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1 ltc1911-1.5/ltc1911-1.8 sn1911 1911is low noise, high efficiency, inductorless step-down dc/dc converter august 2002 the ltc ? 1911 is a switched capacitor step-down dc/dc converter that produces a 1.5v or 1.8v regulated output from a 2.7v to 5.5v input. the part uses switched capaci- tor fractional conversion to achieve high efficiency over the entire input range. no inductors are required. internal cir- cuitry controls the step-down conversion ratio to optimize efficiency as the input voltage and load conditions vary. typical efficiency is over 25% higher than that of a linear regulator. a unique constant frequency architecture provides a low noise regulated output as well as lower input noise than conventional charge pump regulators. high frequency operation (f osc = 1.5mhz) simplifies output filtering to further reduce conducted noise. to optimize efficiency, the part enters burst mode tm operation under light load conditions. low operating current (180 m a with no load, 10 m a in shutdown) and low external parts count (two 1 m f flying capacitors and two 10 m f bypass capacitors) make the ltc1911 ideally suited for space constrained battery- powered applications. the part is short-circuit and overtemperature protected, and is available in an 8-pin msop package. n low noise constant frequency operation n 2.7v to 5.5v input voltage range n no inductors n typical efficiency 25% higher than ldos n shutdown disconnects load from v in n output voltage: 1.8v 4% or 1.5v 4% n output current: 250ma n low operating current: i in = 180 m a typ n low shutdown current: i in = 10 m a typ n oscillator frequency: 1.5mhz n soft-start limits inrush current at turn on n short-circuit and overtemperature protected n available in an 8-pin msop package , ltc and lt are registered trademarks of linear technology corporation. n handheld computers n cellular phones n smart card readers n portable electronic equipment n handheld medical instruments n low power dsp supplies final electrical specifications 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. features descriptio u applicatio s u typical applicatio u v in c2 + c2 gnd 8 6 7 5 1 2 3 4 ss/shdn v out c1 + c1 ltc1911-1.8 1 f* 1-cell li-ion or 3-cell nimh 10 f* *ceramic capacitor 10 f* 1911 ta01 v out = 1.8v i out = 250ma 1 f* 2.7v to 5.5v input single cell li-ion to 1.8v dc/dc converter efficiency burst mode is a trademark of linear technology corporation. input voltage (v) 2 30 efficiency (%) 40 50 60 70 80 90 34 56 1911 g05 ideal ldo 250ma 100ma
2 ltc1911-1.5/ltc1911-1.8 sn1911 1911is parameter conditions min typ max units v in operating voltage l 2.7 5.5 v v out ltc1911-1.5, 0ma i out 250ma, v in = 2.7v to 5.5v l 1.44 1.5 1.56 v ltc1911-1.8, 0ma i out 250ma, v in = 2.7v to 5.5v l 1.73 1.8 1.87 v v in operating current i out = 0ma, v in = 2.7v to 5.5v l 180 350 m a v in shutdown current ss/shdn = 0v, v in = 2.7v to 5.5v l 10 20 m a output ripple (not including esr spike) i out = 10ma 5 mv p-p i out = 250ma 12 mv p-p v out short-circuit current v out = 0v 600 ma switching frequency oscillator free running 1.2 1.5 1.8 mhz ss/shdn input threshold l 0.3 0.6 1 v ss/shdn soft-start current v ss/shdn = 0v (note 3) l C5 C2 C1 m a v ss/shdn = v in 0.01 m a turn-on time c ss = 0pf, v in = 3.3v 0.03 ms c ss = 10nf, v in = 3.3v 10 ms load regulation 0v i out 250ma 0.13 mv/ma line regulation 0v i out 250ma 0.3 %/v (note 1) v in to gnd ...................................................C 0.3v to 6v ss/shdn to gnd ........................ C 0.3v to (v in + 0.3v) v out short-circuit duration ............................ indefinite operating temperature range (note 2) .. C 40 c to 85 c storage temperature range ................. C 40 c to 150 c lead temperature (soldering, 10 sec).................. 300 c order part number ltc1911ems8-1.5 ltc1911ems8-1.8 t jmax = 125 c, q ja = 160 c/ w the l denotes specifications which apply over the full operating temperature range, otherwise specifications are t a = 25 c. v in = 3.6v, c1 = 1 m f, c2 = 1 m f, c in = 10 m f, c out = 10 m f unless otherwise noted. absolute axi u rati gs w ww u package/order i for atio uu w ms8 part marking 1 2 3 4 v in c2 + c2 gnd 8 7 6 5 ss/shdn c1 + v out c1 top view ms8 package 8-lead plastic msop ltmy ltnu electrical characteristics note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the ltc1911e is guaranteed to meet specified performance from 0 c to 70 c. specifications over the C 40 c to 85 c operating temperature range are assured by design, characterization and correlation with statistical process control. note 3: currents flowing into the device are positive polarity. currents flowing out of the device are negative polarity. consult ltc marketing for parts specified with wider operating temperature ranges.
