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1 LT1790 1790fa micropower sot-23 low dropout reference family the lt ? 1790 is a family of sot-23 micropower low dropout series references that combine high accuracy and low drift with low power dissipation and small package size. these micropower references use curvature com- pensation to obtain a low temperature coefficient and trimmed precision thin-film resistors to achieve high output accuracy. in addition, each LT1790 is post-pack- age trimmed to greatly reduce the temperature coefficient and increase the output accuracy. output accuracy is further assured by excellent line and load regulation. special care has been taken to minimize thermally induced hysteresis. the LT1790s are ideally suited for battery-operated sys- tems because of their small size, low supply current and reduced dropout voltage. these references provide supply current and power dissipation advantages over shunt references that must idle the entire load current to operate. since the LT1790 can also sink current, it can operate as a micropower negative voltage reference with the same performance as a positive reference. n handheld instruments n negative voltage references n industrial control systems n data acquisition systems n battery-operated equipment n high accuracy: a grade0.05% max b grade0.1% max n low drift: a grade10ppm/ c max b grade25ppm/ c max n low profile (1mm) thinsot tm package n low supply current: 60 m a max n sinks and sources current n low dropout voltage n guaranteed operational C40 c to 125 c n wide supply range to 18v n available output voltage options: 1.25v, 2.048v, 2.5v, 3v, 3.3v, 4.096v and 5v , ltc and lt are registered trademarks of linear technology corporation. typical v out distribution for LT1790-2.5 positive connection for LT1790-2.5 features descriptio u applicatio s u typical applicatio u 0.1 f 2.6v v in 18v 1 f 1, 2 6 v out = 2.5v 4 LT1790-2.5 1790 ta01 output voltage (v) 2.498 2.499 2.500 2.501 2.502 number of units 30 40 50 1790 ta02 20 10 25 35 45 15 5 0 LT1790b limits LT1790a limits 167 units thinsot is a trademark of linear technology corporation.
2 LT1790 1790fa input voltage .......................................................... 20v specified temperature range commercial ............................................ 0 c to 70 c industrial ............................................ C 40 c to 85 c output short-circuit duration ......................... indefinite order part number LT1790acs6-1.25 LT1790bcs6-1.25 LT1790acs6-2.048 LT1790bcs6-2.048 LT1790acs6-2.5 LT1790bcs6-2.5 LT1790acs6-3 LT1790bcs6-3 LT1790acs6-3.3 LT1790bcs6-3.3 LT1790acs6-4.096 LT1790bcs6-4.096 LT1790acs6-5 LT1790bcs6-5 gnd 1 gnd 2 dnc* 3 6 v out 5 dnc* 4 v in top view s6 package 6-lead plastic sot-23 t jmax = 150 c, q ja = 230 c/w *dnc: do not connect absolute axi u rati gs w ww u package/order i for atio uu w operating temperature range (note 2) ........................................... C 40 c to 125 c storage temperature range (note 3) ........................................... C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c output voltage s6 part marking* * the temperature grades and parametric grades are identified by a label on the shipping container. consult ltc marketing for pa rts specified with wider operating temperature ranges. available optio s u temperature range output initial temperature 0 c to 70 cC40 c to 85 c voltage accuracy coefficeint order part number order part number 1.250v 0.05% 10ppm/ c LT1790acs6-1.25 LT1790ais6-1.25 0.1% 25ppm/ c LT1790bcs6-1.25 LT1790bis6-1.25 2.048v 0.05% 10ppm/ c LT1790acs6-2.048 LT1790ais6-2.048 0.1% 25ppm/ c LT1790bcs6-2.048 LT1790bis6-2.048 2.500v 0.05% 10ppm/ c LT1790acs6-2.5 LT1790ais6-2.5 0.1% 25ppm/ c LT1790bcs6-2.5 LT1790bis6-2.5 3.000v 0.05% 10ppm/ c LT1790acs6-3 LT1790ais6-3 0.1% 25ppm/ c LT1790bcs6-3 LT1790bis6-3 3.300v 0.05% 10ppm/ c LT1790acs6-3.3 LT1790ais6-3.3 0.1% 25ppm/ c LT1790bcs6-3.3 LT1790bis6-3.3 4.096v 0.05% 10ppm/ c LT1790acs6-4.096 LT1790ais6-4.096 0.1% 25ppm/ c LT1790bcs6-4.096 LT1790bis6-4.096 5.000v 0.05% 10ppm/ c LT1790acs6-5 LT1790ais6-5 0.1% 25ppm/ c LT1790bcs6-5 LT1790bis6-5 LT1790ais6-1.25 LT1790bis6-1.25 LT1790ais6-2.048 LT1790bis6-2.048 LT1790ais6-2.5 LT1790bis6-2.5 LT1790ais6-3 LT1790bis6-3 LT1790ais6-3.3 LT1790bis6-3.3 LT1790ais6-4.096 LT1790bis6-4.096 LT1790ais6-5 LT1790bis6-5 1.250v 2.048v 2.500v 3.000v 3.300v 4.096v 5.000v ltxt ltxu ltpz ltqa ltxw ltqb ltqc (note 1)
