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1 lt1241 series the lt ? 1241 series devices are 8-pin, fixed frequency, current mode, pulse width modulators. they are improved plug compatible versions of the industry standard uc1842 series. these devices have both improved speed and lower quiescent current. the lt1241 series is optimized for off-line and dc/dc converter applications. they con- tain a temperature-compensated reference, high gain er- ror amplifier, current sensing comparator and a high current totem pole output stage ideally suited to driving power mosfets. start-up current has been reduced to less than 250 m a. cross-conduction current spikes in the output stage have been eliminated, making 500khz operation practical. several new features have been incor- porated. leading edge blanking has been added to the current sense comparator. trims have been added to the oscillator circuit for both frequency and sink current, and both of these parameters are tightly specified. the output stage is clamped to a maximum v out of 18v in the on state. the output and the reference output are actively pulled low during undervoltage lockout. high speed current mode pulse width modulators n low start-up current: < 250 m a n 50ns current sense delay n current mode operation: to 500khz n pin compatible with uc1842 series n undervoltage lockout with hysteresis n no cross-conduction current n trimmed bandgap reference n 1a totem pole output n trimmed oscillator frequency and sink current n active pull-down on reference and output during undervoltage lockout n high level output clamp: 18v n current sense leading edge blanking d u escriptio s f ea t u re u s a o pp l ic at i n off-line converters n dc/dc converters , ltc and lt are registered trademarks of linear technology corporation. + + 1 2 fb comp 2.5v 2r r 1v 1.5v + 3 i sense blanking 1ma 5.6v 4 r t /c t oscillator r s 18v 7v cc 5 gnd 6 output 8 v ref 5v ref main bias reference pull-down output pull-down reference enable 1241 bd01 t uv lockout w i dagra b l o c k
lt1241 series 2 parameter conditions min typ max units reference section output voltage i o = 1ma, t j = 25 c 4.925 5.000 5.075 v line regulation 12v < v cc < 25v l 320mv load regulation 1ma < i vref < 20ma l C6 C25 mv temperature stability 0.1 mv/ c total output variation line, load, temp l 4.87 5.13 v output noise voltage 10hz < f < 10khz, t j = 25 c50 m v long term stability t a = 125 c, 1000 hrs. 5 25 mv output short-circuit current l C30 C90 C180 ma oscillator section initial accuracy r t = 10k, c t = 3.3nf, t j = 25 c 47.5 50 52.5 khz r t = 13.0k, c t = 500pf, t j = 25 c 228 248 268 khz voltage stability 12v < v cc < 25v, t j = 25 c1% temperature stability t min < t j < t max C 0.05 %/ c amplitude t j = 25 c (pin 4) 1.7 v clock ramp reset current v osc (pin 4) = 2v, t j = 25 c 7.9 8.2 8.5 ma error amplifier section feedback pin input voltage v pin1 = 2.5v l 2.42 2.50 2.58 v input bias current v fb = 2.5v l C2 m a open-loop voltage gain 2 < v o < 4v l 65 90 db unity-gain bandwidth t j = 25 c 0.7 1.3 2 mhz power supply rejection ratio 12v < v cc < 25v l 60 db output sink current v pin2 = 2.7v, v pin1 = 1.1v l 26 ma output source current v pin2 = 2.3v, v pin1 = 5v l C 0.5 C 0.75 ma e lectr ic al c c hara terist ics (notes 1, 2) a u g w a w u w a r b s o lu t exi t i s supply voltage ........................................................ 25v output current ....................................................... 1a* output energy (capacitive load per cycle) ...............5 m j analog inputs (pins 2, 3) ............................... C 0.3 to 6v error amplifier output sink current...................... 10ma power dissipation at t a 25 c ................................ 1w operating junction temperature range lt124xc ............................................. 0 c to 100 c lt124xi......................................... C 40 c to 100 c lt124xm........................................ C 55 c to 125 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c *the 1a rating for output current is based on transient switching requirements. order part number lt124xcj8 lt124xcn8 lt124xcs8 lt124xin8 lt124xis8 LT124XMJ8 s8 part marking 124x 124xi wu u package / o rder i for atio comp fb i sense r t /c t v ref v cc output gnd s8 package 8-lead plastic so n8 package 8-lead pdip j8 package 8-lead cerdip 1 2 3 4 8 7 6 5 top view t jmax = 125 c, q ja = 100 c/w (j8) t jmax = 100 c, q ja = 130 c/w (n8) t jmax = 100 c, q ja = 150 c/w (s8)