3 ltc1911-1.5/ltc1911-1.8 sn1911 1911is typical perfor a ce characteristics uw input operating current vs input voltage input shutdown current vs input voltage ltc1911-1.8 output voltage vs input voltage ltc1911-1.5 output voltage vs input voltage ltc1911-1.5 efficiency vs input voltage (falling input voltage) ltc1911-1.8 efficiency vs output current ltc1911-1.8 output voltage vs output current input voltage (v) 2 input current ( a) 180 190 200 6 1911 g01 170 160 3 4 5 150 210 t a = 85 c t a = 25 c t a = 40 c input voltage (v) 2 input current ( a) 9 11 6 1911 g02 7 5 3 4 5 15 13 t a = 85 c t a = 25 c t a = 40 c v out = 0v v (ss/shdn) = 0v input voltage (v) 2 output voltage (v) 1.80 1.85 6 1911 g03 1.75 1.70 3 4 5 1.90 t a = 40 c t a = 25 c t a = 85 c i out = 250ma input voltage (v) 2 efficiency (%) 60 70 80 6 1911 g05 50 40 20 3 4 5 30 100 90 ideal ldo 100ma 250ma output current (ma) 1 efficiency (%) 50 60 1911 g06 40 30 10 100 1000 90 80 70 2.7v 3.2v 3.7v 4.2v 5.1v 5.5v v in : ltc1911-1.5 efficiency vs output current output current (ma) 0.1 output voltage (v) 1.78 1.80 1000 1911 g08 1.76 1.74 1 10 100 1.84 v in = 3.6v 1.82 t a = 40 c t a = 25 c t a = 85 c ltc1911-1.5 output voltage vs output current input voltage (v) 2 output voltage (v) 1.49 1.51 6 ltxxxx ?tpcxx 1.47 1.45 3 4 5 1.55 1.53 t a = 40 c t a = 25 c t a = 85 c i out = 250ma output current (ma) 1 30 efficiency (%) 40 50 60 70 90 10 100 1911 g07 1000 80 2.8v 3.3v 3.7v 4.3v 5.1v 5.5v v in : output current (ma) 0.1 output voltage (v) 1.48 1.50 1000 1911 g09 1.46 1.44 1 10 100 1.54 1.52 t a = 40 c t a = 85 c t a = 25 c
4 ltc1911-1.5/ltc1911-1.8 sn1911 1911is typical perfor a ce characteristics uw start-up time vs soft-start capacitor output ripple vs output load current output current transient response line transient response soft-start capacitor (nf) 0.1 0.1 start-up time (ms) 1 10 100 110 1911 g10 100 t a = 40 c t a = 25 c t a = 85 c v in = 3.6v 4v 3v v in 500mv/div v out 20mv/div i out = 225ma 20 m s/div 1911 g14 250ma 25ma i out v out 20mv/div v in = 3.6v 10 m s/div 1911 g13 v in (pin 1): input supply voltage. v in may be between 2.7v and 5.5v. suggested bypass for v in is a 10 m f (1 m f min) ceramic low esr capacitor. c2 + (pin 2): flying capacitor two positive terminal. c2 C (pin 3): flying capacitor two negative terminal. gnd (pin 4): ground. connect to a ground plane for best performance. c1 C (pin 5): flying capacitor one negative terminal. v out (pin 6): regulated output voltage. v out is discon- nected from v in during shutdown. bypass v out with a 3 10 m f ceramic low esr capacitor (4 m f min, esr < 0.1 w max). c1 + (pin 7): flying capacitor one positive terminal. uu u pi fu ctio s ss/shdn (pin 8): soft-start/shutdown control pin. this pin is designed to be driven with an external open-drain output. holding the ss/shdn pin below 0.3v will force the ltc1911-x into shutdown mode. an internal pull-up current of 2 m a will force the ss/shdn voltage to climb to v in once the device driving the pin is forced into a hi-z state. to limit inrush current on start-up, connect a capacitor between the ss/shdn pin and gnd. capaci- tance on the ss/shdn pin will limit the dv/dt of the pin during turn on which, in turn, will limit the dv/dt of v out . by selecting an appropriate soft-start capacitor, the user can control the inrush current for a known output capaci- tor during turn-on (see application information). if nei- ther of the two functions are desired, the pin may be left floating or tied to v in . ltc1911-1.8 output voltage ripple v out 50mv/div 2-to-1 mode v in = 5v i out = 250ma 100ns/div 1911 g12 all waveforms ac coupled output load current (ma) 0 0 output ripple (mv p-p ) 5 10 15 20 30 50 100 150 200 1911 g11 250 300 25 t a = 4.7 f t a = 10 f t a = 22 f v out 50mv/div 3-to-2 mode v in = 3.6v v out 50mv/div 1-to-1 mode v in = 2.7v v in (v) 2.5 1.40 frequency (mhz) 1.45 1.50 1.55 1.60 3.0 3.5 4.0 4.5 1911 g15 5.0 5.5 t a = 40 c t a = 25 c t a = 85 c oscillator frequency vs supply voltage
