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1 swbst v inbk v bst ltc3100 fbbst 3.3h 1.87m 1.07m 3.3v at 100ma 10f 2 2.2f v ldo v inbst fbldo swbk pgbk pgbst 102k 25.5k boost ldo buck v batt 1.6v to 3.2v 2.2f fbbk 2m 1m 10f 3100 ta01a mode runbst runldo runbk gnd ff en_burst off on off on off on 4.7h v boost 3v at 50ma v ldo 1.8v at 200ma v buck boost_good buck_good 1m 1m the lt c ? 3100 combines a high efficiency 700ma syn - chronous step-up converter, a 250ma synchronous step- down converter and a 100ma ldo regulator. the l tc3100 features a wide input voltage range of 0.65v to 5v. the step-down converter can be powered by the output of the step-up converter or from a separate power source between 1.8v and 5.5v. the ldo can also be used as a sequencing switch on the output of the boost. a switching frequency of 1.5mhz minimizes solution foot - print by allowing the use of tiny, low profile inductors and ceramic capacitors. the switching regulators use current mode control and are internally compensated, reducing external parts count. each converter automatically transi - tions to burst mode operation to maintain high efficiency over the full load range. burst mode operation can be disabled for low noise applications. the integrated ldo provides a third low noise, low dropout supply. anti-ringing cir cuitry reduces emi by damping the boost inductor in discontinuous mode. additional features include shutdown current of under 1a and overtem - perature shutdown. the ltc3100 is housed in a 16-lead 3mm 3mm 0.75mm qfn package. typical application features applications description 1.5mhz synchronous dual channel dc/dc converter and 100ma ldo two-cell, triple output converter n extremely compact triple-rail solution n burst mode ? operation, i q = 15a n 1.5mhz fixed frequency operation n power good indicators n 700ma synchronous step-up dc/dc 0.65v to 5v v in range 1.5v to 5.25v v out range 94% peak efficiency v in > v out operation output disconnect n 250ma synchronous step-down dc/dc 1.8v to 5.5v v in range 0.6v to 5.5v v out range n ldo (v in internally tied to v bst ) 0.6v to 5.25v v out range 200mv dropout voltage at 100ma n available in a 16-lead 3mm 3mm qfn package n bar code readers n medical instruments n low power portable electronic devices , lt, ltc, ltm and burst mode are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. efficiency and power loss vs load current, v in = 2.4v load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 ta01b boost buck pl, boost pl, buck ltc3100 3100fb for more information www.linear.com/ltc3100
2 pin configuration absolute maximum ratings v inbst and v inbk voltage .............................. C0.3 to 6v swbst , swbk dc voltage ............................. C 0.3 to 6v swbst, swbk pulsed (< 100ns) voltage ...... C 0.3 to 7v fbbst, fbbk, fbldo, pgbst, pgbk voltage . C 0.3 to 6v mode, runbst, runbk, runldo voltage ... C 0.3 to 6v v bst , v ldo ..................................................... C0.3 to 6v operating t emperature (notes 2, 5) ......... C 40c to 85c storage temperature range ................... C 65c to 125c (note 1) 16 15 14 13 5 6 7 17 8 top view ud package 16-lead (3mm 3mm) plastic qfn 9 10 11 12 4 3 2 1swbst v bst v ldo swbk fbbst fbldo runldo fbbk v inbst pgbst runbst mode v inbk pgbk gnd runbk t jmax = 125c, ja = 68c/w, 4-layer board exposed pad (pin 17) is gnd, must be soldered to pcb (note 6) electrical characteristics: step-up converter parameter conditions min typ max units minimum start-up voltage i load = 1ma l 0.65 0.90 v input voltage range after start-up (minimum voltage is load dependent) l 0.5 5 v output voltage adjust range l 1.5 5.25 v feedback voltage l 1.182 1.200 1.218 v feedback input current fbbst = 1.2v 1 50 na quiescent current (v in ): shutdown runbst = 0v, not including switch leakage, v bst = 0v, v inbk = 0v 0.01 1 a quiescent current: active measured on v bst (note 4), runbk = 0v, runldo = 0v 300 500 a quiescent current: burst mode operation measured on v bst , fbbst > 1.25v mode = 1v, runldo = 0v mode = 1v, runldo = 1v 15 28 25 45 a a n-channel mosfet switch leakage current swbst = 5v , v bst = 5v 0.1 5 a p-channel mosfet switch leakage current swbst = 0v, v bst = 5v 0.1 10 a the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v inbst = 1.2v, v bst = 3.3v, t a = 25c, unless otherwise noted. order information lead free finish tape and reel part marking package description temperature range ltc3100eud#pbf ltc3100eud#trpbf ldjr 16-lead (3mm 3mm) plastic qfn C40c to 85c consult ltc marketing for parts specified with wider operating temperature ranges. consult ltc marketing for information on non-standard lead based finish parts. 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/ ltc3100 3100fb for more information www.linear.com/ltc3100
3 parameter conditions min typ max units n-channel mosfet switch-on resistance v bst = 3.3v 0.3 p-channel mosfet switch-on resistance v bst = 3.3v 0.4 n-channel mosfet current limit l 700 850 ma maximum duty cycle v fbbst = 1.15v l 85 90 % minimum duty cycle v fbbst = 1.3v l 0 % switching frequency l 1.2 1.5 1.8 mhz runbst input high voltage l 0.9 v runbst input low voltage l 0.3 v runbst input current runbst = 1.2v 0.8 2 a soft-start time 0.8 ms pgbst threshold, falling referenced to feedback voltage C8 % pgbst hysteresis referenced to feedback voltage 3 % pgbst voltage low 5ma load 65 mv pgbst leakage current pgbst = 5.5v 0.01 10 a electrical characteristics: step-down converter parameter conditions min typ max units input voltage range l 1.8 5.5 v output voltage adjust range l 0.61 5.5 v feedback voltage l 590 600 610 mv feedback input current fbbk = 600mv 1 30 na quiescent current: shutdown measured on v inbk , runbk = 0v, v inbst = 0v, v bst = 0v not including switch leakage 0.01 1 a quiescent current: active measured on v inbk (note 4), runbst = 0v 240 350 a quiescent current: burst mode operation measured on v inbk , fbbk = 620mv, mode = open, runbst = 0v 16 30 a n-channel mosfet switch leakage current v inbk = swbk = 5v 0.1 5 a p-channel mosfet switch leakage current swbk = 0v, v inbk = 5v 0.1 5 a n-channel mosfet switch-on resistance v inbk = 3.3v 0.45 p-channel mosfet switch-on resistance v inbk = 3.3v 0.55 p-channel mosfet current limit l 340 450 ma maximum duty cycle fbbk < 590mv l 100 % minimum duty cycle fbbk > 610mv l 0 % switching frequency l 1.2 1.5 1.8 mhz the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v inbk = 3.3v, t a = 25c, unless otherwise noted. electrical characteristics: step-up converter the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v inbst = 1.2v, v bst = 3.3v, t a = 25c, unless otherwise noted. ltc3100 3100fb for more information www.linear.com/ltc3100
