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1 LTC3803-5 38035f features descriptio u applicatio s u typical applicatio u constant frequency current mode flyback dc/dc controller in thinsot v in and v out limited only by external components 4.8v undervoltage lockout threshold operating junction temperature from 40 c to 150 c adjustable slope compensation internal soft-start constant frequency 200khz operation 1.5% reference accuracy current mode operation for excellent line and load transient response no minimum load requirement low quiescent current: 240 a low profile (1mm) sot-23 package 42v and 12v automotive power supplies telecom power supplies auxiliary/housekeeping power supplies power over ethernet thinsot is a trademark of linear technology corporation. dual output wide input range converter the ltc ? 3803-5 is a constant frequency current mode flyback controller optimized for driving 4.5v and 6v-rated n-channel mosfets in high input voltage applications. the LTC3803-5 operates from inputs as low as 5v. con- stant frequency operation is maintained down to very light loads, resulting in less low frequency noise generation over a wide range of load currents. slope compensation can be programmed with an external resistor. the LTC3803-5 provides 1.5% output voltage accuracy and consumes only 240 a of quiescent current. ground- referenced current sensing allows LTC3803-5-based con- verters to accept input supplies beyond the LTC3803-5s absolute maximum v cc . for simplicity, the LTC3803-5 can be powered from a high v in through a resistor, due to its internal 8v shunt regulator. an internal undervoltage lockout shuts down the ic when the input voltage falls below 3.2v, guaranteeing at least 3.2v of gate drive to the external mosfet. the LTC3803-5 is available in a low profile (1mm) 6-lead sot-23 (thinsot tm ) package. efficiency and power loss vs output power , ltc and lt are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. i th /run gnd v fb LTC3803-5 ngate v cc sense 10mq100n b3100 1 f 100v 3x 13v/0.3a 20ma min load 6.5v/1.2a 38035 ta01 0.012 ? 0.1 f 22k 7.5k 57.6k 8.06k 4.7k 10nf 1 f 100v 1 f 100v phm25nq10t all capacitors are x7r, tdk v in 6v to 50v mmbta42 22 f 10v 47 f 10v pdz9.1b vph5-0155 output power (w) 02 efficiency (%) power loss (w) 90 85 80 75 70 65 60 3.0 2.5 2.0 1.5 1.0 0.5 0 4 6810 38035 ta01b 12 v in = 8v v in = 12v v in = 12v v in = 24v v in = 48v
2 LTC3803-5 38035f order part number (note 1) v cc to gnd (current fed) .................... 25ma into v cc * ngate voltage ......................................... C 0.3v to v cc v fb , i th /run voltages ..............................C 0.3v to 3.5v sense voltage ........................................... C 0.3v to 1v ngate peak output current (<10 s) ........................ 1a operating junction temperature range (note 2) ltc3803e-5 ....................................... C 40 c to 85 c ltc3803h-5 (note 3) ....................... C 40 c to 150 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c ltc3803hs6-5 ltc3803es6-5 t jmax = 150 c, ja = 165 c/w absolute m axi m u m ratings w ww u package/order i n for m atio n w u u symbol parameter conditions min typ max units v turnon v cc turn on voltage 4 4.8 5.7 v v turnoff v cc turn off voltage 3.3 4 4.9 v v hyst v cc hysteresis v turnon C v turnoff 0.05 0.8 v v clamp1ma v cc shunt regulator voltage i cc = 1ma, v ith/run = 0v 6.2 8 9.9 v v clamp25ma v cc shunt regulator voltage i cc = 25ma, v ith/run = 0v 6.3 8.1 10.3 v i cc input dc supply current (note 4) normal operation v ith/run = 1.3v 240 350 a undervoltage v cc = v turnon C 100mv 40 90 a v ithshdn shutdown threshold (at i th /run) v cc = v turnon + 100mv 0.12 0.28 0.45 v i ithstart start-up current source v ith/run = 0v 0.07 0.34 0.8 a v fb regulated feedback voltage 0 c t j 85 c (note 5) 0.788 0.800 0.812 v C40 c t j 85 c (note 5) 0.780 0.800 0.816 v g m error amplifier transconductance i th/run pin load = 5 a (note 5) 200 333 500 a/v ? v o(line) output voltage line regulation v turnoff < v cc < v clamp (note 5) 0.1 mv/v ? v o(load) output voltage load regulation i th /run