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1 for more information www.linear.com/lt3999 typical application features description low noise, 1a, 1mhz push-pull dc/dc driver with duty cycle control the lt ? 3999 is a monolithic, high voltage, high frequency dc/dc transformer driver providing isolated power in a small solution footprint. the lt3999 has two 1a current limited power switches that switch out of phase. the duty cycle is programmable to adjust the output voltage. the switching frequency is programmed up to 1mhz and can be synchronized to an external clock for more accurate placement of switcher harmonics. the input operating range is programmed with the precision undervoltage and overvoltage lockouts. the supply current is reduced to less than 1a during shutdown. a user-defined rc time constant provides an adjustable soft-start capability by limiting the inrush cur - rent at start-up. the lt3999 is available in a 10-lead msop and 3mm 3mm dfn package with exposed pad. 12v to 12v, 10w low noise isolated dc/dc converter lt3999 line regulation with duty cycle control applications n wide input operating range: 2.7v to 36v n dual 1a switches with programmable current limit n programmable switching frequency: 50khz to 1mhz n frequency synchronization up to 1mhz n ?v in compensation using duty cycle control n low noise topology n programmable input over and undervoltage lockout n cross conduction prevention circuitry n programmable soft-start n low shutdown current: <1a n 10- lead msop and dfn packages n low noise isolated supplies n medical instrument and safety n distributed power n multiple output supplies n positive-to-negative supplies n noise immunity in data acquisition, rs232 and?rs485 l, lt , lt c , lt m , linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. v in sync uvlo ovlo/dc rdc lt3999 swa 10f 16v 15.3h v out 12v 0.8a v in 12v swb gnd 49.9k 0.1f 28k 500khz 10k 15.8k 10f 16v 255k 3999 ta01a rt ilim/ss rbias input voltage (v) 10 output voltage (v) 12 14 18 3999 ta01b 10 8 12 14 16 11 13 15 17 16 11 13 9 15 i out = 200ma i out = 800ma i out = 400ma lt 3999 3999fa
2 for more information www.linear.com/lt3999 pin configuration absolute maximum ratings swa , swb ................................................. C0.3 v to 80 v v in , uvlo .................................................. C0.3 v to 60 v ovlo / dc , sync ......................................... C0.3 v to 8 v operating junction temperature range ( note 2) lt 3999 e ............................................ C40 c to 125 c lt 3999 i ............................................. C40 c to 125 c lt 3999 h ............................................ C40 c to 150 c lt 3999 mp ......................................... C55 c to 150 c (note 1) 1 2 3 4 5 swa rbias v in uvlo ovlo/dc 10 9 8 7 6 swb ilim/ss sync rt rdc top view 11 gnd mse package 10-lead plastic msop ja = 40cw, jc = 10cw exposed pad (pin 11) is gnd, must be soldered to pcb top view 11 gnd dd package 10-lead (3mm 3mm) plastic dfn 10 9 6 7 8 4 5 3 2 1 swb ilim/ss sync rt rdc swa rbias v in uvlo ovlo/dc ja = 43c/w, jc = 5.5c/w exposed pad (pin 11) is gnd, must be soldered to pcb order information lead free finish tape and reel part marking* package description temperature range lt3999emse#pbf lt3999emse#trpbf ltgkr 10-lead plastic msop C40c to 125c lt3999imse#pbf lt3999imse#trpbf ltgkr 10-lead plastic msop C40c to 125c lt3999hmse#pbf lt3999hmse#trpbf ltgkr 10-lead plastic msop C40c to 150c lt3999mpmse#pbf lt3999mpmse#trpbf ltgkr 10-lead plastic msop C55c to 150c lt3999edd#pbf lt3999edd#trpbf lgkq 10-lead (3mm 3mm) plastic dfn C40c to 125c lt3999idd#pbf lt3999idd#trpbf lgkq 10-lead (3mm 3mm) plastic dfn C40c to 125c consult lt c marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. consult lt c marketing for information on nonstandard lead based finish parts. 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/ storage temperature range .................. C65 c to 150 c lead temperature ( soldering , 10 sec ) msop ............................................................... 300 c lt 3999 3999fa
