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ltc 3331 1 3331fc for more information www.linear.com/ltc3331 typical application features description nanopower buck-boost dc/dc with energy harvesting battery charger the lt c ? 3331 integrates a high voltage energy harvesting power supply plus a buck-boost dc / dc powered from a rechargeable battery to create a single output supply for alternative energy applications . a 10 ma shunt allows simple charging of the battery with harvested energy while a low battery disconnect function protects the battery from deep discharge . the energy harvesting power supply , consisting of an integrated full-wave bridge rectifier and a high voltage buck dc / dc , harvests energy from piezoelectric , solar , or magnetic sources . either dc / dc converter can deliver en - ergy to a single output . the buck operates when harvested energy is available , reducing the quiescent current draw on the battery to the 200 na required by the shunt charger , thereby extending the life of the battery . the buck-boost powers v out only when harvested energy is unavailable . a supercapacitor balancer is also integrated , allowing for increased energy storage . voltage and current settings for both inputs and outputs are programmable via pin-strapped logic inputs . the ltc3331 is available in a 5mm 5mm qfn-32 package. applications n dual input, single output dc/dcs with input prioritizer n energy harvesting input: 3.0v to 19v buck dc/dc n battery input: up to 4.2v buck-boost dc/dc n 10ma shunt battery charger with programmable float voltages: 3.45v, 4.0v, 4.1v, 4.2v n low battery disconnect n ultra low quiescent current: 950na at no load n integrated supercapacitor balancer n up to 50ma of output current n programmable dc/dc output voltage, buck uvlo, and buck-boost peak input current n integrated low-loss full-wave bridge rectifier n input protective shunt: up to 25ma at v in 20v n 5mm 5mm qfn-32 package n energy harvesting n solar powered systems with battery backup n wireless hvac sensors and security devices n mobile asset tracking l , lt , lt c , lt m , 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. piezomide v25w 1f 6.3v 4.7f, 6.3v 100k gnd ltc3331 3331 ta01a ac1v in capcharge v in2 bat_in bat_out bb_in float[1:0] lbsel ac2 sw swa 22h22h swb v out scap bal ship eh_on pgvout ipk[2:0] out[2:0] uv[3:0] v in3 3v to 19v solar panel 4.7f6.3v 4.7f6.3v li-ion battery 22f25v 2 3 3 4 + 0.1f 6.3v 1.8v to 5v50ma 10mf2.7v 10mf 2.7v optional 47f6.3v +? charging a battery with harvested energy v out 50mv/div ac-coupled eh_on 4v/div i bb_in 200ma/div i charge 1ma/div 0a 0a 0v 100s/div active energy harvester enables charging of the battery in sleep 3331 ta01b bat = 3.6v v out = 1.8v i load = 50ma downloaded from: http:///
ltc 3331 2 3331fc for more information www.linear.com/ltc3331 pin configuration absolute maximum ratings v in low impedance source .......................... C0.3 to 19v* current-fed, i sw = 0a ........................................ 25ma ac1, ac2 ............................................................. 0 to v in bb_in, v out , v in3 , bat_in, scap, pgvout, charge, ship ................................................ C0.3 to 6v bat_out .... C0.3v to [lesser of (bat_in + 0.3v) or 6v] v in2 .................... C0.3 v to [lesser of (v in + 0.3v)] or 6v cap ...................... [higher of C0.3v or (v in C 6v)] to v in bal ............................................ C0.3v to (scap + 0.3v) out[2:0] .......... C0.3v to [lesser of (v in3 + 0.3v) or 6v] ipk[2:0] ........... C0.3v to [lesser of (v in3 + 0.3v) or 6v] eh_on ............. C0.3v to [lesser of (v in3 + 0.3v) or 6v] float[1:0] ... C0.3v to [lesser of (bb_in + 0.3v) or 6v] lbsel ........... C0.3v to [lesser of (bb_in + 0.3v) or 6v] uv[3:0] ............ C0.3v to [lesser of (v in2 + 0.3v) or 6v] i ac1 , i ac2 .............................................................. 50ma i swa , i swb , i vout ..................................................350ma i sw ....................................................................... 500ma operating junction temperature range (notes 2, 3) ............................................ C40c to 125c storage temperature range .................. C65c to 150c *v in has an internal 20v clamp (note 1) 32 33 gnd 31 30 29 28 27 26 25 9 10 11 12 top view uh package 32-lead (5mm 5mm) plastic qfn 13 14 15 16 17 18 19 20 21 22 23 24 8 7 6 5 4 3 2 1 bal scap v in2 uv3uv2 uv1 uv0 ac1 float0 float1 lbsel bat_in bat_out ipk2 ipk1 ipk0 out2out1 out0 eh_on pgvout charge v in3 ship ac2 v in cap sw v out swb swa bb_in t jmax = 125c, ja = 44c/w exposed pad (pin 33) is gnd, must be soldered to pcb order information lead free finish tape and reel part marking* package description temperature range ltc3331euh#pbf ltc3331euh#trpbf 3331 32-lead (5mm 5mm) plastic qfn C40c to 85c ltc3331iuh#pbf ltc3331iuh#trpbf 3331 32-lead (5mm 5mm) plastic qfn C40c to 125c consult ltc marketing for parts specified with wider operating temperature ranges . * the temperature grade is identified by a label on the shipping container . for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ downloaded from: http:///
ltc 3331 3 3331fc for more information www.linear.com/ltc3331 electrical characteristics symbol parameter conditions min typ max units v in buck input voltage range l 19 v v bb_in buck-boost input voltage range (note 7) l 1.8 5.5 v i vin v in quiescent current v in input in uvlo v in input in uvlo buck enabled, sleeping buck enabled, sleeping buck enabled, not sleeping v in = 2.5v, v bb_in = 0v v in = 16v, v bb_in = 0v v in = 4v, v bb_in = 0v v in = 18v, v bb_in = 0v v in = 5v, v bb_in = 0v, i sw = 0a (note 4) 450 800 1300 1800 150 700 1400 2000 2700 225 na na na na a i bb_in bb_in quiescent current (note 6) bb_in input with v in active buck-boost enabled, sleeping buck-boost enabled, not sleeping v bb_in = 3.6v, v in = 5v v bb_in = 3.6v, v in = 0v v bb_in = 3.6 v, v in = 0v, i swa = i swb = 0 a ( note 4) 200 950 200 300 1500 300 na na a i vout v out leakage current 5v output selected, sleeping 100 150 na v in undervoltage lockout thresholds (rising or falling) 3v level selected l 2.91 3.00 3.09 v 4v level selected l 3.88 4.00 4.12 v 5v level selected l 4.85 5.00 5.15 v 6v level selected l 5.82 6.00 6.18 v 7v level selected l 6.79 7.00 7.21 v 8v level selected l 7.76 8.00 8.24 v 9v level selected l 8.73 9.00 9.27 v 10v level selected l 9.70 10.0 10.30 v 11v level selected l 10.67 11.0 11.33 v 12v level selected l 11.64 12.0 12.36 v 13v level selected l 12.61 13.0 13.39 v 14v level selected l 13.58 14.0 14.42 v 15v level selected l 14.55 15.0 15.45 v 16v level selected l 15.52 16.0 16.48 v 17v level selected l 16.49 17.0 17.51 v 18v level selected l 17.46 18.0 18.54 v v shunt v in shunt regulator voltage i vin = 1ma l 19.0 20.0 21.0 v i shunt maximum protective shunt current 25 ma internal bridge rectifier loss (| v ac 1 C v ac 2 | C v in ) i bridge = 10a i bridge = 50ma 700 1350 800 1550 900 1750 mv mv internal bridge rectifier reverse leakage current v reverse = 18v 20 na internal bridge rectifier reverse breakdown voltage i reverse = 1a v shunt 30 v the l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v in = 5v, bat_in = bat_out = bb_in = 3.6v, ship = ov, scap = 0v unless otherwise specified. downloaded from: http:///
ltc 3331 4 3331fc for more information www.linear.com/ltc3331 symbol parameter conditions min typ max units v out regulated buck/buck-boost output voltage 1.8v output selected sleep threshold wake-up threshold l l 1.728 1.806 1.794 1.872 v v 2.5v output selected sleep threshold wake-up threshold l l 2.425 2.508 2.492 2.575 v v 2.8v output selected sleep threshold wake-up threshold l l 2.716 2.809 2.791 2.884 v v 3.0v output selected sleep threshold wake-up threshold l l 2.910 3.010 2.990 3.090 v v 3.3v output selected sleep threshold wake-up threshold l l 3.200 3.311 3.289 3.400 v v 3.6v output selected sleep threshold wake-up threshold l l 3.492 3.612 3.588 3.708 v v 4.5v output selected sleep threshold wake-up threshold l l 4.365 4.515 4.485 4.635 v v 5.0v output selected sleep threshold wake-up threshold l l 4.850 5.017 4.983 5.150 v v pgvout falling threshold as a percentage of v out target (note 5) l 88 92 96 % i peak_bb buck-boost peak switch current 250ma target selected 200 250 350 ma 150ma target selected 120 150 210 ma 100ma target selected 80 100 140 ma 50ma target selected 40 50 70 ma 25ma target selected 20 25 35 ma 15ma target selected 12 15 21 ma 10ma target selected 8 10 14 ma 5ma target selected 4 5 7 ma available buck-boost current i peak_bb = 250ma, v out = 3.3v 50 ma buck-boost pmos input and output switch on-resistance ipk[2:0] = 111 ipk[2:0] = 110 ipk[2:0] = 101 ipk[2:0] = 100 ipk[2:0] = 011 ipk[2:0] = 010 ipk[2:0] = 001 ipk[2:0] = 000 0.8 1.0 1.4 2.4 4.5 7.3 10.7 20.5 buck-boost nmos input and output switch on-resistance ipk2 = 1 ipk2 = 0 0.6 3.9 electrical characteristics the l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v in = 5v, bat_in = bat_out = bb_in = 3.6v, ship = ov, scap = 0v unless otherwise specified. downloaded from: http:///
ltc 3331 5 3331fc for more information www.linear.com/ltc3331 electrical characteristics the l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v in = 5v, bat_in = bat_out = bb_in = 3.6v, ship = ov, scap = 0v unless otherwise specified. symbol parameter conditions min typ max units pmos switch leakage buck/buck-boost regulators C20 20 na nmos switch leakage buck/buck-boost regulators C20 20 na maximum buck duty cycle buck/buck-boost regulators l 100 % i peak_buck buck peak switch current 200 250 500 ma available buck output current 100 ma buck pmos switch on-resistance 1.4 buck nmos switch on-resistance 1.2 maximum battery shunt current 10 ma i bat_in battery disconnect leakage current battery disconnected ship mode engaged C10 C10 0 0 10 10 na na v float shunt charger float voltage (bat_out voltage) float[1:0] = 00, i bb_in = 1ma float[1:0] = 01, i bb_in = 1ma float[1:0] = 10, i bb_in = 1ma float[1:0] = 11, i bb_in = 1ma 3.415 3.960 4.059 4.158 3.45 4.0 4.1 4.2 3.485 4.040 4.141 4.242 v v v v float[1:0] = 00, i bb_in = 1ma float[1:0] = 01, i bb_in = 1ma float[1:0] = 10, i bb_in = 1ma float[1:0] = 11, i bb_in = 1ma l l l l 3.381 3.920 4.018 4.116 3.45 4.0 4.1 4.2 3.519 4.080 4.182 4.284 v v v v v lbd low battery disconnect threshold, bat_in voltage (falling) lbsel = 0, float[1:0] = 00, i bat_in = C1ma lbsel = 1, float[1:0] = 00, i bat_in = C1ma lbsel = 0, float[1:0] = 01, 10, 11, i bat_in = C1ma lbsel = 1, float[1:0] = 01, 10, 11, i bat_in = C1ma l l l l 1.98 2.43 2.62 3.10 2.04 2.51 2.70 3.20 2.10 2.59 2.78 3.30 v v v v v lbc_bat_in low battery connect threshold, bat_in voltage (rising) lbsel = 0, float[1:0] = 00, i bat_in = C1ma lbsel = 1, float[1:0] = 00, i bat_in = C1ma lbsel = 0, float[1:0] = 01, 10, 11, i bat_in = C1ma lbsel = 1, float[1:0] = 01, 10, 11, i bat_in = C1ma 2.26 2.74 2.91 3.39 2.35 2.85 3.03 3.53 2.44 2.96 3.15 3.67 v v v v v lbc_bat_ out low battery connect threshold, bat_out voltage (rising) lbsel = 0, float[1:0] = 00 lbsel = 1, float[1:0] = 00 lbsel = 0, float[1:0] = 01, 10, 11 lbsel = 1, float[1:0] = 01, 10, 11 3.02 3.52 3.70 4.20 v v v v battery disconnect pmos on-resistance bat_in = 3.3v, i bat_in = 10ma 5 charge pin current current out of charge pin l 1 2 ma ma charge pin voltage pmos on-resistance 2ma out of charge pin 60 v scap supercapacitor balancer input range l 2.5 5.5 v i scap supercapacitor balancer quiescent current scap = 5.0v 150 225 na supercapacitor balancer source current scap = 5.0v, bal = 2.4v 10 ma supercapacitor balancer sink current scap = 5.0v, bal = 2.6v 10 ma downloaded from: http:///
