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1 ltc1261l typical applicatio n u descriptio u applicatio s u features switched capacitor regulated voltage inverter n regulated negative voltage from a single positive supply n reg pin indicates output is in regulation n adjustable or fixed output voltages n output regulation: 3.5% n supply current: 650 m a typ n shutdown mode drops supply current to 5 m a n up to 20ma output current n requires only three or four external capacitors n available in ms8 and so-8 packages the ltc ? 1261l is a switched-capacitor voltage inverter designed to provide a regulated negative voltage from a single positive supply. the ltc1261l operates from a single 2.7v to 5.25v supply and provides an adjustable output voltage from C1.23v to C 5v. the ltc1261l-4/ ltc1261l-4.5 needs a single 4.5v to 5.25v supply and provides a fixed output voltage of C 4v to C 4.5v respec- tively. three external capacitors are required: a 0.1 m f flying capacitor and an input and output bypass capaci- tors. an optional compensation capacitor at adj (comp) can be used to reduce the output voltage ripple. each version of the ltc1261l will supply up to 20ma output current with guaranteed output regulation of 3.5%. the ltc1261l includes an open-drain reg output that pulls low when the output is within 5% of the set value. quiescent current is typically 650 m a when operating and 5 m a in shutdown. the ltc1261l is available in 8-pin msop and so pack- ages. , ltc and lt are registered trademarks of linear technology corporation. waveforms for C 4v generator with power valid 1261l tao2 0.1ms/div 0v C4v 1 2 3 4 8 7 6 5 ltc1261l-4 shdn reg out comp v cc c1 + c1 gnd c2 0.1 m f 1261l ta01 c4 3.3 m f v out = 4v at 10ma power valid 5v c1 1 m f 5v 10k c3* 100pf *optional + C 4v generator with power valid n gaas fet bias generators n negative supply generators n battery-powered systems n single supply applications 5v 0v 5v 0v power valid shdn out
2 ltc1261l (note 1) a u g w a w u w a r b s o lu t exi t i s supply voltage (note 2) ........................................ 5.5v output voltage (note 3) ........................... 0.3v to C 5.3v total voltage, v cc to v out (note 2) ..................... 10.8v shdn pin .................................. C 0.3v to (v cc + 0.3v) reg pin ..................................................... C 0.3v to 6v adj pin ........................... (v out C 0.3v) to (v cc + 0.3v) output short-circuit duration ......................... indefinite commercial temperature range ................ 0 c to 70 c extended commercial operating temperature range (note 4) ................. C 40 c to 85 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c wu u package / o rder i for atio order part number ms8 part marking order part number s8 part marking t jmax = 150 c, q ja = 200 c/w 1 2 3 4 v cc c1 + c1 gnd 8 7 6 5 shdn reg out adj (comp) top view ms8 package 8-lead plastic msop ltc1261lcms8 ltc1261lcms8-4 ltc1261lcms8-4.5 1 2 3 4 8 7 6 5 top view shdn reg out adj (comp) v cc c1 + c1 gnd s8 package 8-lead plastic so t jmax = 150 c, q ja = 135 c/w ltc1261lcs8 ltc1261lcs8-4 ltc1261lcs8-4.5 e lectr ic al c c hara terist ics ltfm ltfn ltfp 1261l 1261l4 261l45 consult factory for industrial or military grade parts or additional fixed voltage parts. symbol parameter conditions min typ max units v cc supply voltage (ltc1261lcms8/ltc1261lcs8) l 2.7 5.25 v (ltc1261lcms8-4/ltc1261lcs8-4) (note 5) l 4.35 5.25 v (ltc1261lcms8-4.5/ltc1261lcs8-4.5) (note 5) l 4.75 5.25 v v ref reference voltage 1.23 v i cc supply current v cc = 5.25v, no load, shdn floating l 650 1500 m a v cc = 5.25v, no load, v shdn = v cc l 520 m a f osc internal oscillator frequency v cc = 5v, v out = C 4v 650 khz v ol reg output low voltage i reg = 1ma, v cc = 5v, v out = C 4v l 0.1 0.8 v i reg reg sink current v reg = 0.8v, v cc = 3.3v l 48 ma v reg = 0.8v, v cc = 5v l 512 ma i adj adjust pin current v adj = 1.23v l 0.01 1 m a v ih shdn input high voltage v cc = 5v l 2v v il shdn input low voltage v cc = 5v l 0.8 v i in shdn input current v shdn = v cc l 2.5 25 m a t on turn-on time v cc = 5v, i out = 10ma, C1.5v v out C 4v (ltc1261l) l 250 1500 m s v cc = 5v, i out = 5ma, v out = C 4.5v (ltc1261l) l 250 1500 m s v cc = 5v, i out = 10ma, v out = C 4v (ltc1261l-4) l 250 1500 m s v cc = 5v, i out = 5ma, v out = C 4.5v (ltc1261l-4.5) l 250 1500 m s the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c, c1 = 0.1 m f, c out = 3.3 m f unless otherwise noted. (notes 2, 4)
