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1 lt1170/lt1171/LT1172 100khz, 5a, 2.5a and 1.25a high efficiency switching regulators n wide input voltage range: 3v to 60v n low quiescent current: 6ma n i nternal 5a switch (2.5a for lt1171, 1.25a for LT1172) n shutdown mode draws only 50 m a supply current n very few external parts required n self-protected against overloads n operates in nearly all switching topologies n flyback-regulated mode has fully floating outputs n comes in standard 5-pin packages n LT1172 available in 8-pin minidip and surface mount packages n can be externally synchronized the lt ? 1170/lt1171/LT1172 are monolithic high power switching regulators. they can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and cuk. a high current, high effi- ciency switch is included on the die along with all oscilla- tor, control and protection circuitry. integration of all functions allows the lt1170/lt1171/LT1172 to be built in a standard 5-pin to-3 or to-220 power package as well as the 8-pin packages (LT1172). this makes them extremely easy to use and provides bust proof operation similar to that obtained with 3-pin linear regulators. the lt1170/lt1171/LT1172 operate with supply volt- ages 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 switch- ing techniques, they provide excellent ac and dc load and line regulation. the lt1170/lt1171/LT1172 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 cur- rents with no loss in efficiency. an externally activated shutdown mode reduces total supply current to 50 m a typically for standby operation. boost converter (5v to 12v) maximum output power* , ltc and lt are registered trademarks of linear technology corporation. n logic supply 5v at 10a n 5v logic to 15v op amp supply n battery upconverter n power inverter (+ to C) or (C to +) n fully floating multiple outputs user note: this data sheet is only intended to provide specifications, graphs, and a general functional description of the lt1170/lt1171/LT1172. application circuits are included to show the capability of the lt1170/lt1171/LT1172. 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 lt1170/lt1171/LT1172 by factoring in the higher frequency. a cad design program called switchercad tm is also available. switchercad is a trademark of linear technology corporation. descriptio u features applicatio s u typical applicatio u 1170/1/2 ta01 d1 mbr330 c2 1000 m f c1 1 m f r1 10.7k 1% r2 1.24k 1% lt1170 gnd v in 5v r3 1k *required if input leads 3 2" ** coiltronics 50-2-52 pulse engineering 92114 v sw fb v c output filter l2 10 m h l1** 50 m h c3 100 m f 12v 1a c3* 100 m f + + input voltage (v) 0 power (w) ** 100 80 60 40 20 0 40 lt1170/1/2 ta02 10 20 30 50 * rough guide only. buck mode p out = (5a)(v out ) special topologies deliver more power. ** divide vertical power scale by two for lt1171, by four for LT1172. boost buck-boost v o = 30v flyback buck-boost v o = 5v lt1170
2 lt1170/lt1171/LT1172 * q will vary from approximately 25 c/w with 2.8 sq. in. of 1oz. copper to 45 c/w with 0.20 sq. in. of 1oz. copper. somewhat lower values can be obtained with additional copper layers in multilayer boards. LT1172mj8 LT1172cj8 LT1172cn8 LT1172in8 LT1172cs8 LT1172is8 s8 part marking supply voltage lt1170/71/72hv (note 2) .................................. 60v lt1170/71/72 (note 2) ....................................... 40v switch output voltage lt1170/71/72hv ................................................ 75v lt1170/71/72 ..................................................... 65v LT1172s8 ........................................................... 60v feedback pin voltage (transient, 1ms) ................ 15v storage temperature range ............... C 65 c to 150 c lead temperature (soldering, 10 sec)................. 