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lt1170/lt1171/lt1172 1 117012fh for more information www.linear.com/lt1170 typical application features description 100khz, 5a, 2.5a and 1.25a high efficiency switching regulators 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 efficiency switch is included on the die along with all oscillator, con - trol 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 voltages from 3v to 60v, and draw only 6ma quiescent current. they can deliver load power up to 100w with no exter - nal power devices. by utilizing current-mode switching 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 currents with no loss in efficiency. an externally activated shutdown mode reduces total supply current to 50a typically for standby operation. l , lt, ltc, ltm, linear technology, the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. boost converter (5v to 12v) applications n wide input voltage range: 3v to 60v n low quiescent current: 6ma n internal 5a switch (2.5a for lt1171, 1.25a for lt1172) n shutdown mode draws only 50a 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 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 is also available. maximum output power* 1170/1/2 ta01 d1 mbr330 c21000f c11f r110.7k 1% r21.24k 1% lt1170 gnd v in 5v r31k *required if input leads ? 2" ** coiltronics 50-2-52 pulse engineering 92114 v sw fb v c output filter l2 10h l1** 50 h c3 100f 12v1a c3*100f + + input voltage (v) 0 power (w) ** 100 8060 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-boostv o = 30v flyback buck-boost v o = 5v lt1170 downloaded from: http:///
lt1170/lt1171/lt1172 2 117012fh for more information www.linear.com/lt1170 absolute maximum ratings supply voltage lt1170/lt1171/lt1172hv (note 2) ....................... 60v lt1170/lt1171/lt1172 (note 2) ............................ 40v switch output voltage lt1170/lt1171/lt1172hv ..................................... 75v lt1170/lt1171/lt1172 ......................................... 65v lt1172s8 .............................................................. 60v feedback pin voltage (transient, 1ms) ................... 15v storage temperature range .................. C65c to 150c lead temperature (soldering, 10 sec .................... 300c (note 1) pin configuration operating junction temperature range lt1170m/lt1171m (obsolete) ....... C55c to 150c lt1172m ............................................ C55c to 125c lt1170/lt1171/lt1172hvc, lt1170/lt1171/lt1172c (oper.) ............. 0c to 100c lt1170/lt1171/lt1172hvc lt1170/lt1171/lt1172c (sh. ckt.) ........ 0c to 125c lt1170/lt1171/lt1172hvi, lt1170/lt1171/lt1172i (oper.) .......... C40c to 100c lt1170/lt1171/lt1172hvi, lt1170/lt1171/lt1172i (sh. ckt.) ...... C40c to 125c 12 3 4 87 6 5 top view gnd v c fb nc* e2v sw e1v in j8 package 8-lead cerdip t jmax = 125c, ja = 100c/w * do not connect pin 4 of the lt1172 dip or so to external circuitry. this pin may be active in future revisions. 2 4 1 3 v sw v c fb case is gnd v in k package 4-lead to-3 metal can bottom view lt1170mk: t jmax = 150c, jc = 2c/w, ja = 35c/w lt1170ck: t jmax = 100c, jc = 2c/w, ja = 35c/w lt1171mk: t jmax = 150c, jc = 4c/w, ja = 35c/w lt1171ck: t jmax = 100c, jc = 4c/w, ja = 35c/w lt1172mk: t jmax = 150c, jc = 8c/w, ja = 35c/w lt1172ck: t jmax = 100c, jc = 8c/w, ja = 35c/w based on continuous operation. t jmax = 125c for intermittent fault conditions. obsolete n8 package 8-lead pdip 12 3 4 87 6 5 top view gnd v c fb nc* e2v sw e1v in s8 package 8-lead plastic so t jmax = 100c, ja = 100c/w (n) t jmax = 100c, ja = 120c/w to 150c/w depending on board layout (s) * do not connect pin 4 of the lt1172 dip or so to external circuitry. this pin may be active in future