3 ltc1261l e lectr ic al c c hara terist ics output current (ma) 0 2.25 output voltage (v) 2.00 1.50 1.25 1.00 20 0 1261l g01 1.75 10 525 15 30 0.75 0.50 0.25 t a = 25 c v out = 2v v cc = 2.7v v cc = 3v symbol parameter conditions min typ max units v out output regulation (ltc1261l) 2.70v v cc 5.25v, 0ma i out 10ma l C 1.552 C 1.5 C 1.448 v 3.25v v cc 5.25v, 0ma i out 20ma l C 1.552 C 1.5 C 1.448 v 2.70v v cc 5.25v, 0ma i out 5ma l C 2.070 C 2.0 C 1.930 v 2.95v v cc 5.25v, 0ma i out 10ma l C 2.070 C 2.0 C 1.930 v 3.50v v cc 5.25v, 0ma i out 20ma l C 2.070 C 2.0 C 1.930 v 2.95v v cc 5.25v, 0ma i out 5ma l C 2.587 C 2.5 C 2.413 v 3.30v v cc 5.25v, 0ma i out 10ma l C 2.587 C 2.5 C 2.413 v 3.85v v cc 5.25v, 0ma i out 20ma l C 2.587 C 2.5 C 2.413 v 3.40v v cc 5.25v, 0ma i out 5ma l C 3.105 C 3.0 C 2.895 v 3.70v v cc 5.25v, 0ma i out 10ma l C 3.105 C 3.0 C 2.895 v 4.25v v cc 5.25v, 0ma i out 20ma l C 3.105 C 3.0 C 2.895 v 3.85v v cc 5.25v, 0ma i out 5ma l C 3.622 C 3.5 C 3.378 v 4.10v v cc 5.25v, 0ma i out 10ma l C 3.622 C 3.5 C 3.378 v 4.60v v cc 5.25v, 0ma i out 20ma l C 3.622 C 3.5 C 3.378 v output regulation 4.35v v cc 5.25v, 0ma i out 5ma l C 4.140 C 4.0 C 3.860 v (ltc1261l/ltc1261l-4) 4.60v v cc 5.25v, 0ma i out 10ma l C 4.140 C 4.0 C 3.860 v 5.10v v cc 5.25v, 0ma i out 20ma l C 4.140 C 4.0 C 3.860 v output regulation 4.75v v cc 5.25v, 0ma i out 5ma l C 4.657 C 4.5 C 4.343 v (ltc1261l/ltc1261l-4.5) 5.05v v cc 5.25v, 0ma i out 10ma l C 4.657 C 4.5 C 4.343 v i sc output short-circuit current v out = 0v, v cc = 5.25v l 100 220 ma note 4: the ltc1261l is guaranteed to meet specified performance from 0 c to 70 c and is designed, characterized and expected to meet these extended commercial temperature limits, but is not tested at C 40 c and 85 c. guaranteed i grade parts are available, consult factory. note 5: the ltc1261l-4 and ltc1261l-4.5 will operate with less than the minimum v cc specified in the electrical characteristics table, but they are not guaranteed to meet the 3.5% v out specification. note 1: the absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: all currents into device pins are positive; all currents out of device pins are negative. all voltages are referenced to ground unless otherwise specified. note 3: the output should never be set to exceed v cc C 10.8v. typical perfor m a n ce characteristics u w (see test circuits) output voltage vs output current supply voltage (v) 2.5 3.0 3.5 4.0 4.5 5.0 output voltage (v) 2.00 ?.95 1261l g03 2.05 2.10 ?.90 t a = 40 c v out = 2v t a = 85 c t a = 25 c output current (ma) 0 output voltage (v) 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 5 10 15 20 1261l g02 25 30 t a = 25 c v out = 4v v cc = 4.5v v cc = 5v output voltage vs supply voltage output voltage vs output current the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25 c, c1 = 0.1 m f, c out = 3.3 m f unless otherwise noted. (notes 2, 4)
4 ltc1261l typical perfor m a n ce characteristics u w (see test circuits) supply voltage (v) 4.5 4.15 output voltage (v) 4.10 4.05 4.00 3.95 4.7 4.9 5.1 5.3 1261l g04 3.90 3.85 4.6 4.8 5.0 5.2 v out = 4v t a = 40 c t a = 85 c t a = 25 c output voltage vs supply voltage supply voltage (v) 2.7 maximum output current (ma) 40 50 60 5.1 1261l g06 30 20 0 3.3 3.9 4.5 3.0 5.4 3.6 4.2 4.8 10 80 70 t a = 25 c v out = 2v v out = 3v v out = 4v maximum output current vs supply voltage minimum required v cc vs v out and i out output voltage (v) ? 2.0 positive supply voltage (v) 2.4 3.2 3.6 4.0 ? ? 5.6 1261l g05 2.8 ? ? 