram) the lt3652hv uses average current mode control loop architecture, such that the ic servos directly to average charge current. the lt3652hv senses charger output voltage through a resistor divider via the v fb pin. the difference between the voltage on this pin and an internal 3.3v voltage reference is integrated by the voltage error amplifier (v-ea). this amplifier generates an error volt - age on its output (i th ), which corresponds to the average current sensed across the inductor current sense resistor, r sense , which is connected between the sense and bat pins. the i th voltage is then divided down by a factor of 10, and imposed on the input of the current error amplifier (c-ea). the difference between this imposed voltage and the current sense resistor voltage is integrated, with the resulting voltage (v c ) used as a threshold that is compared against an internally generated ramp. the output of this comparison controls the chargers switch. the i th error voltage corresponds linearly to average current sensed across the inductor current sense resistor, allowing maximum charge current control by limiting the effective voltage range of i th . a clamp limits this voltage to 1v which, in turn, limits the current sense voltage to 100mv. this sets the maximum charge current, or the current delivered while the charger is operating in con - downloaded from: http:///
lt3652hv 11 3652hvfb for more information www.linear.com/lt3652hv applications information stant-current (cc) mode, which corresponds to 100mv across r sense . the i th voltage is pulled down to reduce this maximum charge current should the voltage on the v in_reg pin falls below 2.7v (v in_reg(th) ) or the die tem - perature approaches 125c.if the voltage on the v fb pin is below 2.3v (v fb(pre) ), the lt3652hv engages precondition mode. during the precondition interval, the charger continues to operate in constant-current mode, but the maximum charge current is reduced to 15% of the maximum programmed value as set by r sense . when the charger output voltage approaches the float volt - age, or the voltage on the v fb pin approaches 3.3v (v fb(flt) ), the charger transitions into constant-voltage (cv) mode and charge current is reduced from the maximum value. as this occurs, the i th voltage falls from the limit clamp and servos to lower voltages. the ic monitors the i th volt - age as it is reduced, and detection of c/10 charge current is achieved when i th = 0.1 v . if the charger is configured for c/10 termination, this threshold is used to terminate the charge cycle. once the charge cycle is terminated, the chrg status pin becomes high-impedance and the charger enters low-current standby mode. the lt3652hv contains an internal charge cycle timer that terminates a successful charge cycle after a programmed amount of time. this timer is typically programmed to achieve end-of-cycle (eoc) in 3 hours, but can be con - figured for any amount of time by setting an appropriate timing capacitor value (c timer ). when timer termination is used, the charge cycle does not terminate when c/10 is achieved. because the chrg status pin responds to the c/10 current level, the ic will indicate a fully-charged battery status, but the charger continues to source low currents into the battery until the programmed eoc time has elapsed, at which time the charge cycle will terminate. at eoc when the charging cycle terminates, if the battery did not achieve at least 97.5% of the full float voltage, charging is deemed unsuccessful, the lt3652hv re-initiates, and charging continues for another full timer cycle. use of the timer function also enables bad-battery detec - tion. this fault condition is achieved if the battery does not respond to preconditioning, such that the charger remains in (or enters) precondition mode after 1/8th of the programmed charge cycle time. a bad battery fault halts the charging cycle, the chrg status pin goes high- impedance, and the fault pin is pulled low. when the lt3652hv terminates a charging cycle, whether through c/10 detection or by reaching timer eoc, the average current mode analog loop remains active, but the internal float voltage reference is reduced by 2.5%. because the voltage on a successfully charged battery is at the full float voltage, the voltage error amp detects an over-voltage condition and i th is pulled low. when the voltage error amp output drops below 0.3v, the ic enters standby mode, where most of the internal circuitry is dis - abled, and the v in bias current is reduced to 85a. when the voltage on the v fb pin drops below the reduced float reference level, the output of the voltage error amp will climb, at which point the ic comes out of standby mode and a new charging cycle is initiated. v in input supply the lt3652hv is biased through a reverse-current block - ing element from the charger input supply to the v in pin. this supply provides large switched currents, so a high- quality, low esr decoupling capacitor is recommended to minimize voltage glitches on v in . the v in decoupling capacitor (c vin ) absorbs all input switching ripple current in the charger, so it must have an adequate ripple current rating. rms ripple current (i cvin(rms) ) is: i cvin(rms) ? i chg(max) ? (v bat / v in )?