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1 lt1070/LT1071 5a and 2.5a high efficiency switching regulators n wide input voltage range: 3v to 60v n low quiescent current: 6ma n internal 5a switch (2.5a for LT1071) n very few external parts required n self protected against overloads n operates in nearly all switching topologies n shutdown mode draws only 50 m a supply current n flyback regulated mode has fully floating outputs n comes in standard 5-pin packages n can be externally synchronized (consult factory) features the lt ? 1070/LT1071 are monolithic high power switch- ing regulators. they can be operated in all standard switch- ing configurations including buck, boost, flyback, for- ward, inverting and cuk. a high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. integration of all func- tions allows the lt1070/LT1071 to be built in a standard 5-pin to-3 or t0-220 power package. this makes it ex- tremely easy to use and provides bust proof operation similar to that obtained with 3-pin linear regulators. the lt1070/LT1071 operate with supply voltages from 3v to 60v, and draw only 6ma quiescent current. they can deliver load power up to 100w with no external power devices. by utilizing current mode switching techniques, they provide excellent ac and dc load and line regulation. the lt1070/LT1071 have many unique features not found even on the vastly more difficult to use low power control chips presently available. they use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. an externally activated shutdown mode reduces total supply current to 50 m a typical for standby operation. totally isolated and regulated outputs can be generated by using the optional flyback regulation mode built into the lt1070/LT1071, without the need for optocouplers or extra transformer windings. descriptio n u user note: this data sheet is only intended to provide specifications, graphs and a general functional description of the lt1070/LT1071. application circuits are included to show the capability of the lt1070/LT1071. a complete design manual (an19) should be obtained to assist in developing new designs. this manual contains a comprehensive discussion of both the lt1070 and the external components used with it, as well as complete formulas for calculating the values of these components. the manual can also be used for the LT1071 by factoring in the lower switch current rating. a second application note, an25, which details off-line applications is available. typical applicatio n u + r1 10.7k 1% r2 1.24k 1% 1070/71 ta01 12v 1a r3 1k c1 1 m f c2 1000 m f + c3* 100 m f l1** 150 m h d1 5v v sw v c v in lt1070 gnd fb c3 100 m f l2 10 m h output filter * ** required if input leads 3 2" pulse engineering 92113 input voltage (v) 0 power (w)** 60 80 100 40 1070/71 ta02 40 20 0 10 20 30 50 boost buck/boost v o = 30v flyback isolated buck/boost v o = 5v rough guide only. buck mode p out = 5a ?v out . special topologies deliver more power divide vertical power scale by 2 for LT1071 * ** maximum output power* boost converter (5v to 12v) applicatio n s u n logic supply 5v at 10a n 5v logic to 15v op amp supply n off-line converter up to 200w n battery upconverter n power inverter (+ to C) or (C to +) n fully floating multiple outputs n for lower current applications, see the lt1072 , ltc and lt are registered trademarks of linear technology corporation.