ltc 3331 6 3331fc for more information www.linear.com/ltc3331 typical performance characteristics v in quiescent current in uvlo vs v in v in quiescent current in sleep vs v in buck-boost quiescent current in sleep vs bb_in v in (v) 0 i vin (na) 22002000 1600 1200 18001400 1000 800600 400 200 0 9 6 15 3331 g01 18 3 12 125c 85c 25c C40c bb_in (v) 2.1 0 i bb_in (na) 250 750 1000 1250 25001750 2.7 3.3 3.6 3.9 3331 g03 500 2000 125c 85c25c 22501500 2.4 3 4.2 C40c bat_out tied to bb_in t a = 25c, unless otherwise noted. v in (v) i vin (na) 60005000 4000 3000 2000 1000 0 9 6 15 3331 g02 18 3 12 125c C40c 85c 25c electrical characteristics the l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at t a = 25c (note 2). v in = 5v, bat_in = bat_out = bb_in = 3.6v, ship = ov, scap = 0v unless otherwise specified. 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 ltc3331 is tested under pulsed load conditions such that t j t a . the ltc3331e is guaranteed to meet specifications from 0c to 85c. the ltc3331i is guaranteed over the C40c to 125c operating junction temperature range. note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. note 3: t j is calculated from the ambient t a and power dissipation pd according to the following formula: t j = t a + (p d ? ja ). note 4: dynamic supply current is higher due to gate charge being delivered at the switching frequency. note 5: the pgvout rising threshold is equal to the sleep threshold. see v out specification. note 6: these quiescent currents include the contribution from the internal resistor divider at the bat_out pin as bat_out must be tied to bb_in for all applications. note 7: the buck-boost operating voltage is further constrained to a narrower range by the programmed float voltage and the selected low battery disconnect and connect thresholds. symbol parameter conditions min typ max units v bal supercapacitor balance point percentage of scap voltage l 49 50 51 % v ih digital input high voltage pins: out[2:0], ship, float[1:0], lbsel, ipk[2:0], uv[3:0] l 1.2 v v il digital input low voltage pins: out[2:0], ship, float[1:0], lbsel, ipk[2:0], uv[3:0] l 0.4 v i ih digital input high current pins: out[2:0], ship, float[1:0], lbsel, ipk[2:0], uv[3:0] 0 10 na i il digital input low current pins: out[2:0], ship, float[1:0], lbsel, ipk[2:0], uv[3:0] 0 10 na v oh pgvout, output high voltage eh_on output high voltage bb_in = 5v, 1a out of pin v in = 6v, 1a out of pin l l 4.0 3.8 v v v ol pgvout, eh_on output low voltage bb_in = 5v, 1a into pin l 0.4 v downloaded from: http:///
ltc 3331 7 3331fc for more information www.linear.com/ltc3331 typical performance characteristics uvlo threshold vs temperature v shunt vs temperature v out quiescent current vs temperature total bridge rectifier drop vs bridge current bridge leakage vs temperature bridge frequency response bridge current (a) bridge drop (mv) 18001600 1400 1200 1000 800600 400 200 0 3331 g07 1 10 10m 1m 100 C40c 25c 85c 125c |v ac1 C v ac2 | C v in frequency (hz) v in (v) 3331 g09 2.01.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 10 100 100m 10m 1m 10k 1k 100k 4.8v p-p applied to ac1/ac2 input measured in uvlo t a = 25c, unless otherwise noted. temperature (c) C55 bridge leakage (na) 2018 14 10 1612 6 84 2 0 80 35 125 3331 g08 170 C10 v in = 18v, leakage at ac1 or ac2 temperature (c) C50 i vout (na) 150140 130 120 110 100 9080 60 7050 0 25 50 75 100 3331 g04 125 C25 v out in regulation, sleeping temperature (c) C50 percentage of target setting (%) 103102 101 100 9998 97 0 25 50 75 100 3331 g05 125 C25 applies to each uvlo setting temperature (c) C50 v shunt (v) 21.020.8 20.6 20.4 20.2 20.0 19.8 19.6 19.2 19.419.0 0 25 50 75 100 3331 g06 125 C25 i shunt = 1ma i shunt = 25ma 1.8v output vs temperature 2.5v output vs temperature 2.8v output vs temperature temperature (c) C50 v out (v) 1.841.82 1.80 1.78 1.76 1.74 1.72 1.70 1.68 1.66 1.64 0 25 50 75 100 3331 g10 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 2.552.50 2.45 2.40 2.35 2.30 2.25 0 25 50 75 100 3331 g11 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 2.852.80 2.75 2.70 2.65 2.60 2.55 0 25 50 75 100 3331 g12 125 C25 sleep threshold pgvout falling wake-up threshold downloaded from: http:///
ltc 3331 8 3331fc for more information www.linear.com/ltc3331 typical performance characteristics 3v output vs temperature 3.3v output vs temperature 3.6v output vs temperature 4.5v output vs temperature 5v output vs temperature r ds ( on ) of buck-boost pmos / nmos vs temperature , 250 ma i peak setting temperature (c) C50 v out (v) 3.053.00 2.95 2.90 2.85 2.80 2.75 2.70 0 25 50 75 100 3331 g13 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 3.353.30 3.25 3.20 3.15 3.10 3.05 3.00 0 25 50 75 100 3331 g14 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 3.653.60 3.55 3.50 3.45 3.40 3.35 3.30 3.25 0 25 50 75 100 3331 g15 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 4.604.55 4.50 4.45 4.40 4.35 4.30 4.25 4.20 4.15 4.10 0 25 50 75 100 3331 g16 125 C25 sleep threshold pgvout falling wake-up threshold temperature (c) C50 v out (v) 5.105.00 4.90 4.80 4.70 4.60 4.50 0 25 50 75 100 3331 g17 125 C25 sleep threshold pgvout falling wake-up threshold t a = 25c, unless otherwise noted. r ds(on) of buck-boost pmos/nmos vs temperature, 5ma i peak setting buck-boost peak current vs temperature , 250 ma i peak setting buck-boost peak current vs temperature, 5ma i peak setting temperature (c) C50 i peak_bb (ma) 6.05.8 5.6 5.4 5.2 4.6 4.4 4.2 5.0 4.0 4.8 0 25 50 75 100 3331 g19 125 C25 bb_in = 3.6v temperature (c) C50 i peak_bb (ma) 300290 280 270 260 230 220 210 250 200 240 0 25 50 75 100 3331 g18 125 C25 bb_in = 3.6v temperature (c) C50 0.40 r ds(on) () 0.50 0.70 0.80 0.90 1.401.10 0 50 75 100 3331 g20 0.60 1.20 1.301.00 C25 25 125 pmos, bb_in = 2.1vnmos, bb_in = 2.1v pmos, bb_in = 4.2v nmos, bb_in = 4.2v temperature (c) C50 r ds(on) () 15 45 50 55 0 50 75 3331 g21 5 35 25 10 40 0 30 20 C25 25 100 125 pmos, bb_in = 2.1vnmos, bb_in = 2.1v pmos, bb_in = 4.2v nmos, bb_in = 4.2v downloaded from: http:///
ltc 3331 9 3331fc for more information www.linear.com/ltc3331 typical performance characteristics buck-boost load regulation, v out = 3.3v buck-boost line regulation, v out = 3.3v buck-boost switching waveforms buck load regulation, 3.3v t a = 25c, unless otherwise noted. i load (a) v out (v) 3.4003.375 3.350 3.325 3.300 3.275 3.225 3.2503.200 3331 g27 1 10 10m 100m 1m 100 v in = 4v c out = 100f l = 22h buck peak current vs temperature r ds(on) of buck pmos/nmos vs temperature temperature (c) C50 i peak_buck (ma) 300290 280 270 260 250 240 230 220200 210 0 25 50 75 100 3331 g22 125 C25 v in = 5v temperature (c) C50 r ds(on) () 2.01.8 1.6 1.4 1.2 0.8 1.0 0 25 50 75 100 3331 g23 125 C25 v in = 5v pmos nmos i load (a) 1 10 3.28 v out (v) 3.30 3.32 3.34 3.36 100 1m 10m 100m 3331 g24 3.26 3.243.22 3.20 3.38 3.40 bb_in = 4.1v bb_in = 2.1v c out = 100f l = 22hipk[2:0] = 111 bb_in (v) 2.1 v out (v) 3.375 3 3331 g25 3.300 3.250 2.4 2.7 3.3 3.2253.200 3.400 load = 1ma load = 50ma c out = 100f l = 22hipk[2:0] = 111 3.3503.325 3.275 3.6 3.9 4.2 bat = 2.1v, v out = 3.3v i load = 10ma l = 22h, c out = 100f swa voltage 2v/div swb voltage 2v/div output voltage 50mv/div ac-coupled inductor current 200ma/div 3331 g26 8s/div 0v0v 0ma prioritizer buck to buck-boost transition v in transitions 18v to 17v, uv[3:0] = 1110 bb_in = 4.1v, v out = 3.3v i load = 50ma, c out = 100f, l buck = 22h, l buck-boost = 22h 0v0ma eh_on 5v/div buck inductor current 200ma/div output voltage 50mv/div dc-coupled, offset = 3.3v buck-boost inductor current 200ma/div 0ma 3331 g30 100s/div buck line regulation, 3.3v buck switching waveforms v in (v) 4 v out (v) 3.4003.375 3.350 3.325 3.300 3.275 3.250 3.225 3.200 8 10 12 14 16 3331 g28 18 6 load = 1ma load = 100ma c out = 100f l = 22h v in = 18v, v out = 3.3v i load = 10ma l = 22h, c out = 100f 0v sw voltage 10v/div output voltage 50mv/div ac-coupled inductor current 200ma/div 0ma 3331 g29 8s/div downloaded from: http:///
ltc 3331 10 3331fc for more information www.linear.com/ltc3331 typical performance characteristics buck-boost load step response buck load step response prioritizer buck-boost to buck transition buck efficiency vs i load buck efficiency vs v in for i load = 100ma, l = 22h buck efficiency vs v in for i load = 100ma, l = 100h t a = 25c, unless otherwise noted. bb_in = 3v, v out = 3.3v c out = 100f, l = 22h load step from 1ma to 50ma output voltage 20mv/div ac-coupled load current 25ma/div 1ma 3331 g31 2ms/div v in = 18v, v out = 3.3v c out = 100f, l = 22h load step from 1ma to 50ma output voltage 20mv/div ac-coupled load current 25ma/div 1ma 3331 g32 2ms/div v in transitions 17v to 18v, uv[3:0] = 1110 bb_in = 4.1v, v out = 3.3v i load = 50ma, c out = 100f, l buck = 22h, l buck-boost = 22h 0v0ma eh_on 5v/div buck inductor current 200ma/div output voltage 50mv/div dc-coupled, offset = 3.3v buck-boost inductor current 200ma/div 3331 g33 100s/div 0ma i load (a) efficiency (%) 3331 g34 100 9060 8070 40 5020 10 30 0 1 10 10m 100m 1m 100 v out = 1.8v v out = 2.5v v out = 3.3v v out = 5v v in = 6v , l = 22h, dcr = 0.19 v in (v) efficiency (%) 3331 g35 100 90 9585 80 75 4 6 10 8 12 14 16 18 v out = 1.8v v out = 2.5v v out = 2.8v v out = 3v v out = 3.3v v out = 3.6v v out = 4.5v v out = 5v dcr = 0.19 v in (v) efficiency (%) 3331 g36 100 90 9585 80 75 4 6 10 8 12 14 16 18 dcr = 0.45 v out = 1.8v v out = 2.5v v out = 2.8v v out = 3v v out = 3.3v v out = 3.6v v out = 4.5v v out = 5v buck efficiency vs v in , for v out = 3.3v buck-boost efficiency vs i load , 5ma i peak setting buck-boost efficiency vs i load , 250ma i peak setting v in (v) efficiency (%) 3331 g37 100 8070 60 9050 40 30 20 10 0 4 6 10 8 12 14 16 18 i load = 100ma i load =100a i load =50a i load =30a i load =20a i load =10a i load =5a l = 22h, dcr = 0.19 i load (a) 1 40 efficiency (%) 50 60 70 80 10 100 1m 3331 g38 30 2010 0 90 100 v out = 1.8v v out = 2.5v v out = 3.3v v out = 5.0v bat = 3.6vl = 22h dcr = 5.1 i load (a) 1 10 100 40 efficiency (%) 50 60 70 80 1m 10m 3331 g39 30 2010 0 90 100 v out = 1.8v v out = 2.5v v out = 3.3v v out = 5.0v bat = 3.6vl = 22h r l = 0.36 downloaded from: http:///