300 c order part number t jmax = 100 c, q ja = * c/w lt1170cq lt1170iq lt1170hvcq lt1171cq lt1171iq t jmax q jc q ja lt1170mk 150 c2 c/w 35 c/w lt1170ck 100 c2 c/w 35 c/w lt1171mk 150 c4 c/w 35 c/w lt1171ck 100 c4 c/w 35 c/w LT1172mk 150 c8 c/w 35 c/w LT1172ck 150 c8 c/w 35 c/w based on continuous operation. t jmax = 125 c for intermittent fault conditions. lt1170mk lt1170ck lt1171mk lt1171ck LT1172mk LT1172ck t jmax = 150 c, q ja = 100 c/w (j) t jmax = 100 c, q ja = 100 c/w (n) t jmax = 100 c, q ja = 120 c/w to 150 c/w depending on board layout (s) 1172 n8 package 8-lead pdip 1 2 3 4 8 7 6 5 top view gnd v c fb nc* e2 v sw e1 v in j8 package 8-lead cerdip s8 package 8-lead plastic so * do not connect pin 4 of the LT1172 dip or so to external circuitry. this pin may be active in future revisions. operating junction temperature range lt1170/71/72m ......................... C 55 c to 150 c lt1170/71/72hvc, lt1170/71/72c (oper.) .............. 0 c to 100 c lt1170/71/72hvc lt1170/71/72c (sh. ckt.) .......... 0 c to 125 c lt1170/71/72hvi, lt1170/71/72i (oper.) .......... C 40 c to 100 c lt1170/71/72hvi, lt1170/71/72i (sh. ckt.) ...... C 40 c to 125 c (note 1) t jmax q jc q ja lt1170ct/lt1170hvct 100 c2 c/w 75 c/w lt1171ct/lt1171hvct 100 c4 c/w 75 c/w LT1172ct/LT1172hvct 100 c8 c/w 75 c/w based on continuous operation. t jmax = 125 c for intermittent fault conditions. lt1170ct lt1170it lt1170hvct lt1170hvit lt1171ct lt1171it lt1171hvct lt1171hvit LT1172ct LT1172hvct t jmax = 100 c, q ja = 150 c/w based on continuous operation. t jmax = 125 c for intermittent fault conditions. LT1172csw order part number order part number order part number 2 4 1 3 v sw v c fb case is gnd v in k package 4-lead to-3 metal can bottom view q package 5-lead dd v in v sw gnd fb v c front view 5 4 3 2 1 order part number top view sw package 16-lead plastic so wide 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 nc nc gnd v c fb nc nc nc nc nc e2 v sw e1 v in nc nc t package 5-lead plastic to-220 v in v sw gnd fb v c front view 5 4 3 2 1 1172i lt1171hvcq lt1171hviq LT1172cq LT1172hviq c i package/order i for atio uu w absolute axi u rati gs w ww u
3 lt1170/lt1171/LT1172 symbol parameter conditions min typ max units v ref reference voltage measured at feedback pin 1.224 1.244 1.264 v v c = 0.8v 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 d i c = 25 m a 3000 4400 6000 m mho transconductance l 2400 7000 m mho error amplifier source or v c = 1.5v 150 200 350 m a sink current l 120 400 m a error amplifier clamp hi clamp, v fb = 1v 1.80 2.30 v voltage lo clamp, v fb = 1.5v 0.25 0.38 0.52 v reference voltage line 3v v in v max l 0.03 %/v regulation v c = 0.8v a v error amplifier voltage gain 0.9v v c 1.4v 500 800 v/v minimum input voltage (note 5) 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 0.4 0.45 0.54 v on feedback pin v fb flyback reference voltage i fb = 50 m a 15.0 16.3 17.6 v (note 5) l 14.0 18.0 v change in flyback reference 0.05 i fb 1ma 4.5 6.8 9 v voltage flyback reference voltage i fb = 50 m a 0.01 0.03 %/v line regulation (note 5) 7v v in v max flyback amplifier d i c = 10 m a 150 300 650 m mho transconductance (g m ) flyback amplifier source v c = 0.6v source l 15 32 70 m a and sink current i fb = 50 m asink l 25 40 70 m a bv output switch breakdown 3v v in v max , lt1170/lt1171/LT1172 l 65 90 v voltage i sw = 1.5ma lt1170hv/lt1171hv/LT1172hv l 75 90 v LT1172s8 l 60 80 v v sat output switch lt1170 l 0.15 0.24 w on resistance (note 3) lt1171 l 0.30 0.50 w LT1172 l 0.60 1.00 w control voltage to switch lt1170 8 a/v current transconductance lt1171 4 a/v LT1172 2 a/v i lim switch current limit (lt1170) duty cycle = 50% t j 3 25 c l 510a duty cycle = 50% t j < 25 c l 511a duty cycle = 80% (note 4) l 410a (lt1171) 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 4) l 2.0 5.0 a (LT1172) duty cycle = 50% t j 3 25 c l 1.25 3.0 a duty cycle = 50% t j < 25 c l 1.25 3.5 a duty cycle = 80% (note 4) l 1.00 2.5 a the l denotes the specifications which apply over the full operating tem- perature range, otherwise specifications are at t a = 25 c. v in = 15v, v c = 0.5v, v fb = v ref , output pin open, unless otherwise noted. electrical characteristics