3 lt1241 series parameter conditions min typ max units error amplifier section output voltage high level v pin2 = 2.3v, r l = 15k to gnd l 5 5.6 v output voltage low level v pin2 = 2.7v, r l = 15k to pin 8 l 0.2 1.1 v current sense section gain l 2.85 3.00 3.15 v/v maximum current sense input threshold v pin3 < 1.1v l 0.90 1.00 1.10 v power supply rejection ratio l 70 db input bias current l C1 10 m a delay to output l 50 100 ns blanking time 100 ns blanking override voltage 1.5 v output section output low level i out = 20ma l 0.25 0.4 v i out = 200ma l 0.75 2.2 v output high level i out = 20ma l 12.0 v i out = 200ma l 11.75 v rise time c l = 1nf, t j = 25 c5080ns fall time c l = 1.0nf, t j = 25 c3060ns output clamp voltage i o = 1ma l 18 19.5 v undervoltage lockout start-up threshold lt1241 l 9.0 9.6 10.2 v lt1242/lt1244 l 15 16 17 v lt1243/lt1245 l 7.8 8.4 9.0 v minimum operating voltage lt1241/lt1243/lt1245 l 7.0 7.6 8.2 v lt1242/lt1244 l 9.0 10 11 v hysteresis lt1241 1.6 2.0 v lt1242/lt1244 5.5 6.0 v lt1243/lt1245 0.4 0.8 v pwm maximum duty cycle lt1241/lt1244/lt1245 t j = 25 c4648% lt1242/lt1243 t j = 25 c9496% minimum duty cycle l 0% total device start-up current l 170 250 m a operating current l 710 ma the l denotes those specifications which apply over the full operating temperature range. note 1: unless otherwise specified, v cc = 15v, r t = 10k, c t = 3.3nf. (notes 1, 2) e lectr ic al c c hara terist ics note 2: low duty cycle pulse techniques are used during test to maintain junction temperature close to ambient.
lt1241 series 4 cc hara terist ics uw a t y p i ca lper f o r c e undervoltage lockout C undervoltage lockout C undervoltage lockout C lt1241 lt1242, lt1244 lt1243, lt1245 supply current vs oscillator frequency oscillator frequency oscillator sink current temperature ( c) ?0 6 v cc (v) 7 8 9 10 11 25 25 75 125 lt1241 ?tpc01 0 50 100 minimum operating voltage start-up threshold temperature ( c) ?0 9 v cc (v) 10 11 16 17 25 25 75 125 lt1241 ?tpc02 0 50 100 minimum operating voltage start-up threshold 15 temperature ( c) ?0 6 v cc (v) 7 8 9 10 11 25 25 75 125 lt1241 ?tpc03 0 50 100 minimum operating voltage start-up threshold temperature ( c) ?0 5 i cc (ma) 6 7 8 9 10 25 25 75 125 lt1241 ?tpc06 0 50 100 v cc = 15v r t = 10k c t = 3300pf temperature ( c) ?0 0 start-up current ( m a) 40 80 120 160 200 25 25 75 125 lt1241 ?tpc05 0 50 100 180 140 100 60 20 start-up current start-up current supply current v cc (v) 0 0 start-up current ( m a) 50 100 150 200 2 8 12 18 lt1241 ?tpc04 41014 6 16 lt1241 lt1242/4 lt1243/5 t j = 25 c start-up threshold oscillator frequency (hz) 10k 0 supply current (ma) 2 3 5 7 8 10 100k 1m lt1241 ?tpc18 9 6 4 1 lt1242, lt1243 lt1241, lt1244, lt1245 v cc = 15v r t = 10k c l = 15pf temperature ( c) ?0 40 frequency (khz) 44 48 52 56 60 ?5 25 75 125 lt1241 ?tpc07 0 50 100 42 46 50 54 58 v cc = 5v r t = 10k c t = 3300pf temperature ( c) ?0 7.7 oscillator sink current (ma) 8.7 25 25 75 125 lt1241 ?tpc08 0 50 100 7.8 8.0 8.2 8.4 8.6 8.5 7.9 8.1 8.3 v pin4 = 2v
5 lt1241 series cc hara terist ics uw a t y p i ca lper f o r c e error amplifier open-loop gain and phase current sense clamp voltage current sense input threshold low level output saturation high level output low level output voltage during undervoltage saturation voltage saturation voltage lockout temperature ( c) ?0 20 reference short-circuit current (ma) 140 25 25 75 125 lt1241 ?tpc09 0 50 100 40 80 100 120 60 temperature ( c) ?0 4.95 reference voltage (v) 5.05 25 25 75 125 lt1241 ?tpc10 0 50 100 4.96 5.00 5.01 4.97 4.98 4.99 5.02 5.03 5.04 i o = 1ma reference voltage reference short-circuit current feedback pin input voltage temperature ( c) ?0 2.45 feedback pin input voltage (v) 2.55 25 25 75 125 lt1241 ?tpc11 0 50 100 2.46 2.50 2.51 2.47 2.48 2.49 2.52 2.53 2.54 error amp output voltage (v) 0 0 current sense input threshold (v) 1.2 36 lt1241 ?tpc17 0.6 0.2 0.4 0.8 1.0 12 45 t j = 55 c t j =125 c t j = 25 c temperature ( c) ?0 0.95 current sense clamp voltage (v) 1.05 25 25 75 125 lt1241 ?tpc12 0 50 100 0.96 1.00 1.01 0.97 0.98 0.99 1.02 1.03 1.04 frequency (hz) 10 ?0 a vol open-loop voltage gain (db) 100 10k 10m lt1241 ?tpc16 40 0 20 60 80 100 1k 100k 1m phase gain v cc = 15v v o = 2.0v - 4.0v r l = 100k t a = 25 c phase (deg) 180 ?5 225 90 0 45 135 output source current (ma) 0 0 output saturation voltage (v) 4.0 200 lt1241 ?tpc13 0.5 2.0 2.5 1.0 1.5 3.0 3.5 t j = 55 c t j = 25 c t j = 125 c 100 output sink current (ma) 0 0 output saturation voltage (v) 1.0 100 200 lt1241 ?tpc14 t j = 55 c t j = 25 c t j = 125 c 0.5 output sink current (ma) 0 0 output saturation voltage (v) 4.0 510 lt1241 ?tpc15 2.0 0.5 1.0 1.5 2.5 3.0 3.5 t j = 125 c t j = 55 c t j = 25 c
lt1241 series 6 cc hara terist ics uw a t y p i ca lper f o r c e oscillator frequency (khz) 0 0 % of deadtime 10 20 30 40 50 60 100 1000 lt1241 ?tpc19 5nf 2nf 1nf 100pf 500pf time 50ns/div lt1241 ? tpc22 output voltage output rise and fall time output cross-conduction current current sense delay output voltage 5v/div current sense input 1v/div time 50ns/div lt1241 ? tpc24 time 50ns/div lt1241 ? tpc23 output voltage 5v/div output cross- conduction current 20ma/div output deadtime vs oscillator output deadtime vs oscillator timing resistor vs oscillator frequency C lt1242, lt1244 frequency C lt1241, lt1243,lt1245 frequency oscillator frequency (khz) 0 50 % of deadtime 55 60 65 70 75 100 1000 lt1241 ?tpc20 5nf 2nf 500pf 100pf 10nf 1nf oscillator frequency (hz) 10k 1 r t (k w ) 10 100 100k 1m lt1241 ?tpc21 5nf 2nf 500pf 100pf c t =10nf 1nf 200pf v cc = 15v t j = 25 c v cc = 15v c l = 1nf v cc = 15v c l = 15pf v cc = 15v c l = 1nf
7 lt1241 series pi u fu u c u s o ti comp (pin 1) : compensation pin. this pin is the output of the error amplifier and is made available for loop compen- sation. it can also be used to adjust the maximum value of the current sense clamp voltage to less than 1v. this pin can source a minimum of 0.5ma (0.8ma typ) and sink a minimum of 2ma (4ma typ) fb (pin 2) voltage feedback pin. this pin is the inverting input of the error amplifier. the output voltage is normally fed back to this pin through a resistive divider. the non- inverting input of the error amplifier is internally commit- ted to a 2.5v reference point. i sense (pin 3): current sense pin. this is the input to the current sense comparator. the trip point of the compara- tor is set by, and is proportional to, the output voltage of the error amplifier. r t /c t (pin 4): the oscillator frequency and the deadtime are set by connecting a resistor (r t ) from v ref to r t /c t and a capacitor (c t ) from r t /c t to gnd. the rise time of the oscillator waveform is set by the rc time constant of r t and c t . the fall time, which is equal to the output deadtime, is set by a combination of the rc time constant and the oscillator sink current (8.2ma typ). gnd (pin 5): ground. output (pin 6): this pin is the output of a high current totem pole output stage. it is capable of driving up to 1a of current into a capacitive load such as the gate of a mosfet. v cc (pin 7): this pin is the positive supply of the control ic. v ref (pin 8): reference. this is the reference output of the ic. the reference output is used to supply charging current to the external timing resistor r t . the reference provides biasing to a large portion of the internal circuitry, and is used to generate several internal reference levels includ- ing the v fb level and the current sense clamp voltage. u s a o pp l ic at i wu u i for atio minimum start-up operating maximum device threshold voltage duty cycle replaces lt1241 9.6v 7.6v 50% none lt1242 16v 10v 100% uc1842 lt1243 8.4v 7.6v 100% uc1843 lt1244 16v 10v 50% uc1844 lt1245 8.4v 7.6v 50% uc1845 oscillator the lt1241 series devices are fixed frequency current mode pulse width modulators. the oscillator frequency and the oscillator discharge current are both trimmed and tightly specified to minimize the variations in frequency and deadtime. the oscillator frequency is set by choosing a resistor and capacitor combination, r t and c t . this rc combination will determine both the frequency and the