ltc 3331 11 3331fc for more information www.linear.com/ltc3331 typical performance characteristics buck-boost efficiency vs bb_in for v out = 1.8v, 250ma i peak setting buck-boost efficiency vs bb_in for v out = 3.3v, 250ma i peak setting buck-boost efficiency vs bb_in for v out = 5v, 250ma i peak setting buck-boost efficiency vs bb_in for v out = 1.8v, 5ma i peak setting buck-boost efficiency vs bb_in for v out = 3.3v, 5ma i peak setting buck-boost efficiency vs bb_in for v out = 5v, 5ma i peak setting t a = 25c, unless otherwise noted. bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g40 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 50ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 22hdcr = 0.36 bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g41 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 50ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 22hdcr = 0.36 bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g42 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 50ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 22hdcr = 0.36 bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g43 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 1ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 1000hdcr = 5.1 bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g44 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 1ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 1000hdcr = 5.1 bb_in (v) 2.1 efficiency (%) 80 90 100 3 3.6 3331 g45 70 60 2.4 2.7 3.3 3.9 4.2 50 40 i load = 1ma i load = 100a i load = 50a i load = 20a i load = 10a i load = 5a l = 1000hdcr = 5.1 shunt float voltage load regulation 4v, 4.1v, 4.2v float voltage vs temperature 3.45v float voltage vs temperature temperature (c) C50 float voltage (v) 3.60 25 3331 g46 3.45 3.35 C25 0 50 3.303.25 3.65 i bb_in = 1ma 3.553.50 3.40 75 100 125 temperature (c) C50 float voltage (v) 4.25 25 3331 g47 4.10 4.00 C25 0 50 3.953.90 4.30 i bb_in = 1ma 4.204.15 4.05 75 100 125 i bb_in (a) 2 float voltage deviation (mv) 4 5 7 8 1 100 1m 10m 3331 g48 0 10 63 1 all float settings in sleep downloaded from: http:///
ltc 3331 12 3331fc for more information www.linear.com/ltc3331 r ds(on) of disconnect pmos vs temperature battery connect voltage at bat_in vs i bat_out battery disconnect voltage at bat_in vs i bat_in battery connect voltage at bat_out vs i bat_out battery disconnect voltage at bat_out vs i bat_in battery connect transient battery connect/disconnect vs temperature battery connect/disconnect vs temperature typical performance characteristics t a = 25c, unless otherwise noted. disconnect pmos body diode drop vs current i d (a) 300 pmos body diode drop (mv) 900 1000 200100 800500 700600 400 1 100 1m 10m 3331 g49 0 10 C40c 125c 25c 85c temperature (c) C50 7 8 10 25 75 3331 g50 65 C25 0 50 100 125 40 9 r ds(on) () bat_in = 2.1v bat_in = 3.1v bat_in = 4.1v i bat_out (a) 2.6 bat_in voltage (v) 3.0 3.6 4.02.4 2.8 3.2 3.4 3.8 1 100 1m 10m 3331 g51 2.2 10 4.44.2 4.0, 4.1, 4.2 float, lbsel = 1 4.0, 4.1, 4.2 float, lbsel = 0 3.45 float, lbsel = 1 3.45 float, lbsel = 0 i bat_out (a) 2.6 bat_out voltage (v) 3.0 3.6 4.02.4 2.8 3.2 3.4 3.8 1 100 1m 10m 3331 g52 2.2 10 4.44.2 4.0, 4.1, 4.2 float, lbsel = 1 4.0, 4.1, 4.2 float, lbsel = 0 3.45 float, lbsel = 1 3.45 float, lbsel = 0 i bat_in (a) 2.4 bat_in voltage (v) 3.6 3.82.2 2.0 3.42.8 3.23.0 2.6 1 100 1m 10m 3331 g53 1.8 10 4.0, 4.1, 4.2 float, lbsel = 1 4.0, 4.1, 4.2 float, lbsel = 0 3.45 float, lbsel = 1 3.45 float, lbsel = 0 i bat_in (a) 2.4 bat_out voltage (v) 3.6 3.82.2 2.0 3.42.8 3.23.0 2.6 1 100 1m 10m 3331 g54 1.8 10 4.0, 4.1, 4.2 float, lbsel = 1 4.0, 4.1, 4.2 float, lbsel = 0 3.45 float, lbsel = 1 3.45 float, lbsel = 0 temperature (c) C50 2.0 voltage (v) 2.2 2.6 2.8 3.0 50 3.8 3331 g55 2.4 0 C25 75 100 25 125 3.2 3.4 3.6 connect, bat_out connect, bat_in disconnect, bat_out, bat_in 3.45 floatlbsel = 0 i bat_out = 1ma temperature (c) C50 2.0 voltage (v) 2.2 2.6 2.8 3.0 50 3.8 3331 g56 2.4 0 C25 75 100 25 125 3.2 3.4 3.6 connect, bat_out connect, bat_in disconnect, bat_out, bat_in 3.45 floatlbsel = 1 i bat_out = 1ma 2.5ms/div 3331 g57 v in = 18v, v out in regulation, sleeping 10ma charges bb_in/bat_out c bb_in = 22f float[1:0] = 11, lbsel = 0 1v/div bat_out bat_in 4.2v 0v battery connected downloaded from: http:///
ltc 3331 13 3331fc for more information www.linear.com/ltc3331 supercapacitor balancer quiescent current vs v scap supercapacitor balancer source/sink current battery connect transient battery connect/disconnect vs temperature battery connect/disconnect vs temperature typical performance characteristics t a = 25c, unless otherwise noted. temperature (c) C50 2.6 voltage (v) 2.8 3.2 3.4 3.6 50 4.4 3331 g58 3.0 0 C25 75 100 25 125 3.8 4.0 4.2 connect, bat_out connect, bat_in disconnect, bat_out, bat_in 4.0, 4.1, 4.2 floatlbsel = 0 i bat_out = 1ma temperature (c) C50 2.6 voltage (v) 2.8 3.2 3.4 3.6 50 4.4 3331 g59 3.0 0 C25 75 100 25 125 3.8 4.0 4.2 connect, bat_out connect, bat_in disconnect, bat_out, bat_in 4.0, 4.1, 4.2 floatlbsel = 1 i bat_out = 1ma 500ms/div 3331 g60 c bat_in = 1mf c bb_in = 22f, bb_in tied to bat_out 1ma load at v out float[1:0] = 11, lbsel = 0 500mv/div bat_out bat_in v out 0v battery disconnected v scap (v) 2 i scap (na) 250200 150 100 50 0 3 4 4.5 5 3.5 3330 g61 5.5 2.5 85c 125c 25c C40c v bal /v scap (%) 0 balancer source/sink current (ma) 5040 30 20 10 0 C10C20 20 30 50 60 70 80 90 40 3330 g62 100 10 scap = 5v scap = 2.5v pin functions bal (pin 1): supercapacitor balance point . the common node of a stack of two supercapacitors is connected to bal. a source / sink balancing current of up to 10 ma is available. tie bal along with scap to gnd to disable the balancer and its associated quiescent current. scap ( pin 2): supply and input for supercapacitor balancer. tie the top of a 2 -capacitor stack to scap and the middle of the stack to bal to activate balancing . tie scap along with bal to gnd to disable the balancer and its associated quiescent current. v in2 (pin 3): internal low voltage rail to serve as gate drive for buck nmos switch . connect a 4.7f ( or larger ) capacitor from v in2 to gnd . this pin is not intended for use as an external system rail.uv3, uv 2, uv 1, uv 0 (pins 4, 5, 6, 7): uvlo select bits for the buck switching regulator . tie high to v in2 or low to gnd to select the desired uvlo rising and falling thresholds ( see table 4). the uvlo falling threshold must be greater than the selected v out regulation level. do not float. downloaded from: http:///
ltc 3331 14 3331fc for more information www.linear.com/ltc3331 ac1 (pin 8): input connection for piezoelectric element , other ac source , or current limited dc source ( used in conjunction with ac2 for differential ac inputs). ac2 (pin 9): input connection for piezoelectric element , other ac source , or current limited dc source ( used in conjunction with ac1 for differential ac inputs).v in (pin 10): rectified input voltage . a capacitor on this pin serves as an energy reservoir and input supply for the buck regulator . the v in voltage is internally clamped to a maximum of 20v (typical). cap (pin 11): internal rail referenced to v in to serve as gate drive for buck pmos switch . connect a 1f (or larger) capacitor between cap and v in . this pin is not intended for use as an external system rail. sw (pin 12): switch node for the buck switching regula - tor. connect a 22 h or greater external inductor between this node and v out . v out (pin 13): regulated output voltage derived from the buck or buck-boost switching regulator. swb (pin 14): switch node for the buck-boost switching regulator. connect an external inductor ( value in table 3) between this node and swa. swa (pin 15): switch node for the buck-boost switching regulator. connect an external inductor ( value in table 3) between this node and swb.bb _ in ( pin 16): input for the buck-boost switching regula - tor. bb_in must be tied to bat_out for proper operation . ipk0, ipk 1, ipk 2 (pins 17, 18, 19): i peak_bb select bits for the buck-boost switching regulator . tie high to v in3 or low to gnd to select the desired i peak_bb ( see table 3). do not float. bat_out (pin 20): this is the output side of the battery disconnect switch . bat_out must be connected to bb_in to power the buck-boost regulator. bat_in (pin 21): input for backup battery and the input side to the battery disconnect switch . when the battery is disconnected there will be less than 10 na of quiescent current draw at bat_in. pin functions lbsel (pin 22): low battery disconnect select pin . con - nect lbsel high to bb_in or low to gnd to select the low battery disconnect level. see table 2. do not float. float1, float 0 (pins 23, 24): float voltage select pins . connect high to bb_in or low to gnd to select battery float voltages of 3.45v, 4.0v, 4.1v, and 4.2 v ( see table ?2). do not float. ship (pin 25): input to select ship mode . tie ship to at least 1.2 v to select ship mode in which the battery disconnect switch will be forced off , ensuring there is no drain on the battery. do not float.v in3 (pin 26): internal low voltage rail used by the prioritizer . logic high reference for ipk [2:0] and out [2:0]. connect a 0.1 f capacitor from v in3 to gnd . this pin is not intended for use as an external system rail. charge (pin 27): connect a resistor from charge to the common bat_out = bb_in node to enable charging of the battery . the charge pin is controlled to provide excess energy from the energy harvesting input when the output is in regulation and the buck converter is in sleep mode. pgvout (pin 28): power good output for v out . logic level output referenced to an internal maximum rail (see operation). pgvout transitioning high indicates regula - tion has been reached on v out (v out = sleep rising ). pgvout remains high until v out falls to 92% (typical) of the programmed regulation point. eh_on (pin 29): switcher status . logic level output ref - erenced to v in3 . eh_on is high when the buck switching regulator is in use ( energy harvesting input ). it is pulled low when the buck-boost switching regulator is in use (battery input). out0, out 1, out 2 (pins 30, 31, 32): v out voltage select bits. tie high to v in3 or low to gnd to select the desired v out (see table 1). do not float. gnd ( exposed pad pin 33): ground. the exposed pad should be connected to a continuous ground plane on the second layer of the printed circuit board by several vias directly under the ltc3331. downloaded from: http:///