([v in / v bat ] C 1) 1/2 , where i chg(max) is the maximum average charge current (100mv/r sense ). the above relation has a maximum at v in = 2 ? v bat , where: i cvin(rms) = i chg(max) /2. the simple worst-case of ? ? i chg(max) is commonly used for design. downloaded from: http:///
lt3652hv 12 3652hvfb for more information www.linear.com/lt3652hv bulk capacitance is a function of desired input ripple volt - age ( v in ), and follows the relation: c in(bulk) = i chg(ma x) ? ( v bat /v in )/ v in (f) input ripple voltages above 0.1v are not recommended. 10f is typically adequate for most charger applica - tions.charge current programming the lt3652hv charger is configurable to charge at aver - age currents as high as 2a. maximum charge current is set by choosing an inductor sense resistor (r sense ) such that the desired maximum average current through that sense resistor creates a 100mv drop, or: r sense = 0.1/i chg(ma x) where i chg(max) is the maximum average charge cur - rent. a 2a charger, for example, would use a 0.05 sense resistor. boost supply the boost bootstrapped supply rail drives the internal switch and facilitates saturation of the switch transistor. operating range of the boost pin is 0v to 8.5v, as refer - enced to the sw pin. connect a 1f or greater capacitor from the boost pin to the sw pin. the voltage on the decoupling capacitor is refreshed through a diode, with the anode connected to either the battery output voltage or an external source, and the cathode connected to the boost pin. rate the diode average current greater than 0.1a, and reverse voltage greater than v in(max) . to refresh the decoupling capacitor with a rectifying diode from the battery with battery float voltages higher than 8.4v, a >100ma zener diode can be put in series with the rectifying diode to prevent exceeding the boost pin operating voltage range. applications information figure 1. programming maximum charge current using r sense sw boost sense bat r sense lt3652hv 3652 f01 figure 2. zener diode reduces refresh voltage for boost pin sw boost sense bat lt3652hv 3652 f02 v in / b oost start-up requirement the lt3652hv operates with a v in range of 4.95v to 34v, however, a start-up voltage requirement exists due to the nature of the non-synchronous step-down switcher topology used for the charger. if there is no boost supply available, the internal switch requires (v in C v sw ) 3.3v to reliably operate. this requirement does not exist if the boost supply is available and (v boost C v sw ) > 2v. when an lt3652hv charger is not switching, the sw pin is at the same potential as the battery, which can be as high as v bat(flt) . as such, for reliable start-up, the v in supply must be at least 3.3v above v bat(flt) . once switch - ing begins and the boost supply capacitor gets charged such that (v boost C v sw ) > 2v, the v in requirement no longer applies. downloaded from: http:///
lt3652hv 13 3652hvfb for more information www.linear.com/lt3652hv applications information in low v in applications, the boost supply can be powered by an external source for start-up, eliminating the v in start-up requirement.v b at output decoupling an lt3652hv charger output requires bypass capacitance connected from the bat pin to ground (c bat ). a 10f ceramic capacitor is required for all applications. in systems where the battery can be disconnected from the charger output, additional bypass capacitance may be desired for visual indication for a no-battery condition (see the status pins section). if it is desired to operate a system load from the lt3652hv charger output when the battery is disconnected, additional bypass capacitance is required. in this type of application, excessive ripple and/or low amplitude oscillations can oc - cur without additional output bulk capacitance. for these applications, place a 100f low esr non-ceramic capacitor (chip tantalum or organic semiconductor capacitors such as sanyo os-cons or poscaps) from bat to ground, in parallel with the 10f ceramic bypass capacitor. this additional bypass capacitance may also be required in systems where the battery is connected to the charger with long wires. the voltage rating of c bat must meet or exceed the battery float voltage. inductor selection the primary criterion for inductor value selection in an lt3652hv charger is the ripple current created in that inductor. once the inductance value is determined, an inductor must also have a saturation current equal to or exceeding the maximum peak current in the inductor. an inductor value (l), given the desired amount of peak-to- peak inductor ripple current ( i l ) can be approximated using the relation: l = 10 ?r sense i l i chg(max) ? v bat(flt) ? 