maximum duty cycle. the resistor r t is connected from v ref (pin 8) to the r t /c t pin (pin 4). the capacitor c t is connected from the r t /c t pin to ground. the charging current for c t is determined by the value of r t . the discharge current for c t is set by the difference between the current supplied by r t and the discharge current of the lt124x. the discharge current of the device is trimmed to 8.2ma. for large values of r t discharge time will be determined by the discharge current of the device and the value of c t . as the value of r t is reduced it will have more effect on the discharge time of c t . during an oscillator cycle capacitor c t is charged to approximately 2.8v and discharged to approximately 1.1v. the output is enabled during the charge time of c t and disabled, in an off state, during the discharge time of c t . the deadtime of the circuit is equal to the discharge time of c t . the maximum duty cycle is limited by controlling the deadtime of the oscilla- tor. there are many combinations of r t and c t that will yield a given oscillator frequency, however there is only one combination that will yield a specific deadtime at that frequency. curves of oscillator frequency and deadtime
lt1241 series 8 for various values of r t and c t appear in the typical performance characteristics section. frequency and deadtime can also be calculated using the following formulas: oscillator rise time: t r = 0.583 ? rc u s a o pp l ic at i wu u i for atio oscillator discharge time: oscillator frequency: oscillator period: t osc = t r + t d frequency for lt1241, lt1244 and lt1245. the oscillator of lt1241 series devices will run at frequencies up to 1mhz, allowing 500khz output switching frequencies for all devices. error amplifier the lt1241 series of devices contain a fully compensated error amplifier with a dc gain of 90db and a unity-gain frequency of 1mhz. phase margin at unity-gain is 80 . the noninverting input is internally committed to a 2.5v refer- ence point derived from the 5v reference of pin 8. the inverting input (pin 2) and the output (pin 1) are made available to the user. the output voltage in a regulator circuit is normally fed back to the inverting input of the error amplifier through a resistive divider. the output of the error amplifier is made available for external loop compensation. the output current of the error amplifier is limited to approximately 0.8ma sourcing and approximately 6ma sinking. in a current mode pwm the peak switch current is a function of the output voltage of the error amplifier. in the lt1241 series devices the output of the error amplifier is offset by two diodes (1.4v at 25 c), divided by a factor of three, and fed to the inverting input of the current sense comparator. for error amplifier output voltages less than 1.4v the duty cycle of the output stage will be zero. the maximum offset that can appear at the current sense input is limited by a 1v clamp. this occurs when the error amplifier output reaches 4.4v at 25 c. the output of the error amplifier can be clamped below 4.4v in order to reduce the maximum voltage allowed across the current sensing resistor to less than 1v. the supply current will increase by the value of the output source current when the output voltage of the error amplifier is clamped. t rc r d = () - 346 0 0164 11 73 . .. f t osc osc = 1 maximum duty cycle: lt1241, lt1244, lt1245 d t t tt t max r osc osc d osc == - 22 lt1242, lt1243 the above formulas will give values that will be accurate to approximately 5%, at the oscillator, over the full operating frequency range. this is due to the fact that the oscillator trip levels are constant versus frequency and the discharge current and initial oscillator frequency are trimmed. some fine adjustment may be required to achieve more accurate results. once the final r t /c t combination is selected the oscillator characteristics will be repeatable from device to device. note that there will be some slight differences between maximum duty cycle at the oscillator and maximum duty cycle at the output due to the finite rise and fall times of the output. the output switching frequency will be equal to the oscillator frequency for lt1242 and lt1243. the output switching frequency will be equal to one-half the oscillator d t t tt t max r osc osc d osc == -