ltc 3331 15 3331fc for more information www.linear.com/ltc3331 block diagram 3331 bd bandgap reference internal rail generation prioritizer uvlo uvlo_set sleep v in v ref ac1 20v 10 8 ac2bb_in 9 16 eh_on sleep ilim_set v ref v in2 v in2 v in3 bb_in v out bat_out charge sleep- uvlo bat_in ship lbsel body diode shunt pmos 29 27 20 21 + ? ? + v ref 0.925*v ref sleep ? + ? + v ref v in2 v in3 v in3 cap 11 sw v in2 gnd 33 swa swb v out 15 14 13 pgvout scap bal 28 2 1 v in3 26 buck-boost control ilim_set uvlo_set 12 3 4 3 4, 5, 6, 7 19, 18, 17 3 32, 31, 30 23, 24 out[2:0] float[1:0] uv[3:0] ipk[2:0] buck control ? + bb_in bb_in 2 25 22 ea downloaded from: http:///
ltc 3331 16 3331fc for more information www.linear.com/ltc3331 operation modes of operationthe following four tables detail all programmable settings on the ltc3331. table 1. output voltage selection out2 out1 out0 v out 0 0 0 1.8v 0 0 1 2.5v 0 1 0 2.8v 0 1 1 3.0v 1 0 0 3.3v 1 0 1 3.6v 1 1 0 4.5v 1 1 1 5.0v table 2. float selection lbsel float1 float0 float connect disconnect 0 0 0 3.45v 2.35v 2.04v 0 0 1 4.0v 3.03v 2.70v 0 1 0 4.1v 3.03v 2.70v 0 1 1 4.2v 3.03v 2.70v 1 0 0 3.45v 2.85v 2.51v 1 0 1 4.0v 3.53v 3.20v 1 1 0 4.1v 3.53v 3.20v 1 1 1 4.2v 3.53v 3.20v table 3. i peak_bb selection ipk2 ipk1 ipk0 i lim l min 0 0 0 5ma 1000h 0 0 1 10ma 470h 0 1 0 15ma 330h 0 1 1 25ma 220h 1 0 0 50ma 100h 1 0 1 100ma 47h 1 1 0 150ma 33h 1 1 1 250ma 22h table 4.uvlo selection uv3 uv2 uv1 uv0 uvlo rising uvlo falling 0 0 0 0 4v 3v 0 0 0 1 5v 4v 0 0 1 0 6v 5v 0 0 1 1 7v 6v 0 1 0 0 8v 7v 0 1 0 1 8v 5v 0 1 1 0 10v 9v 0 1 1 1 10v 5v 1 0 0 0 12v 11v 1 0 0 1 12v 5v 1 0 1 0 14v 13v 1 0 1 1 14v 5v 1 1 0 0 16v 15v 1 1 0 1 16v 5v 1 1 1 0 18v 17v 1 1 1 1 18v 5v downloaded from: http:///
ltc 3331 17 3331fc for more information www.linear.com/ltc3331 overview the ltc3331 combines a buck switching regulator and a buck-boost switching regulator to produce an energy harvesting solution with battery backup . the converters are controlled by a prioritizer that selects which converter to use based on the availability of a battery and / or har - vestable energy . if harvested energy is available the buck regulator is active and the buck-boost is off . an onboard 10 ma shunt battery charger with low battery disconnect enables charging of the backup battery to greatly extend the life of the battery . an optional supercapacitor balancer allows for significant energy storage at the output to handle a variety of load requirements. energy harvester the energy harvester is an ultralow quiescent current power supply designed to interface directly to a piezoelectric or alternative a / c power source , rectify the input voltage , and store harvested energy on an external capacitor while maintaining a regulated output voltage . it can also bleed off any excess input power via an internal protective shunt regulator . it consists of an internal bridge rectifier , an undervoltage lockout circuit , and a synchronous buck dc/dc.internal bridge rectifier an internal full-wave bridge rectifier accessible via the dif - ferential ac 1 and ac 2 inputs rectifies ac sources such as those from a piezoelectric element . the rectified output is stored on a capacitor at the v in pin and can be used as an energy reservoir for the buck converter . the bridge rectifier has a total drop of about 800 mv at typical piezo-generated currents (~10a), but is capable of carrying up to 50ma. either side of the bridge can be operated independently as a single-ended ac or dc input. buck undervoltage lockout (uvlo) when the voltage on v in rises above the uvlo rising threshold the buck converter is enabled and charge is transferred from the input capacitor to the output capacitor . when the input capacitor voltage is depleted below the uvlo falling threshold the buck converter is disabled . these thresholds can be set according to table 4 which operation figure 1. ideal v in , v in2 and cap relationship offers uvlo rising thresholds from 4 v to 18 v with large or small hysteresis windows . this allows for program - ming of the uvlo window near the peak power point of the input source . extremely low quiescent current (450na typical) in uvlo allows energy to accumulate on the input capacitor in situations where energy must be harvested from low power sources. internal rail generation (cap, v in2 , v in3 ) two internal rails , cap and v in2 , are generated from v in and are used to drive the high side pmos and low side nmos of the buck converter , respectively . additionally the v in2 rail serves as logic high for the uvlo threshold select bits uv [3:0]. the v in2 rail is regulated at 4.8 v above gnd while the cap rail is regulated at 4.8 v below v in . these are not intended to be used as external rails . bypass capaci - tors are connected to the cap and v in2 pins to serve as energy reservoirs for driving the buck switches . when v in is below 4.8v, v in2 is equal to v in and cap is held at gnd . figure 1 shows the ideal v in , v in2 and cap relationship. v in3 is an internal rail used by the buck and the buck-boost . when the ltc3331 runs the buck v in3 will be a schottky diode drop below v in2 . when it runs the buck-boost v in3 is equal to bb_in. v in (v) 0 voltage (v) 18 12 14 1610 2 4 86 0 10 5 3331 f01 15 v in v in2 cap buck operationthe buck regulator uses a hysteretic voltage algorithm to control the output through internal feedback from the v out sense pin . the buck converter charges an output downloaded from: http:///
ltc 3331 18 3331fc for more information www.linear.com/ltc3331 operation capacitor through an inductor to a value slightly higher than the regulation point . it does this by ramping the inductor current up to i peak_buck through an internal pmos switch and then ramping it down to 0 ma through an internal nmos switch . this efficiently delivers energy to the output capacitor . the ramp rate is determined by v in , v out , and the inductor value . when the buck brings the output voltage into regulation the converter enters a low quiescent current sleep state that monitors the output voltage with a sleep comparator . during sleep load cur - rent is provided by the output capacitor . when the output voltage falls below the regulation point the buck regulator wakes up and the cycle repeats . this hysteretic method of providing a regulated output reduces losses associated with fet switching and maintains the output at light loads . the buck delivers a minimum of 100 ma of average load current when it is switching . v out can be set from 1.8 v to 5 v via the output voltage select bits , out [2:0] ( see table 1). when the sleep comparator senses that the output has reached the sleep threshold the buck converter may be in the middle of a cycle with current still flowing through the inductor . normally both synchronous switches would turn off and the current in the inductor would freewheel to zero through the nmos body diode . instead , the nmos switch is kept on to prevent the conduction loss that would occur in the diode if the nmos were off . if the pmos is on when the sleep comparator trips the nmos will turn on immediately in order to ramp down the current . if the nmos is on it will be kept on until the current reaches zero . though the quiescent current when the buck is switching is much greater than the sleep quiescent current , it is still a small percentage of the average inductor current which results in high efficiency over most load conditions . the buck operates only when sufficient energy has been ac - cumulated in the input capacitor and the length of time the converter needs to transfer energy to the output is much less than the time it takes to accumulate energy . thus , the buck operating quiescent current is averaged over a long period of time so that the total average quiescent current is low . this feature accommodates sources that harvest small amounts of ambient energy. buck-boost converter the buck-boost uses the same hysteretic voltage algorithm as the buck to control the output , v out , with the same sleep comparator . the buck-boost has three modes of operation : buck , buck-boost , and boost . an internal mode comparator determines the mode of operation based on bb _ in and v out . figure 2 shows the four internal switches of the buck-boost converter . in each mode the inductor current is ramped up to i peak _ bb , which is programmable via the ipk[2:0] bits and ranges from 5 ma to 250ma ( see table 3). in buck mode m 4 is always on and m 3 is always off . the inductor current is ramped up through m 1 to i peak _ bb and down to 0 ma through m 2. in boost mode m 1 is always on and m 2 is always off . the inductor current is ramped up to i peak _ bb when m 3 is on and is ramped down to 0 ma when m 4 is on as v out is greater than bb _ in in boost mode . buck-boost mode is very similar to boost mode in that m 1 is always on and m 2 is always off . if bb _ in is less than v out the inductor current is ramped up to i peak _ bb through m 3. when m 4 turns on the current in the inductor will start to ramp down . however , because bb _ in is close to v out and m 1 and m 4 have finite on-resistance the cur - rent ramp will exhibit a slow exponential decay , potentially lowering the average current delivered to v out . for this reason the lower current threshold is set to i peak _ bb /2 in buck-boost mode to maintain high average current to the load . if bb _ in is greater than v out in buck-boost mode the inductor current still ramps up to i peak _ bb and down to i peak _ bb /2. it can still ramp down if bb _ in is greater than v out because the final value of the current in the inductor would be (v in C v out )/( r on 1 + r on 4 ). if bb _ in is exactly i peak _ bb /2 ? (r on 1 + r on 4 ) above v out the inductor current will not reach the i peak _ bb /2 threshold and switches m 1 and m 4 will stay on all the time . for higher bb _ in voltages the mode comparator will switch the converter to buck mode . m 1 and m 4 will remain on for bb _ in voltages up to v out + i peak _ bb ? (r on 1 + r on 4 ). at figure 2: buck-boost power switches 3331 f02 swa swb m1 bb_in m4 v out m3 m2 downloaded from: http:///