2 lt1070/LT1071 symbol parameter conditions min typ max units v ref reference voltage measured at feedback pin, v c = 0.8v 1.224 1.244 1.264 v l 1.214 1.244 1.274 v i b feedback input current v fb = v ref 350 750 na l 1100 na g m error amplifier transconductance d i c = 25 m a 3000 4400 6000 m mho l 2400 7000 m mho error amplifier source or sink current v c = 1.5v 150 200 350 m a l 120 400 m a error amplifier clamp voltage hi clamp, v fb = 1v 1.80 2.30 v lo clamp, v fb = 1.5v 0.25 0.38 0.52 v reference voltage line regulation 3v v in v max , v c = 0.8v l 0.03 %/v a v error amplifier voltage gain 0.9v v c 1.4v 500 800 v/v minimum input voltage l 2.6 3.0 v i q supply current 3v v in v max , v c = 0.6v 6 9 ma control pin threshold duty cycle = 0 0.8 0.9 1.08 v l 0.6 1.25 v normal/flyback threshold on feedback pin 0.4 0.45 0.54 v absolute m axi m u m ratings w ww u supply voltage lt1070/LT1071 (note 2) .................................... 40v lt1070hv/LT1071hv (note 2)........................... 60v switch output voltage lt1070/LT1071 .................................................. 65v lt1070hv/LT1071hv......................................... 75v feedback pin voltage (transient, 1ms) ................ 15v operating junction temperature range commercial (operating) ....................... 0 c to 100 c commercial (short circuit)................... 0 c to 125 c industrial ......................................... C 40 c to 125 c military ............................................ C 55 c to 150 c storage temperature range ................ C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c package/order i n for m atio n w u u order part number lt1070ck lt1070hvck lt1070hvmk lt1070ik lt1070mk LT1071ck LT1071hvck LT1071hvmk LT1071mk order part number lt1070ct lt1070hvct lt1070hvit lt1070it LT1071ct LT1071hvct LT1071hvit LT1071it t jmax = 100 c, q ja = 35 c/ w, q jc = 2 c (lt1070c, i) t jmax = 150 c, q ja = 35 c/ w, q jc = 2 c (lt1070m) t jmax = 100 c, q ja = 35 c/ w, q jc = 4 c (LT1071c, i) t jmax = 150 c, q ja = 35 c/ w, q jc = 4 c (LT1071m) 2 4 1 3 v sw v c fb case is gnd v in k package 4-lead to-3 metal can bottom view t jmax = 100 c, q ja = 75 c/ w, q jc = 2 c (lt1070c, i) t jmax = 100 c, q ja = 75 c/ w, q jc = 4 c (LT1071c) t package 5-lead plastic to-220 v in v sw gnd fb v c front view 5 4 3 2 1 electrical characteristics v in = 15v, v c = 0.5v, v fb = v ref , output pin open unless otherwise specified. (note 1)
3 lt1070/LT1071 electrical characteristics symbol parameter conditions min typ max units v fb flyback reference voltage i fb = 50 m a 15 16.3 17.6 v l 14 18.0 v change in flyback reference voltage 0.05 i fb 1ma 4.5 6.8 8.5 v flyback reference voltage line regulation i fb = 50 m a, 3v v in v max (note 3) 0.01 0.03 %/v flyback amplifier transconductance (g m ) d i c = 10 m a 150 300 650 m mho flyback amplifier source and sink current v c = 0.6v, i fb = 50 m a (source) l 15 32 70 m a v c = 0.6v, i fb = 50 m a (sink) l 25 40 70 m a b v output switch breakdown voltage 3v v in v max , i sw = 1.5ma (lt1070/LT1071) l 65 90 v (lt1070hv/LT1071hv) l 75 90 v v sat output switch on resistance (note 4) lt1070 l 0.15 0.24 w LT1071 l 0.30 0.50 w control voltage to switch current lt1070 8 a/v transconductance LT1071 4 a/v i lim switch current limit (lt1070) duty cycle 50%, t j 3 25 c l 510a duty cycle 50%, t j < 25 c l 511a duty