sinking 5 a (note 5) 3 mv/ a i th /run sourcing 5 a (note 5) 3 mv/ a i fb v fb input current (note 5) 10 50 na f osc oscillator frequency v ith/run = 1.3v 170 200 230 khz dc on(min) minimum switch on duty cycle v ith/run = 1.3v, v fb = 0.8v 6.5 8.5 % dc on(max) maximum switch on duty cycle v ith/run = 1.3v, v fb = 0.8v 70 80 90 % t rise gate drive rise time c load = 3000pf 40 ns t fall gate drive fall time c load = 3000pf 40 ns v imax peak current sense voltage r sl = 0 (note 6) 90 100 115 mv i slmax peak slope compensation output current (note 7) 5 a t sfst soft-start time 0.7 ms ltc3803e-5: the indicates specifications which apply over the full ?0 c to 85 c operating junction temperature range, otherwise specifications are at t j = 25 c. v cc = 5v, unless otherwise noted. (note 2) ltbmh ltbpf consult ltc marketing for parts specified with wider operating temperature ranges. electrical characteristics i th /run 1 gnd 2 v fb 3 6 ngate 5 v cc 4 sense top view s6 package 6-lead plastic tsot-23 *LTC3803-5 internal clamp circuit self regulates v cc voltage to 8v. s6 part marking
3 LTC3803-5 38035f symbol parameter conditions min typ max units v turnon v cc turn on voltage 3.9 4.8 5.7 v v turnoff v cc turn off voltage 3.2 4 4.9 v v hyst v cc hysteresis v turnon C v turnoff 0.05 0.8 v v clamp1ma v cc shunt regulator voltage i cc = 1ma, v ith/run = 0v 6.2 8 10.4 v v clamp25ma v cc shunt regulator voltage i cc = 25ma, v ith/run = 0v 6.3 8.1 10.7 v i cc input dc supply current (note 4) normal operation v ith/run = 1.3v 240 350 a undervoltage v cc = v turnon C 100mv 40 100 a v ithshdn shutdown threshold (at i th /run) v cc = v turnon + 100mv 0.08 0.28 0.45 v i ithstart start-up current source v ith/run = 0v 0.07 0.34 1 a v fb regulated feedback voltage 0 c t j 85 c (note 5) 0.788 0.800 0.812 v C40 c t j 150 c (note 5) 0.780 0.800 0.820 v g m error amplifier transconductance i th/run pin load = 5 a (note 5) 200 333 500 a/v ? v o(line) output voltage line regulation v turnoff < v cc < v clamp (note 5) 0.1 mv/v ? v o(load) output voltage load regulation i th /run sinking 5 a (note 5) 3 mv/ a i th /run sourcing 5 a (note 5) 3 mv/ a i fb v fb input current (note 5) 10 50 na f osc oscillator frequency v ith/run = 1.3v 170 200 230 khz dc on(min) minimum switch on duty cycle v ith/run = 1.3v, v fb = 0.8v 6.5 8.5 % dc on(max) maximum switch on duty cycle v ith/run = 1.3v, v fb = 0.8v 70 80 90 % t rise gate drive rise time c load = 3000pf 40 ns t fall gate drive fall time c load = 3000pf 40 ns v imax peak current sense voltage r sl = 0 (note 6) 85 100 115 mv i slmax peak slope compensation output current (note 7) 5 a t sfst soft-start time 0.7 ms ltc3803h-5: the indicates specifications which apply over the full ?0 c to 150 c operating junction temperature range, otherwise specifications are at t a = 25 c. v cc = 5v, unless otherwise noted. (notes 2, 3) note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the ltc3803h-5 is guaranteed to meet specifications from C40 c to 150 c. the ltc3803e-5 is guaranteed to meet specifications from 0 c to 85 c with specifications over the C40 c to 85 c temperature range assured by design, characterization and correlation with statistical process controls. junction temperature (t j) is calculated from the ambient temperature t a and the power dissipation p d in the LTC3803-5 using the formula: t j = t a + (p d ? 230 c/w) note 3: high junction temperatures degrade operating lifetimes. operating electrical characteristics lifetime at junction temperatures greater than 125 c is derated to 1000 hours. note 4: dynamic supply current is higher due to the gate charge being delivered at the switching frequency. note 5: the LTC3803-5 is tested in a feedback loop that servos v fb to the output of the error amplifier while maintaining i th /run at the midpoint of the current limit range. note 6: peak current sense voltage is reduced dependent on duty cycle and an optional external resistor in series with the sense pin (r sl ). for details, refer to the programmable slope compensation feature in the applications information section. note 7: guaranteed by design.