ltc 3331 19 3331fc for more information www.linear.com/ltc3331 this point the current in the inductor is equal to i peak _ bb and the i peak _ bb comparator will trip turning off m 1 and turning on m 2 causing the inductor current to ramp down to i zero , completing the transition from buck-boost mode to buck mode . v out power good a power good comparator is provided for the v out output . it transitions high the first time the ltc3331 goes to sleep , indicating that v out has reached regulation . it transitions low when v out falls to 92% (typical) of its regulation value . the pgvout output is referenced to an internal rail that is generated to be the highest of v in2 , bb_in, and v out less a schottky diode drop.shunt battery charger the ltc3331 provides a reliable low quiescent current shunt battery charger to facilitate charging a battery with harvested energy . a low battery disconnect feature provides protection to the battery from overdischarge by disconnecting the battery from the buck-boost input at a programmable level. to use the charger connect the battery to the bat_in pin. an internal low battery disconnect pmos switch is connected between the bat_in pin and the bat_out pin. the bat_out pin must be connected to bb_in for proper operation . a charging resistor connected from v in to bat_out or from charge to bat_out will charge the battery through the body diode of the disconnect pmos until the battery voltage rises above the low-battery con - nect threshold . depending on the capacity of the battery and the input decoupling capacitor , the common bat _ out = bb_in node voltage generally rises or falls to v bat_in when the pmos turns on . once the pmos is on the charge current is determined by the charging resistor , the battery voltage, and the voltage of the charging source. as the battery voltage approaches the float voltage , the ltc3331 shunts current away from the battery thereby reducing the charging current . the ltc3331 can shunt up to 10ma. float voltages of 3.45v, 4.0v, 4.1v, and 4.2v are programmable via the float [1:0] pins ( see table 2). charging can occur through a resistor connected to v in or the charge pin . an internal set of back to back pmos switches are connected between charge and v in 2 and are turned on only when the energy harvesting buck converter is sleeping. in this way charging of the battery only hap- pens when there is excess harvested energy available and the v out output is prioritized over charging of the battery . the charge current available from this pin is limited by the strength of the v in 2 ldo and an appropriate charging resis - tor must be selected to limit this current . the on resistance of the internal charge switches combined is approximately 60. to charge with higher currents connect a resistor directly to v in . note that when charging from v in the bat - tery is always being charged . care must be taken to ensure that enough power is available to bring up the v out output . low battery disconnect/connect: lbd/lbc the low battery disconnect (v lbd ) and connect (v lbc ) volt - age levels are programmed by the lbsel and float [1:0] pins ( see table ?2). as shown in the block diagram the bat - tery disconnects from the common bat _ out = bb _ in node by shutting off the pmos switch when the bat_in voltage falls below v lbd . this disconnect function protects li-ion batteries from permanent damage due to deep discharge . disconnecting the battery from the common bat_out = bb_in node prevents the load as well as the ltc3331 quiescent current from further discharging the battery. once disconnected the common bat_out = bb_in node voltage collapses towards ground . when an input supply is reconnected the battery charges through the internal body diode of the disconnect pmos . the input supply voltage should be larger than v lbc _ bat _ out to ensure that the pmos is turned on . when the voltage reaches v lbc_bat_out , the pmos turns on and connects the common bat_out = bb_in node to bat_in. while disconnected , the bat_in pin voltage is indirectly sensed through the pmos body diode. therefore v lbc_bat_in varies with charge current and junction temperature . see the typical performance characteristics section for more information.low battery select the low battery disconnect voltage level is programmed by the lbsel pin for each float setting . the lbsel pin allows the user to trade-off battery run time and maximum shelf life. a lower battery disconnect threshold maximizes run operation downloaded from: http:///
ltc 3331 20 3331fc for more information www.linear.com/ltc3331 time by allowing the battery to fully discharge before the disconnect event . conversely , by increasing the low battery disconnect threshold more capacity remains following the disconnect event which extends the shelf life of the battery . for maximum run time , tie lbsel to gnd . for extended shelf life , tie lbsel to the common bat_out = bb_in node. if a high peak current event is expected , users may temporarily select the lower disconnect threshold . this avoids disconnecting the battery too early when the load works against the battery series resistance and temporarily reduces the common bat_out = bb_in node. ship mode a ship mode is provided which manually disconnects the battery. this may be useful to prevent discharge of the bat - tery in situations when no harvestable energy is expected for a long period of time such as during shipping . bring the ship pin high to engage ship mode . the low battery disconnect pmos will turn off , disconnecting the battery at bat_in from the common bat_out = bb_in node . if no harvestable energy is present to hold up the common bat_out = bb_in node that voltage will collapse . typi - cally an additional 1 a of quiescent current will appear on bb_in while ship mode is engaged. to exit ship mode first bring the ship pin low . if the bb_in voltage had collapsed while in ship mode it must now be brought above the lbc threshold to reconnect the battery . this can be done manually or from an energy harvesting charging source . if harvestable energy had been propping up the common bat_out = bb_in node voltage above the lbc threshold then the battery will be connected immediately. prioritizerthe input prioritizer on the ltc3331 decides whether to use the energy harvesting input or the battery input to power v out . if a battery is powering the buck-boost converter and harvested energy causes a uvlo rising transition on v in , the prioritizer will shut off the buck-boost and turn on the buck , orchestrating a smooth transition that maintains regulation of v out . operation when harvestable energy disappears , the prioritizer will first poll the bb_in voltage . if the bb_in voltage is above 1.8 v the prioritizer will switch back to the buck-boost while maintaining regulation . if the bb_in voltage is below 1.8v the buck-boost is not enabled and v out cannot be supported until harvestable energy is again available . if the battery is connected then the bb_in voltage will be above 1.8v for every float and lbsel combination . if the battery is disconnected the bb_in voltage will have collapsed below 1.8v and the prioritizer will not switch to the buck-boost when harvestable energy goes away . in the event that the battery is depleted and is disconnected while powering the buck-boost the prioritizer will not switch back to v in until harvested energy is again available. if either bb_in or v in is grounded , the prioritizer allows the other input to run if its input is high enough for op - eration. the specified quiescent current in uvlo is valid upon start-up of the v in input and when the battery has taken over regulation of the output . if the battery is less than 1.8v when uvlo is entered and the prioritizer does not enable the buck-boost several hundred nanoamperes of additional quiescent current will appear on v in . when the prioritizer selects the v in input the current on the bb_in input drops to 200na. however , if the voltage on bb_in is higher than v in2 , a fraction of the v in quiescent current will appear on bb_in due to internal level shifting . this only affects a small range of battery voltages and uvlo settings. a digital output , eh_on, is low when the prioritizer has selected the bb_in input and is high when the prioritizer has selected the v in input . the eh_on output is referenced to v in3 . supercapacitor balancer an integrated supercapacitor balancer with 150 na of quiescent current is available to balance a stack of two supercapacitors. typically the input , scap , will tie to v out to allow for increased energy storage at v out with supercapacitors. the bal pin is tied to the middle of the stack and can source and sink 10 ma to regulate the bal pin s voltage to half that of the scap pin s voltage . to disable the balancer and its associated quiescent current the scap and bal pins can be tied to ground. downloaded from: http:///