revisions. q package 5-lead dd v in v sw gndfb v c front view 54 3 2 1 t jmax = 100c, ja = *c/w * will vary from approximately 25c/w with 2.8 sq. in. of 1oz. copper to 45c/w with 0.20 sq. in. of 1oz. copper. somewhat lower values can be obtained with additional copper layers in multilayer boards. top view sw package 16-lead plastic so wide 12 3 4 5 6 7 8 1615 14 13 12 11 10 9 ncnc gnd v c fb ncnc nc ncnc e2 v sw e1v in ncnc t jmax = 100c, ja = 150c/w based on continuous operation. t jmax = 125c for intermittent fault conditions. t package 5-lead plastic to-220 v in v sw gndfb v c front view 54 3 2 1 lt1170ct/lt1170hvct: t jmax =100c, jc = 2c/w, ja = 75c/w lt1171ct/lt1171hvct: t jmax =100c, jc = 4c/w, ja = 75c/w lt1172ct/lt1172hvct: t jmax =100c, jc = 8c/w, ja = 75c/w based on continuous operation. t jmax = 125c for intermittent fault conditions. downloaded from: http:///
lt1170/lt1171/lt1172 3 117012fh for more information www.linear.com/lt1170 order information lead free finish tape and reel part marking* package description temperature range lt1172mj8 lt1172mj8#tr lt1172 8-lead cerdip C55c to 125c lt1172cj8#pbf (obsolete) lt1172cj8#trpbf 8-lead cerdip 0c to 100c lt1170mk#pbf (obsolete) lt1170mk#trpbf 4-lead to-3 metal can C55c to 125c lt1170ck#pbf (obsolete) lt1170ck#trpbf 4-lead to-3 metal can 0c to 100c lt1171mk#pbf (obsolete) lt1171mk#trpbf 4-lead to-3 metal can C55c to 125c lt1171ck#pbf (obsolete) lt1171ck#trpbf 4-lead to-3 metal can 0c to 100c lt1172mk#pbf (obsolete) lt1172mk#trpbf 4-lead to-3 metal can C55c to 125c lt1172ck#pbf (obsolete) lt1172ck#trpbf 4-lead to-3 metal can 0c to 100c lt1172cn8#pbf lt1172cn8#trpbf lt1172 8-lead pdip or 8-lead plastic so 0c to 100c lt1172in8#pbf lt1172in8#trpbf lt1172 8-lead pdip or 8-lead plastic so C40c to 100c lt1172cs8#pbf lt1172cs8#trpbf 1172 8-lead pdip or 8-lead plastic so 0c to 100c lt1172is8#pbf lt1172is8#trpbf 1172i 8-lead pdip or 8-lead plastic so C40c to 100c lt1170cq#pbf lt1170cq#trpbf lt1170 5-lead dd 0c to 100c lt1170iq#pbf lt1170iq#trpbf lt1170 5-lead dd C40c to 100c lt1170hvcq#pbf lt1170hvcq#trpbf lt1170hv 5-lead dd 0c to 100c lt1171cq#pbf lt1171cq#trpbf lt1171 5-lead dd 0c to 100c lt1171iq#pbf lt1171iq#trpbf lt1171 5-lead dd C40c to 100c lt1171hvcq#pbf lt1171hvcq#trpbf lt1171hv 5-lead dd 0c to 100c lt1171hviq#pbf lt1171hviq#trpbf lt1171hv 5-lead dd C40c to 100c lt1172cq#pbf lt1172cq#trpbf lt1172 5-lead dd 0c to 100c lt1172hvcq#pbf lt1172hvcq#trpbf lt1172hv 5-lead dd 0c to 100c lt1172hviq#pbf lt1172hviq#trpbf lt1172hv 5-lead dd C40c to 100c lt1172csw#pbf lt1172csw#trpbf lt1172csw 16-lead plastic so wide 0c to 100c lt1170ct#pbf lt1170cq#trpbf lt1170 5-lead plastic to-220 0c to 100c lt1170it#pbf lt1170it#trpbf lt1170 5-lead plastic to-220 C40c to 100c lt1170hvct#pbf lt1170hvct#trpbf lt1170hv 5-lead plastic to-220 0c to 100c lt1170hvit#pbf lt1170hvit#trpbf lt1170 5-lead plastic to-220 C40c to 100c lt1171ct#pbf lt1171ct#trpbf lt1171 5-lead plastic to-220 0c to 100c lt1171it#pbf lt1171it#trpbf lt1171 5-lead plastic to-220 C40c to 100c lt1171hvct#pbf lt1171hvct#trpbf lt1171hv 5-lead plastic to-220 0c to 100c lt1171hvit#pbf lt1171hvit#trpbf lt1171hv 5-lead plastic to-220 C40c to 100c lt1172ct#pbf lt1172ct#trpbf lt1172 5-lead plastic to-220 0c to 100c lt1172hvct#pbf lt1172hvct#trpbf lt1172hv 5-lead plastic to-220 0c to 100c consult ltc marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ . some packages are available in 500 unit reels through designated sales channels with #trmpbf suffix. http://www.linear.com/product/lt1170#orderinfo downloaded from: http:///