9 lt1241 series u s a o pp l ic at i wu u i for atio change in the error amplifier output voltage. the threshold voltage will be 0.333v for an error amplifier voltage of 2.4v. to reduce the maximum current sense threshold to less than 1v the error amplifier output should be clamped to less than 4.4v. blanking a unique feature of the lt1241 series devices is the built- in blanking circuit at the output of the current sense comparator. a common problem with current mode pwm circuits is erratic operation due to noise at the current sense input. the primary cause of noise problems is the leading edge current spike due to transformer interwinding capacitance and diode reverse recovery time. this current spike can prematurely trip the current sense comparator causing an instability in the regulator circuit. a filter at the current sense input is normally required to eliminate this instability. this filter will in turn slow down the current sense loop. a slow current sense loop will increase the minimum pulse width which will increase the short-circuit current in an overload condition. the lt1241 series devices blank (lock out) the signal at the output of the current sense compara- tor for a fixed amount of time after the switch is turned on. this effectively prevents the pwm latch from tripping due to the leading edge current spike. the blanking time will be a function of the voltage at the feedback pin (pin 2). the blanking time will be 100ns for normal operating conditions (v fb = 2.5v). the blanking time goes to zero as the feedback pin is pulled to 0v. this means that the blanking time will be minimized during start-up and also during an output short-circuit fault. this blanking circuit eliminates the need for an input filter at the current sense input except in extreme cases. eliminating the filter allows the current sense loop to operate with minimum delays, reducing peak currents during fault conditions. current sense comparator and pwm latch lt1241 series devices are current mode controllers. under normal operating conditions the output (pin 6) is turned on at the start of every oscillator cycle, coincident with the rising edge of the oscillator waveform. the output is then turned off when the current reaches a threshold level proportional to the error voltage at the output of the error amplifier. once the output is turned off it is latched off until the start of the next cycle. the peak current is thus proportional to the error voltage and is controlled on a cycle by cycle basis. the peak switch current is normally sensed by placing a sense resistor in the source lead of the output mosfet. this resistor converts the switch current to a voltage that can be fed into the current sense input. for normal operating conditions the peak inductor current, which is equal to the peak switch current, will be equal to: i vv r pk pin s = - () () 1 14 3 . during fault conditions the maximum threshold voltage at the input of the current sense comparator is limited by the internal 1v clamp at the inverting input. the peak switch current will be equal to: i v r pk max s () . = 10 in certain applications, such as high power regulators, it may be desirable to limit the maximum threshold voltage to less than 1v in order to limit the power dissipated in the sense resistor or to limit the short-circuit current of the regulator circuit. this can be accomplished by clamping the output of the error amplifier. a voltage level of approximately 1.4v at the output of the error amplifier will give a threshold voltage of 0v. a voltage level of approxi- mately 4.4v at the output of the error amplifier will give a threshold level of 1v. between 1.4v and 4.4v the threshold voltage will change by a factor of one-third of the