ltc 3331 21 3331fc for more information www.linear.com/ltc3331 applications information the ltc3331 allows for energy harvesting from a variety of alternative energy sources in order to power a wireless sensor system and charge a battery . the extremely low quiescent current of the ltc3331 facilitates harvesting from sources generating only microamps of current . the onboard bridge rectifier is suitable for ac piezoelectric or electromagnetic sources as well as providing reverse protection for dc sources such as solar and thermoe lectric generators. the ltc3331 powers the v out output con - tinuously by seamlessly switching between the energy harvesting and battery inputs. when harvestable energy is available , it is transferred through the bridge rectifier where it accumulates on the v in capacitor. a low quiescent current uvlo mode allows the voltage on the capacitor to increase towards a programmed uvlo rising threshold . when the voltage rises to this level , the buck converter turns on and transfers energy to v out . as energy is transferred the voltage at v in may decrease to the uvlo falling threshold . if this happens , the buck converter turns off and the buck-boost then turns on to service the load from the battery input while more energy is harvested . when the buck is running the quiescent cur - rent on the bb_in pin drops to the 200 na required by the shunt battery charger. the ltc3331 is well suited to wireless systems which consume low average power but occasionally need a higher concentrated burst of power to accomplish a task . if these bursts occur with a low duty cycle such that the total energy needed for a burst can be accumulated between bursts then the output can be maintained entirely by the harvester. if the bursts need to happen more frequently or if harvestable energy goes away the battery will be used . if enough energy is available the energy harvester will bring the output up and enter the low quiescent current sleep state and excess energy can be used to charge the battery . piezo energy harvesting ambient vibrational energy can be harvested with a piezoelectric transducer which produces a voltage and current in response to strain . common piezoelectric elements are pzt ( lead zirconate titanate ) ceramics , pvdf ( polyvinylidene fluoride ) polymers , or other composites . ceramic piezoelectric elements exhibit a piezoelectric effect when the crystal structure of the ceramic is compressed and internal dipole movement produces a voltage . polymer elements comprised of long-chain molecules produce a voltage when flexed as molecules repel each other . ceramics are often used under direct pressure while a polymer is commonly used as a cantilevered beam. a wide range of piezoelectric elements are available and produce a variety of open-circuit voltages and short-circuit currents . typically the open-circuit voltage and short-circuit currents increase with available vibrational energy as shown in figure 3. piezoelectric elements can be placed in series or in parallel to achieve desired open-circuit voltages. piezos produce the most power when they operate at approximately half the open circuit voltage for a given vibration level . the uvlo window can be programmed to straddle this voltage so that the piezo operates near the peak power point . in addition to the normal configuration of connecting the piezo across the ac 1 and ac 2 inputs , a piezo can be connected from either ac 1 or ac 2 to ground . the resulting configuration is a voltage doubler as seen in figure 4 where the intrinsic capacitance of the piezo is used as the doubling capacitor. figure 3. typical piezoelectric load lines for piezo systems t220-a4-503x piezo current (a) 0 piezo voltage (v) 12 96 3 0 20 10 3331 f03 30 increasing vibration energy downloaded from: http:///
ltc 3331 22 3331fc for more information www.linear.com/ltc3331 a second piezo may be connected from ac 2 to ground . this may be of use if the second piezo is mechanically tuned to a different resonant frequency present in the system than the first piezo . to achieve maximum power transfer from the piezo with the doubler the uvlo window should be set to the open circuit voltage of the piezo. piezoelectric elements are available from the manufactur - ers listed in table 5. table 5. piezoelectric element manufacturers advanced cerametrics www.advancedcerametrics.com piezo systems www.piezo.com measurement specialties www.meas-spec.com pi (physik instrumente) www.pi-usa.us mide technology corporation www.mide.com morgan technical ceramics www.morganelectroceramics.com electromagnetic energy harvesting another alternative ac source is an electromagnetic vibra - tion harvester in which a magnet vibrating inside a coil induces an ac voltage and current in the coil that can then be rectified and harvested by the ltc3331. the vibration could be ambient to the system or it could be caused by an impulse as in a spring loaded switch. solar energy harvesting the ltc3331 can harvest solar energy as the bridge recti - fier can be used to provide reverse protection for a solar panel. a solar cell produces current in proportion to the amount of light falling on it . figure 5 shows the relationship between current and voltage for a solar panel illuminated with several levels of light . the maximum power output occurs near the knee of each curve where the cell transi - tions from a constant current device to a constant voltage gnd ltc3331 piezo model v in c in ac1 3331 f04 i p sin( t) c p figure 4. ltc3331 voltage doubler configuration device. fortunately , the peak power point doesn t change much with illumination and an appropriate uvlo window can be selected so that the panel operates near the peak power point for a majority of light conditions. two solar panels can be connected to the ltc3331, one from ac 1 to ground and another from ac 2 to ground . each panel could be aimed in a different direction to capture light from different angles or at different times of the day as the sun moves . the panels should be similar so that the selected uvlo window is optimal for both panels.bb_in/bat_out, bat_in, v in , and v out capacitors the input to the buck-boost , bb _ in , must be connected to bat _ out for proper operation . bat _ out is the output side of the low battery disconnect switch . the series resistance of this switch must be considered when selecting a bypass capacitor for the common bat_out = bb_in node . at least 4.7 f to gnd or greater should be used . for the higher i peak _ bb settings the capacitor may need to be larger to smooth the voltage at the common bat_out = bb_in node. the goal is to average the input current to the buck boost so that the voltage droop at the common bat_out = bb_in node is minimized . a bypass capacitor of 1 f or greater can also be placed at the bat _ in pin . in cases where the series resistance of the battery is high , a larger capacitor may be desired to handle transients . figure 5. typical solar panel characteristics v panel (v) 0 i panel (a) w panel (w) 500400 300 200 100 0 15001200 900 600 300 0 2 3 4 5 3331 f05 6 1 sanyo 1815 solar panel 1800 lux500 lux 200 lux 1000 lux panel current panel power applications information downloaded from: http:///
ltc 3331 23 3331fc for more information www.linear.com/ltc3331 the input capacitor to the buck on v in and the v out capacitor can vary widely and should be selected to op - timize the use of an energy harvesting source depending on whether storage of the harvested energy is needed at the input or the output . storing energy at the input takes advantage of the high input voltage as the energy stored in a capacitor increases with the square of its voltage . storage at the output may be necessary to handle load transients greater than the 100 ma the buck can provide . the input or output capacitor should be sized to store enough energy to provide output power for the length of time required . if enough energy is stored so that the buck does not reach the uvlo falling threshold during a load transient then the battery current will always be zero. spacing load transients so that the average power required to service the application is less than or equal to the power available from the energy harvesting source will then greatly extend the life of the battery . the v in capacitor should be rated to withstand the highest voltage ever present at v in . the following equation can be used to size the input capacitor to meet the power requirements of the output for the desired duration: p load t load = 1 2 c in v in 2 C v uvlofalling 2 ( ) v uvlofalling v in v shunt here is the average efficiency of the buck converter over the input voltage range and v in is the input voltage when the buck begins to switch . typically v in will be the uvlo rising threshold . this equation may overestimate the input capacitor necessary as it may be acceptable to allow the load current to deplete the output capacitor all the way to the lower pgvout threshold . it also assumes that the input source charging has a negligible effect during this time. the duration for which the buck or buck-boost regulator sleeps depends on the load current and the size of the v out capacitor. the sleep time decreases as the load current increases and / or as the output capacitor decreases . the dc sleep hysteresis window is 6 mv for the 1.8 v output and scales linearly with the output voltage setting (12mv for the 3.6 v setting , etc .). ideally this means that the sleep time is determined by the following equation: t sleep = c out 12mv ? v out 1.8v i load this is true for output capacitors on the order of 100f or larger , but as the output capacitor decreases towards 10f, delays in the internal sleep comparator along with the load current itself may result in the v out voltage slew - ing past the dc thresholds . this will lengthen the sleep time and increase v out ripple . a capacitor less than 10f is not recommended as v out ripple could increase to an undesirable level . if transient load currents above 100ma are required then a larger capacitor should be used at the output. this capacitor will be continuously discharged during a load condition and the capacitor can be sized for an acceptable drop in v out : c out = i load C i dc/dc ( ) t load v out + C v out C here v out + is the value of v out when pgvout goes high and v out C is the acceptable lower limit of v out . i dc/dc is the average current being delivered from either the buck converter or the buck-boost converter . the buck converter typically delivers 125 ma on average to the output as the inductor current is ramped up to 250 ma and down to zero . the current the buck-boost delivers depends on the mode of operation and the i peak _ bb setting . in buck mode the deliver - able current is i peak_bb/ 2. in buck-boost and boost modes the deliverable current also depends on the v in to v out ratio : buck-boost mode: i dc/dc = 3 4 i peak_bb v in v out boost mode: i dc/dc = 1 2 i peak_bb v in v out a standard surface mount ceramic capacitor can be used for c out , though some applications may be better suited to a low leakage aluminum electrolytic capacitor or a supercapacitor . these capacitors can be obtained from manufacturers such as vishay , illinois capacitor , avx , or cap-xx . applications information downloaded from: http:///