lt1170/lt1171/lt1172 4 117012fh for more information www.linear.com/lt1170 electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v in = 15v, v c = 0.5v, v fb = v ref , output pin open, unless otherwise noted. symbol parameter conditions min typ max units v ref reference voltage measured at feedback pin v c = 0.8v l 1.224 1.214 1.244 1.244 1.264 1.274 v v i b feedback input current v fb = v ref l 350 750 1100 na na g m error amplifier transconductance ?i c = 25a l 3000 2400 4400 6000 7000 mho mho error amplifier source or sink current v c = 1.5v l 150 120 200 350 400 a a error amplifier clamp voltage hi clamp, v fb = 1v lo clamp, v fb = 1.5v 1.80 0.25 0.38 2.30 0.52 v 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 (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 l 0.8 0.6 0.9 1.08 1.25 v v normal/flyback threshold on feedback pin 0.4 0.45 0.54 v v fb flyback reference voltage (note 5) i fb = 50a l 15.0 14.0 16.3 17.6 18.0 v v change in flyback reference voltage 0.05 i fb 1ma 4.5 6.8 9 v flyback reference voltage line regulation (note 5) i fb = 50a 7v v in v max 0.01 0.03 %/v flyback amplifier transconductance (g m ) ?i c = 10a 150 300 650 mho flyback amplifier source and sink current v c = 0.6v source i fb = 50a sink l l 15 25 32 40 70 70 ma ma bv output switch breakdown voltage 3v v in v max , lt1170/lt1171/lt1172 i sw = 1.5ma lt1170hv/lt1171hv/lt1172hv lt1172s8 l l l 65 75 60 90 90 80 v v v v sat output switch on resistance (note 3) lt1170 lt1171 lt1172 l l l 0.15 0.30 0.60 0.24 0.50 1.00 control voltage to switch current t ransconductance lt1170 lt1171 lt1172 8 4 2 a/v a/v a/v i lim switch current limit (lt1170) duty cycle = 50% t j 25c duty cycle = 50% t j < 25c duty cycle = 80% (note 4) l l l 5 5 4 10 11 10 a a a (lt1171) duty cycle = 50% t j 25c duty cycle = 50% t j < 25c duty cycle = 80% (note 4) l l l 2.5 2.5 2.0 5.0 5.5 5.0 a a a (lt1172) duty cycle = 50% t j 25c duty cycle = 50% t j < 25c duty cycle = 80% (note 4) l l l 1.25 1.25 1.00 3.0 3.5 2.5 a a a ?i in ?i sw supply current increase during switch on-time 25 35 ma/a f switching frequency l 88 85 100 112 115 khz khz downloaded from: http:///
lt1170/lt1171/lt1172 5 117012fh for more information www.linear.com/lt1170 symbol parameter conditions min typ max units dc max maximum switch duty cycle l 85 92 97 % shutdown mode supply current 3v v in v max v c = 0.05v 100 250 a shutdown mode threshold voltage 3v v in v max l 100 50 150 250 300 mv mv flyback sense delay time (note 5) 1.5 s electrical characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. v in = 15v, v c = 0.5v, v fb = v ref , output pin open, unless otherwise noted. note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: minimum effective switch on time for the lt1170/lt1171/ lt1172 (in current limit only) is 0.6s. 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 + r ( ) i l ( ) + vf t ( ) f ( ) buck and inverting moder = 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 = 0.6s, 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. 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. downloaded from: http:///
lt1170/lt1171/lt1172 6 117012fh for more information www.linear.com/lt1170 typical performance characteristics line regulation reference voltage vs temperature feedback bias current vs temperature supply current vs supply voltage (shutdown mode) driver current* vs switch current supply current vs input voltage* switch current limit vs duty cycle* minimum input voltage switch saturation voltage duty cycle (%) 0 switch current (a) 16 12 84 0 40 1170/1/2 g01 20 30 50 60 70 80 90 100 25c 125c C55c 10 * divide vertical scale by two for lt1171, by four for lt1172. temperature (c) C75 minimum input voltage (v) C25 25 50 150 1170/1/2 g02 C50 0 75 100 125 2.92.8 2.7 2.6 2.5 2.4 2.3 switch current = 0a switch current = i max switch current (a)* 0 switch saturation voltage (v) 8 1170/1/2 g03 1 2 3 1.6 1.41.2 