4 LTC3803-5 38035f typical perfor a ce characteristics uw reference voltage vs v cc shunt regulator current reference voltage vs supply voltage reference voltage vs temperature oscillator frequency vs v cc shunt regulator current oscillator frequency vs supply voltage oscillator frequency vs temperature i cc supply current vs temperature v cc shunt regulator voltage vs temperature v cc undervoltage lockout thresholds vs temperature temperature ( c) C50 v fb voltage (mv) 70 90 38035 g01 C10 10 C30 30 50 150 110 130 812 808 804 800 796 792 788 v cc = 5v v cc supply voltage (v) 4.0 v fb voltage (mv) 792 796 812 800 5.0 6.0 6.5 38035 f02 788 804 808 4.5 5.5 7.0 7.5 t a = 25 c v cc v clamp1ma i cc (ma) 0 v fb voltage (mv) 792 796 800 15 25 38035 g03 788 510 20 804 808 812 t a = 25 c temperature ( c) C50 oscillator frequency (khz) C10 30 70 150 110 130 38035 g04 C30 10 50 90 v cc = 5v 220 215 210 205 200 195 190 185 180 v cc supply voltage (v) 4.0 oscillator frequency (khz) 180 190 200 4.5 5.0 5.5 6.0 38035 g05 6.5 7.0 210 220 185 195 205 215 7.5 t a = 25 c i cc (ma) 0 oscillator frequency (khz) 180 190 200 5 10 15 20 38035 g06 210 220 185 195 205 215 25 t a = 25 c temperature ( c) C50 5.0 volts 5.5 4.5 3.5 6.0 C10 30 50 3803 g07 3.0 4.0 C30 10 70 90 150 110 130 v turnon v turnoff temperature ( c) C50 v cc (v) 7.0 7.5 8.0 10.5 9.0 C10 30 50 38035 g08 9.5 10.0 8.5 C30 10 70 90 150 130 110 i cc = 25ma i cc = 1ma temperature ( c) C50 supply current ( a) 200 300 240 C10 30 50 38035 g08 260 280 220 C30 10 70 90 110 130 150 v cc = 5v v ith/run = 1.3v
5 LTC3803-5 38035f typical perfor a ce characteristics uw i th /run shutdown threshold vs temperature start-up i cc supply current vs temperature i th /run start-up current source vs temperature soft-start time vs temperature peak current sense voltage vs temperature temperature ( c) C50 0 start-up supply current ( a) 10 20 30 40 C10 30 70 110 130 150 38035 g10 50 60 70 C30 10 50 90 v cc = v turnon C 0.1v temperature ( c) C50 shutdown threshold (mv) 300 350 400 70 90 250 200 C10 10 C30 30 50 150 110 130 150 100 50 0 450 500 3803 g11 temperature ( c) C50 0 i th /run pin current source (na) 100 200 300 400 C10 30 70 110 130 150 38035 g12 500 600 700 800 900 1000 C30 10 50 90 v cc = v turnon + 0.1v v ith/run = 0v temperature ( c) C50 sense pin voltage (mv) 100 110 150 110 130 38035 g13 90 80 C10 30 70 C30 10 50 90 120 95 105 85 115 v cc = 5v temperature ( c) C50 soft-start time (ms) 0.6 1.0 150 38035 g14 0.2 0 C10 30 70 C30 10 50 130 110 90 1.4 0.4 0.8 1.2 v cc = 5v
6 LTC3803-5 38035f block diagra w C + C + slope comp current ramp v cc gate driver ngate 4 sense 38035 bd 200khz oscillator undervoltage lockout q r current comparator shutdown comparator shutdown s 20mv i th /run error amplifier v fb soft- start clamp v cc shunt regulator switching logic and blanking circuit 6 0.28v v cc < v turnon 0.3 a v cc C + 5 3 gnd 1.2v 2 1 800mv reference uu u pi fu ctio s i th /run (pin 1): this pin performs two functions. it serves as the error amplifier compensation point as well as the run/shutdown control input. nominal voltage range is 0.7v to 1.9v. forcing this pin below 0.28v causes the LTC3803-5 to shut down. in shutdown mode, the ngate pin is held low. gnd (pin 2): ground pin. v fb (pin 3): receives the feedback voltage from an exter- nal resistive divider across the output. sense (pin 4): this pin performs two functions. it moni- tors switch current by reading the voltage across an external current sense resistor to ground. it also injects a current ramp that develops slope compensation voltage across an optional external programming resistor. v cc (pin 5): supply pin. must be closely decoupled to gnd (pin 2). ngate (pin 6): gate drive for the external n-channel mosfet. this pin swings from 0v to v cc .