4 parameter conditions min typ max units runbk input high voltage l 0.9 v runbk input low voltage l 0.3 v runbk input current runbk = 1.2v 0.8 2 a soft-start time 1.3 ms pgbk threshold, falling referenced to feedback voltage C8 % pgbk hysteresis referenced to feedback voltage 3 % pgbk voltage low 5ma load 65 mv pgbk leakage current pgbk = 5.5v 0.01 10 a electrical characteristics: step-down converter the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v inbk = 3.3v, t a = 25c, unless otherwise noted. electrical characteristics: ldo regulator parameter conditions min typ max units input voltage range l 1.8 5.25 v output voltage adjust range (note 3) l 0.618 5.25 v feedback voltage l 582 600 618 mv maximum output current l 100 120 ma feedback input current fbldo = 600mv 1 30 na line regulation v in = 3.3v to 5.25v 0.1 %/ v load regulation from 10ma to 100ma load 0.1 % dropout voltage i out = 100ma l 130 200 mv ripple rejection (psrr) frequency = 1.5mhz at i load = 50ma, c out = 2.2f (note 3) 35 db short-circuit current limit fbldo < 582mv l 120 160 ma soft-start time 0.3 ms runldo input high voltage l 0.9 v runldo input low voltage l 0.3 v runldo input current runldo = 1.2v 0.8 2 a quiescent currentactive runldo = 3.3v, measured on v bst runbst = runbk = 0v, v inbk = 0v 26 40 a the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v bst = 3.3v, v ldo = 3v, t a = 25c, unless otherwise noted. electrical characteristics: common circuitry parameter conditions min typ max units mode input high voltage l 0.9 v mode input low voltage l 0.3 v mode input current mode = 0v mode = 5v C3.3 1.7 C5 3 a a the l denotes the specifications which apply over the full operating temperature range. extended commercial grade: C40c to 85c, v bst or v inbk = 3.3v, t a = 25c, unless otherwise noted. ltc3100 3100fb for more information www.linear.com/ltc3100
5 efficiency vs load current and v in for v o = 1.8v efficiency vs load current and v in for v o = 3.3v 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 ltc3100e is guaranteed to meet performance specifications from 0c to 85c. specifications over C40c to 85c operating temperature range are assured by design, characterization and correlation with statistical process controls. note 3: specification is guaranteed by design and not 100% tested in production. note 4: current measurements are made when the output is not switching. note 5: this ic includes overtemperature protection that is intended to protect the device during momentary overload conditions. junction temperature will exceed 125c when overtemperature protection is active. continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. note 6: failure to solder the exposed backside of the package to the pc board ground plane will result in a thermal resistance much higher than 68c/w. typical performance characteristics t a = 25c, unless otherwise specified. step-up dc/dc converter load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 g01 v in = 1.2v v in = 1.5v pl, v in = 1.2v pl, v in = 1.5v load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 g02 v in = 1.2v v in = 2.4v v in = 3v pl, v in = 1.2v pl, v in = 2.4v pl, v in = 3v efficiency vs load current vbst = 3.3v 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.01 0.1 1 10 100 1000 load current (ma) efficiency(%) 0.01 0.1 1 10 100 1000 power loss (mw) vin=1.2v vin=2.4v vin=3.0v pl, vin=1.2v pl, vin=2.4v pl, vin=3.0v electrical characteristics 3.3v, 100ma efficiency vs v in efficiency vs load current and v in for v o = 5v load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 g03 v in = 1.8v v in = 2.4v v in = 3.6v pl, v in = 1.8v pl, v in = 2.4v pl, v in = 3.6v v inbst (v) efficiency (%) 40 90 100 2.2 2.6 3 20 70 30 80 10 0 60 50 1.8 2 2.4 3.4 4.2 2.8 3.2 3.8 4 3.6 3100 g04 v bst = 3.3v at 100ma ltc3100 3100fb for more information www.linear.com/ltc3100
6 maximum load current during start-up vs v in v inbst (v) 0.7 1 load current (ma) 100 1000 0.9 1.1 0.8 1 1.2 1.3 10 3100 g07 v bst = 1.8v, resistive load v bst = 1.8v, constant-current load v bst = 3.3v, resistive load v bst = 3.3v, constant-current load v bst = 5v, resistive load v bst = 5v, constant-current load typical performance characteristics maximum output current vs v in burst mode threshold current vs v in start-up voltage vs temperature v out and i in during soft-start output voltage ripple in fixed frequency and burst mode operation t a = 25c, unless otherwise specified. step-up dc/dc converter no-load input current vs v in , mode = open, ldo and buck off v inbst (v) 0 output current (ma) 400 600 1 2 3 200 300 100 0 500 0.5 1.5 4 4.5 2.5 3.5 3100 g06 v out = 1.8v v out = 3.3v v out = 5v v inbst (v) 1.0 load current (ma) 40 50 60 2.5 3.5 3100 g08 30 20 1.5 2.0 3.0 4.0 4.5 10 0 l = 3.3h v out = 1.8v v out = 3.3v v out = 5v temperature (c) ?45 input voltage (v) 0.70 0.85 ?15 15 45 0.60 0.65 0.55 0.50 0.80 0.75 ?30 0 75 90 30 60 3100 g09 3100 g10 500s/div i in 200ma/div v bst 1v/div 3100 g11 0.5s/div 100ma load 20mv/div 20s/div 5ma load 20mv/div v bst c out = 20f v inbst (v) 1.0 0 input current (a) 20 60 80 100 3.0 180 3100 g05 40 2.0 1.5 3.5 4.0 2.5 4.5 120 140 160 v out = 5v v out = 3.3v v out = 1.8v ltc3100 3100fb for more information www.linear.com/ltc3100
7 typical performance characteristics load step response, 5ma-100ma burst mode operation enabled dropout voltage vs v out and temperature (i out = 100ma) soft-start time burst mode operation ripple rejection load step response, 10ma-60ma t a = 25c, unless otherwise specified. ldo regulator load step response, 50ma-150ma fixed frequency mode ripple rejection step-up dc/dc converter 3100 g12 100s/div i out 100ma/div v bst 50mv/div v bst c out = 10f 3100 g13 100s/div i out 100ma/div v bst 50mv/div v bst c out = 20f temperature (c) ?45 dropout voltage (v bst_vldo ) 0.200 0.225 60 0.175 0.150 ?15 15 ?30 0 30 75 45 90 0.075 0.050 0.125 0.250 0.100 6105 g14 vldo = 1.5v vldo = 2.5v vldo = 5v t a = 85c t a = 125c vldo = 3.3v frequency (hz) 15 psrr (db) 25 35 0.1 100 1000 10000 0 5 1 10 40 20 30 10 3100 g15 v out = 3v i out = 50ma c out = 2.2f 3100 g16 100s/div runldo 2v/div vldo 1v/div ldo c out = 2.2f 3100 g17 5s/div boost ripple 20mv/div ldo ripple 20mv/div ldo c out = 2.2f 3100 g18 200s/div 50ma/div vldo 100mv/div ldo c out = 2.2f ltc3100 3100fb for more information www.linear.com/ltc3100
8 step-down dc/dc converter typical performance characteristics efficiency vs load current and v in for v o = 1.2v efficiency vs load current and v in for v o = 1.8v no-load input current vs v inbk (mode = open) burst mode operation threshold current vs v in v out and i in during soft-start t a = 25c, unless otherwise specified. output voltage ripple in fixed frequency and burst mode operation load step response, burst mode operation enabled 10ma to 100ma load step response, fixed frequency mode 10ma to 100ma load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 g19 v in = 1.8v v in = 2.4v v in = 3.3v pl, v in = 1.8v pl, v in = 2.4v pl, v in = 3.3v load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 g20 v in = 2.4v v in = 3.3v v in = 5v pl, v in = 2.4v pl, v in = 3.3v pl, v in = 5v v inbk (v) 1.5 input current (a) 2.5 3.5 2 3 4 4.5 5 5 0 15 20 10 3100 g21 v inbk (v) load current (ma) 60 70 50 40 2.5 3.5 2 3 4 4.5 5 10 0 30 80 20 3100 g22 v out = 2.5v v out = 1.8v v out = 1.2v v out = 1.5v 3100 g24 5s/div 50mv/div 50mv/div c out = 10f 3100 g25 200s/div 100ma/div 50mv/div c out = 10f 3100 g26 200s/div 50ma/div 50mv/div c out = 10f 3100 g23 2ms/div input current 50ma/div v out 0.5v/div startup, 200ma load v in = 2.4v v out = 1.2v c out = 10f ltc3100 3100fb for more information www.linear.com/ltc3100