1C v bat(flt) v in(max) ?? ?? ?? ?? h ( ) in the above relation, v in(max) is the maximum operational voltage. ripple current is typically set within a range of 25% to 35% of i chg(max) , so an inductor value can be determined by setting 0.25 < i l /i chg(max) < 0.35. figure 3. 14.4v at 1.5a switched inductor values maximum operational v in voltage (v) 18 20 22 4 switched inductor value (h) 1210 14 2416 18 20 22 34 3652 f03 86 26 28 24 30 32 magnetics vendors typically specify inductors with maxi - mum rms and saturation current ratings. select an inductor that has a saturation current rating at or above i chg(max) + ?i l /i chg(max) , and an rms rating above i chg(max) . in - ductors must also meet a maximum volt-second product requirement. if this specification is not in the data sheet of an inductor, consult the vendor to make sure the maximum volt-second product is not being exceeded by your design. the minimum required volt-second product is: v bat(flt) ? 1 ? v bat(flt) v in(max) ?? ?? ?? ?? v ?s ( ) rectifier selection the rectifier diode from sw to gnd, in a lt3652hv battery charger provides a current path for the inductor current when the main power switch is disabled. the rectifier is selected based upon forward voltage, reverse voltage, and maximum current. a schottky diode is required, as low forward voltage yields the lowest power loss and highest efficiency. the rectifier diode must be rated to withstand reverse voltages greater than the maximum v in voltage. downloaded from: http:///
lt3652hv 14 3652hvfb for more information www.linear.com/lt3652hv applications information the minimum average diode current rating (i diode(max) ) is calculated with maximum output current ( i chg(max) ), maximum operational v in , and output at the precondition threshold (v bat(pre) , or 0.7 ? v bat(flt) ): i diode(max) > i chg(max) ? v in(max) C v bat(pre) v in(max) (a) for example, a rectifier diode for a 7.2v, 2a charger with a 25v maximum input voltage would require: i diode(max) > 2a ? 25v ? 0.7(7.2v) 25v ,or i diode(max) > 1.6a battery float voltage programming the output battery float voltage (v bat(flt) ) is programmed by connecting a resistor divider from the bat pin to v fb . v bat(flt) can be programmed up to 18v. figure 4. feedback resistors from bat to v fb program float voltage bat + v fb r fb2 r fb1 lt3652hv 3652 f04 because the battery voltage is across the v bat(flt) pro - gramming resistor divider, this divider will draw a small amount of current from the battery (i rfb ) at a rate of: i rfb = 3.3/r fb2 precision resistors in high values may be hard to ob - tain, so for some lower v bat(flt) applications, it may be desirable to use smaller-value feedback resistors with an additional resistor (r fb3 ) to achieve the required 250k equivalent resistance. the resulting 3-resistor network, as shown in figure 5, can ease component selection and/or increase output voltage precision, at the expense of additional current through the feedback divider. for a three-resistor network, r fb1 and r fb2 follow the relation: r fb2 /r fb1 = 3.3/(v bat(flt) C 3.3) example: for v bat(flt) = 3.6v: r fb2 /r fb1 = 3.3/(3.6 - 3.3) = 11. setting divider current (i rfb ) = 10a yields: r fb2 = 3.3/10a r fb2 = 330k solving for r fb1 : r fb1 = 330k/11 r fb1 = 30k the divider equivalent resistance is: r fb1 ||r fb2 = 27.5k bat + v fb r fb2 r fb3 r fb1 lt3652hv 3652 f05 figure 5. a three-resistor feedback network can ease component selection using a resistor divider with an equivalent input resistance at the v fb pin of 250k compensates for input bias current error. required resistor values to program desired v bat(flt) follow the equations: r fb1 = (v bat(flt) ? 2.5 ? 10 5 )/3.3 () r fb2 = (r fb1 ? (2.5 ? 10 5 ))/(r fb1 - (2.5 ? 10 5 )) () the charge function operates to achieve the final float voltage of 3.3v on the v fb pin. the auto-restart feature initiates a new charging cycle when the voltage at the v fb pin falls 2.5% below that float voltage. downloaded from: http:///