4 lt1170/lt1171/LT1172 symbol parameter conditions min typ max units d i in supply current increase 25 35 ma/a d i sw during switch on-time f switching frequency 88 100 112 khz l 85 115 khz dc max maximum switch duty cycle l 85 92 97 % shutdown mode 3v v in v max 100 250 m a supply current v c = 0.05v shutdown mode 3v v in v max 100 150 250 mv threshold voltage l 50 300 mv flyback sense delay time (note 5) 1.5 m s transformer designs will tolerate much higher input voltages because leakage inductance limits rate of rise of current in the switch. these designs must be evaluated individually to assure that current limit is well controlled up to maximum input voltage. boost mode designs are never protected against output shorts because the external catch diode and inductor connect input to output. note 3: measured with v c in hi clamp, v fb = 0.8v. i sw = 4a for lt1170, 2a for lt1171, and 1a for LT1172. note 4: for duty cycles (dc) between 50% and 80%, minimum guaranteed switch current is given by i lim = 3.33 (2 C dc) for the lt1170, i lim = 1.67 (2 C dc) for the lt1171, and i lim = 0.833 (2 C dc) for the LT1172. note 5: minimum input voltage for isolated flyback mode is 7v. v max = 55v for hv grade in fully isolated mode to avoid switch breakdown. note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: minimum effective switch on time for the lt1170/71/72 (in current limit only) is ? 0.6 m s. this limits the maximum safe input voltage during an output shorted condition. buck mode and inverting mode input voltage during an output shorted condition is limited to: v in (max, output shorted) = 15v + buck and inverting mode r = inductor dc resistance i l = 10a for lt1170, 5a for lt1171, and 2.5a for LT1172 vf = output catch diode forward voltage at i l t = 0.6 m s, f = 100khz switching frequency maximum input voltage can be increased by increasing r or vf. external current limiting such as that shown in an19, figure 39, will provide protection up to the full supply voltage rating. c1 in figure 39 should be reduced to 200pf. switch current limit vs duty cycle* temperature ( c) ?5 minimum input voltage (v) ?5 25 50 150 1170/1/2 g02 ?0 0 75 100 125 2.9 2.8 2.7 2.6 2.5 2.4 2.3 switch current = 0a switch current = i max minimum input voltage switch saturation voltage duty cycle (%) 0 switch current (a) 16 12 8 4 0 40 1170/1/2 g01 20 30 50 60 70 80 90 100 25 c 125 c ?5 c 10 * divide vertical scale by two for lt1171, by four for LT1172. switch current (a)* 0 switch saturation voltage (v) 8 1170/1/2 g03 1 2 3 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 4567 25 c 150 c ?5 c 100 c * divide current by two for lt1171, by four for LT1172. (r)(i l ) + vf (t)(f) the l denotes the specifications which apply over the full operating tem- perature range, otherwise specifications are at t a = 25 c. v in = 15v, v c = 0.5v, v fb = v ref , output pin open, unless otherwise noted. typical perfor a ce characteristics uw electrical characteristics
5 lt1170/lt1171/LT1172 input voltage (v) 0 supply current (ma) 10 20 30 40 1170/1/2 g09 50 15 14 13 12 11 10 9 8 7 6 5 60 t j = 25 c note that this current does not include driver current, which is a function of load current and duty cycle. 90% duty cycle 50% duty cycle 10% duty cycle 0% duty cycle * under very low output current conditions, duty cycle for most circuits will approach 10% or less. supply current vs input voltage* v c pin voltage (mv) 0 supply current ( m a) 200 180 160 140 120 100 80 60 40 20 0 40 1170/1/2 g10 10 20 30 50 60 70 80 90 100 t j = 150 c ?5 c t j 125 c shutdown mode supply current temperature ( c) transconductance ( m mho) 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1170/1/2 g11 ?5 25 25 50 150 ?0 0 75 100 125 g m = d i (v c pin) d v (fb pin) error amplifier transconductance v c pin characteristics supply voltage (v) 0 supply current ( m a) 10 20 30 40 160 140 120 100 80 60 40 20 0 50 60 1170/1/2 g07 v c = 50mv v c = 0v t j = 25 c supply current vs supply voltage (shutdown mode) driver current* vs switch current switch current (a) 0 driver current (ma) 123 160 140 120 100 80 60 40 20 0 4 5 1170/1/2 g08 t j = 55 c t j = 3 25 c * average lt1170 power supply current is found by multiplying driver current by duty cycle, then adding quiescent current. v c pin voltage (v) 300 200 100 0 100 200 300 400 1170/1/2 g12 v c pin current ( m a) 0 2.0 0.5 1.0 1.5 2.5 v fb = 1.5v (current into v c pin) v fb = 0.8v (current out of v c pin) t j = 25 c reference voltage vs temperature input voltage (v) 0 reference voltage change (mv) 10 20 30 40 1170/1/2 g04 50 5 4 3 2 1 0 ? ? ? ? ? 60 t j = 150 c t j = 55 c t j = 25 c line regulation temperature ( c) reference voltage (v) 1170/1/2 g05 1.250 1.248 1.246 1.244 1.242 1.240 1.238 1.236 1.234 ?5 25 25 50 150 ?0 0 75 100 125 temperature ( c) feedback bias current (na) 1170/1/2 g06 800 700 600 500 400 300 200 100 0 ?5 25 25 50 150 ?0 0 75 100 125 feedback bias current vs temperature typical perfor a ce characteristics uw