9 run pin threshold voltage start-up delay times vs v in typical performance characteristics t a = 25c, unless otherwise specified. pin functions swbst (pin 1): switch pin for the boost converter. connect the boost inductor between swbst and v inbst . keep pcb trace lengths as short and wide as possible to reduce emi. if the inductor current falls to zero, an internal anti-ringing switch is connected from swbst to v inbst to minimize emi. v bst (pin 2): output voltage for the boost converter (which is the drain of the internal synchronous rectifier) and input voltage for the ldo. pcb trace length from v bst to the output filter capacitor (10f minimum) should be as short and wide as possible. v ldo (pin 3): output voltage of the ldo regulator. connect a 1f ceramic capacitor between v ldo and gnd. larger values of capacitance may be used for higher psrr or improved transient response. swbk (pin 4): switch pin for the buck converter. connect the buck inductor between swbk and the buck output filter capacitor. keep pcb trace lengths as short and wide as possible to reduce emi. v inbk (pin 5): input voltage for the buck converter. con nect a minimum of 4.7f ceramic decoupling capacitor from this pin to ground. pgbk (pin 6): open-drain output that pulls low when fbbk is more than 8% below its regulated voltage. con - nect a pull-up resistor from this pin to a positive supply less than 6v . gnd (pin 7): signal ground. provide a short, direct pcb path between gnd and the pc board ground plane con - nected to the exposed pad. runbk (pin 8): logic-controlled shutdown input for the buck converter. there is an internal 4m pull-down on this pin. runbk = high: normal operation runbk = low: shutdown fbbk (pin 9): feedback input to the g m error amplifier for the buck converter. connect the resistor divider tap to this pin. the output voltage can be adjusted from 0.6v to 5.5v by: v out _ buck = 0.600v ? 1 + r6 r5 ? ? ? ? ? ? runldo (pin 10): logic-controlled shutdown input for the ldo regulator. there is an internal 4m pull-down on this pin. runldo = high: normal operation runldo = low: shutdown v in (v) threshold (v) 0.550 0.575 0.600 4 4.5 0.525 1.5 2.5 1 2 3 3.5 5 0.500 0.625 3100 g27 falling rising v in (v) 0.5 delay time (s) 300 350 400 4 250 200 1.5 2.5 1 2 3 4.5 3.5 5 50 0 150 450 100 3100 g28 ldo boost buck ltc3100 3100fb for more information www.linear.com/ltc3100
10 pin functions fbldo (pin 11): feedback input to the g m error amplifier for the ldo regulator. connect the resistor divider tap to this pin. the output voltage can be adjusted from 0.6v to 5.25v by: v out _ ldo = 0.600v ? 1 + r4 r3 ? ? ? ? ? ? fbbst (pin 12): feedback input to the g m error amplifier for the boost converter. connect the resistor divider tap to this pin. the output voltage can be adjusted from 1.5v to 5.25v by: v out _ boost = 1.20v ? 1 + r2 r1 ? ? ? ? ? ? mode (pin 13): logic-controlled mode select pin for both the boost and buck converters. there is an internal 1m pull-up on this pin to the higher of v inbst , v bst or v inbk . mode = float or high: enables burst mode operation for both the boost and the buck. mode = low: disables burst mode operation. both con - verters will operate in fixed frequency mode regardless of load current. runbst (pin 14): logic-controlled shutdown input for the boost converter. there is an internal 4m pull-down on this pin. runbst = high: normal operation runbst = low: shutdown pgbst (pin 15): open-drain output that pulls to ground when fbbst is more than 8% below its regulated volt - age. connect a pull-up resistor from this pin to a positive supply less than 6v. v inbst (pin 16): input voltage for the boost converter. connect a minimum of 1f ceramic decoupling capacitor from this pin to ground. exposed pad (pin 17): the exposed pad must be soldered to the pcb ground plane. it serves as the power ground connection, and as a means of conducting heat away from the die. ltc3100 3100fb for more information www.linear.com/ltc3100
11 block diagram 3100 bd thermal shutdown + ? + ? + ? + ? + ? + ? + ? + ? + ? + ? + ? mode control 1.5mhz osc gate control v ref vref_gd well switch well switch start-up start_osc clk tsd v best v best gate drivers and anti-cross conduction gate drivers and anti-cross conduction shutdown logic logic logic shutdown c in 4.7f 4m c in 2.2f v batt1 , 0.65v to 5v 4m 4m c out 10f v boost , 1.5v to 5.25v r2 r1 c out 4.7f l1 3.3h l1, 3.3h v buck 0.6v to 5v i zero comparator i zero comparator i zero i lim i set r6 fbbst pgbst v ldo v best of 3 v bst vref_gd burst v inbk v sel pad fbldo 100ma 0.15 0.6v runldo from v bst , v batt1 or v batt2 v inbk swbk fbbk v inbst v ref swbst v bst 0.55v gnd pgnd 0.6v vb 1.2v fb ipk slope comparator i pk comparator i pk comparator i lim ref i sense i sense wake soft-start error amplifier r5 c out 1f v ldo 0.6v to 5v r4 r3 8 6 13 14 16 1 2 12 15 3 11 10 5 4 9 7 off on off on off on runbst error amplifier error amplifier/ sleep comparator tsd 1.1v mode slope comparator clk tsd runldo runbk pwm pgbk uvlo shutdown shutdown level shift clamp v bst 1m ltc3100 3100fb for more information www.linear.com/ltc3100
12 operation the ltc3100 includes an 700ma synchronous step-up (boost) converter, a 250ma synchronous step-down (buck) converter and a 100ma low dropout (ldo) linear regulator housed in a 16-lead 3mm 3mm qfn package. both converters utilize current mode pwm control for exceptional line and load regulation and operate from the same 1.5mhz oscillator. the current mode architecture with adaptive slope compensation also provides excellent transient load response, requiring minimal output filter - ing. both converters have internal soft-start and internal loop compensation, simplifying the design process and minimizing the number of external components. with its low r ds(on) and low gate charge internal mosfet switches and synchronous rectifiers, the ltc3100 achieves high efficiency over a wide range of load current. burst mode operation maintains high efficiency at very light loads, but can be disabled for noise-sensitive applications. with separate power inputs for the boost and buck con - verters, along with independent enable and power good functions, the ltc3100 is ver y flexible. the two converters can operate from the same input supply, or from two different sources, or can even be cascaded by powering the buck converter from the output of the boost converter. by using the ldo as well, three different output voltages can be generated from a single alkaline/nimh cell (or the ldo can