lt1241 series 10 u s a o pp l ic at i wu u i for atio undervoltage lockout the lt1241 series devices incorporate an undervoltage lockout comparator which prevents the internal reference circuitry and the output from starting up until the supply voltage reaches the start-up threshold voltage. the quies- cent current, below the start-up threshold, has been reduced to less than 250 m a (170 m a typ.) to minimize the power loss due to the bleed resistor used for start-up in off-line converters. in undervoltage lockout both v ref (pin 8) and the output (pin 6) are actively pulled low by darlington connected pnp transistors. they are designed to sink a few milliamps of current and will pull down to about 1v. the pull-down transistor at the reference pin can be used to reset the external soft start capacitor. the pull- down transistor at the output eliminates the external pull- down resistor required, with earlier devices, to hold the external mosfet gate low during undervoltage lockout. output the lt1241 series devices incorporate a single high current totem pole output stage. this output stage is capable of driving up to 1a of output current. cross- conduction current spikes in the output totem pole have been eliminated. this device is primarily intended for driving mosfet switches. rise time is typically 40ns and fall time is typically 30ns when driving a 1.0nf load. a clamp is built into the device to prevent the output from rising above 18v in order to protect the gate of the mosfet switch. the output is actively pulled low during undervoltage lockout by a darlington pnp. this pnp is designed to sink several milliamps and will pull the output down to approxi- mately 1v. this active pull-down eliminates the need for an external resistor which was required in older designs. the output pin of the device connects directly to the emitter of the upper npn drive transistor and the collector of the lower npn drive transistor in the totem pole. the collector of the lower transistor, which is n-type silicon, forms a p-n junction with the substrate of the device. this junction is reverse biased during normal operation. in some applications the parasitic lc of the external mosfet gate can ring and pull the output pin below ground. if the output pin is pulled negative by more than a diode drop the parasitic diode formed by the collector of the output npn and the substrate will turn on. this can cause erratic operation of the device. in these cases a schottky clamp diode is recommended from the output to ground. reference the internal reference of the lt1241 series devices is a 5v bandgap reference, trimmed to within 1% initial toler- ance. the reference is used to power the majority of internal logic and the oscillator circuitry. the oscillator charging current is supplied from the reference. the feedback pin voltage and the clamp level for the current sense comparator are derived from the reference voltage. the reference can supply up to 20ma of current to power external circuitry. note that using the reference in this manner, as a voltage regulator, will significantly increase power dissipation in the device which will reduce the useful operating ambient temperature range. design/layout considerations lt1241 series devices are high speed circuits capable of generating pulsed output drive currents of up to 1a peak. the rise and fall time for the output drive current is in the range of 10ns to 20ns. high speed circuit techniques must be used to insure proper operation of the device. do not attempt to use proto-boards or wire-wrap techniques to breadboard high speed switching regulator circuits. they will not work properly. printed circuit layouts should include separate ground paths for the voltage feedback network, oscillator capaci- tor, and switch drive current. these ground paths should be connected together directly at the ground pin (pin 5) of the lt124x. this will minimize noise problems due to pulsed ground pin currents. v cc should be bypassed, with a minimum of 0.1 m f, as close to the device as possible. high current paths should be kept short and they should be separated from the feedback voltage network with shield traces if possible.