0 4.4 4.8 5.2 i out = 5ma i out = 10ma i out = 20ma supply voltage (v) 0 supply current (ma) 1.0 2.0 3.0 0.5 1.5 2.5 3.0 3.5 4.0 4.5 1261l g07 5.0 2.5 t a = 40 c t a = 85 c t a = 25 c v out = 2v i out = 0 supply current vs supply voltage reference voltage vs temperature supply current vs supply voltage supply voltage (v) 4.5 0 supply current (ma) 0.5 1.5 2.0 2.5 5.0 3.5 4.7 4.9 5.0 1261l g08 1.0 4.0 4.5 3.0 4.6 4.8 5.1 5.2 5.3 t a = 85 c v out = 4.5v i out = 0 t a = 25 c t a = 40 c temperature ( c) ?5 1.21 reference voltage (v) 1.22 1.23 1.24 1.25 35 15 5 25 1261l g09 45 65 85 105 125 v cc = 5v adj = 0v output short-circuit current vs temperature start-up time vs supply voltage oscillator frequency vs temperature temperature ( c) ?0 oscillator frequency (khz) 625 650 675 80 1261l g10 600 575 525 ?0 20 50 ?5 95 5 35 65 550 725 700 t a = 25 c v out = 4v v cc = 5v supply voltage (v) 2.5 0 start-up time (ms) 0.1 0.3 0.4 0.5 0.7 1261l g11 0.2 0.6 3.0 3.5 4.0 4.5 5.0 v out = 2v v out = 4v t a = 25 c i out = 10ma temperature ( c) ?0 short-circuit current (ma) 80 100 120 80 1261l g12 60 40 0 ?0 20 50 ?5 95 5 35 65 20 160 140 v cc = 5.25v v cc = 5v v cc = 3v v cc = 2.7v
5 ltc1261l pi n fu n ctio n s uuu v cc (pin 1): power supply. this requires an input voltage between 2.7v and 5.25v. v cc must be bypassed to ground with at least a 1 m f capacitor placed in close proximity to the chip. see the applications information section for details. c1 + (pin 2): c1 positive input. connect a 0.1 m f capacitor between c1 + and c1 C . c1 C (pin 3): c1 negative input. connect a 0.1 m f capacitor from c1 + to c1 C . gnd (pin 4): ground. connect to a low impedance ground. a ground plane will help to minimize regulation errors. adj (comp for fixed versions) (pin 5): output adjust/ compensation pin. for adjustable parts this pin is used to set the output voltage. the output voltage is divided down with an external resistor divider and fed back to this pin to set the regulated output voltage. typically the resistor string should draw 3 10 m a from the output to minimize errors due to the bias current at the adjust pin. fixed output voltage parts have the internal resistor string connected to this pin inside the package. the pin can be used to trim the output voltage if desired. it can also be used as an optional feedback compensation pin to reduce output ripple on both the adjustable and fixed output voltage parts. see the applications information section for more information on compensation and out- put ripple. out (pin 6): negative voltage output. this pin must be bypassed to ground with a 1 m f or larger capacitor. the value of the output capacitor and its esr have a strong effect on output ripple. see the applications information section for more details. reg (pin 7): this is an open-drain output that pulls low when the output voltage is within 5% of the set value. it will sink 5ma to ground with a 5v supply. the external circuitry must provide a pull-up or reg will not swing high. the voltage at reg may exceed v cc and can be pulled up to 6v above ground without damage. shdn (pin 8): shutdown. when this pin is at ground the ltc1261l operates normally. an internal 5 m a pull-down keeps shdn low if it is left floating. when shdn is pulled high, the ltc1261l enters shutdown mode. in shut- down, the charge pump is disabled, the output collapses to 0v and the quiescent current drops to 5 m a typically. test circuits fixed output 1 2 3 4 8 7 6 5 shdn reg out comp v cc c1 + c1 gnd 0.1 m f 1261l tco1 3.3 m f v out = 4v (ltc1261l-4) v out = 4.5v (ltc1261l-4.5) 5v 10 m f + + ltc1261l-x adjustable output 1 2 3 4 8 7 6 5 shdn reg out adj v cc c1 + c1 gnd v cc 0.1 m f 1261l tco2 3.3 m f v out + ltc1261l