be used for power sequencing the boost output). operation can be best understood by referring to the block diagram. boost converter low voltage start-up the ltc3100 boost converter includes an independent start-up oscillator designed to start up at an input voltage of 0.65v (typical). soft-start and inrush current limiting are provided during start-up, as well as in normal mode. when either v inbst or v bst exceeds 1.4v (typical), the ic enters normal operating mode. once the output voltage exceeds the input by 0.24v, the ic powers itself from v bst instead of v inbst . at this point, the internal circuitry has no dependency on the input voltage, eliminating the requirement for a large input capacitor. the limiting fac - tor for the application becomes the ability of the power source to supply sufficient energy to the output at low input voltages, and maximum duty cycle of the converter , which is clamped at 90% (typical). note that at low input voltages, even small input voltage drops due to series resistance become critical, and greatly limit the power delivery capability of the converter. low noise fixed frequency operation soft-start the internal soft-start circuitry ramps the peak boost inductor current from zero to its peak value of 700ma in approximately 800s, allowing start-up into heavy loads. the soft-start circuitry is reset in the event of a commanded shutdown or an overtemperature shutdown. oscillator an internal oscillator sets the switching frequency to 1.5mhz. the oscillator allows a maximum duty cycle of 90% (typical) for the boost converter. shutdown the boost converter is shut down by pulling the runbst pin below 0.3v, and activated by pulling the runbst pin above 0.9v. note that runbst can be driven above v in or v out , as long as it is limited to less than the absolute maximum rating. error amplifier the error amplifier is a transconductance type. the non-in - verting input is internally connected to the 1.20v reference and the inverting input is connected to fbbst . clamps limit the minimum and maximum error amp output voltage for improved large signal transient response. power converter control loop compensation is provided internally. a voltage divider from v bst to ground programs the output voltage (via fbbst) from 1.5v to 5.25v, according to the formula: v bst = 1.20v ? 1 + r2 r1 ? ? ? ? ? ? ltc3100 3100fb for more information www.linear.com/ltc3100
13 current sensing lossless current sensing converts the peak current signal of the n-channel mosfet switch into a voltage which is summed with the internal slope compensation. the summed signal is compared to the error amplifier output to provide a peak current control command for the pwm. current limit the current limit comparator shuts off the n-channel mosfet switch once its threshold is reached. peak switch current is no less than 700ma, independent of input or output voltage, unless v out falls below 1v, in which case the current limit is cut in half to minimize power dissipation into a short-circuit. slope compensation current mode control requires the use of slope compen - sation to prevent subharmonic oscillations in the inductor current waveform at high duty cycle operation. this is ac - complished internally on the ltc3100 through the addition of a compensating ramp to the current sense signal. the l tc3100 per forms current limiting prior to addition of the slope compensation ramp and therefore achieves a peak inductor current limit that is independent of duty cycle. zero current comparator the zero current comparator monitors the boost inductor current to the output and shuts off the synchronous rectifier once this current reduces to approximately 30ma. this prevents the inductor current from reversing in polarity, improving efficiency at light loads. synchronous rectifier to control inrush current and to prevent the inductor current from running away when v out is close to v in , the p-channel mosfet synchronous rectifier is only fully enabled when v out > (v in + 0.24v). anti-ringing control the anti-ring circuitry connects a resistor across the boost inductor to prevent high frequency ringing on the sw pin during discontinuous current mode operation. the ringing of the resonant circuit formed by l and c sw (capacitance on swbst pin) is low energy, but can cause emi radiation. pgood comparator the pgbst pin is an open-drain output which indicates the status of the boost converter output voltage. if the boost output voltage falls 8% below the regulation voltage, the pgbst open-drain output will pull low. the output voltage must rise 3% above the falling threshold before the pull- down will turn off. in addition, there is a 60s (typical) deglitching delay in order to prevent false trips due to voltage transients on load steps. the pgbst output will also pull low if the boost converter is disabled. the typical pgbst pull-down switch resistance is 13 when v bst or v inbst equals 3.3v. output disconnect the ltc3100 boost converter is designed to allow true output disconnect by eliminating body diode conduction of the internal p-channel mosfet rectifier. this allows for v out to go to 0v during shutdown, drawing no current from the input source. it also allows for inrush current limiting at turn-on, minimizing surge currents seen by the input supply. note that to obtain the advantages of output disconnect, there must not be an external schottky diode connected between swbst and v bst . the output discon- nect feature also allows v out to be pulled high without any reverse current into the battery. v in > v out operation the ltc3100 boost converter will maintain voltage reg - ulation even when the input voltage is above the desired output voltage. note that the output current capability is slightly reduced in this mode of operation. refer to the t ypical per formance characteristics section. burst mode operation (for boost and buck converters) burst mode operation for both converters can be enabled or disabled using the mode pin. if mode is grounded, burst mode operation is disabled for both the boost and operation ltc3100 3100fb for more information www.linear.com/ltc3100