6 lt1170/lt1171/LT1172 temperature ( c) v c pin voltage (mv) 1170/1/2 g16 400 350 300 250 200 150 100 50 0 ?5 25 25 50 150 ?0 0 75 100 125 400 350 300 250 200 150 100 ?0 0 v c pin current ( m a) current (out of v c pin) voltage v c voltage is reduced until regulator current drops below 300 m a junction temperature ( c) ?5 time ( m s) ?5 25 50 150 1170/1/2 g17 ?0 0 75 100 125 2.2 2.0 1.8 1.6 1.4 1.2 1.0 isolated mode flyback reference voltage temperature ( c) flyback voltage (v) 1170/1/2 g18 23 22 21 20 19 18 17 16 15 ?5 25 25 50 150 ?0 0 75 100 125 r fb = 500 w r fb = 1k r fb = 10k normal/flyback mode threshold on feedback pin temperature ( c) ?0 feedback pin voltage (mv) 500 490 480 470 460 450 440 430 420 410 400 0 50 75 1170/1/2 g20 ?5 25 100 125 150 ?4 ?2 ?0 ?8 ?6 ?4 ?2 ?0 ? ? ? feedback pin current ( m a) feedback pin current (at threshold) feedback pin voltage (at threshold) flyback blanking time shutdown thresholds transconductance of error amplifier frequency (hz) 1k transconductance ( m mho) 7000 6000 5000 4000 3000 2000 1000 0 1000 10k 100k 1170/1/2 g19 1m 10m ?0 0 30 60 90 120 150 180 210 phase (deg) q g m temperature ( c) idle supply current (ma) 11 10 9 8 7 6 5 4 3 2 1 1170/1/2 g13 ?5 25 25 50 150 ?0 0 75 100 125 v supply = 60v v supply = 3v v c = 0.6v feedback pin clamp voltage switch off characteristics idle supply current vs temperature feedback current (ma) 0 feedback voltage (mv) 500 450 400 350 300 250 200 150 100 50 0 0.4 1170/1/2 g14 0.1 0.2 0.3 0.5 0.6 0.7 0.8 0.9 1.0 ?5 c 25 c 150 c switch voltage (v) 0 switch current ( m a) 1000 900 800 700 600 500 400 300 200 100 0 40 1170/1/2 g15 10 20 30 50 60 70 80 90 100 v supply = 55v v supply = 3v v supply = 15v v supply = 40v typical perfor a ce characteristics uw
7 lt1170/lt1171/LT1172 1.24v ref 1170/1/2 bd error amp 100khz osc 2.3v reg v in fb + + shutdown circuit v c comp logic driver anti- sat flyback error amp 16v switch out 5a, 75v switch 0.02 (0.04 (0.16 w w lt1171) w LT1172) 0.16 w current amp gain 6 ? 0.15v always connect e1 to the ground pin on minidip, 8- and 16-pin surface mount packages. e1 and e2 internally tied to ground on to-3 and to-220 packages. ? mode select e1 ? e2 (lt1170 and lt1171 only) LT1172 the lt1170/lt1171/LT1172 are current mode switchers. 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 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 midfrequencies in the energy storage inductor. this greatly simplifies closed- loop frequency compensation under widely varying input voltage or output load conditions. finally, it allows simple pulse-by-pulse current limiting to provide maximum switch protection under output overload or short conditions. a low dropout internal regulator provides a 2.3v supply for all internal circuitry on the lt1170/lt1171/LT1172. this low dropout design allows input voltage to vary from 3v to 60v with virtually no change in device performance. a 100khz oscillator is the basic clock for all internal timing. it turns on the output switch via the logic and driver circuitry. special adaptive anti-sat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. this minimizes 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 operatio u block diagra w
8 lt1170/lt1171/LT1172 function; when pulled low with an external resistor, it programs the lt1170/lt1171/LT1172 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. the lt1170/ lt1171/LT1172 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 regula- tor. by regulating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection between input and output. the output is fully floating up to the breakdown voltage of the transformer windings. mul- tiple floating outputs are easily obtained with additional windings. a special delay network inside the lt1170/ lt1171/LT1172 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 lt1170/lt1171/LT1172 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. extra pins on the minidip and surface mount packages the 8- and 16-pin versions of the