3 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 1.24937 1.250 1.25062 v C0.05 0.05 % LT1790b 1.24875 1.250 1.25125 v C0.10 0.10 % LT1790ac l 1.24850 1.250 1.25150 v l C0.120 0.120 % LT1790ai l 1.24781 1.250 1.25219 v l C0.175 0.175 % LT1790bc l 1.24656 1.250 1.25344 v l C0.275 0.275 % LT1790bi l 1.24484 1.250 1.25516 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 2.6v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma, v in = 2.8v 100 160 ppm/ma l 250 ppm/ma i out sink = 1ma, v in = 3.2v 120 180 ppm/ma l 250 ppm/ma minimum operating voltage (note 7) v in , d v out = 0.1% i out = 0ma 1.95 2.15 v l 2.50 v i out source = 5ma l 2.90 v i out sink = 1ma l 2.95 v supply current no load 35 60 m a l 75 m a minimum operating current v out = C 1.25v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 250 m s output noise (note 8) 0.1hz f 10hz 10 m v p-p 10hz f 1khz 14 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 2.6v, unless otherwise noted. 1.25v electrical characteristics
4 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 2.04697 2.048 2.04902 v C0.05 0.05 % LT1790b 2.04595 2.048 2.05005 v C0.10 0.10 % LT1790ac l 2.04554 2.048 2.05046 v l C0.120 0.120 % LT1790ai l 2.04442 2.048 2.05158 v l C0.175 0.175 % LT1790bc l 2.04237 2.048 2.05363 v l C0.275 0.275 % LT1790bi l 2.03955 2.048 2.05645 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 2.8v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 120 200 ppm/ma l 280 ppm/ma i out sink = 3ma 130 260 ppm/ma l 450 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 500 mv i out source = 5ma l 750 mv i out sink = 3ma l 450 mv supply current no load 35 60 m a l 75 m a minimum operating current v out = C 2.048v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 350 m s output noise (note 8) 0.1hz f 10hz 22 m v p-p 10hz f 1khz 41 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 2.8v, unless otherwise noted. 2.048v electrical characteristics
5 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 2.49875 2.5 2.50125 v C0.05 0.05 % LT1790b 2.4975 2.5 2.5025 v C0.10 0.10 % LT1790ac l 2.4970 2.5 2.5030 v l C0.120 0.120 % LT1790ai l 2.49563 2.5 2.50438 v l C0.175 0.175 % LT1790bc l 2.49313 2.5 2.50688 v l C0.275 0.275 % LT1790bi l 2.48969 2.5 2.51031 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 3v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 80 160 ppm/ma l 250 ppm/ma i out sink = 3ma 70 110 ppm/ma l 300 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 120 mv i out source = 5ma l 450 mv i out sink = 3ma l 250 mv supply current no load 35 60 m a l 80 m a minimum operating current v out = C 2.5v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 700 m s output noise (note 8) 0.1hz f 10hz 32 m v p-p 10hz f 1khz 48 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 3v, unless otherwise noted. 2.5v electrical characteristics
6 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 2.9985 3 3.0015 v C0.05 0.05 % LT1790b 2.9970 3 3.003 v C0.10 0.10 % LT1790ac l 2.99640 3 3.00360 v l C0.120 0.120 % LT1790ai l 2.99475 3 3.00525 v l C0.175 0.175 % LT1790bc l 2.99175 3 3.00825 v l C0.275 0.275 % LT1790bi l 2.98763 3 3.01238 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 3.5v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 80 160 ppm/ma l 250 ppm/ma i out sink = 3ma 70 110 ppm/ma l 300 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 120 mv i out source = 5ma l 450 mv i out sink = 3ma l 250 mv supply current no load 35 60 m a l 80 m a minimum operating current v out = C 3v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 700 m s output noise (note 8) 0.1hz f 10hz 50 m v p-p 10hz f 1khz 56 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 3.5v, unless otherwise noted. 3v electrical characteristics