3 for more information www.linear.com/lt3999 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 parameter conditions min typ max units input supply and shutdown v in minimum operating voltage l 2.7 v v in overvoltage lockout internal, rising l 36 40 42 v v in supply current (note 3) 4.3 ma v in shutdown current v uvlo = 0.3v 0.1 1 a uvlo threshold (rising) l 1.15 1.25 1.35 v uvlo hysteresis 125 mv uvlo pin current v uvlo = 1.25v 10 100 na ovlo/dc threshold (rising) l 1.15 1.25 1.35 v ovlo/dc hysteresis 125 mv ovlo/dc pin current v ovlo/dc = 1.25v 10 100 na power switches ( swa , swb ) switch saturation voltage i sw = 1a 350 mv switch current limit internal default l 1.0 1.4 1.7 a non overlap time 70 ns switch base drive current i sw = 1a 35 ma oscillator/sync switching frequency r t = 316k r t = 49.9k r t = 12.1k l 280 50 300 1000 320 khz khz khz synchronization frequency range 100 1000 khz sync voltage threshold 1.5 v sync pin input resistance 200 k ilim/ss swa and swb current limit r ilim/ss = 43.2k l 0.4 0.5 0.6 a ilim/ ss pin current 10 a duty cycle switch duty cycle ovlo/dc = 0.8v, r dc = 24.3k, r t = 49.9k ovlo/dc = 0.612v, r dc = 24.3k, r t = 49.9k ovlo/dc = 0.3v, r dc = 24.3k, r t = 49.9k l 22 20 25 48 30 % % % 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 the device reliability and lifetime. note 2: the lt3999e is guaranteed to meet performance specifications from 0c to 125c junction temperature. specifications over the C40c to 125c operating junction temperature range are assured by design, characterization, and correlation with statistical process controls. the lt3999i is guaranteed over the C40c to 125c operating junction temperature range. the lt3999h is guaranteed over the full C40c to 150c operating junction temperature range. the lt3999mp is 100% tested and guaranteed over the C55c to 150c junction temperature range. high junction temperatures degrade operating lifetimes; operating lifetime is derated for junction temperatures greater than 125c. note 3: supply current specification does not include switch drive currents. actual supply currents will be higher. lt 3999 3999fa
4 for more information www.linear.com/lt3999 typical performance characteristics switch v cesat switch leakage current switch current limit uvlo threshold voltage ovlo threshold voltage v in shutdown current switching frequency v cesat vs switch current temperature (c) ?50 shutdown current (a) 1.5 2.0 2.5 25 75 150 3999 g01 1.0 0.5 0 ?25 0 50 100 125 temperaure (c) ?50 frequency (khz) 300 350 150 3999 g02 250 200 0 50 100 ?25 25 75 125 400 275 325 225 375 switch current (ma) 0 switch v cesat (mv) 200 250 300 900800 3999 g03 150 100 0 200 400 600 100 1000 300 500 700 50 400 350 temperature (c) ?50 switch v cesat (mv) 400 500 600 25 75 150 3999 g04 300 200 100 ?25 0 50 100 125 switch current = 1a temperature (c) ?50 0 switch current (a) 0.5 1.0 1.5 2.0 0 50 100 150 3999 g05 2.5 3.0 ?25 25 75 125 temperature (c) ?50 0 current limit (ma) 200 600 800 1000 2000 1400 0 50 75 3999 g06 400 1600 1800 1200 ?25 25 100 125 150 r ilim/ss = open r ilim/ss = 80.6k r ilim/ss = 43.2k temperature (c) ?50 0.90 uvlo pin voltage (v) 0.95 1.05 1.10 1.15 1.40 1.25 0 50 75 3999 g07 1.00 1.30 1.35 1.20 ?25 25 100 125 150 uvlo rising uvlo falling temperature (c) ?50 0.90 ovlo pin voltage (v) 0.95 1.05 1.10 1.15 1.40 1.25 0 50 75 3999 g08 1.00 1.30 1.35 1.20 ?25 25 100 125 150 ovlo rising ovlo falling lt 3999 3999fa
5 for more information www.linear.com/lt3999 typical performance characteristics soft-start (ilim/ss) current switch duty cycle pin functions swa , swb (pin 1, pin 10): swa and swb pins are the open-collector nodes of the power switches. these pins drive the transformer and are connected to the outer ter - minals of the center tapped transformer. large currents flow through these pins so keep pcb traces short and wide. rbias (pin 2): the rbias pin sets the bias current of the power switches ( swa and swb). connect the pin to a 49.9k resistor to gnd. v in (pin 3): the v in pin is the main supply pin for the switch driver and internal regulator. short duration, high current pulses are