lt3652hv 15 3652hvfb for more information www.linear.com/lt3652hv to satisfy the 250k equivalent resistance to the v fb pin: r fb3 = 250k ? 27.5k r fb3 = 223k. because the v fb pin is a relatively high impedance node, stray capacitances at this pin must be minimized. spe - cial attention should be given to any stray capacitances that can couple external signals onto the pin, which can produce undesirable output transients or ripple. effects of parasitic capacitance can typically be reduced by adding a small-value (20pf to 50pf) feedforward capacitor from the bat pin to the v fb pin. extra care should be taken during board assembly. small amounts of board contamination can lead to significant shifts in output voltage. appropriate post-assembly board cleaning measures should be implemented to prevent board contamination, and low-leakage solder flux is recommended. input supply voltage regulation the lt3652hv contains a voltage monitor pin that enables programming a minimum operational voltage. connect - ing a resistor divider from v in to the v in_reg pin enables programming of minimum input supply voltage, typically used to program the peak power voltage for a solar panel. maximum charge current is reduced when the v in_reg pin is below the regulation threshold of 2.7v. if an input supply cannot provide enough power to satisfy the requirements of an lt3652hv charger, the supply volt - age will collapse. a minimum operating supply voltage can thus be programmed by monitoring the supply through a resistor divider, such that the desired minimum voltage corresponds to 2.7v at the v in_reg pin. the lt3652hv servos the maximum output charge current to maintain the voltage on v in_reg at or above 2.7v. programming of the desired minimum voltage is ac - complished by connecting a resistor divider as shown in figure 6. the ratio of r in1 /r in2 for a desired minimum voltage (v in(min) ) is: r in1 /r in2 = (v in(min) /2.7) C 1 applications information if the voltage regulation feature is not used, connect the v in_reg pin to v in . mppt temperature compensation a typical solar panel is comprised of a number of series-con - nected cells, each cell being a forward-biased p-n junction. as such, the open-circuit voltage (v oc ) of a solar cell has a temperature coefficient that is similar to a common p-n diode, or about C2mv/c. the peak power point voltage (v mp ) for a crystalline solar panel can be approximated as a fixed voltage below v oc , so the temperature coefficient for the peak power point is similar to that of v oc . panel manufacturers typically specify the 25c values for v oc , v mp , and the temperature coefficient for v oc , making determination of the temperature coefficient for v mp of a typical panel straight forward. the lt3652hv employs a feedback network to program the v in input regulation voltage. manipulation of the network makes for efficient implementation of various temperature compensation schemes for a maximum peak figure 6. resistor divider sets minimum v in v in v in_reg r in2 r in1 lt3652hv input supply 3652 f06 figure 7. temperature characteristics for solar panel output voltage temperature (c) 5 panel voltage (v) 25 45 55 15 35 3652 f07 v oc(25c) v mp(25c) v mp v oc v oc temp co. v oc C v mp downloaded from: http:///
lt3652hv 16 3652hvfb for more information www.linear.com/lt3652hv power tracking (mppt) application. as the temperature characteristic for a typical solar panel v mp voltage is highly linear, a simple solution for tracking that characteristic can be implemented using an lm234 3-terminal temperature sensor. this creates an easily programmable, linear tem - perature dependent characteristic. in the circuit shown in figure 8, applications information battery voltage temperature compensation some battery chemistries have charge voltage require - ments that vary with temperature. lead-acid batteries in particular experience a significant change in charge volt - age requirements as temperature changes. for example, manufacturers of large lead-acid batteries recommend a float charge of 2.25v/cell at 25c. this battery float voltage, however, has a temperature coefficient which is typically specified at C3.3mv/c per cell. in a manner similar to the mppt temperature correction outlined previously, implementation of linear battery charge voltage temperature compensation can be ac - complished by incorporating an lm234 into the output feedback network. for example, a 6-cell lead acid battery has a float charge voltage that is commonly specified at 2.25v/cell at 25c, or 13.5v, and a C3.3mv/c per cell temperature coefficient, or C19.8mv/c. using the feedback network shown in figure 9, with the desired temperature coefficient (tc) figure 8. mppt temperature compensation network v in_reg lt3652hv v in v in lm234 3658 f08 v + v C r r set r in1 r in2 r in1 = Cr set ? (tc ? 