LT1172 have the emitters of the power transistor brought out separately from the ground pin. this eliminates errors due to ground pin voltage drops and allows the user to reduce switch current limit 2:1 by leaving the second emitter (e2) discon- nected. the first emitter (e1) should always be connected to the ground pin. note that switch on resistance doubles when e2 is left open, so efficiency will suffer somewhat when switch currents exceed 300ma. also, note that chip dissipation will actually increase with e2 open during normal load operation, even though dissipation in current limit mode will decrease . see thermal considerations next. thermal considerations when using the minidip and sw packages the low supply current and high switch efficiency of the LT1172 allow it to be used without a heat sink in most applications when the to-220 or to-3 package is se- lected. these packages are rated at 50 c/w and 35 c/w respectively. the minidips, however, are rated at 100 c/w in ceramic (j) and 130 c/w in plastic (n). care should be taken for minidip applications to ensure that the worst case input voltage and load current condi- tions do not cause excessive die temperatures. the follow- ing formulas can be used as a rough guide to calculate LT1172 power dissipation. for more details, the reader is referred to application note 19 (an19), efficiency calcu- lations section. average supply current (including driver current) is: i in ? 6ma + i sw (0.004 + dc/40) i sw = switch current dc = switch duty cycle switch power dissipation is given by: p sw = (i sw ) 2 ? (r sw )(dc) r sw = LT1172 switch on resistance (1 w maximum) total power dissipation is the sum of supply current times input voltage plus switch power: p d(tot) = (i in )(v in ) + p sw in a typical example, using a boost converter to generate 12v at 0.12a from a 5v input, duty cycle is approximately 60%, and switch current is about 0.65a, yielding: i in = 6ma + 0.65(0.004 + dc/40) = 18ma p sw = (0.65) 2 ? (1 w )(0.6) = 0.25w p d(tot) = (5v)(0.018a) + 0.25 = 0.34w *see note under block diagram. operatio u
9 lt1170/lt1171/LT1172 temperature rise in a plastic minidip would be 130 c/w times 0.34w, or approximately 44 c. the maximum am- bient temperature would be limited to 100 c (commercial temperature limit) minus 44 c, or 56 c. in most applications, full load current is used to calculate die temperature. however, if overload conditions must also be accounted for, four approaches are possible. first, if loss of regulated output is acceptable under overload conditions, the internal thermal limit of the LT1172 will protect the die in most applications by shutting off switch current. thermal limit is not a tested parameter , however, and should be considered only for noncritical applications with temporary overloads. a second approach is to use the larger to-220 (t) or to-3 (k) package which, even without a heat sink, may limit die temperatures to safe levels under overload conditions. in critical situations, heat sinking of these packages is required; especially if overload condi- tions must be tolerated for extended periods of time. the third approach for lower current applications is to leave the second switch emitter (minidip only) open. this increases switch on resistance by 2:1, but reduces switch current limit by 2:1 also, resulting in a net 2:1 reduction in i 2 r switch dissipation under current limit conditions. the fourth approach is to clamp the v c pin to a voltage less than its internal clamp level of 2v. the LT1172 switch current limit is zero at approximately 1v on the v c pin and 2a at 2v on the v c pin. peak switch current can be externally clamped between these two levels with a diode. see an19 for details. lt1170/lt1171/LT1172 synchronizing the lt1170/lt1171/LT1172 can be externally synchro- nized in the frequency range of 120khz to 160khz. this is accomplished as shown in the accompanying figures. synchronizing occurs when the v c pin is pulled to ground with an external transistor. to avoid disturbing the dc characteristics of the internal error amplifier, the width of the synchronizing pulse should be under 0.3 m s. c2 sets the pulse width at @ 0.2 m s. the effect of a synchronizing pulse on the lt1170/lt1171/LT1172 amplifier offset can be calculated from: kt = 26mv at 25 c q t s = pulse width f s = pulse frequency i c =v c source current ( ? 