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ltc3526l-2/ltc3526lb-2 1 3526lb2fa typical application description features applications 550ma 2mhz synchronous step-up dc/dc converters in 2mm 2mm dfn the ltc ? 3526l-2/ltc3526lb-2 are synchronous, fixed frequency step-up dc/dc converters with output discon- nect. synchronous rectification enables high efficiency in the low profile 2mm 2mm dfn package. battery life in single aa/aaa powered products is extended further with a 680mv start-up voltage and operation down to 500mv once started. a switching frequency of 2mhz minimizes solution foot- print by allowing the use of tiny, low profile inductors and ceramic capacitors. the current mode pwm design is internally compensated, reducing external parts count. the ltc3526l-2 features burst mode operation at light load conditions allowing it to maintain high efficiency over a wide range of load. the ltc3526lb-2 features fixed frequency operation for low noise applications. anti-ring circuitry reduces emi by damping the inductor in discon- tinuous mode. additional features include a low shutdown current of under 1a and thermal shutdown. the ltc3526l-2/ltc3526lb-2 are housed in a 2mm 2mm 0.75mm dfn package. l , lt, ltc, ltm, linear technology, the linear logo and burst mode are registered trademarks and thinsot is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. patents pending. n medical instruments n noise canceling headphones n wireless mice n bluetooth headsets n delivers 3.3v at 100ma from a single alkaline/ nimh cell or 3.3v at 200ma from two cells n v in start-up voltage: 680mv n 1.5v to 5.25v v out range n up to 94% efficiency n output disconnect n 2mhz fixed frequency operation n v in > v out operation n integrated soft-start n current mode control with internal compensation n burst mode ? operation with 9a i q (ltc3526l-2) n low noise pwm operation (ltc3526lb-2) n internal synchronous rectifier n logic controlled shutdown (i q < 1a) n anti-ring control n low profile (2mm 2mm 0.75mm) 6-lead dfn package sw v in 1.78m1m 3526lb2 ta01a ltc3526l-2 shdn v out fb v in 1.6v to 3.2v v out 3.3v200ma off on 2.2h 4.7f 4.7f 33pf gnd load current (ma) 0.01 40 efficiency (%) power loss (mw) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta01b 30 2010 0 90 100 1 10 100 0.10.01 1000 efficiency power loss v in = 2.4v efficiency and power loss vs load current downloaded from: http:///
ltc3526l-2/ltc3526lb-2 2 3526lb2fa electrical characteristics the l denotes the specifications which apply over the specified operating temperature range of ?40c to 85c, otherwise specifications are at t a = 25c. v in = 1.2v, v out = 3.3v unless otherwise noted. pin configuration absolute maximum ratings order information lead free finish tape and reel part marking package description temperature range ltc3526ledc-2#pbf ltc3526ledc-2#trpbf lffc 6-lead (2mm 2mm) plastic dfn C40c to 85c ltc3526lbedc-2#pbf ltc3526lbedc-2#trpbf lffd 6-lead (2mm 2mm) plastic dfn 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/ v in voltage ................................................... C0.3v to 6v sw voltage dc ............................................................ C0.3v to 6v pulsed <100ns ......................................... C0.3v to 7v shdn , fb voltage ........................................ C0.3v to 6v v out ............................................................. C0.3v to 6v operating temperature range (notes 2, 5) ..............................................C40c to 85c storage temperature range .................. C65c to 150c (note 1) parameter conditions min typ max units minimum start-up input voltage i load = 1ma 0.68 0.8 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 pin voltage l 1.165 1.195 1.225 v feedback pin input current v fb = 1.30v 1 50 na quiescent currentshutdown v shdn = 0v, not including switch leakage, v out = 0v 0.01 1 a quiescent currentactive measured on v out , nonswitching 250 500 a quiescent currentburst measured on v out , fb > 1.230v (ltc3526l-2 only) 9 18 a n-channel mosfet switch leakage current v sw = 5v 0.1 5 a p-channel mosfet switch leakage current v sw = 5v, v out = 0v 0.1 10 a n-channel mosfet switch on resistance v out = 3.3v 0.4 p-channel mosfet switch on resistance v out = 3.3v 0.6 n-channel mosfet current limit l 550 750 ma current limit delay to output (note 3) 60 ns maximum duty cycle v fb = 1.15v, v out = 5v l 87 90 % minimum duty cycle v fb = 1.3v l 0 % switching frequency l 1.8 2 2.4 mhz shdn pin input high voltage 0.8 v shdn pin input low voltage 0.3 v top view v out fbshdn sw gnd v in dc package 6-lead (2mm s 2mm) plastic dfn 7 12 3 65 4 t jmax = 125c, ja = 102c/w (note 6) exposed pad (pin 7) is gnd, must be soldered to pc board downloaded from: http:///
ltc3526l-2/ltc3526lb-2 3 3526lb2fa typical performance characteristics 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 ltc3526le-2/ltc3526lbe-2 are 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 102c/w. efficiency vs load current and v in for v out = 1.8v (ltc3526l-2) efficiency vs load current and v in for v out = 3.3v (ltc3526l-2) efficiency vs load current and v in for v out = 5v (ltc3526l-2) no-load input current vs v in (ltc3526l-2) maximum output current vs v in minimum load resistance during start-up vs v in load current (ma) 0.01 40 efficiency (%) power loss (mw) 50 60 70 80 0.1 1 10 100 1000 3526lb2 g01 30 2010 0 90 100 1 10 100 0.10.01 1000 v in = 0.9v v in = 1.2v v in = 1.5v ploss at v in = 0.9v ploss at v in = 1.2v ploss at v in = 1.5v load current (ma) 0.01 40 efficiency (%) power loss (mw) 50 60 70 80 0.1 1 10 100 1000 3526lb2 g02 30 2010 0 90 100 1 10 100 0.10.01 1000 v in = 1.2v v in = 1.8v v in = 2.4v v in = 3.0v ploss at v in = 1.2v ploss at v in = 1.8v ploss at v in = 2.4v ploss at v in = 3.0v v in (v) 0.5 i in (a) 60 70 80 4.5 3526lb2 g03 50 40 10 1.5 2.5 3.5 1.0 2.0 3.0 4.0 3020 100 90 v out = 3.3v v out = 5v v out = 2.5v v out = 1.8v load current (ma) 0.01 40 efficiency (%) power loss (mw) 50 60 70 80 0.1 1 10 100 1000 3526lb2 g04 30 2010 0 90 100 1 10 100 0.1 1000 v in = 1.2v v in = 2.4v v in = 3.6v v in = 4.2v ploss at v in = 1.2v ploss at v in = 2.4v ploss at v in = 3.6v ploss at v in = 4.2v v in (v) 0.5 i out (ma) 200 300 4.5 3526lb2 g05 100 0 1.5 2.5 3.5 1.0 2.0 3.0 4.0 400150 250 50 350 v out = 3.3v v out = 5v v out = 2.5v v out = 1.8v l = 2.2h v in (v) 0.65 load () 100 1000 10000 1.05 0.95 0.75 1.15 0.85 3526lb2 g06 10 v out = 3.3v electrical characteristics t a = 25c, unless otherwise noted. downloaded from: http:///
ltc3526l-2/ltc3526lb-2 4 3526lb2fa C50 C30 C10 10 30 50 70 90 temperature (c) normalized r ds(on) 1.0 1.1 1.2 3526lb2 g12 0.8 0.7 1.3 0.9 normalized to 25c start-up delay time vs v in burst mode threshold current vs v in (ltc3526l-2) oscillator frequency change vs v out r ds(on) vs v out oscillator frequency change vs temperature r ds(on) change vs temperature v in (v) 1.0 0 delay (s) 10 30 40 50 100 70 2.0 3.0 3.5 3526lb2 g07 20 80 9060 1.5 2.5 4.0 4.5 v in (v) 1.0 0 load current (ma) 5 10 15 20 25 3530 1.6 1.5 1.4 1.3 1.2 1.1 3526lb2 g08a enter burst leave burst v out = 1.8v c out = 10f l = 2.2h burst mode threshold current vs v in (ltc3526l-2) v in (v) load current (ma) 15 20 25 3526lb2 g08b 10 5 0 30 35 40 enter burst leave burst v out = 2.5v c out = 10f l = 2.2h 1.0 2.2 2.0 1.6 1.8 1.4 1.2 burst