6 ltc1261l applicatio n s i n for m atio n wu u u the ltc1261l uses an inverting charge pump to generate a regulated negative output voltage that is either equal to or less than the supply voltage. the ltc1261l needs only three external capacitors and is available in the msop and so-8 packages theory of operation a block diagram of the ltc1261l is shown in figure 1. the heart of the ltc1261l is the charge pump core shown in the dashed box. it generates a negative output voltage by first charging the flying capacitor (c1) between v cc and ground. it then connects the top of the flying capacitor to ground, forcing the bottom of the flying capacitor to a negative voltage. the charge on the flying capacitor is transferred to the output bypass capacitor, leaving it charged to the negative output voltage. this process is driven by the internal 650khz clock. figure 1 shows the charge pump configuration. with the clock low, c1 is charged to v cc by s1 and s3. at the next rising clock edge, s1 and s3 are open and s2 and s4 closed. s2 connects c1 + to ground, c1 C is connected to the output by s4. the charge in c1 is transferred to c out , setting it to a negative voltage. the output voltage is monitored by comp1 which com- pares a divided replica of the output at adj (comp for fixed output voltage parts) to the internal reference. at the beginning of a cycle the clock is low, forcing the output of the and gate low and charging the flying capacitor. the next rising clock edge sets the rs latch, setting the charge pump to transfer charge from the flying capacitor to the output capacitor. as long as the output is below the set point, comp1 stays low, the latch stays set and the charge pump runs at the full 50% duty cycle of the clock gated through the and gate. as the output approaches the set voltage, comp1 will trip whenever the divided signal exceeds the internal 1.23v reference relative to out. this resets the rs latch and truncates the clock pulses, reduc- ing the amount of charge transferred to the output capaci- tor and regulating the output voltage. if the output exceeds the set point, comp1 stays high, inhibiting the rs latch and disabling the charge pump. figure 1. block diagram + + clk 650khz s r q s2 s3 s1 v cc v out 1261l f01 60mv 1.17v v ref = 1.23v c out c1 c1 + c1 s4 r1 internally connected for fixed output voltage parts r2 comp1 comp2 adj (comp) reg out +
7 ltc1261l applicatio n s i n for m atio n wu u u comp2 also monitors the divided signal at adj but it is connected to a 1.17v reference, 5% below the main reference voltage. when the divided output exceeds this lower reference voltage indicating that the output is within 5% of the set value, comp2 goes high turning on the reg output transistor. this is an open drain n-channel device capable of sinking 4ma with a 3.3v v cc and 5ma with a 5v v cc . when in the off state (divided output is more than 5% below v ref ) the drain can be pulled above v cc without damage up to a maximum of 6v above ground. note that the reg output only indicates if the magnitude of the output is below the magnitude of the set point by 5% (i.e., v out > C 4.75v for a C 5v set point). if the magnitude of the output is forced higher than the magnitude of the set point ( i.e., to C 5.25v when the output is set for C 5v) the reg output will stay low. output ripple output ripple in the ltc1261l is present from two sources; voltage droop at the output capacitor between clocks and frequency response of the regulation loop. voltage droop is easy to calculate. with a typical clock frequency of 650khz, the charge on the output capacitor is refreshed once every 1.54 m s. with a 15ma load and a 3.3 m f output capacitor, the output will droop by: i load = 15ma d t c out ) ) = 7mv 1.54 m s 3.3 m f ) ) this can be a significant ripple component when the output is heavily loaded, especially if the output capacitor is small. if absolute minimum output ripple is required, a 10 m f or greater output capacitor should be used. regulation loop frequency response is the other major contributor to output ripple. the ltc1261l regulates the output voltage by limiting the amount of charge trans- ferred to the output capacitor on a cycle-by-cycle basis. the output voltage is sensed at the adj pin (comp for fixed output voltage versions) through an internal or external resistor divider from the out pin to ground. as the flying capacitor is first connected to the output, the output voltage begins to change quite rapidly. as soon as it exceeds the set point comp1 trips, switching the state of the charge pump and stopping the charge transfer. because the rc time constant of the