7 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 3.29835 3.3 3.30165 v C0.05 0.05 % LT1790b 3.2967 3.3 3.3033 v C0.10 0.10 % LT1790ac l 3.29604 3.3 3.30396 v l C0.120 0.120 % LT1790ai l 3.29423 3.3 3.30578 v l C0.175 0.175 % LT1790bc l 3.29093 3.3 3.30908 v l C0.275 0.275 % LT1790bi l 3.28639 3.3 3.31361 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 3.8v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 80 160 ppm/ma l 250 ppm/ma i out sink = 3ma 70 110 ppm/ma l 300 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 120 mv i out source = 5ma l 450 mv i out sink = 3ma l 250 mv supply current no load 35 60 m a l 80 m a minimum operating current v out = C 3.3v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 700 m s output noise (note 8) 0.1hz f 10hz 50 m v p-p 10hz f 1khz 67 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 3.8v, unless otherwise noted. 3.3v electrical characteristics
8 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 4.094 4.096 4.098 v C0.05 0.05 % LT1790b 4.092 4.096 4.10 v C0.10 0.10 % LT1790ac l 4.09108 4.096 4.10092 v l C0.120 0.120 % LT1790ai l 4.08883 4.096 4.10317 v l C0.175 0.175 % LT1790bc l 4.08474 4.096 4.10726 v l C0.275 0.275 % LT1790bi l 4.07910 4.096 4.11290 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 4.6v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 80 160 ppm/ma l 250 ppm/ma i out sink = 3ma 70 110 ppm/ma l 300 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 120 mv i out source = 5ma l 450 mv i out sink = 3ma l 250 mv supply current no load 35 60 m a l 80 m a minimum operating current v out = C 4.096v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 700 m s output noise (note 8) 0.1hz f 10hz 60 m v p-p 10hz f 1khz 89 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 4.6v, unless otherwise noted. 4.096v electrical characteristics
9 LT1790 1790fa parameter conditions min typ max units output voltage (notes 3, 4) LT1790a 4.9975 5 5.0025 v C0.05 0.05 % LT1790b 4.995 5 5.005 v C0.10 0.10 % LT1790ac l 4.99400 5 5.00600 v l C0.120 0.120 % LT1790ai l 4.99125 5 5.00875 v l C0.175 0.175 % LT1790bc l 4.98625 5 5.01375 v l C0.275 0.275 % LT1790bi l 4.97938 5 5.02063 v l C0.4125 0.4125 % output voltage temperature coefficient (note 5) t min t a t max LT1790a l 5 10 ppm/ c LT1790b l 12 25 ppm/ c line regulation 5.5v v in 18v 50 170 ppm/v l 220 ppm/v load regulation (note 6) i out source = 5ma 80 160 ppm/ma l 250 ppm/ma i out sink = 3ma 70 110 ppm/ma l 300 ppm/ma dropout voltage (note 7) v in C v out , d v out = 0.1% i out = 0ma 50 100 mv l 120 mv i out source = 5ma l 450 mv i out sink = 3ma l 250 mv supply current no load 35 60 m a l 80 m a minimum operating current v out = C 5v, 0.1% 100 125 m a negative output (see figure 7) turn-on time c load = 1 m f 700 m s output noise (note 8) 0.1hz f 10hz 80 m v p-p 10hz f 1khz 118 m v rms long-term drift of output voltage (note 9) 50 ppm/ ? khr hysteresis (note 10) d t = 0 c to 70 c l 40 ppm d t = C 40 c to 85 c l 100 ppm the l denotes specifications that apply over the specified temperature range, otherwise specifications are at t a = 25 c. c l = 1 m f and v in = 5.5v, unless otherwise noted. 5v electrical characteristics note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: the LT1790 is guaranteed functional over the operating temperature range of C 40 c to 125 c. the LT1790-1.25 at 125 c is typically less than 2% above the nominal voltage. the other voltage options are typically less than 0.25% above their nominal voltage. note 3: if the part is stored outside of the specified temperature range, the output voltage may shift due to hysteresis. note 4: esd (electrostatic discharge) sensitive device. extensive use of esd protection devices are used internal to the LT1790, however, high electrostatic discharge can damage or degrade the device. use proper esd handling precautions. note 5: temperature coefficient is measured by dividing the change in output voltage by the specified temperature range. incremental slope is also measured at 25 c. note 6: load regulation is measured on a pulse basis from no load to the specified load current. output changes due to die temperature change must be taken into account separately. note 7: excludes load regulation errors. note 8: peak-to-peak noise is measured with a single pole highpass filter at 0.1hz and a 2-pole lowpass filter at 10hz. the unit is enclosed in a still air environment to eliminate thermocouple effects on the leads. the test time is 10 seconds. integrated rms noise is measured from 10hz to 1khz with the hp3561a analyzer.