mode threshold current vs v in (ltc3526l-2) burst mode threshold current vs v in (ltc3526l-2) v in (v) 1.0 0 load current (ma) 20 6050 1.6 2.0 3526lb2 g08c 10 40 30 2.6 1.4 2.4 1.2 2.2 1.8 2.8 3.0 enter burst leave burst v out = 3.3v c out = 10f l = 2.2h v in (v) 1.0 load current (ma) 40 50 7060 2.5 3.5 3526lb2 g08d 3020 1.5 2.0 3.0 4.0 4.5 10 0 enter burst leave burst v out = 5v c out = 10f l = 2.2h v out (v) 1.5 frequency change (%) 1 2 43 3.0 4.0 3526lb2 g09 0 C1 2.0 2.5 3.5 4.5 5.0 C2 C4 C3 normalized to v out = 3.3v v out (v) 1.5 r ds(on) () 0.500.45 0.80 0.85 0.90 2.5 3.5 4.0 3526lb2 g10 0.35 0.70 0.60 0.40 0.750.30 0.65 0.55 2.0 3.0 4.5 5.0 pmos nmos C50 C30 C10 10 30 50 70 90 temperature (c) frequecny change (%) 4 6 8 3526lb2 g11 0 C10 C8 C6 10 2 C2C4 normalized to 25c typical performance characteristics t a = 25c, unless otherwise noted. downloaded from: http:///
ltc3526l-2/ltc3526lb-2 5 3526lb2fa temperature (c) C50 0.50 v in (v) 0.55 0.60 0.65 0.70 0.80 25 0 25 50 3526lb2 g14 75 100 0.75 1ma load no load v fb vs temperature start-up voltage vs temperature load regulation load regulation load regulation burst mode quiesent currentvs v out (ltc3526l-2) temperature (c) C60 C1.00 change in v fb (%) C0.75 C0.50 C0.25 0 C20 20 60 100 3526lb2 g13 0.25 0.50 C40 0 40 80 normalized to 25c v out (v) 1.5 10.0 9.59.0 8.5 8.0 7.5 7.0 3.0 4.0 4.5 3526lb2 g15 2.0 2.5 3.5 5.0 i q ( a) typical performance characteristics t a = 25c, unless otherwise noted. fixed frequency switching waveform and v out ripple burst mode waveforms (ltc3526l-2) v out and i in during soft-start sw pin 2v/div 200ns/div v in = 1.2v v out = 3.3v at 100ma c out = 4.7f 3526lb2 g16 v out 20mv/div ac-coupled sw pin 2v/div 20s/div v in = 1.2v v out = 3.3v at 5ma c out = 10f 3526lb2 g17 v out 20mv/div ac-coupled shdn pin 1v/div input current 0.2a/div 200s/div v out = 3.3v c out = 4.7f 3526lb2 g18 v out 1v/div load (ma) 0.01 change in v out (%) 0.1 1 10 100 1000 3526lb2 g23 C0.5 C0.4 C0.3 C0.2 C0.1 0.50.4 0.3 0.2 0.1 0 v in = 0.9v v in = 1.2v v in = 1.5v v out = 1.8v load (ma) 0.01 change in v out (%) 0.1 1 10 100 1000 3526lb2 g24 C0.5 C0.4 C0.3 C0.2 C0.1 0.50.4 0.3 0.2 0.1 0 v in = 1.2v v in = 1.8v v in = 2.4v v out = 3.3v load (ma) 0.01 change in v out (%) 0.1 1 10 100 1000 3526lb2 g25 C0.5 C0.4 C0.3 C0.2 C0.1 0.50.4 0.3 0.2 0.1 0 v in = 1.2v v in = 2.4v v in = 3.6v v in = 4.2v v out = 5v downloaded from: http:///
ltc3526l-2/ltc3526lb-2 6 3526lb2fa pin functions sw (pin 1): switch pin. connect inductor between sw and v in . keep pcb trace lengths as short and wide as possible to reduce emi. if the inductor current falls to zero or shdn is low, an internal anti-ringing switch is connected from sw to v in to minimize emi. gnd (pin 2, exposed pad pin 7): signal and power ground. provide a short direct pcb path between gnd and the (C) side of the input and output capacitors. the exposed pad must be soldered to the pcb ground plane . it serves as an additional ground connection and as a means of conducting heat away from the package. v in (pin 3): input supply pin. connect a minimum of 1f ceramic decoupling capacitor from this pin to ground using short direct pcb traces. shdn (pin 4): logic controlled shutdown input. there is an internal 4m pull-down on this pin. shdn = high: normal operation shdn = low: shutdown, quiescent current < 1a fb (pin 5): feedback input to the g m error amplifier. con- nect resistor divider tap to this pin. the top of the divider connects to the output capacitor, the bottom of the divider connects to gnd. referring to the block diagram, th e output voltage can be adjusted from 1.5v to 5.25v by: v v r r out = + ?? ? ?? ? 