7 LTC3803-5 38035f operatio u the LTC3803-5 is a constant frequency current mode controller for flyback, sepic and dc/dc boost converter applications in a tiny thinsot package. the LTC3803-5 is designed so that none of its pins need to come in contact with the input or output voltages of the power supply circuit of which it is a part, allowing the conversion of voltages well beyond the LTC3803-5s absolute maximum ratings. main control loop due to space limitations, the basics of current mode dc/dc conversion will not be discussed here; instead, the reader is referred to the detailed treatment in application note 19, or in texts such as abraham pressmans switch- ing power supply design . please refer to the block diagram and the typical applica- tion on the front page of this data sheet. an external resistive voltage divider presents a fraction of the output voltage to the v fb pin. the divider must be designed so that when the output is at the desired voltage, the v fb pin voltage will equal the 800mv from the internal reference. if the load current increases, the output voltage will decrease slightly, causing the v fb pin voltage to fall below 800mv. the error amplifier responds by feeding current into the i th /run pin. if the load current decreases, the v fb voltage will rise above 800mv and the error amplifier will sink current away from the i th /run pin. the voltage at the i th /run pin commands the pulse-width modulator formed by the oscillator, current comparator and rs latch. specifically, the voltage at the i th /run pin sets the current comparators trip threshold. the current comparator monitors the voltage across a current sense resistor in series with the source terminal of the external mosfet. the LTC3803-5 turns on the external power mosfet when the internal free-running 200khz oscillator sets the rs latch. it turns off the mosfet when the current comparator resets the latch or when 80% duty cycle is reached, whichever happens first. in this way, the peak current levels through the flyback transformers primary and secondary are controlled by the i th /run voltage. since the i th /run voltage is increased by the error ampli- fier whenever the output voltage is below nominal, and decreased whenever output voltage exceeds nominal, the voltage regulation loop is closed. for example, whenever the load current increases, output voltage will decrease slightly, and sensing this, the error amplifier raises the i th /run voltage by sourcing current into the i th /run pin, raising the current comparator threshold, thus increasing the peak currents through the transformer primary and secondary. this delivers more current to the load, bring- ing the output voltage back up. the i th /run pin serves as the compensation point for the control loop. typically, an external series rc network is connected from i th /run to ground and is chosen for optimal response to load and line transients. the imped- ance of this rc network converts the output current of the error amplifier to the i th /run voltage which sets the current comparator threshold and commands consider- able influence over the dynamics of the voltage regulation loop. start-up/shutdown the LTC3803-5 has two shutdown mechanisms to disable and enable operation: an undervoltage lockout on the v cc supply pin voltage, and a forced shutdown whenever external circuitry drives the i th /run pin low. the ltc3803- 5 transitions into and out of shutdown according to the state diagram (figure 1). LTC3803-5 shut down v ith/run < v ithshdn (nominally 0.28v) 38035 f01 v cc < v turnoff (nominally 4v) v ith/run > v ithshdn and v cc > v turnon (nominally 4.8v) LTC3803-5 enabled figure 1. start-up/shutdown state diagram