produced during the turn on and turn off of the power switches. connect a low esr capacitor of 4.7f or greater. uvlo (pin 4): the uvlo pin has a precision threshold with hysteresis to implement an accurate v in undervolt - age lockout. the uvlo function disables switching and sets the part into a low current shutdown mode. connect the uvlo pin directly to v in or to a resistor divider string. ovlo / dc ( pin 5): the ovlo / dc pin has a precision thresh - old with hysteresis to implement an accurate v in overvolt - age lockout. the ovlo function disables the switching. connect ovlo/dc pin to ground to disable the function or to a resistor divider string to program the duty cycle. rdc (pin 6): the rdc pin is the duty cycle control pin. a resistor to ground sets the duty cycle. if unused leave the pin floating or connect to the ovlo/dc pin. rt (pin 7): the rt pin sets the switching frequency of the power switches. sync (pin 8): the sync pin synchronizes the part to an external clock. set the internal oscillator frequency below the external clock frequency. synchronizing the clock to an external reference is useful for creating more stable positioning of the switcher voltage or current harmonics. connect the sync pin to ground if not used. ilim/ss (pin 9): the ilim/ss pin sets a threshold level for the cycle by cycle maximum switch current. imple- ment soft-start with a capacitor, c ss , placed on this pin to ground. an internal current source charges the capacitor. the r ilim , c ss time constant sets the soft-start time and ramps the maximum switch current threshold at start-up. if the ilim/ss function is not used, float this pin and the current limit will default to the internal limit. gnd ( pin 11): the ground pin is the exposed pad of the package. solder the exposed pad directly to the ground plane. temperature (c) ?50 4 soft-start current (a) 5 7 8 9 14 11 0 50 75 3999 g09 6 12 13 10 ?25 25 100 125 150 temperature (c) ?50 10 duty cycle (%) 15 20 25 30 0 50 100 150 3999 g10 35 40 ?25 25 75 125 lt 3999 3999fa
6 for more information www.linear.com/lt3999 block diagram + ? ? + ? + + + + + ? v out d1 t1 d2 2 9 swb switch b ilim/ss gnd r ilim c ss rbias r bias switch a r sense 3999 bd swa 3 v in switch control oscillator bandgap linear regulator internal bias duty cycle control 11 rt 7 sync 8 rdc r dc r t 6 ovlo/dc 5 uvlo v in c in r a2 r a1 r b 4 ? + ? + ? + 10 1 lt 3999 3999fa
7 for more information www.linear.com/lt3999 operation overview the lt3999 is a monolithic isolated push-pull dc trans- former driver. it includes functions such as duty cycle control, soft-start and protection features. push-pull topology in a push-pull topology, a pair of switches operating out of phase generate a square wave voltage pulse on the primary side of a center tapped transformer. the diodes on the secondary side rectify the voltage and generate the output voltage. this voltage is simply v in times the transformer turns ratio. duty cycle control the lt3999 duty cycle control provides, to a degree, line regulation. the duty cycle is programmed by a resistor on the rdc pin and the ovlo/dc voltage. by making the ovlo/dc voltage a function of v in the duty cycle will adjust with varying v in thereby keeping v out constant. this feature is useful in cases where an ldo is used to post regulate the output of the lt3999. by pseudo regulating the output with the duty cycle control the power dissipa- tion in the ldo is minimized. leaving the rdc pin floating or connecting it to the ovlo/ dc pin disables the duty cycle function and the lt3999 operates at close to 50% duty cycle. current limit and soft-start the lt3999 ilim/ss pin programs the cycle-by-cycle switch current limit and the soft-start time. a resistor on the ilim/ss pin sets the current limit. a capacitor on the pin in conjunction with the resistor sets the soft-start time. when the programmed current limit is reached the switch is immediately turned off and remains off for the remainder of the cycle. leaving the ilim/ss pin unconnected will disable the programmable current limit and the lt3999 will default to its internal