1 195 1 2 1 . v out (pin 6): output voltage sense and drain of the internal synchronous rectifier. pcb trace from v out to the output filter capacitor (4.7f minimum) should be as short and wide as possible. load step response (from burst mode operation) (ltc3526l-2) load step response (fixed frequency) load current 50ma/div 100s/div v in = 1.2v v out = 3.3v 50ma to 100ma stepc out = 4.7f 3526lb2 g21 v out 100mv/div ac-coupled load current 50ma/div 50s/div v in = 1.2v v out = 3.3v 5ma to 100ma stepc out = 10f 3526lb2 g22 v out 100mv/div ac-coupled typical performance characteristics t a = 25c, unless otherwise noted. load step response (from burst mode operation) (ltc3526l-2) load current 50ma/div 100s/div v in = 3.6v v out = 5v 20ma to 170ma stepc out = 10f 3526lb2 g19 v out 100mv/div ac-coupled load step response (fixed frequency) load current 50ma/div 100s/div v in = 3.6v v out = 5v 50ma to 150ma stepc out = 4.7f 3526lb2 g20 v out 100mv/div ac-coupled downloaded from: http:///
ltc3526l-2/ltc3526lb-2 7 3526lb2fa block diagram 3 3 +C +C gate drivers and anti-cross conduction logic clk i pk i pk comp slope comp i zero comp error amp sleep comp i zero wake exposed pad + C well switch mode control uvlo v ref v ref 4m shdn v best start-up 2mhz osc tsd thermal shutdown shutdown anti-ring v sel v in 1 6 sw v out l1 2.2h v b shutdown clamp c ss v ref v out 5 7 gnd 3526lb2 bd 2 fb r2 c out 4.7 f v out 1.5vto 5.25v r1 4 c in 2.2 f v in 0.8v to 5v (refer to block diagram) operation the ltc3526l-2/ltc3526lb-2 are 2mhz synchronous boost converters housed in a 6-lead 2mm 2mm dfn package. with a guaranteed ability to start up and oper- ate from inputs less than 0.8v, this device features fixed frequency, current mode pwm control for exceptional line and load regulation. the current mode architecture with adaptive slope compensation provides excellent transient load response, requiring minimal output filtering. internal soft-start and internal loop compensation simplifies the design process while minimizing the number of external components. with its low r ds(on) and low gate charge internal n-channel mosfet switch and p-channel mosfet synchronous rect i- fier, the ltc3526l-2 achieves high efficiency over a wide range of load currents. burst mode operation maintains high efficiency at very light loads, reducing the quiescent current to just 9a. operation can be best understood by referring to the block diagram. low voltage start-up the ltc3526l-2/ltc3526lb-2 include an independent start-up oscillator designed to start up at an input voltage of 0.68v (typical). soft-start and inrush current limiting are provided during start-up, as well as normal mode. when either v in or v out exceeds 1.3v typical, the ic enters normal operating mode. when the output voltage downloaded from: http:///
ltc3526l-2/ltc3526lb-2 8 3526lb2fa exceeds the input by 0.24v, the ic powers itself from v out instead of v in . at this point the internal circuitry has no dependency on the v in input voltage, eliminating the requirement for a large input capacitor. the input voltage can drop as low as 0.5v. the limiting factor for the ap- plication becomes the availability of the power source to supply sufficient energy to the output at low voltages, and maximum duty cycle, which is clamped at 90% typical. note that at low input voltages, small 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 ltc3526l-2/ltc3526lb-2 contain internal circuitry to provide soft-start operation. the soft-start circuitry slowly ramps the peak inductor current from zero to its peak value of 750ma (typical) in approximately 0.5ms, allowing start-up into heavy loads. the soft-start circuitry is reset in the event of a