14 buck converters. in this case, both converters will remain in fixed frequency operation, even at light load currents. if the load is very light, they will exhibit pulse-skip operation. if mode is raised above 0.9v, or left open, burst mode operation will be enabled for both converters. in this case, either converter may enter burst mode operation at light load, and return to fixed frequency operation when the load current increases. refer to the typical performance characteristics section to see the output load burst mode threshold vs v in and v out . the two converters can enter or leave burst mode operation independent of each other. in burst mode operation, each converter still switches at a frequency of 1.5mhz, using the same error amplifier and loop compensation for peak current mode control. this control method eliminates any output transient when switching between modes. in burst mode operation, energy is delivered to the output until it reaches the nominal reg - ulation value, then the ltc3100 transitions to sleep mode where the outputs are off and the l tc3100 consumes only 15a of quiescent current from v bst . once the output voltage has drooped slightly, switching resumes again. this maximizes efficiency at very light loads by minimizing switching and quiescent losses. burst mode operation output ripple is typically 1% peak-to-peak. burst mode operation for the boost converter is inhibited during start-up, and until soft-start is complete and v bst is at least 0.24v greater than v inbst . short-circuit protection the ltc3100 output disconnect feature allows output short-circuit while maintaining a maximum internally set current limit. to reduce power dissipation under short-cir - cuit conditions, the boost peak switch current limit is reduced to 400ma (typical). schottky diode although it is not required, adding a schottky diode from swbst to v bst will improve efficiency by about 2%. note that this defeats the boost output disconnect and short-circuit protection features. buck converter operation the buck converter provides a high efficiency, lower voltage output and supports 100% duty cycle operation to extend battery life. the buck converter uses the same 1.5mhz oscillator used by the boost converter. pwm mode operation when the mode pin is held low, the ltc3100 buck converter uses a constant-frequency, current mode control architec - ture. both the main (p-channel mosfet) and synchronous rectifier (n-channel mosfet) switches are internal. at the start of each oscillator cycle, the p-channel switch is turned on and remains on until the current waveform with superimposed slope compensation ramp exceeds the error amplifier output. at this point, the synchronous rectifier is turned on and remains on until the inductor current falls to zero or a new switching cycle is initiated. as a result, the buck converter operates with discontinuous inductor current at light loads which improves efficiency . at extremely light loads, the minimum on-time of the main switch will be reached and the buck converter will begin turning off for multiple cycles (pulse-skipping) in order to maintain regulation. burst mode operation when the mode pin is forced high, or left open, the buck converter will automatically transition between burst mode operation at sufficiently light loads (below approximately 10ma) and pwm mode at heavier loads. burst mode oper - ation entry is determined by the peak inductor current and therefore the load current at which burst mode operation will be entered depends on the input voltage, the output voltage and the inductor value. typical curves for burst mode operation entry threshold are provided in the typical performance characteristics section of this data sheet. the quiescent current on v inbk in burst mode operation is only 15a. if the boost converter is enabled and v inbst or v bst are at a higher potential than v inbk , some of the quiescent current will be supplied by the boost converter, reducing the burst quiescent current on v inbk to just 9a. operation ltc3100 3100fb for more information www.linear.com/ltc3100
15 dropout operation as the input voltage decreases to a value approaching the output regulation voltage, the duty cycle increases toward the maximum on-time. further reduction of the supply voltage will force the main switch to remain on for more than one cycle until 100% duty cycle operation is reached where the main switch remains on continuously. in this dropout state, the output voltage will be determined by the input voltage less the resistive voltage drop across the main switch and series resistance of the inductor. slope compensation current mode control requires the use of slope compen - sation to prevent subharmonic oscillations in the inductor current waveform at high duty cycle operation. this is ac - complished internally on the ltc3100 through the addition of a compensating ramp to the current sense signal. in some current mode ics, current limiting is per formed by clamping the error amplifier voltage to a fixed maximum. this leads to a reduced output current capability at low step-down ratios. in contrast, the l tc3100 performs cur - rent limiting prior to addition of the slope compensation ramp and therefore achieves a peak inductor current limit that is independent of duty cycle. short-circuit protection when the buck output is shorted to ground, the error am - plifier will saturate high and the p-channel mosfet switch will turn on at the start of each cycle and remain on until the current limit trips. during this minimum on-time, the inductor current will increase rapidly and will decrease very slowly during the remainder of the period due to the very small reverse voltage produced by a hard output short. to eliminate the possibility of inductor current runaway in this situation, the buck converter switching frequency is reduced to approximately 375khz when the voltage on fbbk falls below 0.3v. soft-start the buck converter has an internal voltage mode soft-start circuit with a nominal duration of 1.3ms. the converter remains in regulation during soft-start and will therefore respond to output load transients which occur during this time. in addition, the output voltage rise time has minimal dependency on the size of the output capacitor or load current. error amplifier and compensation the ltc3100 buck converter utilizes an internal transcon - ductance error amplifier. compensation of the feedback loop is per formed internally to reduce the size of the application cir cuit and simplify the design process. the compensation network has been designed to allow use of a wide range of output capacitors while simultaneously ensuring rapid response to load transients. undervoltage lockout if the v inbk supply voltage decreases below 1.6v (typical), the buck converter will be disabled. the soft-start for the buck converter will be reset during undervoltage lockout to provide a smooth restart once the input voltage rises above the undervoltage lockout threshold. pgood comparator the pgbk pin is an open-drain output which indicates the status of the buck converter output voltage. if the buck output voltage falls 8% below the regulation voltage, the pgbk open-drain output will pull low. the output voltage must rise 3% above the falling threshold before the pull- down will turn off. in addition, there is a 60s typical deg - litching delay in order to prevent false trips due to voltage transients on load steps. the pgbk output will also pull low during overtemperature shutdown and undervoltage lockout to indicate these fault conditions, or if the buck converter is disabled. the typical pgbk pull-down switch resistance is 13 when v inbk = 3.3v. schottky diode although it is not required, adding a schottky diode from swbk to the ground plane will improve efficiency by about 2%. operation ltc3100 3100fb for more information www.linear.com/ltc3100