capacitors and the switches is quite short, the adj pin must have a wide ac bandwidth to be able to respond to the output in time. external parasitic capacitance at the adj pin can reduce the bandwidth to the point where the comparator cannot respond by the time the clock pulse finishes. when this happens the comparator will allow a few complete pulses through, then overcorrect and disable the charge pump until the output drops below the set point. under these conditions the output will remain in regulation but the output ripple will increase as the comparator hunts for the correct value. to prevent this from happening, an external capacitor can be connected from adj (or comp for fixed output voltage parts) to ground to compensate for external parasitics and increase the regulation loop bandwidth (figure 2). this sounds counterintuitive until we remember that the inter- nal reference is generated with respect to out, not ground. the feedback loop actually sees ground as its output, thus the compensation capacitor should be connected across the top of the resistor divider, from adj (or comp) to ground. by the same token, avoid adding capacitance between adj (or comp) and v out . this will slow down the feedback loop and increase output ripple. a 100pf capacitor from adj or comp to ground will compensate the loop properly under most conditions for fixed voltage versions of the ltc1261l. for the adjustable ltc1261l, the capacitor value will be dependent upon the values of the external resistors in the divider network. figure 2. regulator loop compensation comp1 1.23v r2 v out adj/comp resistors are internal for fixed output voltage parts 1261l f02 r1 c c 100pf to charge pump ref +
8 ltc1261l applicatio n s i n for m atio n wu u u capacitor type for both the input bypass capacitor and the flying capacitor. in applications where the maximum load current is well- defined and output ripple is critical or input peak currents need to be minimized, the flying capacitor value can be tailored to the application. reducing the value of the flying capacitor reduces the amount of charge trans- ferred with each clock cycle. this limits maximum output current, but also cuts the size of the voltage step at the output with each clock cycle. the smaller capacitor draws smaller pulses of current out of v cc as well, limiting peak currents and reducing the demands on the input supply. table 1 shows recommended values of flying capacitor vs maximum load capacity. table 1. typical max load (ma) vs flying capacitor value at t a = 25 c, v out = C 4v flying capacitor max load (ma) value ( m f) v cc = 5v 0.1 20 0.047 15 0.033 10 0.022 5 0.01 1 the output capacitor performs two functions: it provides output current to the load during half of the charge pump cycle and its value helps to set the output ripple voltage. for applications that are insensitive to output ripple, the output bypass capacitor can be as small as 1 m f. larger output capacitors will reduce output ripple further at the expense of turn-on time. capacitor esr output capacitor equivalent series resistance (esr) is another factor to consider. excessive esr in the output capacitor can fool the regulation loop into keeping the output artificially low by prematurely terminating the charg- ing cycle. as the charge pump switches to recharge the output a brief surge of current flows from the flying capacitors to the output capacitor. this current surge can be as high as 100ma under full load conditions. a typical output filtering if extremely low output ripple (< 5mv) is required, addi- tional output filtering is required. because the ltc1261l uses a high 650khz switching frequency, fairly low value rc or lc networks can be used at the output to effectively filter the output ripple. a 10 w series output resistor and a 3.3 m f capacitor will cut output ripple to below 3mv (figure 3). further reductions can be obtained with larger filter capacitors or by using an lc output filter. ltc1261l-4 v cc 5v c1 + c1 4 6 5 2 3 out 0.1 m f 100pf 3.3 m f 10 w comp 1261l f03 gnd v out = 4v 1 m f + 3.3 m f + figure 3. output