current limit. the soft - start function ramps the maximum switch current over the programmed soft-start time. the purpose of the soft - start is to reduce inrush current from the input supply . other features the lt3999 protection features include overvoltage lock- out (ovlo), undervoltage lockout (uvlo) and thermal shutdown. the ovlo function is programmed with the ovlo/dc pin. switching is disabled during an ovlo event. an internal overvoltage lockout on the v in pin is also provided to protect the lt3999. the uvlo function is programmed with the uvlo pin. switching is disabled during a uvlo event. the uvlo pin is also used to put the lt3999 into a low quiescent shutdown state. at a junction temperature above the operating tempera- ture range the thermal shutdown function turns off both switches. lt 3999 3999fa
8 for more information www.linear.com/lt3999 applications information switching frequency the lt3999 drives two output power switches out of phase, thus the oscillator frequency is two times the actual switching frequency of each power switch. the choice of switching frequency is a trade-off between power ef- ficiency and the size of capacitive and inductive storage components. operating at low switching frequency reduces the switch- ing losses ( transient losses ) and consequently improves the power converter efficiency. however, the lower switching frequency requires greater inductance for a given amount of ripple current, resulting in a larger design footprint and higher cost. the lt3999 switching frequency is set in the range of 50khz to 1mhz. the value of r t for a given operating frequency is chosen from table 1 or from the following equation: table 1. recommended 1% standard values r t f sw 316k 50khz 158k 100khz 76.8k 200khz 49.9k 300khz 36.5k 400khz 28k 500khz 22.6k 600khz 19.1k 700khz 16.2k 800khz 14k 900khz 12.1k 1000khz r t k ? ( ) = 1 2 ? f sw C 70ns ? ? ? ? ? ? ? 3.25 ?10 10 oscillator sync in applications where a more precise frequency is desired to accurately place high frequency harmonics, the lt3999 oscillator can be synchronized to an external clock. set the internal oscillator frequency 10% to 50% lower than the external sync frequency. the switching frequency is one-half the sync frequency. drive the sync pin with a 2v or greater square wave. the rising edge of the sync square wave will initiate clock discharge. if unused, connect the sync pin to ground. duty cycle to run the lt3999 at full duty cycle leave the rdc pin unconnected. variations in v in are, to a first order, compensated with the lt3999 duty cycle control function. the duty cycle function is implemented with a resistor divider on v in connected to the ovlo/dc pin and a resistor to ground on the rdc pin. use the following formula to calculate the rdc resistor or duty cycle: duty cycle dc ( ) = 1.25 ?rdc v in ? r b r a + r b ?r t ? 4 rdc = v in ? r b r a + r b ?r t ?dc ? 4 1.25 where r a and r b are the resistors from the v in to ovlo/ dc resistor divider and r t is the frequency setting resis- tor. see figure 1. setting the ovlo/dc pin to be 0.612v at the nominal v in voltage yields good line regulation over a wide input range. the duty cycle refers to the duty cycle of the individual switch. normally each switch operates at close to 50% duty cycle. lt 3999 3999fa
9 for more information www.linear.com/lt3999 applications information soft-start and current limit the lt3999 soft-start ramps the peak switch current over a time programmed by either a capacitor or a resistor and capacitor on the ilim/ss pin. when programming the soft - start time with a capacitor only the soft-start time is calculated with the following formula: t ss (ms) = c ss ? 80 where c ss is in f. the current limit defaults to the internally set value because there is no resistor on the pin. when programming the soft-start time with a resistor and capacitor on the ilim/ss pin the soft-start time is calculated with the following formula: = rc where 3 will be 95% of the maximum current. the cycle-by-cycle current limit of the lt3999 is set with a resistor on the ilim/ss pin. use the following formula to calculate the value of the resistor: r ilim (k) = i lim ? 