16 ldo regulator operation the ldo regulator utilizes an internal 1.3 (typical) p-channel mosfet pass device to supply up to 100ma of load current with a typical dropout voltage of 130mv . the input voltage to the ldo is internally connected to the boost output (v bst pin), and can share the same filter capacitor. the ldo can be operated independently of the boost (or buck) converter, providing a sufficient voltage is present on v bst . soft-start and current limit the ldo has an independent current limit circuit that limits output current to 120ma (typical). to minimize loading on the boost converter output when enabling the ldo, the ldo current limit is soft-started over a 500s period. therefore the rise time of the ldo output voltage will depend on the amount of capacitance on the v ldo pin. reverse current blocking the ldo is designed to prevent any reverse current from v ldo back to the v bst pin, both in normal operation and in shutdown. if v ldo is pulled above v bst and v bst is above 1v, there will be a small (1a typical) current from v ldo to ground. common functions oscillator the 1.5mhz oscillator is shared by the boost and buck converters. it will be oscillating if either converter is en - abled. if both converters are enabled, the boost n-channel mosfet switch will be turned on coincident with the buck p-channel mosfet switch. mode control the mode pin is used to for ce fixed frequency opera - tion (mode < 0.3v) or to enable burst mode operation (mode > 0.9v) for both the boost and buck converters. with burst mode operation enabled, the two converters will automatically enter or leave burst mode operation independently , based on their respective load conditions. there is an internal 1m pull-up on mode, in the event that the pin is left open. note: leaving the pin open, or connecting it to the high - est of v inbk or v bst , will result in the lowest burst mode quiescent current. overtemperature shutdown if the die temperature exceeds 150c (typical) both con - verters and the ldo regulator will be disabled. all power devices will be turned off and all switch nodes will be high impedance. the soft-start cir cuits for both converters and the ldo are reset during overtemperature shutdown to provide a smooth recover y once the overtemperature condition is eliminated. both converters and the ldo will restart (if enabled) when the die temperature drops to approximately 130c. operation ltc3100 3100fb for more information www.linear.com/ltc3100
17 pc board layout guidelines the ltc3100 switches large currents at high frequen - cies. special care should be given to the pc board layout to ensure stable, noise-free operation. y ou will not get advertised per formance with a careless layout. figure 1 depicts the recommended pc board layout. a large ground pin copper area will help to lower the chip temperature. a multilayer board with a separate ground plane is ideal, but not absolutely necessary. a few key guidelines follow: 1. all circulating high current paths should be kept as short as possible. capacitor ground connections should via down to the ground plane in the shortest route possible. the bypass capacitors on all v in and v out applications information figure 1. recommended component placement for two-layer pc board pins should be placed as close to the ic as possible and should have the shortest possible paths to ground. 2. to prevent large circulating currents from disrupting the output voltage sensing, the ground for each resistor divider should be returned directly to the ground plane near the ic. 3. use of vias in the die attach pad of the ic will enhance the thermal environment of the converter, especially if the vias extend to a ground plane region on the exposed bottom surface of the pc board. 4. keep the connection from the resistor dividers to the feedback pins as short as possible and away from the switch pin connections. 16 ltc3100 3100 f01 15 14 13 5 6 8 7 12 11 10 9 1 2 3 4 fbbst v inbst pgbst runbst mode v inbk pgbk gnd runbk swbst v bst v ldo v buck swbk fbldo runldo fbbk ltc3100 3100fb for more information www.linear.com/ltc3100
18 applications information component selection boost output voltage programming the boost output voltage is set by a resistive divider ac - cording to the following formula: v out = 1.200v ? 1 + r2 r1 ? ? ? ? ? ? the external divider is connected to the output as shown in the block diagram. a feedforward capacitor may be placed in parallel with resistor r2 to improve the noise immunity of the feedback node, improve transient response and reduce output ripple in burst mode operation. a value of 33pf will generally suffice. boost inductor selection the ltc3100 boost converter can utilize small surface mount and chip inductors due to the fast 1.5mhz switching frequency. inductor values between 2.2h and 4.7h are suitable for most applications. larger values of induc - tance will allow slightly greater output current capability by reducing the inductor ripple current. increasing the inductance above 10h will increase size while providing little improvement in output current capability. the minimum boost inductance value is given by: l > v in(min) ? v out(max) ? v in(min) ( ) 1.5 ? ripple ? v out(max) where: ripple = allowable inductor current ripple (amps peak- to-peak) v in(min) = minimum input voltage v out(max) = maximum output voltage the inductor current ripple is typically set for 20% to 40% of the maximum inductor current. high frequency ferrite core inductor materials reduce frequency dependent power losses compared to cheaper powdered iron types, improving efficiency. the inductor should have low dcr (series resistance of the winding) to reduce the i 2 r power losses, and must not saturate at peak inductor current levels. molded chokes and some chip inductors usually do not have enough core area to support the peak induc - tor currents of 800ma seen on the ltc3100. to minimize radiated noise, use a shielded inductor . see t able 1 for suggested components and suppliers. table 1. recommended boost inductors vendor part/style coilcraft (847) 639-6400 www.coilcraft.com lps4012, lps4018 mss4020, mss5131 coiltronics sd14, sd3814, sd3118 fdk mipsa2520 mipw3226 murata www.murata.com lqh43c sumida (847) 956-0666 www.sumida.com cdrh2d18, cdrh2d16 cdrh3d14, cdrh3d16 cdrh4d14, cdrh4d16 t aiyo-y uden www.t-yuden.com nr3015 np03sb tdk www.tdk.com vlp vlf, vlcf toko (408) 432-8282 www .tokoam.com d518lc d52lc dp418c wrth (201) 785-8800 www.we-online.com we-tpc t ype s, m boost input and output capacitor selection the internal loop compensation of the ltc3100 boost con - verter is designed to be stable with output capacitor values of 4.7f or greater. low esr (equivalent series resistance) capacitors should be used to minimize the output voltage ripple. multilayer ceramic capacitors are an excellent choice as they have extremely low esr and are available in small footprints. a 4.7f to 10f output capacitor is sufficient for most fixed frequency applications. for applications where burst mode operation is enabled, a minimum value of 20f is recommended. larger values may be used to obtain very low output ripple and to improve transient response. x5r and x7r dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. y5v types should not be used. case sizes smaller than 0805 are not recommended due to their increased dc bias effect. ltc3100 3100fb for more information www.linear.com/ltc3100