5 ltc1911-1.5/ltc1911-1.8 sn1911 1911is si plified w block diagra w + + 300k c in v in 50k 150k v ref + adj offset mode control step-down charge pump 1 r a + + amp1 + + + amp2 soft-start 1.26v v ref comp1 burst threshold c1 + c1 c2 + c2 r sense v out c c 6 gnd 1911 bd 4 3 2 5 7 + comp2 600mv 600mv shdn short-circuit threshold overtemp detect 1.5mhz oscillator 60k 140k v ref ramp + 2 a ss/shdn v in 8 + shdn
6 ltc1911-1.5/ltc1911-1.8 sn1911 1911is applicatio s i for atio wu uu general operation the ltc1911 uses a switch capacitor-based dc/dc con- version to provide the efficiency advantages associated with inductor-based circuits as well as the cost and simplicity advantages of a linear regulator. the ltc1911s unique constant frequency architecture provides a low noise regulated output as well as lower input noise than conventional switch-capacitor charge pump regulators. the ltc1911 uses an internal switch network and frac- tional conversion ratios to achieve high efficiency over widely varying v in and output load conditions. internal control circuitry selects the appropriate step-down con- version ratio based on v in and load conditions to optimize efficiency. the part has three possible step-down modes: 2-to-1, 3-to-2 or 1-to-1 step-down mode. only two exter- nal flying caps are needed to operate in all three modes. 2-to-1 mode is chosen when v in is greater than two times the desired v out . 3-to-2 mode is chosen when v in is greater than 1.5 times v out but less than 2 times v out . 1- to-1 mode is chosen when v in falls below 1.5 times v out . an internal load current sense circuit controls the switch point of the step-down ratio as needed to maintain output regulation over all load conditions. regulation is achieved by sensing the output voltage and regulating the amount of charge transferred per cycle. this method of regulation provides much lower input and output ripple than that of conventional switched capacitor charge pumps. the constant frequency charge transfer also makes additional output or input filtering much less demanding than conventional switched capacitor charge pumps. the ltc1911 also has a burst mode function that delivers a minimum amount of charge for one cycle then goes into a low current state until the output drops enough to require another burst of charge. burst mode operaton allows the ltc1911 to achieve high efficiency even at light loads. the part has shutdown capability as well as user-controlled inrush current limiting. in addition, the part has short- circuit and overtemperature protection. step-down charge transfer operation figure 1a shows the switch configuration that is used for 2-to-1 step down mode. in this mode, a 2-phase clock generates the switch control signals. on phase one of the clock, the top plate of c1 is connected to v in through r a and s4, the bottom plate is connected to v out through s3. the amount of charge transferred to c1 (and v out ) is set by the value of r a . on phase two, flying capacitor c1 is connected to v out through s1 and to gnd through s2. the charge that was transferred onto c1 from the previous cycle is now trans- ferred to the output. thus, in 2-to-1 mode, charge is transferred to v out on both phases of the clock. since charge current is sourced from gnd on the second phase of the clock, current multiplication is realized with respect to v in , i.e., i out equals approximately 2 ? i in . this results in significant efficiency improvement relative to a linear regulator. the value of r a is set by the control loop of the regulator. v in v out c1 r a c1 + c1 1911 f01a s4 f 1 s1 f 2 s3 f 1 s2 