1.0 0.8 0.6 0.4 0.2 0 4 5 6 7 25c 150c C55c 100c * divide current by two for lt1171, by four for lt1172. input voltage (v) 0 reference voltage change (mv) 10 20 30 40 1170/1/2 g04 50 54 3 2 1 0 C1C2 C3 C4 C5 60 t j = 150c t j = C55c t j = 25c temperature (c) reference voltage (v) 1170/1/2 g05 1.250 1.2481.246 1.244 1.242 1.240 1.238 1.236 1.234 C75 C25 25 50 150 C50 0 75 100 125 temperature (c) feedback bias current (na) 1170/1/2 g06 800 700600 500 400 300 200 100 0 C75 C25 25 50 150 C50 0 75 100 125 supply voltage (v) 0 supply current (a) 10 20 30 40 160 140120 100 8060 40 20 0 50 60 1170/1/2 g07 v c = 50mv v c = 0v t j = 25c switch current (a) 0 driver current (ma) 1 2 3 160 140120 100 8060 40 20 0 4 5 1170/1/2 g08 t j = C55c t j = 25c * average lt1170 power supply current is found by multiplying driver current by duty cycle, then adding quiescent current. input voltage (v) 0 supply current (ma) 10 20 30 40 1170/1/2 g09 50 1514 13 12 11 10 98 7 6 5 60 t j = 25c note that this current does notinclude 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. downloaded from: http:///
lt1170/lt1171/lt1172 7 117012fh for more information www.linear.com/lt1170 typical performance characteristics idle supply current vs temperature feedback pin clamp voltage switch ?off? characteristics shutdown thresholds flyback blanking time isolated mode flyback reference voltage shutdown mode supply current error amplifier transconductance vc pin characteristics v c pin voltage (mv) 0 supply current (a) 200180 160 140 120 100 8060 40 20 0 40 1170/1/2 g10 10 20 30 50 60 70 80 90 100 t j = 150c ?55c t j 125c temperature (c) transconductance (mho) 50004500 4000 3500 3000 2500 2000 1500 1000 500 0 1170/1/2 g11 C75 C25 25 50 150 C50 0 75 100 125 g m = ? i (v c pin) ? v (fb pin) v c pin voltage (v) 300 200100 0 C100C200 C300 C400 1170/1/2 g12 v c pin current (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 = 25c temperature (c) idle supply current (ma) 11 10 98 7 6 5 4 3 2 1 1170/1/2 g13 C75 C25 25 50 150 C50 0 75 100 125 v supply = 60v v supply = 3v v c = 0.6v feedback current (ma) 0 feedback voltage (mv) 500 450400 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 C55c 25c 150c switch voltage (v) 0 switch current (a) 1000 900800 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 temperature (c) v c pin voltage (mv) 1170/1/2 g16 400350 300 250 200 150 100 50 0 C75 C25 25 50 150 C50 0 75 100 125 C400C350 C300 C250 C200 C150 C100 C50 0 v c pin current (a) current (out of v c pin) voltage v c voltage is reduced until regulator current drops below 300a junction temperature (c) C75 time (s) C25 25 50 150 1170/1/2 g17 C50 0 75 100 125 2.22.0 1.8 1.6 1.4 1.2 1.0 temperature (c) flyback voltage (v) 1170/1/2 g18 23 2221 20 19 18 17 16 15 C75 C25 25 50 150 C50 0 75 100 125 r fb = 500 r fb = 1k r fb = 10k downloaded from: http:///
lt1170/lt1171/lt1172 8 117012fh for more information www.linear.com/lt1170 typical performance characteristics block diagram frequency (hz) 1k transconductance (mho) 70006000 5000 4000 3000 2000 1000 0 C1000 10k 100k 1170/1/2 g19 1m 10m C300 30 60 90 120 150 180 210 phase (deg) g m temperature (c) C50 feedback pin voltage (mv) 500490 480 470 460 450 440 430 420 410 400 0 50 75 1170/1/2 g20 C25 25 100 125 150 C24C22 C20 C18 C16 C14 C12 C10 C8 C6 C4 feedback pin current (a) feedback pin current (at threshold) feedback pin voltage (at threshold) transconductance of error amplifier normal/flyback mode threshold onfeedback pin 1.24v ref 1170/1/2 bd error amp 100khz osc 2.3v reg v in fb + C +C shutdowncircuit v c comp logic driver anti- sat flyback error amp 16v switch out 5a, 75v switch 0.02(0.04 (0.16 lt1171)lt1172) 0.16 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 downloaded from: http:///