19 applications information low esr input capacitors reduce input switching noise and reduce the peak current drawn from the battery. it follows that ceramic capacitors are also a good choice for input decoupling and should be located as close as pos - sible to the device. a 2.2f input capacitor on the v inbst pin is sufficient for most applications. larger values may be used without limitations. for applications where the power source is more than a few inches away, a larger bulk decoupling capacitor is recommended on the input to the boost converter. table 2 shows a list of several ceramic capacitor manu - facturers. consult the manufacturers directly for detailed information on their selection of capacitors. note that even x5r and x7r type ceramic capacitors have a dc bias effect which reduces their capacitance with a dc voltage applied. this effect is particularly bad for capacitors in the smallest case sizes. consult the manufacturer s data for the capacitor you select to be assured of having the necessary capacitance in your application. table 2.capacitor vendor information supplier phone web site avx (803) 448-9411 www.avxcorp.com murata (714) 852-2001 www.murata.com taiyo-yuden (408) 573-4150 www.t-yuden.com tdk (847) 803-6100 www.component.tdk.com buck inductor selection the choice of buck inductor value influences both the efficiency and the magnitude of the output voltage ripple. larger inductance values will reduce inductor current ripple and will therefore lead to lower output voltage ripple. for a fixed dc resistance, a larger value inductor will yield higher efficiency by lowering the peak current to be closer to the average. however, a larger value inductor within the same family will generally have a greater series resistance, thereby offsetting this efficiency advantage. given a desired peak to peak current ripple, di l , the required inductance can be calculated via the following expression, where f represents the switching frequency in mhz: l = 1 f d i l ? 1 ? v out v in ? ? ? ? ? ? h ( ) a reasonable choice for ripple current is di l = 100ma which represents 40% of the maximum 250ma load current. the dc current rating of the inductor should be at least 450ma to avoid saturation under overload or short-circuit conditions. to optimize efficiency the inductor should have a low series resistance. in particularly space restricted applications it may be advantageous to use a much smaller value inductor at the expense of larger ripple current. in such cases, the converter will operate in discontinuous conduction for a wider range of output loads and efficiency will be reduced. in addition, there is a minimum inductor value required to maintain stability of the current loop (given the fixed internal slope compensation). specifically, if the buck converter is going to be utilized at duty cycles over 40%, the inductance value must be at least l min as given by the following equation: l min = 2.5 ? v out (h) table 3 depicts the minimum required inductance for several common output voltages. table 3.buck minimum inductance output voltage minimum inductance 0.6v 1.5h 0.8v 2h 1.2v 3h 2v 5h 2.7v 6.8h 3.3v 8.3h larger values of inductor will also provide slightly greater output current capability before reaching current limit (by reducing the peak-to-peak ripple current). ltc3100 3100fb for more information www.linear.com/ltc3100
20 applications information table 4. recommended buck inductors vendor part/style coilcraft (847) 639-6400 www.coilcraft.com lps3008, lps3010, lps3015 coiltronics sd3114, sd3118, sd3112 fdk mipf2016 mipf2520, mips2520 murata www.murata.com lqh32c lqm31p sumida (847) 956-0666 www.sumida.com cdrh2d11, cdrh2d09 cmd4d06-4r7mc cmd4d06-3r3mc t aiyo-y uden www.t-yuden.com nr3010, nr3012 tdk www.tdk.com vlf3010, vlf3012 lemc3225, lbc2518 toko (408) 432-8282 www .tokoam.com d3010 db3015 d312, d301f wrth (201) 785-8800 www.we-online.com we-tpc t ype xs, s buck output capacitor selection a low esr output capacitor should be utilized at the buck output in order to minimize voltage ripple. multilayer ce - ramic capacitors are an excellent choice as they have low esr and are available in small footprints. in addition to controlling the output ripple magnitude, the value of the output capacitor also sets the loop crossover frequency and therefore can impact loop stability. there is both a minimum and maximum capacitance value required to ensure stability of the loop. if the output capacitance is too small, the loop crossover frequency will increase to the point where switching delay and the high frequency parasitic poles of the error amplifier will degrade the phase margin. in addition, the wider bandwidth produced by a small output capacitor will make the loop more susceptible to switching noise. at the other extreme, if the output capacitor is too large, the crossover frequency can decrease too far below the compensation zero and also lead to degraded phase margin. table 5 provides a guideline for the range of al - lowable values of low esr output capacitors. larger value output capacitors can be accommodated provided they have sufficient esr to stabilize the loop or by increasing the value of the feedfor ward capacitor in parallel with the upper resistor divider resistor . note that even x5r and x7r type ceramic capacitors have a dc bias effect which reduces their capacitance with a dc voltage applied. this effect is particularly bad for capacitors in the smallest case sizes. consult the manufacturers data for the capacitor you select to be assured of having the necessary capacitance in your application. table 5. buck output capacitor range v out c min c max 0.6v 15f 300f 0.8v 15f 230f 1.2v 10f 150f 1.8v 6.8f 90f 2.7v 6.8f 70f 3.3v 6.8f 50f buck input capacitor selection the v inbk pin provides current to the buck converter power switch and is also the supply pin for the bucks internal control circuitry. it is recommended that a low esr ceramic capacitor with a value of at least 4.7f be used to bypass this pin. the capacitor should be placed as close to the pin as possible and have a short return to ground. for applications where the power source is more than a few inches away, a larger bulk decoupling capacitor is recommended. buck output voltage programming the output voltage is set by a resistive divider according to the following formula: v out = 0.600v ? 1 + r6 r5 ? ? ? ? ? ? the external divider is connected to the output as shown in the block diagram. it is recommended that a feedfor - ward capacitor be placed in parallel with resistor r6 to improve the noise immunity of the feedback node and reduce output ripple in burst mode operation. a value of 10pf will generally suffice. ltc3100 3100fb for more information www.linear.com/ltc3100