200 m a) v c = operating v c voltage (1v to 2v) r3 = resistor used to set mid-frequency zero in frequency compensation network. with t s = 0.2 m s, f s = 150khz, v c = 1.5v, and r3 = 2k, offset voltage shift is ? 3.8mv. this is not particularly bother- some, but note that high offsets could result if r3 were reduced to a much lower value. also, the synchronizing transistor must sink higher currents with low values of r3, so larger drives may have to be used. the transistor must be capable of pulling the v c pin to within 200mv of ground to ensure synchronizing. synchronizing with mos transistor synchronizing with bipolar transistor d v kt q tfi v r i os ssc c c = ? ? ? ? ()() + ? ? ? ? 3 1170/1/2 op01 c2 39pf r1 3k r2 2.2k lt1170 gnd v in v c c1 r3 2n2369 from 5v logic 1170/1/2 op02 d1 1n4158 r2 2.2k lt1170 gnd v in v c c1 r3 from 5v logic c2 100pf d2 1n4158 * siliconix or equivalent vn2222* operatio u
10 lt1170/lt1171/LT1172 flyback converter lcd contrast supply 1170/1/2 ta03 d1 c1 2000 m f c4* 100 m f c2 0.15 m f r1 3.74k r2 1.24k v in 20v to 30v r3 1.5k *required if input leads 3 2" lt1170 v in v sw fb v c optional filter l2 5 m h c4 100 m f v out 5v 6a v snub clamp turn-on spike primary flyback voltage = lt1170 switch voltage area ??= area b?to maintain zero dc volts across primary secondary voltage area ??= area ??to maintain zero dc volts across secondary primary current secondary current lt1170 switch current snubber diode current v out + v f n 0v v in a b 0v c d v out + v f n v in d i i pri 0 i pri /n i pri i pri t = (i pri )(l l ) v snub 0 0 0 1 n* = 1/3 n* d3 25v 1w d2 mur110 gnd + + c4 0.047 m f v out 10v to 26v 1170/1/2 ta04 r3 15k optional shutdown r2 100k r1 200k c1 1 m f tantalum d1 1n914 c3 0.0047 m f c2*** 2 m f tantalum d2 vn2222 5v* l1** 50 m h v bat * 3v to 20v v in v c fb v sw LT1172 e2 e1 gnd d3 * ** *** d2, d3 = er82.004 600ma schottky. other fast switching types may be used. v in and battery may be tied together. maximum value for v bat is equal to the ? negative output ? + 1v. with higher battery voltages, highest efficiency is obtained by running the LT1172 v in pin from 5v. shutting off the 5v supply will automatically turn off the LT1172. efficiency is about 80% at i out = 25ma. r1, r2, r3 are made large to minimize battery drain in shutdown, which is approximately v bat /(r1 + r2 + r3). for high efficiency, l1 should be made on a ferrite or molypermalloy core. peak inductor currents are about 600ma at p out = 0.7 w . inductor series resistance should be less than 0.4 w for high efficiency. output ripple is about 200mv p-p to 400mv p-p with c2 = 2 m f tantalum. if lower ripple is desired, increase c2, or add a 10 w , 1 m f tantalum output filter. + + typical applicatio s u
11 lt1170/lt1171/LT1172 negative-to-positive buck-boost converter ? driving high voltage fet (for off-line applications, see an25) (note that maximum output currents are divided by 2 for lt1171, by 4 for LT1172.) negative buck converter external current limit external current limit 1170/1/2 ta05 v in v sw lt1170 gnd 10v to 20v d1 + d g q1 1170/1/2 ta06 v x d1 lt1170 gnd r2 ? 2v v c r1 500 w c4* 100 m f v out 12v 2a 1170/1/2 ta07 r3 2.2k c2 1000 m f d1 c1 0.22 m f q1 v in v c fb v sw lt1170 gnd optional input filter l3 v in 20v required if input leads 3 2" pulse engineering 92114, coiltronics 50-2-52 * ** r2 1.24k l1** 50 m h optional output filter c3 l2 r1 11.3k this circuit is often used to convert 48v to 5v. to guarantee full short-circuit protection, the current limit circuit shown in an19, figure 39, should be added with c1 reduced to 200pf. ? + + 1170/1/2 ta08 r2 c2 v in v c fb v sw lt1170 gnd v in note that the lt1170 gnd pin is no longer common to v in . r1 1k + c1 1000pf q1 r s c3* 100 m f 5.2v 4.5a 1170/1/2 ta09 r3 l1** 50 m h r1 4.64k c2 1000 m f d1 c1 q1 2n3906 v in v c fb v sw lt1170 gnd optional input filter l3 v in 20v load required if input leads 3 2" pulse engineering 92114 coiltronics 50-2-52 * ** r2 1.24k r4 12k l2 4 m h optional output filter c4 200 m f + + + typical applicatio s u