lt1170/lt1171/lt1172 9 117012fh for more information www.linear.com/lt1170 operation 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 er - ror 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 turnoff 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 lt1170/lt1171/lt1172 to disconnect the main error ampli - fier output and connects the output of the flyback amplifier to the comparator input. the l t1170/l t1171/lt1172 will then regulate the value of the flyback pulse with respect to the supply voltage.* this flyback pulse is directly pro - portional to output voltage in the traditional transformer coupled flyback topology regulator. 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. multiple floating outputs are easily obtained with additional windings. a special delay network inside the l t1170/ 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 func - tions. it is used for frequency compensation, current limit adjustment, soft-starting, and total regulator shutdown. 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 50a supply current for shutdown circuitry biasing. see application note 19 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) disconnected. 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 50c/w and 35c/w respectively . the minidips, however , are rated at 100c/w in ceramic (j) and 130c/w in plastic (n). *see note under block diagram. downloaded from: http:///
lt1170/lt1171/lt1172 10 117012fh for more information www.linear.com/lt1170 operation care should be taken for minidip applications to ensure that the worst case input voltage and load current conditions do not cause excessive die temperatures. the following 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 calculations 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 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)(0.6) = 0.25w p d(tot) = (5v)(0.018a) + 0.25 = 0.34w temperature rise in a plastic minidip would be 130c/w times 0.34w, or approximately 44c. the maximum ambi - ent temperature would be limited to 100c (commercial temperature limit) minus 44c, or 56c. 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 conditions 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 0.3s. c2 sets the pulse width at ? 0.2s. the effect of a synchronizing pulse on the lt1170/lt1171/lt1172 amplifier offset can be calculated from: ? v os = kt q ?? ? ?? ? t s ( ) f s ( ) i c + v c r3 ?? ? ?? ? i c kt q = 26mv at 25c t c = pulse width f s = pulse frequency i c = v c source current (200a) v c = operating v c voltage (1v to 2v) r3 = resistor used to set mid-frequency zero in frequency compensation network. downloaded from: http:///
lt1170/lt1171/lt1172 11 117012fh for more information www.linear.com/lt1170 operation with t s = 0.2s, 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 bipolar transistor synchronizing with mos transistor 1170/1/2 op01 c2 39pf r1 3k r22.2k lt1170 gnd v in v c c1 r3 2n2369 from 5v logic 1170/1/2 op02 d1 1n4158 r22.2k lt1170 gnd v in v c c1 r3 from 5v logic c2 100pf d21n4158 * siliconix or equivalent vn2222* typical applications flyback converter 1170/1/2 ta03 d1 c12000f c4* 100f c20.15f r13.74k r21.24k v in 20v to 30v r31.5k *required if input leads 2" lt1170 v in v sw fb v c optional filter l2 5h c4 100f v out 5v 6a v snub clamp turn-on spike primary flyback voltage =lt1170 switch voltage area a = area b to maintain zero dc volts across primary secondary voltage area c = area d to maintain zero dc volts across secondary primary current secondary current lt1170 switch current snubber diode current v out + vf n 0v v in a b 0v c d v out + v f n ? v in ? i i pri 0 i pri /n i pri i pri t = (i pri )(l l ) v snub 0 00 1 n* = 1/3 n* d325v 1w d2mur110 gnd + + downloaded from: http:///