f 2 figure 1a. step-down charge transfer in 2-to-1 mode the 3-to-2 conversion mode also uses a nonoverlapping clock for switch control but requires two flying capacitors and a total of seven switches (see figure 1b). on phase one of the clock, the two capacitors are connected in parallel to v in through r a by switches s5 and s7, and to v out through s4 and s6. the amount of charge transferred to c1|| c2 (and v out ) is set by the regulator control loop which determines the value of r a . on phase two, c1 and c2 are connected in series from v out to gnd through switches s1, s2 and s3. on phase two, half of the charge
7 ltc1911-1.5/ltc1911-1.8 sn1911 1911is transferred to the parallel combination of c1 and c2 is transferred to the v out . in this manner, charge is again transferred from the flying capacitors to the output on both phases of the clock. as in 2-to-1 mode, charge current is sourced from gnd on phase two of the clock resulting in increased power efficiency. i out in 3-to-2 mode equals approximately (3/2)i in . in 1-to-1 mode (see figure 1c), switch s1 is always closed connecting the top plate of c1 to v out . switch s2 remains closed for almost the entire clock period, opening only briefly at the end of clock phase one. in this manner, v out is connected to v in through r a . the value of r a is set by the regulator control loop which determines the amount of current transferred to v out during the on period of s2. the ltc1911 acts much like a linear regulator in this mode. since all of the v out current is sourced from v in , the efficiency in 1-to-1 mode is approximately equal to that of a linear regulator. mode selection the optimal step-down conversion mode is chosen based on v in and output load conditions. two internal compara- tors are used to select the default step-down mode based on the input voltage. each comparator has an adjustable offset built in that increases (decreases) in proportion to the increasing (decreasing) output load current. in this manner, the mode switch point is optimized to provide peak efficiency over all supply and load conditions. each comparator also has built-in hysteresis of about 300mv to ensure that the ltc1911 does not oscillate between modes when a transition point is reached. soft-start/shutdown operation the ss/shdn pin is used to implement both low current shutdown and soft-start. the soft-start feature limits inrush currents when the regulator is initially powered up or taken out of shutdown. forcing a voltage lower than 0.6v (typ) on the ss/shdn pin will put the ltc1911 into shutdown mode. shutdown mode disables all control circuitry and forces v out into a high impedance state. a 2 m a pull-up current on the ss/shdn pin will force the part into active mode if the pin is left floating or is driven with an open-drain output that is in a high impedance state. if the pin is not driven with an open-drain device, it must be forced to a logic high voltage of 2.2v (min) to ensure proper v out regulation. the ss/shdn pin should not be driven to a voltage higher than v in . to implement soft- start, the ss/shdn pin must be driven with an open-drain device and a capacitor must be connected from the ss/ shdn pin to gnd. once the open-drain device is turned off, the 2 m a pull-up current will begin charging the external soft-start capacitor and force the voltage on the pin to ramp towards v in . as soon as the shutdown threshold is reached (0.6v typ), the internal reference voltage that controls the v out regulation point will follow the ramp voltage on the ss/shdn pin (minus a 0.6v offset to account for the shutdown threshold) until the reference reaches its final band gap voltage. this occurs when the voltage on the ss/shdn pin reaches approximately 1.9v. since the ramp rate on the ss/shdn pin controls the ramp rate on v out , the average inrush current can be controlled through the selection of c ss and c out . for example, a applicatio s i for atio wu uu v in v out c1 r a c1 + c1 c2 + c2 s5 f 1 s7 f 1 s4 f 1 s1 f 2 s2 f 2 gnd c2 1911 f01b s6 f 1 s3 f 2 figure 1b. step-down charge transfer in 3-to-2 mode v in v out c1 r a c1 + c1 1911 f01c s2 s1 figure 1c. step-down charge transfer in 1-to-1 mode