12 lt1170/lt1171/LT1172 positive-to-negative buck-boost converter high efficiency constant current charger backlight ccfl supply (see an45 for details) c4 1 m f v in 10v to 30v 1170/1/2 ta10 r3 5k c5 100 m f* d3 ? 1n4001 c2 0.1 m f v in v c fb v sw lt1170 gnd v out ?2v 2a required if input leads 3 2" pulse engineering 92114, coiltronics 50-2-52 * ** r2 1.24k l1** 50 m h r5 ? 470 w , 1w to avoid startup 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 . ? c3 2 m f d2 1n914 r4 47 w c1 ? 1000 m f d1 r6 470 w r1 10.7k + + + + d2 mbr340 1170/1/2 ta11 input voltage > v bat + 2v < 35v c2 2.2 m f 35v tantalum r7 22k r8 1k c3 0.47 m f v + v r4 1k c4 200 m f 25v battery 2v to 25v l2* 10 m h, 1a l1 100 m h, 1a r5 0.05 w r3 25k r2 1k run = 0v shutdown = 5v * l2 reduces ripple current into the battery by about 20 :1. it may be omitted if desired. i = 1.244v ?r4 r3 ?r5 = 1a as shown chrg r6 78k v in c v fb v sw gnd d1 1n5819 c4 0.01 m f lt1006 + + lt1171 c1 200 m f 35v 1a 2n3904 + + + + gnd 2 m f 1170/1/2 ta12 d1 1n914 33pf 3kv 10 m f tant r3 10k 50k intensity adjust 1n5818 l1** 300 m h input voltage ? 4.5v to 20v q1,q2 = bcp56 or mps650/561 coiltronics ctx300-4 sumida 6345-020 or coiltronics 110092-1 a modification will allow operation down to 4.5v. consult factory. * ** *** ? c6 1 f m r1 560 w 1k LT1172 in v v c v sw e2 e1 d2 1n914 lamp fb l2*** 0.02 m f a b q1* q2* + + typical applicatio s u
13 lt1170/lt1171/LT1172 positive buck converter negative boost regulator driving high voltage npn c5* 100 m f v in 1170/1/2 ta13 r3 470 w 5v, 4.5a d2 1n914 c1 1 m f v in v c fb v sw lt1170 gnd required if input leads 3 2" pulse engineering 92114 coiltronics 50-2-52 * ** r1 3.74k l1** 50 m h r4 10 w c3 2.2 m f d1 r r2 1.24k c2 1 m f c4 1000 m f 100ma minimum d3 optional output filter c5 200 m f l2 4 m h + + + + c4* 470 m f 1170/1/2 ta14 r3 3.3k c3 10 m f d1 c2 0.22 m f v in v c fb lt1170 gnd v in 15v required if input leads 3 2" * r2 1.24k d2 r1 27k v sw l1 50 m h c1 1000 m f r o (minimum load) v out 28v, 1a + + + 1170/1/2 ta15 d2 c1 sets i b (on) sets i b (off) * ** r2** v in v sw lt1170 gnd d1 q1 r1* typical applicatio s u
14 lt1170/lt1171/LT1172 high efficiency 5v buck converter forward converter 1170/1/2 ta16 c1 2000 m f c3 r4 r2 1.24k v in 20v to 30v r3 lt1170 v in v sw fb v c 1 n d3 l1 25 m h c4 r6 330 w r5 1 w c2 m d2 d1 v out 5v, 6a t1 q1 d4 r1 3.74k gnd + + v sw fb gnd v in v c lt1170 + c1 330 m f 35v c6 0.02 m f c4 0.1 m f r1 680 w c5 0.03 m f d1 mbr330p c3 4.7 m f tant d2 1n4148 l1 50 m h r2* 0.013 w c2 390 m f 16v v out 5v 3a** + mode logic 220pf <0.3v = normal mode >2.5v = shutdown open = burst mode * r2 is made from pc board copper traces. ** maximum current is determined by the choice of lt1070 family. see application section. v in 1170/1/2 ta17 optional output filter 100 m f 16v 10 m h 3a + v c gnd mode diode v out v lim v + lt1432 v in typical applicatio s u
15 lt1170/lt1171/LT1172 j8 package 8-lead cerdip (narrow 0.300, hermetic) (ltc dwg # 05-08-1110) j8 1298 0.014 ?0.026 (0.360 ?0.660) 0.200 (5.080) max 0.015 ?0.060 (0.381 ?1.524) 0.125 3.175 min 0.100 (2.54) bsc 0.300 bsc (0.762 bsc) 0.008 ?0.018 (0.203 ?0.457) 0 ?15 0.005 (0.127) min 0.405 (10.287) max 0.220 ?0.310 (5.588 ?7.874) 12 3 4 87 65 0.025 (0.635) rad typ 0.045 ?0.068 (1.143 ?1.727) full lead option 0.023 ?0.045 (0.584 ?1.143) half lead option corner leads option (4 plcs) 0.045 ?0.065 (1.143 ?1.651) note: lead dimensions apply to solder dip/plate or tin plate leads dimensions in inches (millimeters) unless otherwise noted. u package descriptio
16 lt1170/lt1171/LT1172 n8 package 8-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) k package 4-lead to-3 metal can (ltc dwg # 05-08-1311) k4(to-3) 1098 72 18 0.490 ?0.510 (12.45 ?12.95) 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) n8 1098 0.100 (2.54) bsc 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.130 0.005 (3.302 0.127) 0.020 (0.508) min 0.018 0.003 (0.457 0.076) 0.125 (3.175) min 12 3 4 87 6 5 0.255 0.015* (6.477 0.381) 0.400* (10.160) max 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.325 (7.620 ?8.255) 0.325 +0.035 0.015 +0.889 0.381 8.255 () *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.254mm) dimensions in inches (millimeters) unless otherwise noted. u package descriptio