cycle = 80% (note 5) l 410a switch current limit (LT1071) duty cycle 50%, t j 3 25 c l 2.5 5.0 a duty cycle 50%, t j < 25 c l 2.5 5.5 a duty cycle = 80% (note 5) l 2.0 5.0 a d i in supply current increase during 25 35 ma/a d i sw switch on time f switching frequency 35 40 45 khz l 33 47 khz dc (max) maximum switch duty cycle 90 92 97 % flyback sense delay time 1.5 m s shutdown mode supply current 3v v in v max , v c = 0.05v 100 250 m a shutdown mode threshold voltage 3v v in v max 100 150 250 mv l 50 300 mv v in = 15v, v c = 0.5v, v fb = v ref , output pin open unless otherwise specified. the l denotes the specifications which apply over the full operating temperature range. note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: minimum switch on time for the lt1070/LT1071 in current limit is ? 1 m s. this limits the maximum input voltage during short-circuit conditions, in the buck and inverting modes only , to ? 35v. normal (unshorted) conditions are not affected. mask changes are being implemented which will reduce minimum on time to 1 m s, increasing maximum short-circuit input voltage above 40v. if the present lt1070/LT1071 (contact factory for package date code) is being operated in the buck or inverting mode at high input voltages and short-circuit conditions are expected, a resistor must be placed in series with the inductor, as follows: the value of the resistor is given by: r = ?r l t ?f ?v in ?v f i limit t = minimum on time of lt1070/LT1071 in current limit, ? 1 m s f = operating frequency (40khz) v f = forward voltage of external catch diode at i limit i limit = current limit of lt1070 ( ? 8a), LT1071 ( ? 4a) r l = internal series resistance of inductor note 3: v max = 55v for lt1070hv and LT1071hv to avoid switch breakdown. note 4: measured with v c in hi clamp, v fb = 0.8v. i sw = 4a for lt1070 and 2a for LT1071. note 5: for duty cycles (dc) between 50% and 80%, minimum guaranteed switch current is given by i lim = 3.33 (2 C dc) for the lt1070 and i lim = 1.67 (2 C dc) for the LT1071.
4 lt1070/LT1071 typical perfor m a n ce characteristics uw switch current limit vs duty cycle duty cycle (%) 0 switch current (a) 16 14 12 10 8 6 4 2 0 80 1070/71 g01 20 40 60 100 70 10 30 50 90 for LT1071, divide vertical scale by 2 ?5 c 125 c 25 c flyback blanking time junction temperature ( c) ?5 1.0 time ( m s) 1.2 1.6 1.8 2.0 ?5 25 50 150 1070/71 g03 1.4 ?0 0 75 100 125 2.2 junction temperature ( c) ?5 90 duty cycle (%) 91 93 94 95 ?5 25 50 150 1070/71 g02 92 ?0 0 75 100 125 96 maximum duty cycle minimum input voltage temperature ( c) ?5 2.3 minimum input voltage (v) 2.4 2.6 2.7 2.8 ?5 25 50 150 1070/71 g04 2.5 ?0 0 75 100 125 2.9 switch current = 5a switch current = 0a switch saturation voltage switch current (a) 0 switch saturation voltage (v) 0.8 1.2 8 1070/71 g05 0.4 0 1.0 25 c 1.4 0.6 0.2 2 4 6 1 3 5 7 1.6 for LT1071, divide current by 2 100 c ?5 c 150 c isolated mode flyback reference voltage temperature ( c) ?5 flyback voltage (v) 19 20 21 125 1070/71 g06 18 17 15 ?5 25 75 50 150 0 50 100 16 23 22 r feedback = 500 w r feedback = 1k r feedback = 10k line regulation feedback bias current vs temperature input voltage (v) 0 ? reference voltage change (mv) ? ? 1 10 20 30 40 1070/71 g07 50 3 5 ? ? 0 2 4 60 t j = 150 c t j = 25 c t j = 55 c temperature ( c) ?5 feedback bias current (na) 600 500 400 300 200 100 0 125 1070/71 g09 ?5 25 75 50 150 0 50 100 800 700 reference voltage vs temperature temperature ( c) ?5 reference voltage (v) switching frequency (khz) 1.246 1.244 1.242 1.240 1.238 1.236 1.234 125 1070/71 g08 ?5 25 75 50 150 0 50 100 1.250 1.248 40 39 38 37 36 35 34 42 41 switching frequency reference v0ltage