lt1170/lt1171/lt1172 12 117012fh for more information www.linear.com/lt1170 typical applications (note that maximum output currents are divided by 2 for lt1171, by 4 for lt1172.) lcd contrast supply c40.047f v out C10v to C26v 1170/1/2 ta04 r315k optional shutdown r2 100k r1 200k c11f tantalum d11n914 c30.0047f c2***2f tantalum d2 vn2222 5v* l1** 50h v bat * 3v to 20v v in v c fb v sw lt1172 e2e1 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. inductor series resistance should be less than 0.4 for high efficiency. output ripple is about 200mv p-p to 400mv p-p with c2 = 2f tantalum. if lower ripple is desired, increase c2, or add a 10, 1f tantalum output filter. + + driving high voltage fet (for off-line applications, see an25) 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 downloaded from: http:///
lt1170/lt1171/lt1172 13 117012fh for more information www.linear.com/lt1170 typical applications (note that maximum output currents are divided by 2 for lt1171, by 4 for lt1172.) negative-to-positive buck-boost converter ? external current limit negative buck converter c4* 100f v out 12v2a 1170/1/2 ta07 r32.2k c21000f d1 c10.22f q1 v in v c fb v sw lt1170 gnd optional input filter l3 v in C20v required if input leads 2"pulse engineering 92114, coiltronics 50-2-52 * ** r21.24k l1** 50h optional output filter c3 l2 r111.3k this circuit is often used to convert C48v to 5v. to guaranteefull 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 lt1170gnd pin is no longer common to v in C . r1 1k + C c11000pf q1 r s c3* 100f C5.2v4.5a 1170/1/2 ta09 r3 l1** 50h r14.64k c21000f d1 c1 q1 2n3906 v in v c fb v sw lt1170 gnd optional input filter l3 v in C20v load required if input leads 2"pulse engineering 92114 coiltronics 50-2-52 * ** r21.24k r4 12k optional output filter c4200f + + + downloaded from: http:///
lt1170/lt1171/lt1172 14 117012fh for more information www.linear.com/lt1170 typical applications positive-to-negative buck-boost converter c4 1f v in 10v to30v 1170/1/2 ta10 r35k c5100f* d3 ? 1n4001 c20.1f v in v c fb v sw lt1170 gnd v out C12v2a required if input leads 2"pulse engineering 92114, coiltronics 50-2-52 * ** r21.24k l1** 50h r5 ? 470?, 1w to avoid startup problems for input voltagesbelow 10v, connect anode of d3 to v in , and remove r5. c1 may be reduced for lower outputcurrents. c1 (500f)(i out ). for 5v outputs, reduce r3 to 1.5k, increase c2 to0.3f, and reduce r6 to 100. ? c32f d2 1n914 r4 47 c1 ? 1000f d1 r6470 r1 10.7k + + + + high efficiency constant current charger d2mbr340 1170/1/2 ta11 input voltage > v bat + 2v < 35v c2 2.2 f 35v tantalum r722k r81k c30.47 f v + v C r41k c4200f 25v battery2v to 25v l2* 10 h, 1a l1 100 h, 1a r5 0.05 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 c40.01 f lt1006 + ? + lt1171 c1 200 f 35v 1a 2n3904 + + + + gnd 2f 1170/1/2 ta12 d1 1n914 33pf 3kv 10f tant r3 10k 50k intensity adjust 1n5818 l1** 300h input voltage ? 4.5v to 20v q1,q2 = bcp56 or mps650/561coiltronics ctx300-4 sumida 6345-020 or coiltronics 110092-1 a modification will allow operation down to 4.5v. consult factory. * ** *** ? c6 1f r1 560 1k lt1172 in v v c v sw e2e1 d21n914 lamp fb l2*** 0.02f a b q1* q2* + + backlight ccfl supply (see an45 for details) downloaded from: http:///
lt1170/lt1171/lt1172 15 117012fh for more information www.linear.com/lt1170 typical applications positive buck converter c5*100f v in 1170/1/2 ta13 r3470 5v, 4.5a d2 1n914 c11f v in v c fb v sw lt1170 gnd required if input leads 2"pulse engineering 92114 coiltronics 50-2-52 * ** r1 3.74k l1** 50h r410 c3 2.2f d1 r r21.24k c21f c4 1000f 100maminimum d3 optional output filter c5200f l2 4h + + + + negative boost regulator c4* 470f 1170/1/2 ta14 r33.3k c310f d1 c20.22f v in v c fb lt1170 gnd v in C15v required if input leads 2" * r21.24k d2 r127k v sw l1 50h c11000f r o (minimumload) v out C28v, 1a + + + driving high voltage npn 1170/1/2 ta15 d2 c1 sets i b (on) sets i b (off) * ** r2** v in v sw lt1170 gnd d1 q1 r1* downloaded from: http:///