shutdown command or a thermal shutdown. oscillator an internal oscillator sets the switching frequency to 2mhz. shutdown shutdown is accomplished by pulling the shdn pin below 0.3v and enabled by pulling the shdn pin above 0.8v. although shdn can be driven above v in or v out (up to the absolute maximum rating) without damage, the ltc3526l-2/ltc3526lb-2 have a proprietary test mode that may be engaged if shdn is held in the range of 0.5v to 1v higher than the greater of v in or v out . if the test mode is engaged, normal pwm switching action is interrupted, which can cause undesirable operation in some applications. therefore, in applications where shdn may be driven above v in , a resistor divider or other means must be employed to keep the shdn voltage below (v in + 0.4v) to prevent the possibility of the test mode being engaged. please refer to figure 1 for two possible implementations. error amplifier the positive input of the transconductance error amplifier is internally connected to the 1.195v reference and the negative input is connected to fb. clamps limit the mini- mum and maximum error amp output voltage for improv ed large-signal transient response. power converter control loop compensation is provided internally. an external resistive voltage divider from v out to ground programs the output voltage via fb from 1.5v to 5.25v. v v r r out = + ?? ? ?? ? 1 195 1 2 1 . current sensing lossless current sensing converts the peak current signal of the n-channel mosfet switch into a voltage that 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. the cur- rent limit comparator delay to output is typically 60ns. peak switch current is limited to approximately 750ma, independent of input or output voltage, unless v out falls below 0.7v, in which case the current limit is cut in half. (refer to block diagram) operation zetex zc2811e 3526lb2 f01 ltc3526l-2/ltc3526lb-2 shdn v in v cntrl 4m 30% ltc3526l-2/ltc3526lb-2 shdn 4m 30% 1m r v cntrl 1m r > (v cntrl /(v in + 0.4) C 1)m figure 1. recommended shutdown circuits when driving shdn above v in downloaded from: http:///
ltc3526l-2/ltc3526lb-2 9 3526lb2fa zero current comparator the zero current comparator monitors the inductor cur- rent to the output and shuts off the synchronous rectifier when 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 enabled when v out > (v in + 0.24v). anti-ringing control the anti-ring circuit connects a resistor across the in- ductor to prevent high frequency ringing on the sw pin during discontinuous current mode operation. although the ringing of the resonant circuit formed by l and c sw (capacitance on sw pin) is low energy, it can cause emi radiation. output disconnect the ltc3526l-2/ltc3526lb-2 are 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 zero volts during shutdown, drawing no cur- rent 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 sw and v out . the output disconnect feature also allows v out to be pulled high, without any reverse current into a battery connected to v in . thermal shutdown if the die temperature exceeds 160c, the ltc3526l-2/ ltc3526lb-2 will go into thermal shutdown. all switches will be off and the soft-start capacitor will be discharged. the device will be enabled again when the die temperature drops by about 15c. burst mode operation the ltc3526l-2 will enter burst mode operation at light load current and return to fixed frequency pwm mode when the load increases. refer to the typical performance characteristics to see the output load burst mode thresh- old current vs v in . the load current at which burst mode operation is entered can be changed by adjusting the inductor value. raising the inductor