4405), and r i n2 = r in 1 /({[v mp(25c) + r in 1 ? ( 0.0674/r set )]/v in_reg } C 1) where: tc = temperature coefficient (in v/c), and v mp(25c) = maximum power voltage at 25c for example, given a common 36-cell solar panel that has the following specified characteristics: open circuit voltage (v oc ) = 21.7v maximum power voltage (v mp ) = 17.6v open-circuit voltage temperature coefficient (v oc ) = C78mv/c as the temperature coefficient for v mp is similar to that of v oc , the specified temperature coefficient for v oc (tc) of C78mv/c and the specified peak power voltage (v mp(25c) ) of 17.6v can be inserted into the equations to calculate the appropriate resistor values for the tempera - ture compensation network in figure 8. with r set equal to 1000, then: r set = 1k r in1 = C1k ? (C0.078 ? 4405 ) = 344k r in2 = 344k/({[17.6 + 344k ? (0.0674/1k)]/2.7} C 1) = 24.4k lt3652hv r fb3 215k r fb2 43k r set 2.4k r fb1 210k 6-cell lead-acid battery lm234 3652 f09a v + v C r bat v fb + figure 9. lead-acid 6-cell float charge voltage vs temperature has ?19.8mv/c characteristic using lm234 with feedback network temperature (c) C10 v float (v) 10 50 40 60 0 20 30 3652 f09b 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.3 C19.8mv/c downloaded from: http:///
lt3652hv 17 3652hvfb for more information www.linear.com/lt3652hv applications information and 25c float voltage (v float(25c) ) specified, and using a convenient value of 2.4k for r set , necessary resistor values follow the relations:r fb1 = Cr set ? (tc ? 4405) = C2.4k ? (C0.0198 ? 4405) = 210k r fb2 = r fb1 /({[v float(25c) + r fb1 ? (0.0674/ r set )] / v fb } C 1) = 210k/({[13.5 + 210k ? (0.0674/2.4k)]/3.3} C 1) = 43k r fb3 = 250k - r fb1 ||r fb2 = 250k C 210k||43k = 215k (see the battery float voltage programming section) while the circuit in figure 9 creates a linear temperature characteristic that follows a typical C3.3mv/c per cell lead-acid specification, the theoretical float charge voltage characteristic is slightly nonlinear. this nonlinear charac - teristic follows the relation v float(1-cell) = 4 10 C5 (t 2 ) C 6 10 C3 (t) + 2.375 (with a 2.18v minimum), where t = temperature in c. a thermistor-based network can be used to approximate the nonlinear ideal temperature characteristic across a reasonable operating range, as shown in figure 10. status pins the lt3652hv reports charger status through two open collector outputs, the chrg and fault pins. these pins can accept voltages as high as v in , and can sink up to 10ma when enabled.the chrg pin indicates that the charger is delivering current at greater that a c/10 rate, or 1/10th of the pro - grammed maximum charge current. the fault pin signals bad battery and ntc faults. these pins are binary coded, and signal following the table below, where on indicates pin pulled low, and off indicates pin high-impedance: status pins state charger status chrg fault off off not charging standby or shutdown mode off on bad battery fault (precondition timeout / eoc failure) on off normal charging at c/10 or greater on on ntc fault (pause) if the battery is removed from an lt3652hv charger that is configured for c/10 termination, a sawtooth waveform lt3652hv 196k 198k 6-cell lead-acid battery 22kb = 3380 3652 f10a bat 69k69k v fb + temperature (c) C10 v float (v) 10 50 40 60 0 20 30 3652 f10b 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.614.4 14.2 14.8 theoretical v float programmed v bat(float) figure 10. thermistor-based temperature compensation network progr ams v float to closely match ideal lead-acid float charge voltage for 6-cell charger downloaded from: http:///
lt3652hv 18 3652hvfb for more information www.linear.com/lt3652hv applications information of approximately 100mv appears at the charger output, due to cycling between termination and recharge events, this cycling results in pulsing at the chrg output. an led connected to this pin will exhibit a blinking pattern, indicating to the user that a battery is not present. the frequency of this blinking pattern is dependent on the output capacitance. c/10 termination the lt3652hv supports a low-current based termination scheme, where a battery charge cycle terminates when the current output from the charger falls to below one-tenth of the maximum current, as programmed with r sense . the c/10 threshold current corresponds to 10mv across r sense . this termination mode is engaged by shorting the timer pin to ground. when c/10 termination is used, a lt3652hv charger will source battery charge current as long as the average current level remains above the c/10 threshold. as the full-charge float voltage is achieved, the charge current falls until the c/10 threshold is reached, at which time the charger terminates and the lt3652hv enters standby mode. the chrg status pin follows the charger cycle, and is high impedance when the charger is not actively charging.when v bat drops below 97.5% of the full-charged float voltage, whether by battery loading or replacement of the battery, the charger automatically re-engages and starts charging. there is no provision for bad battery detection if c/10 termination is used. timer termination the lt3652hv supports a timer based termination scheme, in which a battery charge cycle is terminated after a spec ific amount of time elapses. timer termination is engaged when a capacitor (c timer ) is connected from the timer pin to ground. the timer cycle eoc (t eoc ) occurs based on c timer following the relation: c timer = t eoc ? 