lt1170/lt1171/lt1172 16 117012fh for more information www.linear.com/lt1170 typical applications forward converter 1170/1/2 ta16 c1 2000 f c3 r4 r21.24k v in 20v to 30v r3 lt1170 v in v sw fb v c 1 n d3 l1 25h c4 r6 330 r51 c2 m d2 d1 v out 5v, 6a t1 q1 d4 r13.74k gnd + high efficiency 5v buck converter + v sw fb gnd v in v c lt1170 + c1330f 35v c60.02f c4 0.1f r1680 c5 0.03f d1 mbr330p c3 4.7f tant d2 1n4148 l1 50h r2* 0.013 c2390f 16v v out 5v3a** + 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 optionaloutput filter 100f 16v 10h 3a + v c gnd mode diode v out v lim v + lt1432 v in downloaded from: http:///
lt1170/lt1171/lt1172 17 117012fh for more information www.linear.com/lt1170 j8 package 8-lead cerdip (narrow .300 inch, hermetic) (reference ltc dwg # 05-08-1110) j8 0801 .014 ? .026 (0.360 ? 0.660) .200 (5.080) max .015 ? .060 (0.381 ? 1.524) .125 3.175 min .100 (2.54) bsc .300 bsc (7.62 bsc) .008 ? .018 (0.203 ? 0.457) 0 ? 15 .005 (0.127) min .405 (10.287) max .220 ? .310 (5.588 ? 7.874) 12 3 4 87 65 .025 (0.635) rad typ .045 ? .068 (1.143 ? 1.650) full lead option .023 ? .045 (0.584 ? 1.143) half lead option corner leads option (4 plcs) .045 ? .065 (1.143 ? 1.651) note: lead dimensions apply to solder dip/plate or tin plate leads k package 4-lead to-3 metal can (reference ltc dwg # 05-08-1311) k4(to-3) 0801 72 18 .490 ? .510 (12.45 ? 12.95) r .470 tp p.c.d. .167 ? .177 (4.24 ? 4.49) r .151 ? .161 (3.84 ? 4.09) dia 2 plc .655 ? .675 (16.64 ? 19.05) 1.177 ? 1.197 (29.90 ? 30.40) .038 ? .043 (0.965 ? 1.09) .060 ? .135 (1.524 ? 3.429) .320 ? .350 (8.13 ? 8.89) .420 ? .480 (10.67 ? 12.19) .760 ? .775 (19.30 ? 19.69) (obsolete package) package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. downloaded from: http:///
lt1170/lt1171/lt1172 18 117012fh for more information www.linear.com/lt1170 package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. n8 rev i 0711 .065 (1.651) typ .045 C .065 (1.143 C 1.651) .130 .005 (3.302 0.127) .020 (0.508) min .018 .003 (0.457 0.076) .120 (3.048) min .008 C .015 (0.203 C 0.381) .300 C .325 (7.620 C 8.255) .325 +.035C.015 +0.889C0.381 8.255 ( ) 1 2 3 4 8 7 6 5 .255 .015* (6.477 0.381) .400* (10.160) max note:1. dimensions are inches millimeters *these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .010 inch (0.254mm) .100 (2.54) bsc n package 8-lead pdip (narrow .300 inch) (reference ltc dwg # 05-08-1510 rev i) downloaded from: http:///
lt1170/lt1171/lt1172 19 117012fh for more information www.linear.com/lt1170 package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. q(dd5) 0811 rev f .028 C .038 (0.711 C 0.965) typ .143 +.012C.020 ( ) 3.632 +0.305C0.508 .067 (1.702) bsc .013 C .023 (0.330 C 0.584) .095 C .115 (2.413 C 2.921) .004 +.008C.004 ( ) 0.102 +0.203C0.102 .050 .012 (1.270 0.305) .059 (1.499) typ .045 C .055 (1.143 C 1.397) .165 C .180 (4.191 C 4.572) .330 C .370 (8.382 C 9.398) .060 (1.524) typ .390 C .415 (9.906 C 10.541) 15 typ .420 .350 .585 .090 .042 .067 recommended solder pad layout .325 .205 .080 .585 .090 recommended solder pad layout for thicker solder paste applications .042 .067 .420 .276 .320 note:1. dimensions in inch/(millimeter) 2. drawing not to scale .300 (7.620) .075 (1.905) .183 (4.648) .060 (1.524) .060 (1.524) .256 (6.502) bottom view of dd pak hatched area is solder plated copper heat sink q package 5-lead plastic dd pak (reference ltc dwg # 05-08-1461 rev f) detail a detail a 0 C 7 typ 0 C 7 typ downloaded from: http:///