5 lt1070/LT1071 typical perfor m a n ce characteristics uw supply current vs supply voltage (shutdown mode) driver current* vs switch current switch current (a) 0 driver current (ma) 160 140 120 100 80 60 40 20 0 4 1070/71 g10 1 * 23 5 t j 3 25 c average lt1070 power supply current is found by multiplying driver current by duty cycle, then adding quiescent current t j = 55 c supply voltage (v) 0 supply current ( m a) 60 80 100 30 50 1070/71 g12 40 20 0 10 20 40 120 140 160 60 t j = 25 c v c = 50mv v c = 0v supply current vs input voltage* input voltage (v) 0 6 input current (ma) 8 10 12 10 20 30 * 40 1070/71 g11 50 14 under very low output current conditions, duty cycle for most circuits will approach 10% or less 16 7 9 11 13 15 60 t j = 25 c i switch 10ma 90% duty cycle 50% duty cycle 0% duty cycle 10% duty cycle feedback pin clamp voltage shutdown thresholds temperature ( c) ?5 v c pin voltage (mv) v c pin current ( m a) 300 250 200 150 100 50 0 125 1070/71 g16 ?5 25 75 50 150 0 50 100 400 350 300 250 200 150 100 ?0 0 400 350 v c voltage is reduced until regulator current drops below 300 m a voltage current (out of v c pin) feedback current (ma) 0 feedback voltage (mv) 300 400 500 0.8 1070/71 g18 200 100 250 350 450 150 50 0 0.2 0.4 0.6 0.1 0.9 0.3 0.5 0.7 1.0 ?5 c 25 c 150 c temperature ( c) ?5 idle supply current (ma) 7 9 11 125 1070/71 g14 5 3 6 8 10 4 2 1 ?5 25 75 50 150 0 50 100 v c = 0.6v v supply = 60v v supply = 3v idle supply current vs temperature normal/flyback mode threshold on feedback pin temperature ( c) ?0 400 feedback pin voltage (mv) feedback pin current ( m a) 410 430 440 450 500 470 0 50 75 1070/71 g13 420 480 490 460 ? ? ?0 ?2 ?4 ?4 ?8 ? ?0 ?2 ?6 ?5 25 100 125 150 feedback pin voltage (at threshold) feedback pin current (at threshold) error amplifier transconductance temperature ( c) ?5 transconductance ( m mho) 3000 4000 5000 125 1070/71 g14 2000 1000 2500 3500 4500 1500 500 0 ?5 25 75 50 150 0 50 100 g m = (v c pin) (fb pin) d i d v shutdown mode supply current v c pin voltage (mv) 0 supply current ( m a) 120 160 200 80 1070/71 g14 80 40 100 140 180 60 20 0 20 40 60 10 90 30 50 70 100 t j = 150 c ?5 c t j 125 c
6 lt1070/LT1071 typical perfor m a n ce characteristics uw voltage is obtained by using the output of a voltage sensing error amplifier to set current trip level. this technique has several advantages. first, it has immediate response to input voltage variations, unlike ordinary switchers which have notoriously poor line transient response. second, it reduces the 90 phase shift at the lt1070/LT1071 is a current mode switcher. this means that switch duty cycle is directly controlled by switch current rather than by output voltage. referring to the block diagram, the switch is turned on at the start of each oscillator cycle. it is turned off when switch current reaches a predetermined level. control of output operatio n u switch off characteristics switch voltage (v) 0 switch current ( m a) 600 800 1000 80 1070/71 g19 400 200 500 700 900 300 100 0 20 40 60 10 90 30 50 70 100 v supply = 3v 15v 40v 55v