value will lower the load current at which burst mode operation is entered. in burst mode operation, the ltc3526l-2 still switches at a fixed frequency of 2mhz, 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 opera- tion, energy is delivered to the output until it reaches the nominal regulation value, then the ltc3526l-2 transi- tions to sleep mode where the outputs are off and the ltc3526l-2 consumes only 9a of quiescent current f rom v out . when the output voltage droops slightly, switching resumes. this maximizes efficiency at very light loads by minimizing switching and quiescent losses. burst mode output voltage ripple, which is typically 1% peak-to-peak, can be reduced by using more output capacitance (10f or greater), or with a small capacitor (10pf to 50pf) con- nected between v out and fb. as the load current increases, the ltc3526l-2 will au- tomatically leave burst mode operation. note that larger output capacitor values may cause this transition to oc- cur at lighter loads. once the ltc3526l-2 has left burst mode operation and returned to normal operation, it will remain there until the output load is reduced below the burst threshold current. burst mode operation is inhibited during start-up and soft- start and until v out is at least 0.24v greater than v in . the ltc3526lb-2 features continuous pwm operation at 2mhz. at very light loads, the ltc3526lb-2 will exhibit pulse-skipping operation. (refer to block diagram) operation downloaded from: http:///
ltc3526l-2/ltc3526lb-2 10 3526lb2fa v in > v out operation the ltc3526l-2/ltc3526lb-2 will maintain voltage regu- lation even when the input voltage is above the desired output voltage. note that the efficiency is much lo wer in this mode, and the maximum output current capability will be less. refer to the typical performance characteristics. s hor t-circuit protection the ltc3526l-2/ltc3526lb-2 output disconnect feature allows output short circuit while maintaining a maximum internally set current limit. to reduce power dissipation under short-circuit conditions, the peak switch current limit is reduced to 400ma (typical). s chottky diode although not recommended, adding a schottky diode f rom sw to v out will improve efficiency by about 2%. note that this defeats the output disconnect and short-circuit protection features. pcb la yout guidelines the high speed operation of the ltc3526l-2/ltc3526l b-2 demands careful attention to board layout. a careless layout will result in reduced performance. figure 2 shows the recommended component placement. a large ground pin copper area will help to lower the die temperature. a multilayer board with a separate ground plane is ideal, but not absolutely necessary. component selectioninductor selection the ltc3526l-2/ltc3526lb-2 can utilize small surface mount chip inductors due to their fast 2mhz switching frequency. inductor values between 1.5h and 4.7h are suitable for most applications. larger values of inductance will allow slightly greater output current capability (and lower the burst mode threshold) by reducing the inductor ripple current. increasing the inductance above 6.8h will increase component size while providing little impr ovement in output current capability. the minimum inductance value is given by: l v v v ripple v in min out max in min ou > ( ) ( ) ( ) ( ) C 2 tt max ( ) where: ripple = allowable inductor current ripple (amps peak- 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 depen- dent power losses compared to cheaper powdered iron types, improving efficiency. the inductor should have low esr (series resistance of the windings) to reduce the i 2 r power losses, and must be able to support the peak figure 2. recommended component placement for single layer board + sw ltc3526l-2 1 gnd minimizetrace on fb and sw 2 v in multiple vias to ground plane v in v out fbshdn 3526lb2 f02 3 6 5 4 applications information downloaded from: http:///