2.27 10 C7 (hours) timer eoc is typically set to 3 hours, which requires a 0.68f capacitor. the chrg status pin continues to signal charging at a c/10 rate, regardless of what termination scheme is used. when timer termination is used, the chrg status pin is pulled low during a charging cycle until the charger output current falls below the c/10 threshold. the charger continues to top-off the battery until timer eoc, when the lt3652hv terminates the charging cycle and enters standby mode. termination at the end of the timer cycle only occurs if the charging cycle was successful. a successful charge cycle is when the battery is charged to within 2.5% of the full-charge float voltage. if a charge cycle is not successful at eoc, the timer cycle resets and charging continues for another full timer cycle. when v bat drops below 97.5% of the full-charge float voltage, whether by battery loading or replacement of the battery, the charger automatically reengages and starts charging. preconditioning and bad battery fault a lt3652hv has a precondition mode, where charge cur - rent is limited to 15% of the programmed i chg(max) , as set by r sense . the precondition current corresponds to 15mv across r sense . precondition mode is engaged while the voltage on the v fb pin is below the precondition threshold (2.3v, or 0.7 ? v bat(flt) ). once the v fb voltage rises above the precondition threshold, normal full-current charging can commence. the lt3652hv incorporates 70mv of threshold hysteresis to prevent mode glitching. downloaded from: http:///
lt3652hv 19 3652hvfb for more information www.linear.com/lt3652hv when the internal timer is used for termination, bad battery detection is engaged. there is no provision for bad battery detection if c/10 termination is used. a bad battery fault is triggered when the voltage on v fb remains below the precondition threshold for greater than 1/8 of a full timer cycle (1/8 eoc). a bad battery fault is also triggered if a normally charging battery re-enters precondition mode after 1/8 eoc. when a bad battery fault is triggered, the charging cycle is suspended, so the chrg status pin becomes high- impedance. the fault pin is pulled low to signal a fault detection. cycling the chargers power or shdn function initiates a new charging cycle, but a lt3652hv charger does not require a reset. once a bad battery fault is detected, a new timer charging cycle initiates when the v fb pin exceeds the precondition threshold voltage. during a bad battery fault, 0.5ma is sourced from the charger, so removing the failed battery allows the charger output voltage to rise and initi - ate a charge cycle reset. as such, removing a bad battery resets the lt3652hv, so a new charge cycle is started by connecting another battery to the charger output. battery temperature monitor and fault the lt3652hv can accommodate battery temperature monitoring by using an ntc (negative temperature co-effi - cient) thermistor close to the battery pack. the temperature monitoring function is enabled by connecting a 10k, b = 3380 ntc thermistor from the ntc pin to ground. if the ntc function is not desired, leave the pin unconnected. the ntc pin sources 50a, and monitors the voltage dropped across the 10k thermistor. when the voltage on this pin is above 1.36v (0c) or below 0.29v (40c), the battery temperature is out of range, and the lt3652hv triggers an ntc fault. the ntc fault condition remains until the voltage on the ntc pin corresponds to a temperature within the 0c to 40c range. both hot and cold thresholds incorporate hysteresis that correspond to 5c. applications information if higher operational charging temperatures are desired, the temperature range can be expanded by adding series resistance to the 10k ntc resistor. adding a 0.91k resistor will increase the effective hot temperature to 45c. during an ntc fault, charging is halted and both status pins are pulled low. if timer termination is enabled, the timer count is suspended and held until the fault condi - tion is relieved.thermal foldback the lt3652hv contains a thermal foldback protection feature that reduces maximum charger output current if the ic junction temperature approaches 125c. in most cases, on-chip temperatures servo such that any exces - sive temperature conditions are relieved with only slight reductions in maximum charger current. in some cases, the thermal foldback protection feature can reduce charger currents below the c/10 threshold. in applications that