8 LTC3803-5 38035f the undervoltage lockout (uvlo) mechanism prevents the LTC3803-5 from trying to drive a mosfet with insuf- ficient v gs . the voltage at the v cc pin must exceed v turnon (nominally 4.8v) at least momentarily to enable LTC3803-5 operation. the v cc voltage is then allowed to fall to v turnoff (nominally 4v) before undervoltage lock- out disables the LTC3803-5. the i th /run pin can be driven below v shdn (nominally 0.28v) to force the LTC3803-5 into shutdown. an internal 0.3 a current source always tries to pull this pin towards v cc . when the i th /run pin voltage is allowed to exceed v shdn , and v cc exceeds v turnon , the LTC3803-5 begins to operate and an internal clamp immediately pulls the i th /run pin up to about 0.7v. in operation, the i th /run pin voltage will vary from roughly 0.7v to 1.9v to repre- sent current comparator thresholds from zero to maxi- mum. internal soft-start an internal soft-start feature is enabled whenever the LTC3803-5 comes out of shutdown. specifically, the i th /run voltage is clamped and is prevented from reach- ing maximum until roughly 0.7ms has passed. this allows the input and output currents of LTC3803-5- based power supplies to rise in a smooth and controlled manner on start-up. operatio u powering the LTC3803-5 in the simplest case, the LTC3803-5 can be powered from a high voltage supply through a resistor. a built-in shunt regulator from the v cc pin to gnd will draw as much current as needed through this resistor to regulate the v cc voltage to around 8v as long as the v cc pin is not forced to sink more than 25ma. this shunt regulator is always active, even when the LTC3803-5 is in shutdown, since it serves the vital function of protecting the v cc pin from seeing too much voltage. the v cc pin must be bypassed to ground immediately adjacent to the ic pins with a ceramic or tantalum capaci- tor. proper supply bypassing is necessary to supply the high transient currents required by the mosfet gate driver. 10 f is a good starting point. adjustable slope compensation the LTC3803-5 injects a 5 a peak current ramp out through its sense pin which can be used for slope compensation in designs that require it. this current ramp is approximately linear and begins at zero current at 6.5% duty cycle, reaching peak current at 80% duty cycle. additional details are provided in the applications infor- mation section.
9 LTC3803-5 38035f applicatio s i for atio wu uu many LTC3803-5 application circuits can be derived from the topology shown in figure 2. the LTC3803-5 itself imposes no limits on allowed power output, input voltage v in or desired regulated output voltage v out ; these are all determined by the ratings on the external power components. the key factors are: q1s maximum drain-source voltage (bv dss ), on-resistance (r ds(on) ) and maximum drain current, t1s saturation flux level and winding insulation breakdown voltages, c in and c out s maximum working voltage, esr, and maxi- mum ripple current ratings, and d1 and r sense s power ratings. transformer design considerations transformer specification and design is perhaps the most critical part of applying the LTC3803-5 successfully. in addition to the usual list of caveats dealing with high frequency power transformer design, the following should prove useful. turns ratios due to the use of the external feedback resistor divider ratio to set output voltage, the user has relative freedom in selecting transformer turns ratio to suit a given applica- tion. simple ratios of small integers, e.g., 1:1, 2:1, 3:2, etc. can be employed which yield more freedom in setting total turns and mutual inductance. simple integer turns ratios also facilitate the use of off-the-shelf configurable trans- formers such as the coiltronics versa-pac tm series in applications with high input to output voltage ratios. for example, if a 6-winding versa-pac is used with three windings in series on the primary and three windings in parallel on the secondary, a 3:1 turns ratio will be achieved. turns ratio can be chosen on the basis of desired duty cycle. however, remember that the input supply voltage plus the secondary-to-primary referred version of the flyback pulse (including leakage spike) must not exceed the allowed external mosfet breakdown rating. leakage inductance transformer leakage inductance (on either the primary or secondary) causes a voltage spike to occur after the output switch (q1) turn-off. this is increasingly promi- nent at higher load currents, where more stored energy must be dissipated. in some cases a snubber circuit will be required to