17 lt1170/lt1171/LT1172 q package 5-lead plastic dd pak (ltc dwg # 05-08-1461) q(dd5) 1098 0.028 ?0.038 (0.711 ?0.965) 0.143 +0.012 0.020 () 3.632 +0.305 0.508 0.067 (1.70) bsc 0.013 ?0.023 (0.330 ?0.584) 0.095 ?0.115 (2.413 ?2.921) 0.004 +0.008 0.004 () 0.102 +0.203 0.102 0.050 0.012 (1.270 0.305) 0.059 (1.499) typ 0.045 ?0.055 (1.143 ?1.397) 0.165 ?0.180 (4.191 ?4.572) 0.330 ?0.370 (8.382 ?9.398) 0.060 (1.524) typ 0.390 ?0.415 (9.906 ?10.541) 15 typ 0.300 (7.620) 0.075 (1.905) 0.183 (4.648) 0.060 (1.524) 0.060 (1.524) 0.256 (6.502) bottom view of dd pak hatched area is solder plated copper heat sink s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 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 1298 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) typ 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) bsc 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) 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 * ** dimensions in inches (millimeters) unless otherwise noted. u package descriptio
18 lt1170/lt1171/LT1172 sw package 16-lead plastic small outline (wide 0.300) (ltc dwg # 05-08-1620) s16 (wide) 1098 note 1 0.398 ?0.413* (10.109 ?10.490) 16 15 14 13 12 11 10 9 1 23 4 5 6 78 0.394 ?0.419 (10.007 ?10.643) 0.037 ?0.045 (0.940 ?1.143) 0.004 ?0.012 (0.102 ?0.305) 0.093 ?0.104 (2.362 ?2.642) 0.050 (1.270) bsc 0.014 ?0.019 (0.356 ?0.482) typ 0 ?8 typ note 1 0.009 ?0.013 (0.229 ?0.330) 0.016 ?0.050 (0.406 ?1.270) 0.291 ?0.299** (7.391 ?7.595) 45 0.010 ?0.029 (0.254 ?0.737) note: 1. pin 1 ident, notch on top and cavities on the bottom of packages are the manufacturing options. the part may be supplied with or without any of the options 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 * ** dimensions in inches (millimeters) unless otherwise noted. u package descriptio
19 lt1170/lt1171/LT1172 dimensions in inches (millimeters) unless otherwise noted. t package 5-lead plastic to-220 (standard) (ltc dwg # 05-08-1421) t5 (to-220) 0399 0.028 ?0.038 (0.711 ?0.965) 0.067 (1.70) 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) bsc seating plane * measured at the seating plane i nformation 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. u package descriptio
20 lt1170/lt1171/LT1172 ? linear technology corporation 1991 117012fes, sn117012 lt/tp 1299 2k rev e ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 l (408) 432-1900 fax: (408) 434-0507 l telex: 499-3977 l www.linear-tech.com part number description comments lt1070/lt1071/lt1072 5a/2.5a/1.25a high efficiency switching regulators 40khz, v in to 60v, v sw to 75v lt1074/lt1076 5.5a/2a step-down switching regulators 100khz, also for positive-to-negative conversion lt1082 1a, high voltage, high efficiency switching regulator v in to 75v, v sw to 100v, telecom lt1268/lt1268b 7.5a, 150khz switching regulators v in to 30v, v sw to 60v lt1269/lt1271 4a high efficiency switching regulators 100khz/60khz, v in to 30v, v sw to 60v lt1270/lt1270a 8a and 10a high efficiency switching regulators 60khz, v in to 30v, v sw to 60v lt1370 500khz high efficiency 6a switching regulator high power boost, flyback, sepic lt1371 500khz high efficiency 3a switching regulator good for boost, flyback, inverting, sepic lt1372/lt1377 500khz and 1mhz high efficiency 1.5a switching regulators directly regulates v out lt1373 250khz low supply current high efficiency 1.5a switching regulator low 1ma quiescent current lt1374 4a, 500khz step-down switching regulator synchronizable, v in to 25v lt1375/lt1376 1.5a, 500khz step-down switching regulators up to 1.25a out from an so-8 lt1425 isolated flyback switching regulator 6w output, 5% regulation, no optocoupler needed lt1507 500khz monolithic buck mode switching regulator 1.5a switch, good for 5v to 3.3v lt1533 ultralow noise 1a switching regulator push-pull, <100 m v p-p output noise related parts positive current boosted buck converter 1170/1/2 ta18 c1 0.33 m f 470 w 2w r7 1k v in 28v r3 680 w lt1170 v in v sw fb v c 1: n d2 r2 1.24k c3 0.47 m f d1 v out 5v, 10 a n ? 0.25 r4 1.24k gnd c5* 100 m f r6 470 w c6 0.002 m f + c4 0.01 m f 7 v in 6 4 8 200pf 2 3 r5 5k r1 5k c2 5000 m f * required if input leads 3 2" lm308 + + u typical applicatio

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