10 LT1790 1790fa note 9: long-term drift typically has a logarithmic characteristic and therefore changes after 1000 hours tend to be smaller than before that time. long-term drift is affected by differential stress between the ic and the board material created during board assembly. see applications information. electrical characteristics note 10: hysteresis in the output voltage is created by package stress that differs depending on whether the ic was previously at a higher or lower temperature. output voltage is always measured at 25 c, but the ic is cycled to 85 c or C 40 c before a successive measurements. hysteresis is roughly proportional to the square of the temperature change. hysteresis is not a problem for operational temperature excursions where the instrument might be stored at high or low temperature. see applications information. 1.25v typical perfor a ce characteristics uw output voltage temperature drift load regulation (sourcing) minimum input-output voltage differential (sourcing) minimum input-output voltage differential (sinking) load regulation (sinking) supply current vs input voltage temperature ( c) ?0 1.247 output voltage (v) 1.248 1.249 1.250 1.251 ?0 30 70 110 17091.25 g01 1.252 1.253 ?0 10 50 90 four typical parts input-output voltage (v) output current (ma) 10 17901.25 g02 0.1 1 0.5 2.5 2 1.5 1 0 t a = 125 ct a = 55 c t a = 25 c temperature ( c) ?0 0 voltage differential (v) 0.1 0.3 0.4 0.5 1.0 0.7 ?0 30 50 130 17091.25 g03 0.2 0.8 0.9 0.6 ?0 10 70 90 110 5ma 100 a 1ma output current (ma) 0.1 2000 output voltage change (ppm) ?600 ?200 800 400 110 17901.25 g04 0 ?800 ?400 ?000 600 200 t a = 55 c t a = 25 c t a = 125 c output current (ma) 0.1 0 output voltage change (ppm) 400 800 1200 1600 110 17901.25 g05 2000 200 600 1000 1400 1800 t a = 55 c t a = 25 c t a = 125 c input voltage (v) supply current ( m a) 60 80 100 15 17901.25 g06 40 20 50 70 90 30 10 0 5 0 10 20 t a = 55 c t a = 25 c t a = 125 c each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves.
11 LT1790 1790fa line regulation output impedance vs frequency power supply rejection ratio vs frequency input voltage (v) 0 output voltage (v) 1.255 1.265 1.275 1.285 16 17901.25. g07 1.245 1.235 1.250 1.260 1.270 1.280 1.240 1.230 1.225 4 8 12 218 6 10 14 20 t a = 55 c t a = 25 c t a = 125 c frequency (hz) ?0 power supply rejection ratio (db) 0 10 ?0 ?0 ?0 ?0 ?0 ?0 ?0 100 10k 100k 1m 17901.25 g08 ?0 1k v in = 3v c l = 1 f frequency (hz) 1 output impedance ( ) 10 100 100 10k 100k 17901.25 g09 0 1k 500 v in = 3v c l = 0.47 f c l = 4.7 f c l = 1 f 1.25v typical perfor a ce characteristics uw each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. C 1.25v characteristics long-term drift (data points reduced after 500 hr) output noise 0.1hz to 10hz output voltage noise spectrum output to ground voltage (v) 0 current in r l (ma) 0.10 0.20 0.30 0.05 0.15 0.25 2.0 ?.5 ?.0 0.5 17091.25 g10 0 2.5 ? ee v out 3v r l 5k 4 2 1 6 1 f LT1790-1.25 r1 10k t a = 25 c t a = 125 c t a = 55 c hours 0 ppm 60 100 140 800 17901.25 g10 20 ?0 40 80 120 0 ?0 ?0 200 400 600 1000 LT1790s6-1.25v 2 typical parts soldered to pcb t a = 30 c time (sec) 0 output noise (5 v/div) 8 17901.2 g12 246 10 7 135 9 frequency (hz) 10 2.0 noise voltage ( v/ hz) 2.5 3.0 3.5 4.0 100 1k 10k 17901.25 g13 1.5 1.0 0.5 0 4.5 5.0 c l = 1 f i o = 100 a i o = 0 a i o = 250 a i o = 1ma integrated noise 10hz to 1khz frequency (hz) 10 1 integrated noise ( v rms ) 10 100 100 1000 LT1790 g01
12 LT1790 1790fa output voltage temperature drift load regulation (sourcing) minimum input-output voltage differential (sourcing) minimum input-output voltage differential (sinking) load regulation (sinking) supply current vs input voltage each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. 