use c/10 termination (timer = 0v), the lt3652hv will suspend charging and enter standby mode until the excessive temperature condition is relieved. layout considerations the lt3652hv switch node has rise and fall times that are typically less than 10ns to maximize conversion efficiency. the switch node (pin sw) trace should be kept as short as possible to minimize high frequency noise. the input capacitor (c in ) should be placed close to the ic to minimize this switching noise. short, wide traces on these nodes also help to avoid voltage stress from inductive ringing. the boost decoupling capacitor should also be in close proximity to the ic to minimize inductive ringing. the sense and bat traces should be routed together, and these and the v fb trace should be kept as short as pos - sible. shielding these signals from switching noise with a ground plane is recommended. downloaded from: http:///
lt3652hv 20 3652hvfb for more information www.linear.com/lt3652hv applications information high current paths and transients should be kept iso - lated from battery ground, to assure an accurate output voltage reference. effective grounding can be achieved by considering switched current in the ground plane, and careful component placement and orientation can effectively steer these high currents such that the battery reference does not get corrupted. figure 11 illustrates an effective grounding scheme using component placement to control ground currents. when the switch is enabled (loop #1), current flows from the input bypass capacitor (c in ) through the switch and inductor to the battery posi - sw v in r sense sense bat v fb + gnd lt3652hv d f c in c bat v bat 2 3652 f11 1 figure 11. component orientation isolates high current paths from sensitive nodes tive terminal. when the switch is disabled (loop #2), the current to the battery positive terminal is provided from ground through the freewheeling schottky diode (d f ). in both cases, these switch currents return to ground via the output bypass capacitor (c bat ). the lt3652hv packaging has been designed to efficiently remove heat from the ic via the exposed pad on the backside of the package, which is soldered to a copper footprint on the pcb. this footprint should be made as large as possible to reduce the thermal resistance of the ic case to ambient air. downloaded from: http:///
lt3652hv 21 3652hvfb for more information www.linear.com/lt3652hv typical applications 2a solar panel power manager with 7.2v lifepo 4 battery and 17v peak power tracking solar panel input voltage regulation, tracks max power point to greater than 98% sw v in v in 6v to 34v (40v max) v in_reg v fb boost sense bat ntc timer cmdsh2-4l systemload 1f 30k 223k 3652 ta05 + 10f c310f 0.05 5.6h lt3652hv shdn chrg fault cmsh3-40ma cmsh3-40ma 330k lifepo 4 cell basic 2a 1-cell lifepo 4 charger (3.6v float) with c/10 termination sw v in solar panel input (<40v oc voltage) v in_reg v fb boost sense bat ntc timer cmsh3-40ma system load 1f 542k 459k 3652 ta02 10kb = 3380 2-cell lifepo 4 (2 3.6v) battery pack + 10f cmsh1-40ma 10f 10h 0.05 lt3652hv 530k100k shdn chrg fault cmsh3-40ma charger output current (a) 0.2 input regulation voltage (v) 10 12 14 2018 16 0.6 1 1.2 3652 ta03 22 0.4 0.8 1.6 1.4 2 1.8 100% to 98% peak power 98% to 95% peak power t a = 25c downloaded from: http:///
lt3652hv 22 3652hvfb for more information www.linear.com/lt3652hv 3.00 0.10 (4 sides) note:1. drawing is not a jedec package outline 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 and tie bars shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom viewexposed pad 1.65 0.10 0.75 0.05 r = 0.115 typ 1 6 12 7 pin 1 top mark (see note 6) 0.200 ref 0.00 C 0.05 (dd12) dfn 0106 rev a 0.23 0.05 pin 1 notchr = 0.20 or 0.25 45 chamfer 2.38 0.10 2.25 ref 0.45 bsc recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 0.25 0.05 2.25 ref 2.38 0.05 1.65 0.05 2.10 0.05 0.70 0.05 3.50 0.05 packageoutline 0.45 bsc dd package 12-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1725 rev a) please refer to http://www.linear.com/product/lt3652hv#packaging for the most recent package drawings. msop (mse12) 0213 rev g 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.22 C?0.38 (.009 C .015) typ 0.86 (.034) ref 0.650 (.0256) bsc 12 12 11 10 9 8 7 7 detail b 1 6 note:1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 6. exposed pad dimension does include mold flash. mold flash on e-pad shall not exceed 0.254mm (.010") per side. 0.254 (.010) 0 C 6 typ detail a detail a gauge plane recommended solder pad layout bottom view of exposed pad option 2.845 0.102 (.112 .004) 2.845 0.102 (.112 .004) 4.039 0.102 (.159 .004) (note 3) 1.651 0.102 (.065 .004) 1.651 0.102 (.065 .004) 0.1016 0.0508 (.004 .002) 1 2 3 4 5 6 3.00 0.102 (.118 .004) (note 4) 0.406 0.076 (.016 .003) ref 4.90 0.152 (.193 .006) detail b corner tail is part of the leadframe feature. for reference only no measurement purpose 0.12 ref 0.35ref 5.10 (.201) min 3.20 C 3.45 (.126 C .136) 0.889 0.127 (.035 .005) 0.42 0.038 (.0165 .0015) typ 0.65 (.0256) bsc mse package 12-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1666 rev g) package description downloaded from: http:///