frequency (hz) 1000 transconductance ( m mho) phase ( ) 3000 4000 6000 7000 1k 100k 1m 10m 1070/71 g21 1000 10k 5000 2000 0 150 90 q 60 0 ?0 210 30 120 180 g m transconductance of error amplifier v c pin characteristics v c pin voltage (v) 0 400 v c pin current ( m a) 300 200 100 300 100 0.5 1.0 200 0 1.5 2.0 2.5 1070/71 g20 v fb = 1.5v (current into v c pin) v fb = 0.8v (current out of v c pin) t j = 25 c block diagra m w + + error amp current amp 0.02 w (0.04 w LT1071) shutdown circuit mode select 40khz osc logic driver antisat 16v 5a, 75v switch v in fb v c comp gain ? 6 0.15v 1070/71 bd 1.24v ref 2.3v reg flyback error amp switch out
7 lt1070/LT1071 operatio n u midfrequencies in the energy storage inductor. this greatly simplifies closed-loop frequency compensation under widely varying input voltage or output load condi- tions. finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short-circuit conditions. a low drop- out internal regulator provides a 2.3v supply for all internal circuitry of the lt1070/LT1071. this low drop- out design allows input voltage to vary from 3v to 60v with virtually no change in device performance. a 40khz oscillator is the basic clock for all internal timing. it turns on the output switch via the logic and driver circuitry. special adaptive antisat circuitry detects onset of satura- tion in the power switch and adjusts driver current instantaneously to limit switch saturation. this mini- mizes driver dissipation and provides very rapid turn-off of the switch. a 1.2v bandgap reference biases the positive input of the error amplifier. the negative input is brought out for output voltage sensing. this feedback pin has a second function; when pulled low with an external resistor, it programs the lt1070/LT1071 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. the lt1070/ LT1071 will then regulate the value of the flyback pulse with respect to the supply voltage. this flyback pulse is directly proportional to output voltage in the traditional transformer coupled flyback topology regulator. by regu- lating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection be- tween input and output. the output is fully floating up to the breakdown voltage of the transformer windings. multiple floating outputs are easily obtained with addi- tional windings. a special delay network inside the lt1070/ LT1071 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation. the error signal developed at the comparator input is brought out externally. this pin (v c ) has four different functions. it is used for frequency compensation, current limit adjustment, soft starting and total regulator shut- down. during normal regulator operation this pin sits at a voltage between 0.9v (low output current) and 2.0v (high output current). the error amplifiers are current output (g m ) types, so this voltage can be externally clamped for adjusting current limit. likewise, a capacitor coupled external clamp will provide soft start. switch duty cycle goes to zero if the v c pin is pulled to ground through a diode, placing the lt1070/LT1071 in an idle mode. pulling the v c pin below 0.15v causes total regulator shutdown, with only 50 m a supply current for shutdown circuitry biasing. see an19 for full application details. typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071) r1* r2** 1070/71 ta16 d1 sets i b(on) sets i b(off) * ** d2 c1 v sw v in lt1070/LT1071 gnd q1 driving high voltage npn driving high voltage fet (for off-line applications, see an25) 1070/71 ta03 10v to 20v d1 v sw g d s q1 v in lt1070/LT1071 gnd +