avoid overvoltage breakdown at the mosfets drain node. application note 19 is a good reference on snubber design. a bifilar or similar winding technique is a good way to minimize troublesome leakage inductances. however, remember that this will limit the primary-to-secondary breakdown voltage, so bifilar winding is not always practical. v cc i th /run LTC3803-5 gnd ngate sense v fb 5 6 4 1 2 3 d1 ? ? c out c in l sec l pri c vcc c c v out 38035 f02 r sense r sl r1 r vcc r2 q1 t1 v in figure 2. typical LTC3803-5 application circuit selecting feedback resistor divider values the regulated output voltage is determined by the resistor divider across v out (r1 and r2 in figure 2). the ratio of r2 to r1 needed to produce a desired v out can be calculated: r vv v r out 2 08 08 1 = C. . ? choose resistance values for r1 and r2 to be as large as possible in order to minimize any efficiency loss due to the static current drawn from v out , but just small enough so that when v out is in regulation, the error caused by the nonzero input current to the v fb pin is less than 1%. a good rule of thumb is to choose r1 to be 80k or less. versa-pac is a trademark of coiltronics, inc.
10 LTC3803-5 38035f current sense resistor considerations the external current sense resistor (r sense in figure 2) allows the user to optimize the current limit behavior for the particular application. as the current sense resistor is varied from several ohms down to tens of milliohms, peak switch current goes from a fraction of an ampere to several amperes. care must be taken to ensure proper circuit operation, especially with small current sense resistor values. for example, a peak switch current of 5a requires a sense resistor of 0.020 ? . note that the instantaneous peak power in the sense resistor is 0.5w and it must be rated accordingly. the LTC3803-5 has only a single sense line to this resistor. therefore, any parasitic resistance in the ground side connection of the sense resistor will increase its apparent value. in the case of a 0.020 ? sense resistor, one milliohm of parasitic resistance will cause a 5% reduction in peak switch current. so the resistance of printed circuit copper traces and vias cannot necessarily be ignored. programmable slope compensation the LTC3803-5 injects a ramping current through its sense pin into an external slope compensation resistor (r sl in figure 2). this current ramp starts at zero right after the ngate pin has been high for the LTC3803-5s minimum duty cycle of 6.5%. the current rises linearly towards a peak of 5 a at the maximum duty cycle of 80%, shutting off once the ngate pin goes low. a series resistor (r sl ) connecting the sense pin to the current sense resistor (r sense ) thus develops a ramping voltage drop. from the perspective of the sense pin, this ramping voltage adds to the voltage across the sense resistor, effectively reducing the current comparator threshold in proportion to duty cycle. this stabilizes the control loop against subharmonic oscillation. the amount of reduction in the current comparator threshold ( ? v sense ) can be calculated using the following equation: ? = v duty cycle ar sense sl C.% .% ?? 65 73 5 5 note: LTC3803-5 enforces 6.5% < duty cycle < 80%. a good starting value for r sl is 5.9k, which gives a 30mv drop in current comparator threshold at 80% duty cycle. designs not needing slope compensation may replace r sl with a short circuit. v cc shunt regulator an internal shunt regulator allows the LTC3803-5 to be powered through a single dropping resistor from v in to v cc , in conjunction with a bypass capacitor, c vcc , that closely decouples v cc to gnd (see figure 3). the shunt regulator can draw up to 25ma through the v cc pin to gnd to drop enough voltage across r vcc to regulate v cc to around 8v. for applications where v in is low enough such that the static power dissipation in r vcc is accept- able, using the v cc shunt regulator is the simplest way to power the LTC3803-5. external preregulator the circuit in figure 4 shows another way to power the LTC3803-5. an external series preregulator consisting of series pass transistor q1, zener diode d1, and bias resis- tor r b brings v cc above the v cc turn-on threshold, en- abling the LTC3803-5. applicatio s i for atio wu uu LTC3803-5 v cc r vcc c vcc 38035 f03 v in gnd LTC3803-5 v cc r b 100k d1 6.8v q1 mmbta42 c vcc 0.1 f 38035 f04 8v to 75 v in gnd figure 3. powering the LTC3803-5 via the internal shunt regulator figure 4. powering the LTC3803-5 with an external preregulator