8 ltc1911-1.5/ltc1911-1.8 sn1911 1911is 4.7nf capacitor on ss/shdn results in a 3ms ramp time from 0.6v to 1.9v on the pin. if c out is 10 m f, the 3ms v ref ramp time results in an average c out charge current of only 6ma (see figure 2). low current burst mode operation to improve efficiency at low output currents, a burst mode function was included in the design of the ltc1911. an output current sense circuit is used to detect when the required output current drops below 30ma typ. when this occurs, the oscillator shuts down and the part goes into a low current operating state. the ltc1911 will remain in the low current operating state until v out has dropped enough to require another burst of current. unlike tradi- tional charge pumps whos burst current is dependant on many factors (i.e., supply, switch strength, capacitor selection, etc.), the ltc1911 burst current is set by the burst threshold. this means that the output ripple voltage during burst mode operaton will be fixed and is typically 5mv. short-circuit/thermal protection the ltc1911 has built-in short-circuit current limiting as well as overtemperature protection. during short-circuit conditions it will automatically limit its output current to approximately 600ma. the ltc1911 will shut down if the junction temperature exceeds approximately 160 c. un- der normal operating conditions, the ltc1911 should not go into thermal shutdown but it is included to protect the ic in cases of excessively high ambient temperatures, or in cases of excessive power dissipation inside the ic (i.e., overcurrent or short circuit). the charge transfer will reactivate once the junction temperature drops back to approximately 150 c. the ltc1911 can cycle in and out of thermal shutdown indefinitely without latch-up or damage until the fault condition is removed. v out ripple and capacitor selection the type and value of capacitors used with the ltc1911 determine several important parameters such as regulator control loop stability, output ripple and charge pump strength. the value of c out directly controls the amount of output ripple for a given load current. increasing the size of c out will reduce the output ripple. applicatio s i for atio wu uu figure 2. shutdown/soft-start operation ss/shdn c ss on off v ctrl 6 8 v out r load ltc1911 (2a) v ctrl 2v/div v out 1v/div c ss = 0nf 2ms/div 1911 f02b c out = 10 m f r load = 10 w (2b) v ctrl 2v/div v out 1v/div c ss = 4.7nf 2ms/div 1911 f02c c out = 10 m f r out = 10 w (2c)
9 ltc1911-1.5/ltc1911-1.8 sn1911 1911is to reduce output noise and ripple, it is suggested that a low esr ( 0.1 w ) ceramic capacitor (10 m f or greater) be used for c out . tantalum and aluminum capacitors are not recommended because of their high esr (equivalent series resistance). both the style and value of c out can significantly affect the stability of the ltc1911. as shown in the block diagram, the part uses a control loop to adjust the strength of the charge pump to match the current required at the output. the error signal of this loop is stored directly on the output charge storage capacitor. the charge storage capacitor also serves to form the dominant pole for the control loop. to prevent ringing or instability it is important for the output capacitor to maintain at least 4 m f of capacitance over all conditions (see ceramic capacitor selection guidelines). likewise excessive esr on the output capacitor will