lt1170/lt1171/lt1172 20 117012fh for more information www.linear.com/lt1170 package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. .016 C .050 (0.406 C 1.270) .010 C .020 (0.254 C 0.508) 45 0 C 8 typ .008 C .010 (0.203 C 0.254) so8 rev g 0212 .053 C .069 (1.346 C 1.752) .014 C .019 (0.355 C 0.483) typ .004 C .010 (0.101 C 0.254) .050 (1.270) bsc 1 2 3 4 .150 C .157 (3.810 C 3.988) note 3 8 7 6 5 .189 C .197 (4.801 C 5.004) note 3 .228 C .244 (5.791 C 6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note:1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm) 4. pin 1 can be bevel edge or a dimple s8 package 8-lead plastic small outline (narrow .150 inch) (reference ltc dwg # 05-08-1610 rev g) downloaded from: http:///
lt1170/lt1171/lt1172 21 117012fh for more information www.linear.com/lt1170 sw package 16-lead plastic small outline (wide .300 inch) (reference ltc dwg # 05-08-1620) s16 (wide) 0502 note 3 .398 ? .413 (10.109 ? 10.490) note 4 16 15 14 13 12 11 10 9 1 n 23 4 5 6 78 n/2 .394 ? .419 (10.007 ? 10.643) .037 ? .045 (0.940 ? 1.143) .004 ? .012 (0.102 ? 0.305) .093 ? .104 (2.362 ? 2.642) .050 (1.270) bsc .014 ? .019 (0.356 ? 0.482) typ 0 ? 8 typ note 3 .009 ? .013 (0.229 ? 0.330) .005 (0.127) rad min .016 ? .050 (0.406 ? 1.270) .291 ? .299 (7.391 ? 7.595) note 4 45 .010 ? .029 (0.254 ? 0.737) inches (millimeters) note:1. dimensions in 2. drawing not to scale 3. 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 4. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm) .420 min .325 .005 recommended solder pad layout .045 .005 n 12 3 n/2 .050 bsc .030 .005 typ package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. downloaded from: http:///
lt1170/lt1171/lt1172 22 117012fh for more information www.linear.com/lt1170 t package 5-lead plastic to-220 (standard) (reference ltc dwg # 05-08-1421) t5 (to-220) 0801 .028 ? .038 (0.711 ? 0.965) .067 (1.70) .135 ? .165 (3.429 ? 4.191) .700 ? .728 (17.78 ? 18.491) .045 ? .055 (1.143 ? 1.397) .095 ? .115 (2.413 ? 2.921) .013 ? .023 (0.330 ? 0.584) .620 (15.75) typ .155 ? .195* (3.937 ? 4.953) .152 ? .202 (3.861 ? 5.131) .260 ? .320 (6.60 ? 8.13) .165 ? .180 (4.191 ? 4.572) .147 ? .155 (3.734 ? 3.937) dia .390 ? .415 (9.906 ? 10.541) .330 ? .370 (8.382 ? 9.398) .460 ? .500 (11.684 ? 12.700) .570 ? .620 (14.478 ? 15.748) .230 ? .270 (5.842 ? 6.858) bsc seating plane * measured at the seating plane package description please refer to http://www.linear.com/product/lt1170#packaging for the most recent package drawings. downloaded from: http:///
lt1170/lt1171/lt1172 23 117012fh for more information www.linear.com/lt1170 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 representa - tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. revision history rev date description page number g 3/10 updated to reactivate lt1172m from obsoleted parts list 2 h 6/16 removed #pbf from mj8 part number in first line 3 (revision history begins at rev g) downloaded from: http:///
lt1170/lt1171/lt1172 24 117012fh for more information www.linear.com/lt1170 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 ? linear technology corporation 1991 lt 0616 rev h ? printed in usa (408) 432-1900 fax : (408) 434-0507 www.linear.com/lt1170 related parts typical application positive current boosted buck converter 1170/1/2 ta18 c10.33 f 4702w r7 1k v in 28v r3680 lt1170 v in v sw fb v c 1: n d2 r2 1.24k c30.47 f d1 v out 5v, 10a n 0.25 r4 1.24k gnd c5* 100f r6470 c6 0.002 f ? + c40.01 f 7 v in 6 4 8 200pf 2 3 r5 5k r15k c25000f * required if input leads 2" lm308 + + 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, <100v p-p output noise downloaded from: http:///

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