lt3652hv 23 3652hvfb for more information www.linear.com/lt3652hv information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology co rporation makes no representa - tion that the interconnection of its circuits as described herein will no t infringe on existing patent rights. revision history rev date description page number a 01/13 added new battery bias current curve 6 b 01/16 enhanced pin coniguration added note 2 to top of electrical characteristics enhanced note 2 changed name of pin 13 modiied inductor selection section modiied battery float voltage programming equations 2 3, 4 48 1315 downloaded from: http:///
lt3652hv 24 3652hvfb for more information www.linear.com/lt3652hv ? linear technology corporation 2010 lt 0116 rev b ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/lt3652hv related parts typical application 1a solar panel powered 3-stage 12v lead-acid fast/float charger; 1a cha rger fast charges with cc/cv characteristics up to 14.4v; when charge current falls to 0.1a charger swi tches to 13.5v float charge mode; charger re-initiates 14.4v fast charge mode if battery voltage fal ls below 13.2v and trickle charges at 0.15a if battery voltage is below 10v; 0c to 45c battery tempera ture charging range sw v in solar panel input <40v oc voltage 16v peak power voltage v in_reg v fb boost sense bat ntc timer 22h mbrs340 309k100k 1f 1n4148 bzx84c6v2l 910174k 1n4148 1m systemload wurth 7447779122 12v lead acid battery 10k b = 3380 murata ncp18xh103 + 10f 0.1 100f lt3652hv 10f 4.7f shdn chrg fault 499k 100k + 3652 ta04 mbrs140 part number description comments lt3650-8.2/lt3650-8.4 monolithic 2a switch mode 2-cell li-ion battery charger standalone, 9v v in 32v (40v absolute maximum), 1mhz, 2a programmable charge current, timer or c/10 termination, small and few external components, 3mm 3mm dfn12 package, C8.2 for 2 4.1v float voltage batteries, C8.4 for 2 4.2v float voltage batteries ltc4001/ltc4001-1 monolithic 2a switch mode synchronous li-ion battery charger standalone, 4v v in 5.5v (6v absolute maximum , 7v transient), 1.5mhz, synchronous rectification efficiency >90%, adjustable timer ter mination, small and few external components, 4mm 4mm qfn-16 package C 1 for 4.1v float voltage batteries ltc4002 switch mode lithium-ion battery charger standalone, 4.7v v in 24v, 500khz frequency, 3 hour charge termination ltc4006 small, high efficiency, fixed voltage, lithium-ion battery charger with termination and thermistor sensor complete charger for 3- or 4-cell li-ion batteries, ac adapter current li mit, 16-pin narrow ssop package ltc4007 high efficiency, programmable voltage battery charger with termination complete charger for 3- or 4-cell li-ion batteries, ac adapter current li mit, thermistor sensor and indicator outputs ltc4008 4a, high efficiency, multi-chemistry battery charger constant-current/constant-voltage switching regulator cha rger, resistor voltage/current programming, ac adapter current limit and thermis tor sensor and indicator outputs ltc4012/ltc4012-1/ ltc4012-2/ ltc4012-3 4a, high efficiency, multi-chemistry battery charger with powerpath ? control powerpath control, constant-current/constant-voltage swit ching regulator charger, resistor voltage/current programming, ac adapter curre nt limit and thermistor sensor and indicator outputs 1 to 4 cell li, up to 18 cell ni, sla and supercap compatible; 4mm 4mm qfn-20 package C1 version for 4.1v li cells, C2 version for 4.2v li cells, C3 version has extra gnd pin ltc4015 multichemistry buck battery charger controller with digital telemetry system multichemistry li-ion/polymer, lifepo 4 , or lead-acid battery charger with termination, digital telemetry system monitors v bat , i bat , r bat , ntc ratio (battery temperature), v in , i in , v system , die temperature, coulomb counter and integrated 14-bit adc, maximum power point tracking, wide charging inp ut voltage range: 4.5v to 35v, wide battery voltage range: up to 35v, 5mm 7mm qfn-38 package ltc4020 55v buck-boost multi-chemistry battery charger wide voltage range: 4.5v to 55v input, up to 55v output (60v absolute maximums), synchronous buck-boost dc/dc controller, li-ion and le ad-acid charge algorithms, input voltage regulation for high impedance inpu t supplies and solar panel peak power operation, low proile (0.75mm) 38-pin 5mm 7mm qfn package downloaded from: http:///

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