tend to degrade the loop stability of the ltc1911. the closed- loop output resistance of the part is designed to be 0.13 w . for a 250ma load current change, the output voltage will change by about 33mv. if the output capacitor has 0.13 w or more of esr, the closed-loop frequency response will cease to roll-off in a simple 1-pole fashion and poor load transient response or instability could result. ceramic capacitors typically have exceptional esr performance, and combined with a tight board layout, should yield excellent stability and load transient performance. v in capacitor selection the constant frequency architecture used by the ltc1911 makes input noise filtering much less demand- ing than with conventional regulated charge pumps. de- pending on the mode of operation the input current of the ltc1911 can vary from i out to 0ma on a cycle-by-cycle basis. lower esr will reduce the voltage steps caused by changing input current, while the absolute capacitor value will determine the level of ripple. for optimal input noise and ripple reduction, it is recommended that a low esr ceramic capacitor be used for c in . a tantalum capacitor may be used for c in but the higher esr will lead to more input noise. the ltc1911 will operate with capacitors applicatio s i for atio wu uu less than 1 m f but the increasing input noise will feed through to the output causing degraded performance. for best performance a 1 m f or greater capacitor is sug- gested for c in . aluminum capacitors are not recom- mended because of their high esr. flying capacitor selection warning: a polarized capacitor such as tantalum or aluminum should never be used for the flying capacitors since their voltage can reverse upon start-up of the ltc1911. ceramic capacitors should always be used for the flying capacitor. the flying capacitor controls the strength of the charge pump. in order to achieve the rated output current it is necessary for the flying capacitor to have at least 0.4 m f of capacitance over operating temperature with a 2v bias (see ceramic capacitor selection guidelines). if only 100ma or less of output current is required the flying capacitor minimum can be reduced to 0.15 m f. ceramic capacitor selection guidelines capacitors of different materials lose their capacitance with higher temperature and voltage at different rates. for example, a ceramic capacitor made of x7r material will retain most of its capacitance from C 40 c to 85 c whereas a z5u or y5v style capacitor will lose considerable capaci- tance over that range (60% to 80% loss typ). z5u and y5v capacitors may also have a very strong voltage coefficient causing them to lose an additional 60% or more of their capacitance when the rated voltage is applied. therefore, when comparing different capacitors it is often more appropriate to compare the amount of achievable capaci- tance for a given case size rather than discussing the specified capacitance value. for example, over rated volt- age and temperature conditions, a 4.7 m f, 10v, y5v ce- ramic capacitor in a 0805 case may not provide any more capacitance than a 1 m f, 10v, x7r available in the same 0805 case. in fact, over bias and temperature range, the 1 m f, 10v, x7r will provide more capacitance than the 4.7 m f, 10v, y5v. the capacitor manufacturers data sheet should be consulted to determine what value of capacitor