ltc3526l-2/ltc3526lb-2 11 3526lb2fa inductor current without saturating. molded chokes and some chip inductors usually do not have enough core area to support the peak inductor current of 750ma seen on the ltc3526l-2 /ltc3526lb-2 . to minimize radiated noise, use a shielded inductor. see table 1 for suggested components and suppliers. table 1. recommended inductors vendor part/style coilcraft (847) 639-6400 www.coilcraft.com lpo4815 lps4012, lps3314 mss4020 me3220 coiltronics www.cooperet.com sd10, sd12, sd3114, sd3118 fdk (408) 432-8331 www.fdk.com mip3226d mipf2520d mipwt3226d mipsz2012d mips2520d murata (714) 852-2001 www.murata.com lqh3np lqh32p lqm2mpn sumida (847) 956-0666 www.sumida.com cdrh2d14 cdrh2d11 cdrh3d11 taiyo-yuden www.t-yuden.com nr3010t nr3015t nr3012t tdk (847) 803-6100 www.component.tdk.com vlp vlf, vlcf toko (408) 432-8282 www.tokoam.com d412c wrth (201) 785-8800 www.we-online.com we-tpc type s, m, th, xs output and input capacitor selection 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 ap- plications. larger values may be used to obtain extremely low output voltage ripple and 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. the internal loop compensation of the ltc3526l-2/ ltc3526lb-2 are designed to be stable with output ca- pacitor values of 4.7f or greater (without the need for any external series resistor). although ceramic capacitors are recommended, low esr tantalum capacitors may be used as well. a small ceramic capacitor in parallel with a larger tantalum capacitor may be used in demanding applications tha t have large load transients. another method of improving the transient response is to add a small feed-forward c apacitor across the top resistor of the feedback divider (from v out to fb). a typical value of 22pf will generally suffice. 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 possible to the device. a 2.2f input capacitor is sufficient for most applications, although larger values may be used without limitations. table 2 shows a list of several ceramic capacitor manufacturers. consult the manufa ctur- ers directly for detailed information on their selection of ceramic capacitors. table 2. capacitor vendor information supplier phone website 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 samsung (408) 544-5200 www.sem.samsung.com applications information downloaded from: http:///
ltc3526l-2/ltc3526lb-2 12 3526lb2fa 1-cell to 1.8v converter with <1mm maximum height fixed frequency 1-cell to 2.85v low noise converter 1-cell to 3.3v sw v in 511k fdk mipwt3226d2r2 murata grm219r60j106ke19d * ** 1m 2.2h* 1f 10f** 68pf 3526lb2 ta02a ltc3526l-2 shdn v out fb v in 0.8v to 1.6v v out 1.8v150ma off on gnd sw v in 1.4m1m *sumida cdrh2d11np-2r2n 3526lb2 ta03a ltc3526lb-2 shdn v out fb v in 0.8v to 1.6v v out 2.85v100ma off on gnd 2.2h* 1f 4.7f sw v in 1.78m 1m *taiyo-yuden nr3015t2r2m 33pf 3526lb2 ta04a ltc3526l-2 shdn v out fb v in 0.8v to 1.6v v out 3.3v75ma off on gnd 2.2h* 1f 10f load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta02b 30 2010 0 90 100 v in = 1.5v v in = 1.2v v in = 0.9v v out = 1.8v load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta03b 30 2010 0 90 100 v in = 1.5v v in = 1.2v v in = 0.9v v out = 2.85v load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta04b 30 2010 0 90 100 v in = 1.5v v in = 1.2v v in = 0.9v v out = 3.3v typical applications downloaded from: http:///