2.048v typical perfor a ce characteristics u w temperature ( c) ?0 output voltage (v) 70 90 110 2.056 2.054 2.052 2.050 2.048 2.046 2.044 2.042 17902.048 g01 30 ?0 10 30 50 130 four typical parts input-output voltage (v) 0.1 0.1 1 10 0.3 17902.048 g02 output current (ma) 0 0.7 0.2 0.4 0.5 0.6 t a = 25 c t a = 125 c t a = 55 c temperature ( c) ?0 ?0 voltage differential (mv) ?0 10 30 50 70 130 17902.048 g03 ?0 10 130 50 ?0 110 30 ?0 90 70 90 110 5ma 1ma 100 a output current (ma) 0.1 2000 output voltage change (ppm) ?600 ?200 800 400 110 17902.048 g04 0 ?800 ?400 ?000 600 200 t a = 25 c t a = 125 c t a = 55 c output current (ma) 0.1 0 output voltage change (ppm) 400 800 1200 1600 110 17902.048 g05 2000 200 600 1000 1400 1800 t a = 40 c t a = 25 c t a = 125 c input voltage (v) 0 supply current ( a) 40 50 60 20 17902.048 g06 30 20 0 5 10 15 10 80 70 t a = 55 c t a = 25 c t a = 125 c line regulation output impedance vs frequency power supply rejection ratio vs frequency input voltage (v) output voltage (v) 2.054 2.052 2.050 2.048 2.046 2.044 2.042 4 8 12 16 17902.048 g07 20 2 0 6 10 14 18 t a = 55 c t a = 25 c t a = 125 c frequency (hz) ?0 power supply rejection ratio (db) 10 0 20 ?0 ?0 ?0 ?0 ?0 ?0 ?0 100 10k 100k 1m 17902.048 g08 1k c l = 1 f frequency (hz) 10k 1 output impedance ( ) 10 100 1000 100k 1m 10m 17902.048 g09 c l = 0.47 f c l = 4.7 f c l = 1 f
13 LT1790 1790fa each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. 2.048v typical perfor a ce characteristics u w C 2.048v characteristics long-term drift output noise 0.1hz to 10hz output voltage noise spectrum output to ground voltage (v) 0 current in r l (ma) 0.10 0.20 0.30 0.05 0.15 0.25 3.5 3 2.5 2 ?.5 ? 0.5 17092.048 g10 0 ? ? ee v out 3v r l 5k 4 2 1 6 1 f LT1790-2.048 r1 10k t a = 125 c t a = 25 c t a = 55 c frequency (hz) 10 4 noise voltage ( v/ hz) 5 6 7 8 100 1k 10k 17902.048 g13 3 2 1 0 9 10 c l = 1 f i o = 100 a i o = 0 a i o = 250 a i o = 1ma time (sec) 0 output noise (10 v/div) 8 17902.048 g12 246 10 7 135 9 hours 0 ppm 60 100 800 17901.048 g11 20 ?0 40 80 0 ?0 ?0 ?0 ?00 200 400 600 1000 t a = 30 c 2 typical parts soldered to pcb integrated noise 10hz to 1khz frequency (hz) 10 1 integrated noise ( v rms ) 10 100 100 1000 LT1790 g02
14 LT1790 1790fa output voltage temperature drift load regulation (sourcing) minimum input-output voltage differential (sinking) load regulation (sinking) supply current vs input voltage each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. line regulation output impedance vs frequency power supply rejection ratio vs frequency 2.5v typical perfor a ce characteristics uw temperature ( c) ?0 output voltage (v) 30 70 17902.5 g01 ?0 ?0 50 90 110 2.508 2.506 2.504 2.502 2.500 2.498 2.496 2.494 10 130 four typical parts input-output voltage (v) 0 0.1 0.2 0.1 output current (ma) 1 10 0.3 0.4 0.5 0.6 17902.5 g02 t a = 55 ct a = 125 c t a = 25 c temperature ( c) ?0 ?0 voltage differential (mv) ?0 30 50 70 ?0 30 50 130 17902.5 g03 10 ?0 10 70 90 110 90 100 a 5ma 1ma output current (ma) 0.1 2000 output voltage change (ppm) ?600 ?200 800 400 110 17902.5 g04 0 ?800 ?400 ?000 600 200 t a = 25 c t a = 125 c t a = 55 c output current (ma) 0.1 0 output voltage change (ppm) 400 800 1200 1600 110 17902.5 g05 2000 200 600 1000 1400 1800 t a = 55 c t a = 25 c t a = 125 c input voltage (v) 0 supply current ( a) 40 50 60 20 17902.5 g06 30 20 0 5 10 15 10 80 70 t a = 55 c t a = 25 c t a = 125 c input voltage (v) output voltage (v) 2.515 2.510 2.505 2.500 2.495 2.490 2.489 4 8 12 16 17902.5 g07 20 2 0 6 10 14 18 t a = 55 c t a = 25 c t a = 125 c frequency (hz) power supply rejection ratio (db) ?0 ?0 ?0 0 20 ?0 ?0 ?0 ?0 ?0 10 100 10k 100k 1m 17902.5 g08 1k c l = 1 f frequency (hz) 100 1 output impedance ( ) 10 100 1000 1k 10k 100k 17902.5 g09 c l = 4.7 f c l = 0.47 f c l = 1 f minimum input-output voltage differential (sourcing)
15 LT1790 1790fa each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. C 2.5v characteristics long-term drift (data points reduced after 500 hr) output noise 0.1hz to 10hz output voltage noise spectrum 2.5v typical perfor a ce characteristics uw output to ground voltage (v) 0 0 current in r l (ma) 0.05 0.10 0.15 0.20 1.0 2.0 3.0 4.0 17902.5 g10 0.25 0.30 0.5 1.5 2.5 3.5 t a = 25 c t a = 125 c t a = 55 c ? ee v out 3v r l 5k 4 1, 2 6 1 f LT1790-2.5 r1 10k time (sec) 0 output noise (10 v/div) 8 17901.5 g12 246 10 7 135 9 hours 0 ppm 60 100 140 800 17902.5 g11 20 ?0 40 80 120 0 ?0 ?0 200 400 600 1000 t a = 30 c 2 typical parts soldered to pcb integrated noise 10hz to 1khz frequency (hz) 10 noise voltage ( v/ ? hz) 10 8 6 4 2 0 100 1k 10k 1790 g05 c l = 1 f i o = 0 a i o = 1ma i o = 250 a frequency (hz) 10 1 integrated noise ( v rms ) 10 100 100 1000 LT1790 g03