11 LTC3803-5 38035f i th /run LTC3803-5 gnd ngate v cc v fb sense 6 5 1 2 4 3 primary ground 2.2 f 1 f 2.2 f 1 f 38035 ta03 0.1 ? 22k 9.2k 1nf primary side 10v, 100ma output secondary side 10v, 100ma output v in 36v to 75v 5.6k fdc2512 t1: pulse engineering pa0648 or tyco tti8698 1k 220k bas516 t1 secondary side ground bas516 ? ? ? 806 ? bas516 2w isolated housekeeping telecom converter typical applicatio s u u package descriptio s6 package 6-lead plastic tsot-23 (reference ltc dwg # 05-08-1636) 1.50 C 1.75 (note 4) 2.80 bsc 0.30 C 0.45 6 plcs (note 3) datum a 0.09 C 0.20 (note 3) s6 tsot-23 0302 2.90 bsc (note 4) 0.95 bsc 1.90 bsc 0.80 C 0.90 1.00 max 0.01 C 0.10 0.20 bsc 0.30 C 0.50 ref pin one id note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 4. dimensions are exclusive of mold flash and metal burr 5. mold flash shall not exceed 0.254mm 6. jedec package reference is mo-193 3.85 max 0.62 max 0.95 ref recommended solder pad layout per ipc calculator 1.4 min 2.62 ref 1.22 ref 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.
12 LTC3803-5 38035f ? linear technology corporation 2004 lt/tp 1104 1k ? printed in the usa part number description comments lt ? 1425 isolated flyback switching regulator no optoisolator or third winding required, up to 6w output with no external power devices lt1725 general purpose isolated flyback controller no optoisolator required, v in and v out limited only by external power components ltc1772 sot-23 constant frequency current mode step-down 550khz switching frequency, 2.4v to 9.8v v in range dc/dc controller ltc1871 wide input range, no r sense tm current mode adjustable switching frequency, programmable undervoltage flyback, boost and sepic controller lockout, optional burst mode ? operation at light load ltc1872 sot-23 constant frequency current mode boost dc/dc 550khz switching frequency, 2.4v to 9.8v v in range controller lt1950 current mode pwm controller controller for forward converters from 30w to 300w lt1952 current mode pwm controller synchronous controller for forward converters from 30w to 500w lt3420 photoflash capacitor charger with automatic refresh specialized flyback charges high voltage photoflash capacitors quickly and efficiently lt3468/lt3468-1 photoflash capacitor charger in 5-pin sot-23 minimal component count, uses small transformers; v in from 2.5v to 16v ltc3806 synchronous flyback controller high efficiency (89%); multiple output with excellent cross regulation ltc4441 6a n-channel mosfet driver gate drive adjustable from 5v to 8v, adjustable blanking prevents ringing, 10-lead mssop package burst mode is a registered trademark of linear technology corporation. no r sense is a trademark of linear technology corporation. related parts linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com typical applicatio s u i th /run LTC3803-5 gnd gate sense v out * 3.3v 1.5a 38035 ta04a d1 c in 33k q1 q2 t1: pulse engineering pa1006 q1: fairchild fdc2512 q2: vishay si9803 t1 ? ? 0.1 f ? 1n 8.06k 25.5k* r fb v out v cc v in 36v to 72v v fb 270k 1 f 10v 560 5k c o r cs 1 2 3 6 5 4 d1: philips bas516 c in : tdk 1 f, 100v, x5r c o : tdk 100 f, 6.3v, x5r r cs : vishay or irc, 80m ? *for 5v output change r fb to 42.2k output current (a) 0.5 efficiency (%) 90 91 38035 ta04b 89 88 1.0 1.5 2.0 output current (a) 0.5 92 91 90 89 88 87 86 85 2.0 38035 ta04c 1.0 1.5 2.5 efficiency (%) 90% efficient synchronous flyback converter synchronous flyback 3.3v out synchronous flyback 5v out

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