ltc3526l-2/ltc3526lb-2 13 3526lb2fa 2-cell to 3.3v sw v in 1.78m1m *coilcraft lps3314-222ml 3526lb2 ta05a ltc3526l-2 shdn v out fb v in 1.6v to 3.2v v out 3.3v200ma off on gnd 2.2h* 1f 4.7f 33pf load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta05b 30 2010 0 90 100 v in = 3.0v v in = 2.4v v in = 1.8v v out = 3.3v typical applications 2-cell to 5v sw v in 3.24m1.02m *coilcraft lps4018-332ml 33pf 3526lb2 ta06a ltc3526l-2 shdn v out fb v in 1.6v to 3.2v v out 5v150ma off on gnd 3.3h* 1f 10f li-ion to 5v sw v in 3.24m 1.02m *wurth 744031003 22pf 3526lb2 ta08a ltc3526l-2 shdn v out fb v in 2.7v to 4.3v v out 5v200ma off on gnd 3.6h* 1f 10f load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta06b 30 2010 0 90 100 v in = 3.0v v in = 2.4v v in = 1.8v v out = 5v load current (ma) 0.01 40 efficiency (%) 50 60 70 80 0.1 1 10 100 1000 3526lb2 ta08b 30 2010 0 90 100 v in = 4.2v v in = 3.6v v in = 3.0v v out = 5v downloaded from: http:///
ltc3526l-2/ltc3526lb-2 14 3526lb2fa 2.00 p 0.10 (4 sides) note:1. drawing to be made a jedec package outline m0-229 variation of (wccd-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 0.40 p 0.10 bottom view?exposed pad 0.56 p 0.05 (2 sides) 0.75 p 0.05 r = 0.125 typ r = 0.05 typ 1.37 p 0.05 (2 sides) 1 3 6 4 pin 1 bar top mark (see note 6) 0.200 ref 0.00 ? 0.05 (dc6) dfn rev b 1309 0.25 p 0.05 0.50 bsc 0.25 p 0.05 1.42 p 0.05 (2 sides) recommended solder pad pitch and dimensions 0.61 p 0.05 (2 sides) 1.15 p 0.05 0.70 p 0.05 2.55 p 0.05 packageoutline 0.50 bsc pin 1 notch r = 0.20 or 0.25 s 45 o chamfer package description dc package 6-lead plastic dfn (2mm 2mm) (reference ltc dwg # 05-08-1703 rev b) downloaded from: http:///
ltc3526l-2/ltc3526lb-2 15 3526lb2fa information furnished by linear technology corporat ion is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. revision history rev date description page number a 9/10 changed 60c/w to 102c/w in note 6 updated pin 2 text in pin functionsupdated shutdown section updated related parts 36 8 16 downloaded from: http:///
ltc3526l-2/ltc3526lb-2 16 3526lb2fa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ?? linear technology corporation 2009 lt 0910 rev a ? printed in usa 3.3v converter with output or?d with 5v usb input sw v in 1.78m 1m mbr120esft 3526lb2 ta07a ltc3526l-2 shdn v out fb v batt 1.8v to 3.2v 5v usb v out 3.3v/5v usb off on gnd ldo dc/dc 2.2h* 1f 10f *murata lqh3npn2r2nm0 33pf related parts part number description comments ltc3526/ltc3526b ltc3526-2/ltc3526b-2 ltc3526l/ltc3526lb 500ma, 1mhz/2.2mhz, synchronous step-up dc/dc converters with output disconnect 94% efficiency v in : 0.85v to 5v, v out(max) = 5.25v, i q = 9a, i sd < 1a, 2mm 2mm dfn-6 package ltc3525l-3 400ma micropower synchronous step-up dc/dc converter with output disconnect 93% efficiency v in : 0.88v to 4.5v, v out = 3v, i q = 7a, i sd < 1a, sc-70 package ltc3525-3 ltc3525-3.3 ltc3525-5 400ma micropower synchronous step-up dc/dc converter with output disconnect 95% efficiency v in : 1v to 4.5v, v out(max) = 3.3v or 5v, i q = 7a, i sd < 1a, sc-70 package ltc3427 500ma i sw , 1.2mhz, synchronous step-up dc/dc converter with output disconnect 93% efficiency v in : 1.8v to 4.5v, v out(max) = 5v, 2mm 2mm dfn package ltc3400/ltc3400b 600ma i sw , 1.2mhz, synchronous step-up dc/dc converters 92% efficiency v in : 1v to 5v, v out(max) = 5v, i q = 19a/300a, i sd < 1a, thinsot? package ltc3527/ltc3527-1 dual 600ma/400ma i sw , 1.2mhz/2.2mhz synchronous step-up dc/dc converters 94% efficiency v in : 0.7v to 5v, v out(max) = 5.25v, i q = 12a, i sd < 1a, 3mm 3mm qfn-16 package typical application downloaded from: http:///

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