8 lt1070/LT1071 typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071) negative current boosted buck converter 1070/71 ta13 r3 r2 1.24k q1 2n3906 r4 12k c2 c3 r1 minimum load = 10ma ? out 5v 10a d1 t1 1:n r5 c1 v sw v c v in ? in lt1070 gnd fb + + v out ?0.6v 1ma r1 = 1070/71 ta12 r3 r2 1.24k * ** required if input leads 3 2" pulse engineering 92113 q1 2n3906 r1 4.64k c1 c2 1000 m f c3 100 m f v in 20v 5.2v 4.5a d1 l1** 200 m h v sw v c v in lt1070 gnd optional input filter fb load c4 200 m f l2 4 m h optional output filter + + + l3 negative buck converter positive buck converter r2 1.24k r4 10 w 100ma minimum 1070/71 ta14 5v 4.5a r3 470 w c1 1 m f d1 r + c3 2.2 m f + c5* 100 m f + c2 1 m f + c4 1000 m f l1** 100 m h v sw v c v in v in lt1070 r1 3.74k d2 1n914 gnd fb d3 l2 4 m h c5 200 m f optional output filter * ** required if input leads 3 2" pulse engineering 92112
9 lt1070/LT1071 typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071) positive current boosted buck converter r3 680 w c1 0.33 m f 200pf *required if input leads 3 2" r4 1.24k c2 5000 m f v out 5v 10a v in 28v r1 5k v sw v in c3 0.47 m f c6 0.002 m f d2 470 w 2w 1:n n ? 0.25 lt1070 gnd v c fb 1070/71 ta19 r6 470 w + comp lm308 v in r2 1k r7 1.24k r5 5k v 7 d1 2 3 8 4 6 v + + c5* 100 m f + positive to negative buck/boost converter + r1 11.3k 1070/71 ta05 v out 12v 2a v in 12v r3 2.2k c1 0.22 m f r2 1.24k * ** required if input leads 3 2" pulse engineering 92113 c2 1000 m f + c4* 100 m f l1** 150 m h q1 d1 v sw v c v in lt1070 gnd fb c3 l2 optional output filter l3 optional input filter + r6 470 w 1070/71 ta09 v in 10v to 30v * ** required if input leads 3 2" pulse engineering 92113 ? to avoid start-up problems for input voltages below 10v, connect anode of d3 to v in and remove r5. c1 may be reduced for lower output currents. c1 ? (500 m f)(i out ) for 5v outputs, reduce r3 to 1.5k, increase c2 to 0.3 m f and reduce r6 to 100 w . v out 12v 2a r3 5k r2 1.24k c1 0.1 m f c5* 100 m f c3 2 m f + c4 5 m f + c1 ? 1000 m f l1** 200 m h v sw v c v in lt1070 r5 ? 470 w 1w d3 ? 1n4001 r1 10.7k r4 47 w d2 1n914 d1 gnd fb negative to positive buck/boost converter
10 lt1070/LT1071 typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071) current boosted boost converter + r4 1070/71 ta11 r3 r2 1.24k r1 27k c2 c3 i n c1 v out 28v 4a d2 d1 v sw v c v in lt1070 gnd v in 16v to 24v fb + r1 27k r o (minimum load) r2 1.24k 1070/71 ta15 r3 3.3k c2 0.22 m f c3 10 m f + + c1 1000 m f + c4* 470 m f v in ?5v v out 28v 1a l1 200 m h d2 d1 v sw v c v in lt1070 gnd fb *required if input leads 3 2" + r4 680 w 1w 1070/71 ta10 1 l1 n = 5 total inductance = 4mh interleave primary and secondary for low leakage inductance r3 10k r2 1.24k r1 98k c2 0.047 m f c3 0.68 m f c1 200 m f v out 100v 300ma d2 d1 v sw v c v in lt1070 gnd v in 15v fb + voltage boosted boost converter negative boost regulator negative input/negative output flyback converter + r5 r4 1.24k c2 v sw q1 2n3906 v in c3 c1 ? out 1070/71 ta17 r6 r1* t1 1:n lt1070/LT1071 gnd v c fb ? in r3 1k r2 5k + *r1 = ? v out ? ?1.6v 200 m a external current limit external current limit 1070/71 ta04 lt1070/LT1071 v c gnd d1 v x r1 500 w r2 = 2v 1070/71 ta06 r2 v in r1 1k c2 c1 1000pf note that the lt1070/LT1071 gnd pin is no longer common to v in v sw v c r s v in lt1070/LT1071 gnd fb + q1