ltc 3331 24 3331fc for more information www.linear.com/ltc3331 cap, v in2 , and v in3 capacitors a 1 f or larger capacitor must be connected between v in and cap and a 4.7 f capacitor must be connected between v in2 and gnd . these capacitors hold up the internal rails during buck switching and compensate the internal rail generation circuits . in applications where the voltage at v in is limited to less than 6v, the cap pin can be tied to gnd and the v in2 pin can be tied to v in as shown in figure 6. an optional 5.6 v zener diode can be connected to v in to clamp v in in this scenario . the leakage of the zener diode below its clamping voltage should be considered as it could be comparable to the quiescent current of the ltc3331. this circuit does not require the capacitors on v in2 and cap , saving two components and allowing for a lower voltage rating for the single v in capacitor. a 0.1 f bypass capacitor must be connected from v in3 to ground . v in3 is an internal rail that is shared by both the buck and buck-boost . it is not intended for use as a system rail . it is used as a the logic high reference level for the ipk [2:0] and out [2:0] digital inputs . in the event that these pins are dynamically driven in the application , external inverters may be needed and they must use v in3 as a rail . however , care must be taken not to overload v in3 and the quiescent current of such logic should be kept minimal . the output resistance of the v in3 pin is typically 15k. figure 6. low voltage solar harvester with reduced component count (v in < 6v) applications information ltc3331 3331 f06 ac1 v in cap v in2 ac2 swa swb v out sw scap bal pgvout eh_on v in3 ipk2ipk1 ipk0 out2 22h 1.8v out1out0 0.1f 6.3v li-ion uvlo rising = 4v uvlo falling = 3v ipeak_bb = 150ma 22f6.3v 5.6v (optional) uv3uv2 uv1 uv0 bat_in float1 float0 lbsel ship gnd charge bat_out bb_in + 22f6.3v 33h solar panel +? solar panel +? 22f 6.3v 1f 6.3v 12k 4.2v downloaded from: http:///
ltc 3331 25 3331fc for more information www.linear.com/ltc3331 inductor selectionthe buck is optimized to work with a 22 h inductor in typical applications . a larger inductor will benefit high voltage applications by increasing the on-time of the pmos switch and improving efficiency by reducing gate charge loss. choose an inductor with a dc current rating greater than 500ma. the dcr of the inductor can have an impact on efficiency as it is a source of loss . tradeoffs between price, size, and dcr should be evaluated. applications information the buck-boost is optimized to work with a minimum induc - tor of 22 h for the 250ma i peak_bb setting . for the other seven i peak_bb settings the inductor value should increase as the i peak_bb selection decreases to maintain the same i peak_bb ? l product . the minimum inductor values for the buck-boost for each i peak_bb setting are listed in table 3. larger inductors may increase efficiency . choose an inductor with an i sat rating at least 50% greater than the selected i peak value . table 6 lists several inductors that work well with both the buck and the buck-boost. table 6. recommended inductors for the ltc3331 part number l(h) manufacturer size (mm) (l w h) max idc (ma) max dcr () 744043102 lps5030-105ml lps4018-105ml lps3314-105ml b82442t1105k050 1000 wrth elektronik coilcraft coilcraft coilcraft epcos 4.8 4.8 2.8 5.51 5.51 2.9 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 80 110 98 99 150 7 5.1 18 31 9.5 744043471 lps 4018-474ml lps3314-474ml b82442t147k050 470 wrth elektronik coilcraft coilcraft epcos 4.8 4.8 2.8 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 125 160 110 240 2.6 7.8 12 4.73 744042331 lps4018-334ml lps3314-334ml b82442t1334k050 330 wrth elektronik coilcraft coilcraft epcos 4.8 4.8 1.8 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 130 190 110 280 4.5 5.9 9.3 3.29 744042221 lps4018-224ml lps3314-224ml b82442t1224k050 220 wrth elektronik coilcraft coilcraft epcos 4.8 4.8 1.8 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 160 260 160 330 3.2 3.7 6 2.2 744031101 lps4018-104ml lps3314-104ml b82442t1104k050 100 w rth elektronik coilcraft coilcraft epcos 3.8 3.8 1.65 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 180 360 230 510 2.4 1.4 2.75 0.99 744031470 lps4018-473ml lps3314-473ml b82442t1473k050 47 wrth elektronik coilcraft coilcraft epcos 3.8 3.8 1.65 3.9 3.9 1.7 3.3 3.3 1.3 5.6 5 5 250 550 330 700 1 0.65 1.4 0.519 744031330 lps4018-333ml lps3314-333ml 1070bs-330ml b82442t1333k050 33 wrth elektronik coilcraft coilcraft toko epcos 3.8 3.8 1.65 3.9 3.9 1.7 3.3 3.3 1.3 3.2 3.2 2 5.6 5 5 320 640 380 230 840 0.66 0.42 0.92 0.61 0.36 744031220 lps5030-223ml lps4018-223ml lps3314-223ml 1070as-220m b82442t1223k050 22 wrth elektronik coilcraft coilcraft coilcraft toko epcos 3.8 3.8 1.65 5.51 5.51 2.9 3.9 3.9 1.7 3.3 3.3 1.3 3.2 3.2 2 5.6 5 5 360 750 800 450 410 1040 0.45 0.19 0.36 0.72 0.64 0.238 744029220 1069bs-220m 22 wrth elektronik toko 2.8 2.8 1.35 3.2 3.2 1.8 300 290 0.97 0.495 downloaded from: http:///
ltc 3331 26 3331fc for more information www.linear.com/ltc3331 applications information supercapacitor balancer if supercapacitors are used at v out the onboard supercapacitor balancer can be used to balance them with 10 ma of balance current . a list of supercapacitor suppliers is provided in table 7. table 7. supercapacitor manufacturers cap-xx www.cap-xx.com ness cap www.nesscap.com maxwell www.maxwell.com bussman www.cooperbussman.com avx www.avx.com illinois capacitor www.illcap.com tecate group www.tecategroup.com by seamlessly combining a battery source and an en- ergy harvesting source , the ltc3331 enables the use of supercapacitors in energy harvesting applications . the battery provides the initial current required to overcome the effects of the diffusion current when voltage is first applied to the supercapacitors . the energy harvesting source can then support the lower steady state leakage current and average load current. summary of digital inputs and outputs there are 14 digital pin-strapped logic inputs to the ltc3331 and two digital logic outputs . these and the rails they are referenced to are summarized in table 8. table 8. digital pin summary input pin logic high level uv[3:0] v in2 ipk[2:0] v in3 out[2:0] v in3 float[1:0], lbsel bat_out = bb_in ship 1.2v output pin logic high level pgvout max (bb_in, v in2 , v out ) eh_on v in3 battery considerations the shunt battery charger is designed to work with any single li-ion , lifep 0 4 , or other chemistry with a termination voltage compatible with the available levels . table 9 lists some batteries , their capacities and their equivalent series resistance (esr). the esr causes bat_out and bat_in to droop by the product of the load current amplitude multiplied by the esr . this droop may trigger the low battery disconnect while the battery itself may still have ample capacity . an appropriate bypass capacitor placed at bat_out will help prevent large , low duty cycle load transients from pulling down on bat_out. the bypass capacitor used at bb_in, which is tied to bat_out, to bypass the buck-boost may be sufficient. table 9. low capacity li-ion and thin-film batteries manufacturer p/n capacity resistance v min cymbet cbc012 12ah 5k to 10k 3.0v cymbet cbc050 50ah 1500 to 3k 3.0v gm battery gmb031009 8mah 10 to 20 2.75v gs nanotech n/a 500ah 40 3.0v power stream lir2032 40mah 0.6 3.0v charging the battery charging the battery with the charge pin allows the battery to be charged only when the energy harvester is sleeping , which prioritizes the v out output over the battery . the current that the charge pin can supply is limited to 2 ma and an appropriately chosen current limiting resistor should be used . use the following equation to calculate the value of this resistor: r charge = 4.8v C v lbd i charge C 60 ? here 4.8 v is the output of the v in2 ldo which is the sup - ply to the charge pin , v lbd is the selected low battery disconnect threshold , 60 is the resistance of the charge pin pmos , and i charge is the desired charge current . for high charging currents approaching 2ma, a larger v in2 capacitor may improve transient behavior. downloaded from: http:///
ltc 3331 27 3331fc for more information www.linear.com/ltc3331 figure 8. dual 5v power supply applications information for applications where more charging current is avail - able a resistor tied to v in or the circuit of figure 7 can be used to provide up to 10 ma to the battery . the circuit of figure ?7 uses the charge pin to only allow charging when the energy harvester is sleeping . for applications q2 cmpt3906e q1bndc7001c q1andc7001c r21m r156.2 r4100k cmosh-3 3331 f07 r31m charge ltc3331 bb_in v in figure 7 requiring even more charging current , the ltc3331 can be paired with the ltc4071 shunt battery charger connected at the bb_in pin.ltc3331 system solutions the ltc3331 can be paired with other linear technology low quiescent current integrated circuits to form a multirail sys - tem. figure 8 shows an ltc3331 powering an ltc3388-3 from its 5 v output . the ltc3388-3, an 800 na buck converter, is configured here to produce a negative 5v rail by tying the v out pin to ground and tying its gnd pin to the regulated C5 v output . the result is a 5 v energy harvesting power supply with battery backup. higher efficiency battery powered buck if the battery voltage will always be higher than the regu - lated output of the ltc3331 then the battery powered buck-boost will always run in buck mode . in this case the inductor that is usually placed between swa and swb can go directly to v out from swa , bypassing internal switch m 4 of the buck-boost (figure 9). this will reduce conduction losses in the converter and improve the ef - ficiency at higher loads. ltc3331 ac1 v in capv in2 ac2 swa swb v out sw scap bal pgvout eh_on v in3 ipk2ipk1 ipk0 out2 22h 5v out1out0 0.1f 6.3v li-ion uvlo rising = 12v** uvlo falling = 11v ipeak_bb = 250ma 22f25v 4.7f 6.3v 1f 6.3v uv3uv2 uv1 uv0 bat_in float1 float0 lbsel ship gnd charge bat_out bb_in + 22f6.3v 22h mide v25w 22f6.3v 1f 6.3v 68k 4.1v 3331 f08 *exposed pad must be electrically isolated from system ground and connected to the C5v rail **for peak power transfer, center the uvlo window at half the rectified open circuit voltage of the piezo v in pgood capv in2 sw en v out ltc3388-3* gnd d1 d0 stby 4.7f6.3v 1f 6.3v 22f6.3v C5v 2.2f10v 22h downloaded from: http:///