86.4 ovlo/dc and uvlo the uvlo pin has a precision voltage threshold with hysteresis to enable the lt3999. the pin is typically con- nected to v in through a resistor divider; however, it can be directly connected to v in . the ovlo/dc pin has a precision voltage threshold with hysteresis to disable the lt3999 switching operation. the pin is typically connected to v in through a resistor divider. the ovlo/dc pin can be directly connected to gnd to disable the function. it is possible to use two separate resistor divider strings for ovlo/dc and uvlo pins or combine them together and use one resistor divider string to drive both pins. see figure 1. resistors are chosen by first selecting r b . then calculate r a with the following formula: r a = r b v th 1.25v C 1 ? ? ? ? ? ? ? ? where v th is the v in referred voltage at which the supply is enabled (uvlo) or disabled (ovlo/dc). transformer design table 3 lists recommended center tapped transformers for a variety of input voltage, output voltage and power combinations. these transformers will yield slightly high output voltages so that they can accommodate an ldo regulator on the output. if your application is not listed, the lt c applications group is available to assist in the choice and/or the design of the transformer. in the design/selection of the transformer the following characteristics are critical and should be considered: table 3. recommended center tapped transformers nominal input voltage (v) nominal output voltage (v) output power (w) part number 5 5 5 coilcraft pa 6383 5 12 1 coilcraft pa 6381 5 12 3 cooper bussmann ctx02-19064 12 12 10 coilcraft pa 6384 24 24 20 cooper bussmann ctx02-19061 v in uvlo r a2 r a1 r a r b r b 3999 f01 ovlo/dc v in uvlo or ovlo/dc figure 1. precision uvlo and ovlo resistor divider lt 3999 3999fa
10 for more information www.linear.com/lt3999 applications information turns ratio the turns ratio of the transformer determines the output voltage. the following equation is used as a first pass to calculate the turns ratio: n s n p = v out + v f 2 v in C v sw ( ) dc where v f is the forward voltage of the output diode, v sw is the voltage drop across the internal switches (see the typical performance curves ) and dc is the duty cycle. sufficient margin should be added to the turns ratio to account for voltage drops due to transformer winding resistance. magnetizing current the magnetizing inductance of the transformer causes a ripple current that is independent of load current. this ripple current is calculated by: ? i = v in ?dc f sw ?l m where ? i and l m are primary ripple current and magnetizing inductance referred to the primary side of the transformer, respectively. increasing the transformer magnetizing in- ductance , l m , reduces the ripple current . the ripple current formula shows the effect of the switching frequency on the magnetizing inductance. setting the lt3999 at high switching frequency reduces the ripple current for the same magnetizing inductance. therefore, it is possible to reduce the transformer turns and still achieve low ripple current. this helps to reduce the power converter footprint as well. the transformer magnetizing inductance should be designed for the worst-case duty cycle and input line voltage combination. a good rule of thumb is to set the primary current ripple amplitude 10% to 30% of the average primary current, i p : i p = p out v in ? eff where p out is the output power of the converter and eff is the converter efficiency, typically around 85%. winding resistance resistance in either the primary or secondary winding reduces overall efficiency and degrades load regulation. if efficiency or load regulation is unsatisfactory , verify that the voltage drops in the transformer windings are not excessive. capacitors in applications with full duty cycle operation, the input supply current is approximately constant . therefore, large input hold-up type capacitors are not necessary . a low value (>4.7f), low esr ceramic will be adequate to filter high frequency noise at