11 lt1241 series u s a o pp l ic at i ty p i ca l lt1241 ?ta01 5v ref oscillator external sync input 0.01 m f 47 w c t d1 r t r t /c t v ref d1 is required if the sync amplitude is large enough to pull the bottom of c t more than 300mv below ground. 8 4 + + + 1 2 + 3 lt1241 ?ta02 r v ref fb comp i sense c 2.5v 2r r 1v 1.5v 1ma 5.6v 8 5v ref + + 2 + 4 1 8 7 5 6 lt1241 ?ta03 fb comp r t /c t v ref v in r s r2 c r1 v clamp ? 1.67 r2 + 1 r1 ( ( i pk (max) ? v clamp r s where: 0v v clamp 1.0v t soft start = ?n 1 ? v c c r1 r2 3 ?v clamp r1 + r2 i sense 2.5v 2r r 1v 1.5v blanking 1ma 5.6v oscillator r s 18v v cc uv lockout gnd output 5v ref main bias reference pull-down output pull-down reference enable t 3 100k external clock synchronization soft start adjustable clamp level with soft start
lt1241 series 12 300khz off-line power supply u s a o pp l ic at i ty p i ca l lt1241 ?ta06 hot neu 90vac to 240vac r5 1m 1/2w c2 0.1 m f 250v mp3-x2 24 13 t1 balen c3 0.1 m f 250v mp3-x2 c4 4700pf 250v y-cap d5 + 2kbpo8m c5 4700pf 250v y-cap ac gnd c6 4700pf 250v y-cap r1 200k 1/2w + c14 100 m f 400v r t1 mcid404 2kbpoo5m r3 200k 1/2w d6 1n5245b 15v r2 660k 1/10w r4 660k 1/10w c1 470pf r5 27k 2w d1 mur160 30t 8 2 13t 3 6 30t 7 1 r7 510 1/10w c7 0.22 m f mks-2 r8 152k c8 100pf d7 bav21 v cc gnd r t /c t v ref comp c10 0.1 m f mks-2 r9 200k c9 0.01 m f, 100v mks-2 2 7 1 8 4 r13 12k c11 220pf r10 20k lt1241 5 output i sense r12 1k 1/10w 6 3 d4 bat 85 r18 2 w 1/4w r16 2 w 1/4w r17 2 w 1/4w r11 12 q1 mpt2n60 c12 22 m f 25v r14 39 d2 bav21 lp = 100 m h 12t 4 5 t2 d3 mur420 c15 3.3 m f 50v r15 750 w 1w l1 5 1/2 turn aircore c16 3.3 m f 50v c13 4700pf 1kv y-cap 20v 1.5a rtn notes: unless otherwise specified 1. all resistances are in ohms, 1/4w, 5%. 2. all capacitances are in microfarads, 50v, 10%. 1212-r6103 coiltronics ctx210433-1 fb
13 lt1241 series u s a o pp l ic at i ty p i ca l + + + lt1241 ?ta04 r t c t fb comp r t /c t v ref v in r s i sense 2 2.5v 2r r 1v 1.5v blanking 1ma 5.6v oscillator r s 18v 7 v cc uv lockout 5 gnd 6 output 5v ref main bias reference pull-down output pull-down reference enable t 1 8 3 4 slope compensation at i sense pin u package d e sc r i pti o j8 0694 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 0.010 (2.540 0.254) 0.300 bsc (0.762 bsc) 0.008 ?0.018 (0.203 ?0.457) 0 ?15 0.385 0.025 (9.779 0.635) 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 ?0.068 (1.143 ?1.727) note: lead dimensions apply to solder dip/plate or tin plate leads. j8 package 8-lead cerdip (narrow 0.300, hermetic) (ltc dwg # 05-08-1110) dimensions in inches (millimeters) unless otherwise noted.
lt1241 series 14 u package d e sc r i pti o dimensions in inches (millimeters) unless otherwise noted. n8 package 8-lead pdip (narrow 0.300) (ltc dwg # 05-08-1510) n8 0695 0.005 (0.127) min 0.100 0.010 (2.540 0.254) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.130 0.005 (3.302 0.127) 0.015 (0.380) 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 +0.025 0.015 +0.635 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)
15 lt1241 series u package d e sc r i pti o dimensions in inches (millimeters) unless otherwise noted. s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) 1 2 3 4 0.150 ?0.157** (3.810 ?3.988) 8 7 6 5 0.189 ?0.197* (4.801 ?5.004) 0.228 ?0.244 (5.791 ?6.197) 0.016 ?0.050 0.406 ?1.270 0.010 ?0.020 (0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010 (0.203 ?0.254) so8 0695 0.053 ?0.069 (1.346 ?1.752) 0.014 ?0.019 (0.355 ?0.483) 0.004 ?0.010 (0.101 ?0.254) 0.050 (1.270) bsc 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 * ** 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.
lt1241 series 16 ? linear technology corporation 1992 1241fa lt/tp 0297 5k rev a ? 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 lt1241 ?ta05 fb comp r t / c t v ref i sense + + 2.5v 2r r 1v 1.5v + blanking 1ma 5.6v 4 oscillator r s 18v 7 v cc uv lockout 5 gnd 6 output 5v ref main bias reference pull-down output pull-down reference enable t 8 3 r slope to v out 2 r f r t c t 1 slope compensation at error amp related parts part number description comments lt1246 1mhz current mode pwm 16v start-up threshold, 10v minimum operating voltage lt1248/lt1249 power factor controllers minimal parts count lt1372 high efficiency switching regulator 500khz 1.5a boost regulator lt1376 1.5a 500khz step-down switching regulator steps down from up to 25v using 4.7 m h inductors lt1509 power factor and pwm controller complete solution for universal off-line switching power supplies typical applicatio n u

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