10 ltc1911-1.5/ltc1911-1.8 sn1911 1911is applicatio s i for atio wu uu is needed to ensure that minimum capacitance values are met over operating temperature and bias voltage. table 1 is a list of ceramic capacitor manufacturers and how to contact them. table 1. ceramic capacitor manufacturers avx 1-(803)-448-1943 www.avxcorp.com kemet 1-(864) 963-6300 www.kemet.com murata 1-(800) 831-9172 www.murata.com taiyo yuden 1-(800) 348-2496 www.t-yuden.com vishay 1-(800) 487-9437 www.vishay.com layout considerations due to the high switching frequency and transient cur- rents produced by the ltc1911, careful board layout is necessary for optimal performance. a true ground plane and short connections to all capacitors will optimize performance, reduce noise and ensure proper regulation over all conditions. figure 3 shows the recommended layout configuration. additional output filtering can be achieved by placing a second output capacitor, connected to the ground plane, about 2cm or more from the ltc1911 output capacitor (c4). the inductance of the trace running to the second output capacitor will significantly attenuate the high speed switching transients of the ltc1911. even small capaci- tors as low as 0.1 m f will provide excellent results. thermal management the power dissipation in the ltc1911 can cause the junction temperature to rise at rates of up to 160 c/w. if the specified operating conditions are followed, the junc- tion temperature should never exceed the 160 c thermal shutdown temperature. the junction temperature can come very close and possibly exceed the specified 125 c operating junction temperature. to reduce the maximum junction temperature, a good thermal connection to the pc board is recommended. connecting the gnd pin (pin 4) to a ground plane, and maintaining a solid ground plane under the device on two layers of the pc board, can reduce the thermal resistance of the package and pc board considerably. c1 1911 f03 c4 out gnd c2 v in ss/shdn : connect to gnd plane on back of board c3 u1 figure 3. recommended component placement and grounding
11 ltc1911-1.5/ltc1911-1.8 sn1911 1911is u package descriptio ms8 package 8-lead plastic msop (reference ltc dwg # 05-08-1660) msop (ms8) 1001 0.53 0.015 (.021 .006) seating plane note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.18 (.077) 0.254 (.010) 1.10 (.043) max 0.22 ?0.38 (.009 ?.015) 0.13 0.05 (.005 .002) 0.86 (.34) ref 0.65 (.0256) bcs 0 ?6 typ detail ? detail ? gauge plane 12 3 4 4.88 0.1 (.192 .004) 8 7 6 5 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) note 4 0.52 (.206) ref 5.23 (.206) min 3.2 ?3.45 (.126 ?.136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.42 0.04 (.0165 .0015) typ 0.65 (.0256) bsc
12 ltc1911-1.5/ltc1911-1.8 sn1911 1911is ? linear technology corporation 2001 lt/tp 0802 1.5k ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com part number description comments ltc1474/ltc1475 low quiescent current step-down dc/dc converters i out to 250ma, i q = 10ma, 8-lead msop ltc1502-3.3 single cell to 3.3v quadrupler charge pump v in = 0.9v to 1.8v, i out = 10ma, i q = 40 m a ltc1503-1.8 1.8v charge pump with shutdown in ms8 package 100ma output current, i cc = 25 m a ltc1514/ltc1515 micropower, regulated 5v step-up/step-down 2v to 10v input range, up to 50ma output current short-circuit and charge pump dc/dc converters overtemperature protected ltc1555l-1.8 sim power supply and level translator step-up/step-down charge pump generates 5v, 3v or 1.8v ltc1627 monolithic synchronous buck step-down 2.65v to 8.5v input range, v out from 0.8v, i out to 500ma, switching regulator low dropout operation, 100% duty cycle ltc1701 1mhz step-down dc/dc converter in thinsot tm v in = 2.5v to 5.5v; v out = 1.25v to 5v; i out = 500ma ltc1754-3.3 3.3v/5v doubler charge pump with shutdown in thinsot 50ma output current, i cc = 13 m a thinsot is a trademark of linear technology corporation. typical applicatio u dc/dc converter with shutdown and soft-start v in c2 + c2 gnd 8 7 6 5 1 2 3 4 ss/shdn c1 + v out c1 ltc1911-1.5 1 f* 1-cell li-ion or 3-cell nimh 10 f* 10 f* 2n7002 on off 10nf 1911 ta03 v out = 1.5v i out = 250ma 1 f* *ceramic capacitor 2.7v to 5.5v input related parts

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