16 LT1790 1790fa output voltage temperature drift load regulation (sourcing) minimum input-output voltage differential (sourcing) minimum input-output voltage differential (sinking) load regulation (sinking) supply current vs input voltage each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. line regulation output impedance vs frequency power supply rejection ratio vs frequency 5v typical perfor a ce characteristics uw temperature ( c) ?0 output voltage (v) 5.005 5.010 5.015 110 17905 g01 5.000 4.995 4.985 ?0 30 70 30 130 10 50 90 4.990 5.025 5.020 four typical parts input-output voltage (v) 0 0.1 0.2 0.1 output current (ma) 1 10 0.3 0.4 0.5 0.6 17905 g02 t a = 55 c t a = 125 c t a = 25 c temperature ( c) ?0 ?0 voltage differential (mv) ?0 10 30 70 90 17905 g03 ?0 ?0 30 ?0 90 10 50 130 110 50 70 100 a 1ma 5ma output current (ma) 0.1 2000 output voltage change (ppm) ?600 ?200 800 400 110 17905 g04 0 ?800 ?400 ?000 600 200 t a = 25 c t a = 125 c t a = 55 c output current (ma) 0.1 0 output voltage change (ppm) 400 800 1200 1600 110 17905 g05 2000 200 600 1000 1400 1800 t a = 40 c t a = 25 c t a = 125 c input voltage (v) 0 supply current ( a) 40 50 60 20 17905 g06 30 20 0 5 10 15 10 80 70 t a = 55 c t a = 25 c t a = 125 c input voltage (v) output voltage (v) 5.04 5.02 5.00 4.98 4.96 4.94 4.92 4 8 12 16 17905 g07 20 2 0 6 10 14 18 t a = 55 c t a = 25 c t a = 125 c frequency (hz) ?0 power supply rejection ratio (db) 10 0 20 ?0 ?0 ?0 ?0 ?0 ?0 ?0 100 10k 100k 1m 17905 g08 1k c l = 1 f frequency (hz) 100 1 output impedance ( ) 10 100 1000 1k 10k 100k 17905 g09 c l = 4.7 f c l = 0.47 f c l = 1 f
17 LT1790 1790fa each of the voltage options have similar performance curves. for the 3v, 3.3v and the 4.096v options, the curves can be estimated based on the 2.5v and 5v curves. C 5v characteristics long-term drift output noise 0.1hz to 10hz output voltage noise spectrum 5v typical perfor a ce characteristics uw output to ground voltage (v) 0 current in r l (ma) 0.10 0.20 0.30 0.05 0.15 0.25 ? ? ? ? 17905 g10 0 ? 10 ? ? ? 1 ? ee v out 5.5v r l 5k 4 2 1 6 1 f LT1790-5 r1 10k t a = 55 c t a = 125 c t a = 25 c time (sec) 0 output noise (20 v/div) 8 17905 g12 246 10 7 135 9 hours 0 ppm 60 100 800 17905 g11 20 ?0 40 80 0 ?0 ?0 ?0 ?00 200 400 600 1000 t a = 30 c 2 typical parts soldered to pcb intergrated noise 10hz to 1khz frequency (hz) 10 noise voltage ( v/ ? hz) 10 8 6 4 2 0 100 1k 10k 1790 g05 c l = 1 f i o = 0 a i o = 1ma i o = 250 a frequency (hz) 10 integrated noise ( v rms ) 1000 100 10 1 100 1000 1790 g04
18 LT1790 1790fa applicatio n s i n for m atio n wu u u bypass and load capacitors the LT1790 voltage references should have an input bypass capacitor of 0.1 m f or larger, however the bypass- ing of other local devices may serve as the required component. these references also require an output ca- pacitor for stability. the optimum output capacitance for most applications is 1 m f, although larger values work as well. this capacitor affects the turn-on and settling time for the output to reach its final value. all LT1790 voltages perform virtually the same, so the LT1790-2.5 is used as an example. figure 1 shows the turn-on time for the LT1790-2.5 with a 1 m f input bypass and 1 m f load capacitor. figure 2 shows the output response to a 0.5v transient on v in with the same capacitors. the test circuit of figure 3 is used to measure the stability of various load currents. with r l = 1k, the 1v step produces a current step of 1ma. figure 4 shows the response to a 0.5ma load. figure 5 is the output re- sponse to a sourcing step from 4ma to 5ma, and figure 6 is the output response of a sinking step from C 4ma to C 5ma. figure 1. turn-on characteristics of LT1790-2.5 3v 2v 1v 0v v in v out 1790 f01 figure 2. output response to 0.5v ripple on v in 3v 2v 1v 0v v in v out 1790 f02 figure 3. response time test circuit figure 4. LT1790-2.5 sourcing and sinking 0.5ma 3v 2v v gen v out (ac coupled) 1790 f04 figure 5. LT1790-2.5 sourcing 4ma to 5ma C3v C2v v gen v out (ac coupled) 1790 f05 LT1790-2.5 c in 0.1 f c l 1 f v gen 1790 f03 1v v in 3v 4 1, 2 1k 6