filter cuts ripple below 3mv capacitor selection capacitor sizing the performance of the ltc1261l is affected by the capacitors to which it connects. the ltc1261l requires bypass capacitors to ground for both the v cc and out pins. the input capacitor provides most of ltc1261ls supply current while it is charging the flying capacitors. this capacitor should be mounted as close to the package as possible and its value should be at least ten times larger than the flying capacitor. ceramic capacitors generally provide adequate performance. avoid using a tantalum capacitor as the input bypass unless there is at least a 0.1 m f ceramic capacitor in parallel with it. the charge pump capacitor is somewhat less critical since its peak current is limited by the switches inside the ltc1261l. most applications should use a 0.1 m f as the flying capacitor value. conveniently, ceramic capacitors are the most common type of 0.1 m f capacitor and they work well here. usually the easiest solution is to use the same
9 ltc1261l applicatio n s i n for m atio n wu u u 3.3 m f tantalum capacitor has 1 w or 2 w of esr; 100ma 2 w = 200mv. if the output is within 200mv of the set point this additional 200mv surge will trip the feedback com- parator and terminate the charging cycle. the pulse dissi- pates quickly and the comparator returns to the correct state, but the rs latch will not allow the charge pump to respond until the next clock edge. this prevents the charge pump from going into very high frequency oscillation under such conditions but it also creates an output error as the feedback loop regulates based on the top of the spike, not the average value of the output (figure 4). the resulting output voltage behaves as if a resistor of value c esr (i pk /i ave ) w was placed in series with the output. to avoid this nasty sequence of events, connect a 0.1 m f ceramic capacitor in parallel with the larger output capaci- tor. the ceramic capacitor will eat the high frequency spike, preventing it from fooling the feedback loop, while the larger but slower tantalum or aluminum output capaci- tor supplies output current to the load between charge cycles. approaches half of a clock period (the time the capacitors have to share charge at full duty cycle) the output current capability of the ltc1261l starts to diminish. for a 0.1 m f flying capacitor, this gives a maximum total series resis- tance of: = / 0.1 m f = 7.7 w 1 2 ) ) t clk c fly 1 2 ) ) 1 650khz most of this resistance is already provided by the internal switches in the ltc1261l. more than 1 w or 2 w of esr on the flying capacitors will start to affect the regulation at maximum load. resistor selection resistor selection is easy with the fixed output voltage versions of the ltc1261l no resistors are needed! selecting the right resistors for the adjustable parts is only a little more difficult. a resistor divider should be used to divide the signal at the output to give 1.23v at the adj pin with respect to v out (figure 5). the ltc1261l uses a positive reference with respect to v out , not a negative reference with respect to ground (figure 1 shows the reference connection). be sure to keep this in mind when connecting the resistors! if the initial output is not what you expected, try swapping the two resistors. the ltc1261l can be internally configured for other fixed output voltages. contact the linear technology marketing department for details. low esr output cap clock v out average v set comp1 output v out high esr output cap v out average v set comp1 output v out 1261l f04 figure 4. output ripple with low and high esr capacitors note that esr in the flying capacitor will not cause the same condition; in fact, it may actually improve the situa- tion by cutting the peak current and lowering the ampli- tude of the spike. however, more flying capacitor esr is not necessarily better. as soon as the rc time constant ltc1261l gnd r1 4 5 6 1261l f05 v out = ?.23v r2 r1 + r2 r2 adj out () figure 5. external resistor connections