ltc 3331 28 3331fc for more information www.linear.com/ltc3331 figure 9a. higher efficiency battery-powered buck regulator figure 9b. efficiency comparison between normal buck-boost and bypassed swb configuration applications information alternative power sources the ltc3331 can accommodate a wide variety of input sources. figure 10 shows the ltc3331 internal bridge rectifier connected to a 120 v rms ac line in series with four 3.9 k current limiting resistors . this produces a peak current of 10 ma with the ltc3331 shunt holding v in at 20v. this current may be increased by reducing the resistor values since the shunt can sink 25 ma and the bridge is rated for 50ma. an optional external zener diode (shown) may be required if the current exceeds 25ma. a transformer may also be used to step down the voltage and reduce the power loss in the current limiting resistors . the 3.3 k charging resistor charges the battery from v in with approximately 5ma. this is a high voltage application and minimum spacing between the line , neutral , and any high voltage components should be maintained per the applicable ul specification . for general off-line applica - tions refer to ul regulation 1012. figure 11 shows an application where copper panels are placed near a standard fluorescent room light to capacitively harvest energy from the electric field around the light . the frequency of the emission will be double the line frequency for magnetic ballasts but could be higher if the light uses electronic ballast . the peak ac voltage and the total available energy will scale with the size of the panels used and with the proximity of the panels to the electric field of the light. the ltc 3331 could also be used to wirelessly harvest energy and charge a battery by using a transmitter and receiver consisting of loosely coupled tuned resonant tanks as shown in figure 12. using eh_on to program v out the eh _ on output indicates whether the energy harvesting input or the battery is powering the output . the application ltc3331 3331 f09a ac1 v in capv in2 ac2 swa swb sw 1.8v v out scap bal pgvout eh_on v in3 ipk2ipk1 ipk0 out2out1 out0 22h uvlo rising = 12v* uvlo falling = 11v ipeak_bb = 250ma 22f25v 1f 6.3v 4.7f 6.3v uv3uv2 uv1 uv0 bb_in bat_in bat_out charge float0 float1 lbsel ship gnd 22h 22f6.3v 22f6.3v mide v25w 68k 4.0v *for peak power transfer, center the uvlo window at half the rectified open circuit voltage of the piezo 0.1f 6.3v li-ion + 1f 6.3v bb_in (v) 2.6 efficiency (%) 90 95 100 3.2 3.6 4.2 3331 f09b 85 80 75 2.8 3 3.4 3.8 4 v out = 1.8v, bypass swb v out = 1.8v, include swb v out = 3.3v, bypass swb v out = 3.3v, include swb downloaded from: http:///
ltc 3331 29 3331fc for more information www.linear.com/ltc3331 dangerous and lethal potentials are present in offline circuits ! before proceeding any further , the reader is warned that caution must be used in the construction , testing and use of offline circuits . extreme caution must be used in working with and making connections to these circuits . repeat : offline circuits contain dangerous , ac line-connected high voltage potentials , use caution . all testing performed on an offline circuit must be done with an isolation transformer connected between the offline circuit s input and the ac line . users and constructors of offline circuits must observe this precaution when connecting test equipment to the circuit to avoid electric shock . repeat : an isolation transformer must be connected between the circuit input and the ac line if any test equipment is to be connected . figure 10. ac line powered 5v ups applications information ltc3331 3331 f10 ac1 v in capv in2 ac2 3.9k 3.9k 120vac 60hz swa swb sw v out v in3 scap bal pgvout out2out1 out0 eh_on ipk2ipk1 ipk0 uvlo rising = 18v uvlo falling = 5v ipeak_bb = 250ma 22f25v 1f 6.3v 4.7f 6.3v 3.3k uv3uv2 uv1 uv0 bat_in float0 float1 lbsel ship gnd chargebb_in bat_out 22f6.3v 0.1f 6.3v 18v (optional) 3.3v 22f6.3v 22h 22h 3.9k 3.9k danger high voltage 4.0v li-ion + 1f 6.3v on the last page of this data sheet shows the eh_on output tied to the out 2 input . when eh_on is low the output is programmed to 2.5 v and the battery powers the output . when energy harvesting is available eh_on is high and the output is programmed to 3.6 v allowing for increased storage of harvested energy . if energy harvesting goes away, the output is again programmed to 2.5 v and the buck-boost converter will be in sleep until the output is discharged to the wake-up threshold . if the energy stored at 3.6 v is enough to ride through a temporary loss of energy harvesting then the only drain on the battery will be the quiescent current in sleep. downloaded from: http:///
ltc 3331 30 3331fc for more information www.linear.com/ltc3331 figure 11. electric field energy harvester applications information ltc3331 3331 f10 ac1 v in capv in2 ac2 copper panel (12" 24") swa v out sw swb scap bal pgvout eh_on ipk2ipk1 ipk0 out2out1 out0 v in3 uvlo rising = 14v uvlo falling = 5v ipeak_bb = 5ma 22f25v 1f 6.3v 4.7f 6.3v uv3uv2 uv1 uv0 bat_in float1 float0 lbsel ship gnd chargebb_in bat_out 0.1f 6.3v 300k 100mf2.7v 100mf2.7v 100h 22h 2.5v copper panel (12" 24") 22f6.3v 22f6.3v 4.2v li-ion + 1f 6.3v downloaded from: http:///
ltc 3331 31 3331fc for more information www.linear.com/ltc3331 figure 12. wireless battery charger applications information ltc3331 3331 f12 ac1 v in capv in2 ac2 swa v out sw swb scap bal pgvout eh_on ipk2ipk1 ipk0 out2out1 out0 v in3 uvlo rising = 14v uvlo falling = 5v ipeak_bb = 5ma 22f25v 1f 6.3v 4.7f 6.3v uv3uv2 uv1 uv0 bat_in float1 float0 lbsel ship gnd chargebb_in bat_out 0.1f 6.3v 4.3k 100mf2.7v 100mf2.7v 100h 270 22h 2.5v 22f6.3v 22f6.3v 3.45v li-ion capacitor taiyo yuden 200f 1f 6.3v 100nf25v 47h 5h power 300nf50v dcsource + C 130khz transmitter linear technology dc1968a part of dc1969a-b kit gnd t x t y downloaded from: http:///
ltc 3331 32 3331fc for more information www.linear.com/ltc3331 package description please refer to http:// www .linear.com/designtools/packaging/ for the most recent package drawings. 5.00 0.10 (4 sides) note:1. drawing proposed to be a jedec package outline m0-220 variation whhd-(x) (to be approved) 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 0.20mm 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 pin 1top mark (note 6) 0.40 0.10 31 12 32 bottom viewexposed pad 3.50 ref (4-sides) 3.45 0.10 3.45 0.10 0.75 0.05 r = 0.115 typ 0.25 0.05 (uh32) qfn 0406 rev d 0.50 bsc 0.200 ref 0.00 C 0.05 0.70 0.05 3.50 ref (4 sides) 4.10 0.05 5.50 0.05 0.25 0.05 package outline 0.50 bsc recommended solder pad layout apply solder mask to areas that are not soldered pin 1 notch r = 0.30 typ or 0.35 45 chamfer r = 0.05 typ 3.45 0.05 3.45 0.05 uh package 32-lead plastic qfn (5mm 5mm) (reference ltc dwg # 05-08-1693 rev d) downloaded from: http:///
ltc 3331 33 3331fc for more information www.linear.com/ltc3331 information furnished by linear technology corporation is believed to be accurate and reliable . however, no responsibility is assumed for its use . linear technology corporation makes no representa - tion that the interconnection of its circuits as described herein will not infringe on existing patent rights . revision history rev date description page number a 07/14 clarified i q on the ltc3330 in the related parts list 34 b 11/14 clarified description clarified available buck-boost current conditions replaced pgood with pgvout in graphs clarified table 2 replaced pgood with pgvout in text clarified t sleep formula clarified figure 6 schematic clarified inductor selection paragraph clarified typical application schematic clarified ltc3330 comments in related parts 1 4 7, 8 16 23 23 24 25 34 34 c 08/15 changed c out equation 23 downloaded from: http:///
ltc 3331 34 3331fc for more information www.linear.com/ltc3331 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 ? linear technology corporation 2014 lt 0815 rev c ? printed in usa (408) 432-1900 fax : (408) 434-0507 www.linear.com/ltc3331 ups system for wireless mesh networks with output supercapacitor energy storage ltc3331 3331 ta02 ac1 v in capv in2 ac2 swb swa sw v out scap bal pgvout eh_on ipk2ipk1 ipk0 out2out0 out1 v in3 0.1f 6.3v uvlo rising = 12v* uvlo falling = 11v ipeak_bb = 50ma 22f25v 1f 6.3v 4.7f 6.3v uv3uv2 uv1 uv0 bat_in float1 float0 lbsel ship gnd charge 130k bb_in bat_out linear technology dc9003a-ab dust mote for wireless mesh networks pgood ehorbat t x v supply gnd v out = 3.6v for eh_on = 1 v out = 2.5v for eh_on = 0 1f2.7v 1f2.7v 22f6.3v 100h 22h *for peak power transfer, center the uvlo window at half the rectified open circuit voltage of the piezo 22f6.3v 3.45v lifepo 4 + 1f 6.3v mide v25w related parts typical application part number description comments ltc3330 nanopower buck-boost dc/dc with energy harvesting battery life extender v in : 3.0v to 19v; bat : 1.8v to 5.5v, 750na i q 5mm 5mm qfn-32 package ltc3588-1/ ltc3588-2 nanopower energy harvesting power supply with up to 100ma of output current v in : 2.7v to 20v; v out : fixed 1.8v to 5v; i q = 950na; i sd = 450na; msop-10, 3mm 3mm dfn-10 packages lt1389 nanopower precision shunt voltage reference v ref : 1.25v, 2.25v, 4.096v; i q = 800na; i sd < 1a; so-8 package ltc1540 nanopower comparator with reference v in : 2v to 11v; i q = 0.3a; i sd < 1a; 3mm 3mm dfn-8 package lt3009 3a i q , 20ma low dropout linear regulator v in : 1.6v to 20v; v out : 0.6v, fixed 1.2v to 5v; i q = 3a; i sd < 1a; sc-70-8, 2mm 2mm dfn-8 packages ltc3105 400ma step-up converter with mppc and 250mv start-up v in : 0.2v to 5v; v out : max 5.25v; i q = 22a; i sd < 1a; 3mm 3mm dfn-10, msop-12 package ltc3108 ultralow voltage step-up converter and power manager v in : 0.02v to 1v; v out : fixed 2.35v to 5v; i q = 7a; i sd < 1a; tssop-16, 3mm 4mm dfn-12 packages ltc3109 auto-polarity, ultralow voltage step-up converter and power manager v in : 0.03v to 1v; v out : fixed 2.35v to 5v; i q = 7a; i sd < 1a; ssop-20, 4mm 4mm qfn-20 packages ltc3388-1/ltc3388-3 20v, 50ma high efficiency nanopower step-down regulator v in : 2.7v to 20v; v out : fixed 1.1v to 5.5v; i q = 720na; i sd = 400na; msop-10, 3mm 3mm dfn-10 packages ltc4070 50ma micropower shunt li-ion charger v out(min) : 4v, 4.1v, 4.2v; i q = 450na; i sd = 45na; msop-8, 2mm 3mm dfn-8 packages ltc4071 50ma micropower shunt li-ion charger with powerpath? control v out(min) : 4v, 4.1v, 4.2v; i q = 450na; i sd = 45na; msop-8, 2mm 3mm dfn-8 packages ltc3129/ ltc3129-1 micropower 200ma synchronous buck-boost dc/dc converter v in : 2.42v to 15v; v out : 1.4v to 15v; i q = 1.3a; i sd = 10na; msop-16e, 3mm 3mm qfn-16 packages downloaded from: http:///

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