19 LT1790 1790fa applicatio n s i n for m atio n wu u u figure 6. LT1790-2.5 sinking C 4ma to C 5ma 6v 4v 2v 0v v gen v out (ac coupled) 1790 f06 positive or negative operation series operation is ideal for extending battery life. if an LT1790 is operated in series mode it does not require an external current setting resistor. the specifications guar- antee that the LT1790 family operates to 18v. when the circuitry being regulated does not demand current, the series connected LT1790 consumes only a few hundred m w, yet the same connection can sink or source 5ma of load current when demanded. a typical series connection is shown on the front page of this data sheet. the circuit in figure 7 shows the connection for a C 2.5v reference, although any LT1790 voltage option can be configured this way to make a negative reference. the LT1790 can be used as very stable negative references, however, they require a positive voltage applied to pin 4 to bias internal circuitry. this voltage must be current limited with r1 to keep the output pnp transistor from turning on and driving the grounded output. c1 provides stability during load transients. this connection main- tains nearly the same accuracy and temperature coeffi- cient of the positive connected LT1790. long-term drift long-term drift cannot be extrapolated from acceler- ated high temperature testing. this erroneous tech- nique gives drift numbers that are widely optimistic. the only way long-term drift can be determined is to mea- sure it over the time interval of interest. the LT1790s6 drift data was taken on over 100 parts that were soldered into pc boards similar to a real world application. the boards were then placed into a constant temperature oven with t a = 30 c, their outputs scanned regularly and measured with an 8.5 digit dvm. long-term drift curves are shown in the typical performance characteristics. hysteresis hysteresis data shown in figures 8 and 9 represent the worst-case data taken on parts from 0 c to 70 c and from C40 c to 85 c. units were cycled several times over these temperature ranges and the largest change is shown. as expected, the parts cycled over the higher temperature range have higher hysteresis than those cycled over the lower range. when an LT1790 is ir reflow soldered onto a pc board, the output shift is typically just 150ppm (0.015%). higher input voltage the circuit in figure 10 shows an easy way to increase the input voltage range of the LT1790. the zener diode can be anywhere from 6v to 18v. for equal power sharing be- tween r1 and the zener (at 30v), the 18v option is better. the circuit can tolerate much higher voltages for short periods and is suitable for transient protection. assuming 80 m a max supply current for the LT1790, a 25 m a load, 120mv max dropout and a 4v to 30v input specification, the largest that r1 can be is (4v C 3.3v C 120mv)/(80 m a + 25 m a) = 5.5k. furthermore, assuming 220mw of dissipation in the 18v sot-23 zener, this gives a max current of (220mw)/(18v) = 12.2ma. so the smallest that r1 should be is (30v C 18v)/12.2ma = 1k, rated at 150mw. 8v LT1790-2.5 c l 1 f c1 0.1 f 1790 f07 4 1, 2 6 r1 10k v out = 2.5v v ee 3v r l = v ee ?v out 125 a figure 7. using the LT1790-2.5 to build a C2.5v reference
20 LT1790 1790fa applicatio n s i n for m atio n wu u u figure 9. worst-case C40 c to 85 c hysteresis on 30 units figure 8. worst-case 0 c to 70 c hysteresis on 30 units with r1 = 1k, and assuming a 450mv worst-case dropout, the LT1790 can deliver a minimum current of (4v C 3.3vC 450mv)/(1k) = 250 m a. in figure 10, r1 and c1 provide filtering of the zener noise when the zener is in its noisy v-i knee. there are other variations for higher voltage operation that use a pass transistor shown in figures 11 and 12. these circuits allow the input voltage to be as high as 160v while maintaining low supply current. more output current the circuit in figure 13 is a compact, high output current, low dropout precision supply. the circuit uses the sot-23 lt1782 and the thinsot LT1790. resistive divider r1 and r2 set a voltage 22mv below v s . for under 1ma of output current, the LT1790 supplies the load. above 1ma of load current, the (+) input of the lt1782 is pulled below the 22mv divider reference and the output