11 lt1070/LT1071 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. typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071) t5 (to-220) 0398 0.028 ?0.038 (0.711 ?0.965) 0.057 ?0.077 (1.448 ?1.956) 0.135 ?0.165 (3.429 ?4.191) 0.700 ?0.728 (17.78 ?18.491) 0.045 ?0.055 (1.143 ?1.397) 0.095 ?0.115 (2.413 ?2.921) 0.013 ?0.023 (0.330 ?0.584) 0.620 (15.75) typ 0.155 ?0.195 (3.937 ?4.953) 0.152 ?0.202 (3.861 ?5.131) 0.260 ?0.320 (6.60 ?8.13) 0.165 ?0.180 (4.191 ?4.572) 0.147 ?0.155 (3.734 ?3.937) dia 0.390 ?0.415 (9.906 ?10.541) 0.330 ?0.370 (8.382 ?9.398) 0.460 ?0.500 (11.684 ?12.700) 0.570 ?0.620 (14.478 ?15.748) 0.230 ?0.270 (5.842 ?6.858) k4(to-3) 0695 72 18 0.495 ?0.525 (12.57 ?13.34) r 0.470 tp p.c.d. 0.167 ?0.177 (4.24 ?4.49) r 0.151 ?0.161 (3.84 ?4.09) dia 2 plc 0.655 ?0.675 (16.64 ?19.05) 1.177 ?1.197 (29.90 ?30.40) 0.038 ?0.043 (0.965 ?1.09) 0.060 ?0.135 (1.524 ?3.429) 0.320 ?0.350 (8.13 ?8.89) 0.420 ?0.480 (10.67 ?12.19) 0.760 ?0.775 (19.30 ?19.69) flyback converter 1070/71 ta08 *required if input leads 3 2" a b v snub c2 0.15 m f r3 1.5k r1 3.74k r2 1.24k c4* 100 m f v in 20v to 30v v out 5v 6a v sw v c v in lt1070 gnd fb c3 0.47 m f c1 2000 m f d2 d1 r4 1n + + primary flyback voltage = lt1070/LT1071 switch voltage area ??= area ??to maintain zero dc volts across primary secondary voltage area ??= area ??to maintain zero dc volts across secondary primary current v out + v f n 0v v in clamp turn-on spike c4 200 m f l2 10 m h optional filter c d i d v out + v f (n)(v in ) i pri 0v 0 lt1070 switch current snubber diode current i pri i pri t = (i pri )(l l ) v snub secondary current i pri n 0 0 n = 1/3 package descriptio n u dimensions in inches (millimeters) unless otherwise noted. t package 5-lead plastic to-220 (standard) (ltc dwg # 05-08-1421) k package 4-lead to-3 metal can (ltc dwg # 05-08-1311)
12 lt1070/LT1071 10701fd lt/tp 1098 2k rev d ? printed in usa ? linear technology corporation 1989 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear-tech.com related parts part number description comments lt1074/lt1076 high voltage switching regulators 40v input (60v for hv versions), 100khz, 5a and 2a lt1170/lt1171/ 100khz high efficiency switching regulators 40v input (65v for hv versions), 5a/2.5a/1.25a internal switch lt1172 lt1370/lt1371 500khz high efficiency switching regulators 35v, 6a/3a internal switch lt1374/lt1376 100khz high efficiency switching regulators 25v input, 4.5a/1.5a internal switch forward converter totally isolated converter 1070/71 ta07 r4 1.5k 5k 500 w n = 0.875 = 7:8 for v out = 15v *required if input leads 3 2" r2 secondary voltage 0v v out t off t on ? 16v (n)(v in ) c2 0.01 m f c5* 100 m f v in 5v v sw v c v in lt1070/LT1071 gnd fb + c3 0.47 m f n d1 1:n n + l1 10 m f l2 10 m f 15v com + c4 500 m f c1 500 m f + + c6 200 m f c5 200 m f optional output filter + 15v switch voltage v f (diode forward voltage) 0v v in + r3 r6 330 w r5 1 w q1 c3 c4 v sw l1 70 m h v in c2 d3 c1 2000 m f d1 v out 5v 6a r4 t1 lt1070 gnd v c fb v in 20v to 30v d4 imn d2 1070/71 ta18 r1 3.74k r2 1.24k typical applicatio n s u (note that maximum output currents are divided by 2 for the LT1071)

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