the input. the output capacitors supply energy to the output load only during switch transitions. therefore, large capacitance values are not necessary on the output. transformer winding capacitance between the isolated primary and secondary has parasitic currents that can cause noise on the grounds. providing a high frequency, low impedance path between the primary and secondary gives the parasitic currents a local return path. a 2.2nf, 1kv ceramic capacitor is recommended. optional lc filter an optional lc filter, as shown on the typical application on the first page of this data sheet, should be included if ultralow noise and ripple are required. it is recommended that the corner frequency of the filter should be set a decade below the switching frequency so that the switch noise is attenuated by a factor of 100. for example, if the f osc = 100khz, then f corner = 10khz where: f corner = 1 2 ? lc switching diode selection a fast recovery , surface mount diode such as a schottky is recommended. the proximity of the diodes to the transformer outputs is important and should be as close as possible with short, wide traces connecting them. lt 3999 3999fa
11 for more information www.linear.com/lt3999 applications information output voltage regulation the output voltage of the dc transformer topology is unregulated. variations in the input voltage will cause the output voltage to vary because the output voltage is a function of the input voltage and the transformer turn ratio. also, variations in the output load will cause the output voltage to change because of circuit parasitics, such as the transformer dc resistance and power switch on resistance. if regulation is necessary , a post regulator such as a linear regulator can be added to the output of the supply. see the typical applications for examples of adding a linear regulator. power consideration the current derived from the v in pin and the swa and swb switching currents are the sources of the lt3999 power dissipation. the power dissipation is the sum of : 1) the quiescent current and switch drive power dissipation: p vin = v in i sw ?dc 30 + 4ma ? ? ? ? ? ? ? ? where i sw is the average switch current. 2) the conducting power dissipation of the switches during on state: p vcesat = v cesat ? i sw ? 2dc where dc is the duty cycle and v cesat is the collector to emitter voltage drop during the switch saturation. 3) the dynamic power dissipation due to the switching transitions: p sw = v in ? i sw ? f osc ? (t r + t f ) where t r and t f are the rise and fall times. the junction temperature is computed as: t j = t amb + p d ? ja where: p d = p vin + p vcesat + p sw and ja is the package thermal resistance. layout consideration check list the following is a list of recommended layout consider - ations: ? locate the bypass capacitor on the v in pin of the trans- former close to the transformer. ? create a solid gnd plane, preferably on layer two of the pcb. ? use short wide traces to connect to the transformer. ? the transformer and pcb routing should be care- fully designed to maximize the symmetry between two switching half cycles. ? solder the lt3999 exposed pad to the pcb. add multiple vias to connect the exposed pad to the gnd plane. more help an70: a monolithic switching regulator with 100mv output noise contains much information concerning applications and noise measurement techniques. lt 3999 3999fa
12 for more information www.linear.com/lt3999 typical applications 30v to 12v, 10w push-pull dc transformer 5v to 5v, 4w low part count push-pull dc transformer 10v-15v to 12v, 200ma isolated switching regulator v in sync uvlo ovlo/dc rdc lt3999 swa c out 10f 16v d1, d2: diodes inc. b260 l1: coilcraft m56132-153 t1: cooper bussmann ctx02-19062 l1 optional t1 d1 d2 v out 12v 0.8a v in 30v swb gnd r bias 49.9k c1 0.1f r t 28k 500khz r1 499k r2 19.1k c in 10f 50v 3999 ta02 rt ilim/ss rbias v in uvlo sync ovlo/dc rdc lt3999 swa c out 10f 10v d1, d2: central semi. cmsh1-20m t1: coilcraft pa6383 t1 d1 d2 v out 5v 0.8a v in 5v swb gnd r bias 49.9k r t 12.1k 1mhz c in 47f 10v 3999 ta03 rt ilim/ss rbias v in sync uvlo ovlo/dc lt3999 l2 39h l1 39h d1 t1 d2 d3 d4 swa v in 10v to 15v swb gnd r1 715k r2 36.5k r8 52.3k r3 66.5k r4 39k r bias 49.9k r t 12.1k 1mhz r dc 13.3k c ss 0.01f c in 10f 100v r7 10k c1 10f 50v c3 180pf c out1 10f 25v v out 12v 200ma c2 10f 50v d1-d4: central semi. cmsh1-200he l1, l2: coilcraft xfl3012-393meg t1: wrth 750314781 rdc rt ilim/ss rbias lt3065 out adj ref/byp shdn in r10 243k c out2 10f 25v ?v out ?12v 200ma lt3090 gnd 3999 ta04 out set shdn in ilim 1m r6 10k 0.01f lt 3999 3999fa