21 applications information ldo output capacitor selection the ldo is designed to be stable with a minimum 1f output capacitor. no series resistor is required when using low esr capacitors. for most applications, a 2.2f ceramic capacitor is recommended. larger values will improve transient response, and raise the power supply rejection ratio (psrr) of the ldo. refer to the typical performance characteristics for the allowable range of output capacitor to ensure loop stability. ldo output voltage programming the output voltage is set by a resistive divider according to the following formula: v out = 0.600v ? 1 + r4 r3 ? ? ? ? ? ? the external divider is connected to the output as shown in the block diagram. for improved transient response, a feedforward capacitor may be placed in parallel with resistor r4. ltc3100 3100fb for more information www.linear.com/ltc3100
22 typical applications single-cell boost and buck with voltage sequencing output voltages during soft-start for sequenced converter swbst v inbk v bst ltc3100 fbbst l1 3.3h 3.5v r2 1m r1 523k c1 10f 2 c in 2.2f v ldo v inbst fbldo swbk pgbk pgbst r4 115k r3 25.5k v batt 0.9v to 1.5v c2 2.2f fbbk 12 3 11 4 16 15 9 r6 1m r5 1m c3 10f 3100 ta02a mode runbst runldo runbk gnd 16 13 14 10 8 1 5 2 7 ff en_burst off on l2 3.3h +3.3v at 50ma v_i/o 120ma at v batt = 0.9v 220ma at v batt = 1.2v v_core = 1.2v boost_good buck_good r7 1m r8 1m + 3100 ta02b 1ms/div v core , 1v/div v bst , 1v/div v i/o , 1v/div swbst v inbk v bst ltc3100 fbbst boost l1 3.3h r2 2m r1 634k c1 10f 2 c2 2.2f c in 4.7f v ldo v inbst fbldo swbk pgbk pgbst v in 2.5v to 5v li-ion fbbk 12 3 11 4 16 15 9 r6 976k r5 487k c3 10f 3100 ta03a mode runbst runldo runbk gnd 16 13 14 10 8 1 5 2 7 off on ldo buck off on off on l2 4.7h +5v at 200ma v boost r4 115k r3 25.5k +3.3v at 50ma v_i/o +1.8v at 250ma v_core boost_good buck_good r7 100k r8 100k c ff2 10pf li-ion input, triple output converter efficiency vs load current load current (ma) 30 efficiency (%) power loss (mw) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 100 0.01 1000 1 10 0.1 3100 ta03b 1.8v buck 5v boost buck power loss boost power loss v in = 3.6v ltc3100 3100fb for more information www.linear.com/ltc3100
23 swbst v inbk v bst ltc3100 fbbst r1 1.07m r2 324k r3 301k c2 10f r4 20k c1 4.7f c4 4.7f v ldo v inbst fbldo swbk pgbk pgbst v batt 0.9v to 3.3v usb input fbbk 12 3 11 4 16 15 9 r5 200k r6 100k c3 10f 3100 ta04a mode runbst runldo runbk gnd 16 13 14 10 8 1 5 2 7 l2 10h 1.8v at 50ma vldo v out r7 64.9k l1 3.3h mbr0520 c4 2.2f 3.3v at: 100ma for v batt = 1.2v 300ma for v batt = 2.4v 250ma for usb input typical applications single-cell/two-cell or usb input to 3.3v/1.8v converter efficiency vs load current load current (ma) 30 efficiency (%) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 3100 ta04b v in = 1.2v 3.3v output v in = 2.4v v in = 5v usb ltc3100 3100fb for more information www.linear.com/ltc3100
24 package description 3.00 0.10 (4 sides) recommended solder pad pitch and dimensions 1.45 0.05 (4 sides) note: 1. drawing conforms to jedec package outline mo-220 variation (weed-2) 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package pin 1 top mark (note 6) 0.40 0.10 bottom view?exposed pad 1.45 0.10 (4-sides) 0.75 0.05 r = 0.115 typ 0.25 0.05 1 pin 1 notch r = 0.20 typ or 0.25 45 chamfer 15 16 2 0.50 bsc 0.200 ref 2.10 0.05 3.50 0.05 0.70 0.05 0.00 ? 0.05 (ud16) qfn 0904 0.25 0.05 0.50 bsc package outline ud package 16-lead plastic qfn (3mm 3mm) (reference ltc dwg # 05-08-1691 rev ?) ltc3100 3100fb for more information www.linear.com/ltc3100
25 information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. revision history rev date description page number b 01/14 change maximum duty cycle minimum specification 3 (revision history begins at rev b) ltc3100 3100fb for more information www.linear.com/ltc3100
26 ? linear technology corporation 2008 lt 0114 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/ltc3100 related parts typical application part number description comments ltc3442 1.2a (i out ), 2mhz synchronous buck-boost dc/dc converter v in : 2.4v to 5.5v, v out(range) : 2.4v to 5.25v, i q = 35a, i sd < 1a, dfn package ltc3455 dual dc/dc converter with usb power manager and li-ion battery charger 96% efficiency, seamless transition between inputs, i q = 110a, i sd < 2a, qfn package ltc3456 2-cell multi-output dc/dc converter with usb power manager 92% efficiency, seamless transition between inputs, i q = 180a, i sd < 1a, qfn package ltc3520 synchronous 1a buck-boost and 600ma step-down dc/ dc converter v in : 2.2v to 5.5v, v out(min) = 0.6v, i q = 55a, i sd < 1a, 4mm 4mm qfn package l tc3522 synchronous 400ma buck-boost and 200ma step-down dc/dc converter v in : 2.4v to 5.5v, v out(min) = 0.6v, i q = 25a, i sd < 1a, 3mm 3mm qfn-16 package l tc3527/l tc3527-1 dual (400ma/800ma) synchronous boost converter v in : 0.5v to 5v, v out : 1.5v to 5.25v, i q = 12a, i sd < 2a, 3mm 3mm qfn package l tc3530 600ma (i out ), 2mhz synchronous buck-boost dc/dc converter v in : 1.8v to 5.5v, v out(range) : 1.8v to 5.5v, i q = 40a, i sd < 1a, dfn and msop packages ltc3532 500ma (i out ), 2mhz synchronous buck-boost dc/dc converter v in : 2.4v to 5.5v, v out(range) : 2.4v to 5.25v, i q = 35a, i sd < 1a, dfn and msop packages ltc3537 600ma (i sw ), 2.2mhz synchronous boost converter with 100ma ldo v in : 0.68v to 5v, v out(max) = 5.5v, i q = 30a, i sd < 1a, 3mm 3mm qfn package l tc3538 600ma (i out ), 2mhz synchronous buck-boost dc/dc converter v in : 2.4v to 5.5v, v out(range) : 1.5v to 5.5v, i q = 35a, i sd < 1a, dfn package ltc3544/ltc3544b 300ma, 200ma 2, 100ma, 2.25mhz quad output synchronous step-down dc/dc converter v in : 2.25v to 5.5v, v out(min) = 0.8v, i q = 70a, i sd < 1a, qfn package l tc3545 t riple output, 3ma 800ma, 2.25mhz synchronous step-down dc/dc converter v in : 2.25v to 5.5v, v out(min) = 0.6v, i q = 58a, i sd < 1a, qfn package single-cell to 1.2v/1.8v converter efficiency vs load current (v buck ) swbst v inbk v bst ltc3100 fbbst r2 1m r1 1m c1 10f 2 c2 2.2f v ldo v inbst fbldo swbk pgbk pgbst fbbk 12 3 11 4 6 15 9 r6 1m r5 1m c3 10f 3100 ta05a mode runbst runldo runbk gnd 16 13 14 10 8 1 5 2 7 off on l2 3.3h r4 200k r3 100k vldo 1.8v at 50ma 2.4v vbuck buck_good r7 100k c in 2.2f v batt 0.9v to 1.6v l1 3.3h + 1.2v at: 120ma for v batt = 0.9v 250ma for v batt = 1.2v load current on v buck (ma) 30 efficiency (%) 50 80 0.01 10 100 1000 0 10 0.1 1 100 70 90 40 60 20 3100 ta05b v in = 0.9v v in = 1.2v v in = 1.5v ltc3100 3100fb for more information www.linear.com/ltc3100

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