10 ltc1261l typical applicatio n s n u 5v input, C 0.5v output gaas fet bias generator 1 2 3 4 8 7 6 5 shdn reg out adj v cc c1 + c2 gnd 100pf 1261 ta05 0.5v bias 10k p-channel power switch 0.1 m f shutdown 5v v bat 3.3 m f ltc1261l gaas transmitter 43.2k 1% 12.4k 1% 1 m f + 1mv ripple, 5v input, C 4v output gaas fet bias generator 1 2 3 4 8 7 6 5 shdn reg out comp v cc c1 + c2 gnd 100pf 1261 ta04 10 m f 4v bias 100 m h 10k p-channel power switch 0.1 m f shutdown 5v v bat 10 m f ltc1261l-4 gaas transmitter 1 m f + + 5v input, C 4v output gaas fet bias generator 1 2 3 4 8 7 6 5 shdn reg out comp v cc c1 + c2 gnd 100pf 1261 ta03 3.3 m f 4v bias 10k p-channel power switch 0.1 m f shutdown 5v v bat ltc1261l-4 gaas transmitter 1 m f +
11 ltc1261l package descriptio n u dimensions in inches (millimeters) unless otherwise noted. 1 2 3 4 0.150 ?0.157** (3.810 ?3.988) 8 7 6 5 0.189 ?0.197* (4.801 ?5.004) 0.228 ?0.244 (5.791 ?6.197) 0.016 ?0.050 0.406 ?1.270 0.010 ?0.020 (0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010 (0.203 ?0.254) so8 0996 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) typ dimension does not include mold flash. mold flash shall not exceed 0.006" (0.152mm) per side dimension does not include interlead flash. interlead flash shall not exceed 0.010" (0.254mm) per side * ** s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) ms8 package 8-lead plastic msop (ltc dwg # 05-08-1660) msop (ms8) 1197 * dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.006" (0.152mm) per side ** dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.006" ( 0.152mm ) per side 0.021 0.006 (0.53 0.015) 0 ?6 typ seating plane 0.007 (0.18) 0.040 0.006 (1.02 0.15) 0.012 (0.30) ref 0.006 0.004 (0.15 0.102) 0.034 0.004 (0.86 0.102) 0.0256 (0.65) typ 12 3 4 0.192 0.004 (4.88 0.10) 8 7 6 5 0.118 0.004* (3.00 0.102) 0.118 0.004** (3.00 0.102) 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.
12 ltc1261l part number description comments lt1121 micropower low dropout regulator with shutdown 0.4v dropout voltage at 150ma, low noise, switched capacitor regulated voltage inverter ltc1429 clock synchronized switched capacitor regulated voltage inverter gaas fet bias ltc1503-1.8/ltc1503-2 high efficiency inductorless step-down dc/dc converter fixed 1.8v or 2v output from 2.4v to 6v input, i out = 100ma ltc1514/ltc1515 step-up/step-down switched capacitors dc/dc converters v in 2v to 10v, v out is fixed or adjustable, i out up to 50ma ltc1516 micropower, regulated 5v charge pump dc/dc converter i out = 20ma (v in 3 2v), i out = 50ma (v in 3 3v) ltc1517-5 micropower, regulated 5v charge pump dc/dc converter ltc1522 without shutdown and packaged in sot-23 ltc1522 micropower, regulated 5v charge pump dc/dc converter i out = 10ma (v in 3 2.7v), i out = 20ma (v in 3 3v) ltc1550l/ltc1551l low noise switched capacitor regulated voltage inverter gaas fet bias with linear regulator, < 1mv ripple, msop ltc1555/ltc1556 sim power supply and level translator step-up/step-down sim power supply and level translators lt1611 1.4mhz inverting mode switching regulator C5v at 150ma from a 5v input, 5-lead sot-23 lt1614 inverting 600khz switching regulator with low-battery detector C5v at 200ma from 5v input in msop lt1617/lt1617-1 micropower inverting dc/dc converters C15v at 12ma from 2.5v input, 5-lead sot-23 ltc1682/ltc1682-3.3/ low noise doubler charge pumps output noise = 60 m v rms , 2.5v to 5.5v output ltc1682-5 ltc1754-5 micropower, regulated 5v charge pump with shutdown in sot-23 i cc = 13 m a, i out = 50ma (v in 3 3v), i out = 25ma (v in 3 2.7v) ? linear technology corporation 1999 1261lf lt/tp 0200 4k ? printed in usa typical applicatio n s n u minimum parts count C 4.5v generator 1 2 3 4 8 7 6 5 shdn reg out comp v cc c1 + c1 gnd 0.1 m f 1261l ta07 3.3 m f v out = 4.5v at 5ma 5v 1 m f + ltc1261l-4.5 low output voltage generator 2 3 5 6 ltc1261l adj out c1 + c1 1261l ta06 3.3 m f = v cc ?9.92 m a (r s + 124k) = 0.5v (r s = 432k) = 1v (r s = 487k) 1n5817 1 5v 4 0.1 m f 1 m f 100pf r s v out v cc gnd 124k + related parts linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com

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