fet turns on to supply the load current. capacitor c1 stops oscillations in LT1790-3.3 4v to 30v c1 0.1 f bzx84c18 1 f v out r1 1790 f10 figure 10. extended supply range reference distribution (ppm) 80 ?0 60 50 40 30 ?0 ?0 010 20 30 40 50 number of units 8 1790 f08 6 4 0 2 7 5 3 1 70 c to 25 c 0 c to 25 c distribution (ppm) ?40 ?00 ?60 ?20 ?0 ?0 0 40 80 number of units 8 10 12 1790 f09 6 4 0 2 16 85 c to 25 c ?0 c to 25 c 14 the transition region. the no load standing current is only 120 m a, yet the output can deliver over 300ma. noise an estimate of the total integrated noise from 10hz to 1khz can be made by multiplying the flat band spot noise by ? bw. for example, from the typical performance curves, the LT1790-1.25 noise spectrum shows the average spot noise to be about 450nv/ ? hz. the square root of the bandwidth is ? 990 = 31.4. the total noise 10hz to 1khz noise is (450nv)(31.4) = 14.1 m v. this agrees well with the measured noise. this estimate may not be as good with higher voltage options, there are several reasons for this. higher voltage options have higher noise and they have higher variability due to process variations. 10hz to 1khz noise may vary by 2db on the LT1790-5 and 1db on the LT1790-2.5. measured noise may also vary because of peaking in the noise spectrum. this effect can be seen in the range of 1khz to 10khz with all voltage options sourcing different load currents. from the typical performance curves the 10hz to 1khz noise spectrum of the LT1790-5 is shown to be 3 m v/ ? hz at low frequency. the estimated noise is (3 m v)(31.4) = 93.4 m v. the actual integrated 10hz to 1khz noise measures 118.3 m v. the peaking shown causes this larger number. peaking is a function of output capacitor as well as load current and process variations.
21 LT1790 1790fa applicatio n s i n for m atio n wu u u LT1790 c1 0.1 f c2 1 f on semi mmbt5551 v s 6v to 160v v out 1790 f11 r2 4.7k r1 330k bzx84c12 LT1790 c2 1 f bav99 v out 1790 f12 c1 0.1 f r1 330k v s 6.5v to 160v on semi mmbt5551 + LT1790-2.5 lt1782 17909 f13 c2 1 f note: not current limited v out = 2.5v i load = 0ma to 300ma r3 22 5% r1 680 5% v s 2.8v to 3.3v no load supply current 120 a r2 100k 5% c1 0.1 f r4 1k 5% vishay siliconix si3445dv figure 11. extended supply range reference figure 12. extended supply range reference figure 13. compact, high output current, low dropout, precison 2.5v supply
22 LT1790 1790fa 4 v in 6 v out 1, 2 gnd 1790 ss si plified sche atic ww
23 LT1790 1790fa u package descriptio s6 package 6-lead plastic sot-23 (reference ltc dwg # 05-08-1636) 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. 1.50 ?1.75 (.059 ?.069) (note 3) 2.60 ?3.00 (.102 ?.118) .25 ?.50 (.010 ?.020) (6plcs, note 2) l datum ? .09 ?.20 (.004 ?.008) (note 2) a1 s6 sot-23 0401 2.80 ?3.10 (.110 ?.118) (note 3) .95 (.037) ref a a2 1.90 (.074) ref .20 (.008) .90 ?1.45 (.035 ?.057) .00 ?0.15 (.00 ?.006) .90 ?1.30 (.035 ?.051) .35 ?.55 (.014 ?.021) 1.00 max (.039 max) a a1 a2 l .01 ?.10 (.0004 ?.004) .80 ?.90 (.031 ?.035) .30 ?.50 ref (.012 ?.019 ref) pin one id millimeters (inches) note: 1. controlling dimension: millimeters 2. dimensions are in 3. drawing not to scale 4. dimensions are inclusive of plating 5. dimensions are exclusive of mold flash and metal burr 6. mold flash shall not exceed .254mm 7. package eiaj reference is: sc-74a (eiaj) for original jedec mo-193 for thin sot-23 (original) sot-23 (thinsot)
24 LT1790 1790fa lt/cpi 0202 1.5k rev a ? printed in usa related parts part number description comments lt1019 precision reference low noise bandgap, 0.05%, 5ppm/ c ltc ? 1798 micropower low dropout reference 0.15% max, 6.5 m a supply current lt1460 micropower precison series reference bandgap, 130 m a supply current, 10ppm/ c, available in sot-23 lt1461 micropower precision low dropout reference bandgap 0.04%, 3ppm/ c, 50 m a max supply current ? linear technology corporation 2000 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com C 2.5v negative 50ma series reference no load supply current i cc = 1.6ma i ee = 440 m a typical applicatio u LT1790-2.5 1 f 2k v z = 5.1v v cc = 5v mps2907a v ee = 5v 5.1k 1790 ta03 4 1, 2 6 2.5v 50ma

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