13 for more information www.linear.com/lt3999 package description please refer to http://www .linear.com/designtools/packaging/ for the most recent package drawings. msop (mse) 0213 rev i 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 ?0.27 (.007 ? .011) typ 0.86 (.034) ref 0.50 (.0197) bsc 1 2 3 4 5 4.90 0.152 (.193 .006) 0.497 0.076 (.0196 .003) ref 8910 10 1 7 6 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 6. exposed pad dimension does include mold flash. mold flash on e-pad shall not exceed 0.254mm (.010") per side. 0.254 (.010) 0 ? 6 typ detail ?a? detail ?a? gauge plane 5.10 (.201) min 3.20 ? 3.45 (.126 ? .136) 0.889 0.127 (.035 .005) recommended solder pad layout 1.68 0.102 (.066 .004) 1.88 0.102 (.074 .004) 0.50 (.0197) bsc 0.305 0.038 (.0120 .0015) typ bottom view of exposed pad option 1.68 (.066) 1.88 (.074) 0.1016 0.0508 (.004 .002) detail ?b? detail ?b? corner tail is part of the leadframe feature. for reference only no measurement purpose 0.05 ref 0.29 ref mse package 10-lead plastic msop, exposed die pad (reference ltc dwg # 05-08-1664 rev i) lt 3999 3999fa
14 for more information www.linear.com/lt3999 package description please refer to http://www .linear.com/designtools/packaging/ for the most recent package drawings. 3.00 0.10 (4 sides) note: 1. drawing to be made a jedec package outline m0-229 variation of (weed-2). check the ltc website data sheet for current status of variation assignment 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom view?exposed pad 1.65 0.10 (2 sides) 0.75 0.05 r = 0.125 typ 2.38 0.10 (2 sides) 1 5 10 6 pin 1 top mark (see note 6) 0.200 ref 0.00 ? 0.05 (dd) dfn rev c 0310 0.25 0.05 2.38 0.05 (2 sides) recommended solder pad pitch and dimensions 1.65 0.05 (2 sides) 2.15 0.05 0.50 bsc 0.70 0.05 3.55 0.05 package outline 0.25 0.05 0.50 bsc dd package 10-lead plastic dfn (3mm 3mm) (reference ltc dwg # 05-08-1699 rev c) pin 1 notch r = 0.20 or 0.35 45 chamfer lt 3999 3999fa
15 for more information www.linear.com/lt3999 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 a 04/15 corrected pin assignments revised schematics 5 13, 16 lt 3999 3999fa
16 for more information www.linear.com/lt3999 ? linear technology corporation 2014 lt 0415 rev a ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/lt3999 related parts typical application part number description comments lt3439 slew rate controlled ultralow noise 1a isolated dc/dc transformer driver v in : 2.7v to 17.5v, i q (supply) = 12ma, i sd < 12ma, so-16, low noise: <100mv p-p , independent control of switch voltage and current slew rates lt1533 slew rate controlled ultralow noise 1a switching regulator v in : 2.7v to 23v, i q (supply) = 12ma, i sd < 12ma, so-16, low noise: <100mv p-p , independent control of switch voltage and current slew rates lt1683 slew rate controlled ultralow noise push-pull controller v in : 2.7v to 20v, i q (supply) = 25ma, i sd < 24ma, ssop-20, low noise: <200mv p-p , independent control of switch voltage and current slew rates lt1738 slew rate controlled ultralow noise dc/dc controller v in : 2.7v to 20v, i q (supply) = 12ma, i sd < 24ma, ssop-20, greatly reduced conducted and radiated emi , independent control of switch voltage and current slew rates 5v to 12v, 1w low power push-pull dc transformer v in sync uvlo ovlo/dc rdc lt3999 swa c out 2.2f 16v d1, d2: vishay bat54c t1: cooper bussmann ctx02-19065r t1 d1a d1b v out 12v 0.08a v in 5v swb gnd r ilim 40.3k r bias 49.9k c ss 0.1f r t 12.1k 1mhz r1 261k r2 100k c in 10f 10v 3999 ta05 rt ilim/ss rbias lt 3999 3999fa

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