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ltm 8045 1 8045fa for more information www.linear.com/8045 typical application features description inverting or sepic module dc/dc converter with up to 700ma output current the lt m ? 8045 is a module ? ( micromodule ) dc / dc converter that can be configured as a sepic or inverting converter by simply grounding the appropriate output rail. in a sepic configuration the regulated output voltage can be above , below or equal to the input voltage . the ltm 8045 includes power devices, inductors, control circuitry and passive components. all that is needed to complete the design are input and output capacitors, and small resis- tors to set the output voltage and switching frequency. other components may be used to control the soft-start and undervoltage lockout. the ltm8045 is packaged in a compact (6.25mm 11.25mm) overmolded ball grid array (bga) package suit- able for automated assembly by standard surface mount equipment. the ltm8045 is rohs compliant. l, lt , lt c , lt m , linear technology, the linear logo, module and polyphase are registered trademarks and soft-start is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. applications n sepic or inverting topology n wide input voltage range: 2.8v to 18v n up to 700ma output current at v in = 12v, v out = 2.5v or C2.5v n up to 375ma output current at v in = 12v, v out =15v or C15v n 2.5v to 15v or C2.5v to C15v output voltage n selectable switching frequency: 200khz to 2mhz n programmable soft-start? n user configurable undervoltage lockout n 6.25 mm 11.25mm 4.92mm bga package n battery powered regulator n local negative voltage regulator n low noise amplifier power use tw o ltm8045s to generate 5v 4.7f v in 2.8vdc to 18vdc ? ? v in v out ? v out ?5v v out 5v fb v out + run ltm8045 ss rt sync gnd 60.4k 22f 130k ? ? v in v out ? fb 8045 ta01b v out + run ltm8045 ss rt sync gnd 45.3k 100f 115k maximum output current vs input voltage input voltage (v) 100 700 600 800 200 300 500 400 8045 ta01b output current (ma) 2 8 10 4 6 12 14 16 18 2.5v out 3.3v out 5v out 8v out 12v out 15v out
ltm 8045 2 8045fa for more information www.linear.com/8045 pin configuration absolute maximum ratings v in , run ................................................................... 20 v rt , sync .................................................................... 5 v ss , fb ...................................................................... 2.5 v v out + ( v out C = 0 v ) ................................................... 16 v v out C ( v out + = 0 v ) ................................................. C16 v maximum internal temperature ............................ 125 c maximum solder temperature .............................. 250 c storage temperature .............................. C55 c to 125 c (note 1) v in bank 4 gnd bank 3 fb run sync v out ? bank 1 v out + bank 2 h ba dc 5 1 2 3 4 e f bga package 40-lead (11.25mm 6.25mm 4.92mm) g top view ss rt t jmax = 125c, ja = 28.7c/w, jb = 7.6c/w, jctop = 40.3c/w, jcbottom = 10.5c/w values determined per jedec 51-9, 51-12 weight = 0.9g order information lead free finish tray part marking* package description temperature range (note 2) ltm8045ey#pbf ltm8045ey#pbf ltm8045y 40-lead (11.25mm 6.25mm 4.92mm) bga C40c to 125c ltm8045iy#pbf ltm8045iy#pbf ltm8045y 40-lead (11.25mm 6.25mm 4.92mm) bga C40c to 125c ltm8045mpy#pbf ltm8045mpy#pbf ltm8045y 40-lead (11.25mm 6.25mm 4.92mm) bga C55c 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. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ this product is only offered in trays. for more information go to: http://www.linear.com/packaging/
ltm 8045 3 8045fa for more information www.linear.com/8045 electrical characteristics 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: the ltm8045e is guaranteed to meet performance specifications from 0c to 125c. specifications over the C40c to 125c internal temperature range are assured by design, characterization and correlation with statistical process controls. ltm8045i is guaranteed to meet specifications over the full C40c to 125c internal operating temperature range. the ltm8045mp is guaranteed to meet specifications over the the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. run = 12v unless otherwise specified. (note 2) parameter conditions min typ max units input dc voltage l 2.8 18 v positive output dc voltage i out = 0.7a, r fb = 15.4k, v out C grounded i out = 0.375a, r fb =165k, v out C grounded 2.5 15 v v negative output dc voltage i out = 0.7a, r fb = 30.0k, v out + grounded i out = 0.375a, r fb =178k, v out + grounded C2.5 C15 v v continuous output dc current v in = 12v, v out = 2.5v or C2.5v v in = 12v, v out = 15 v or C15v 0.7 0.375 a a v in quiescent current v run = 0v not switching 0 10 1 a ma line regulation 4v v in 18v, i out = 0.2a 0.6 % load regulation 0.01a i out 0.58a 0.2 % output rms voltage ripple v in = 12v, v out = 5v, i out = 580ma, 100khz to 4mhz 4 mv input short- circuit current v out + = v out C = 0v, v in = 12v 200 ma switching frequency r t = 45.3k r t = 464k l l 1800 180 2000 200 2200 220 khz khz voltage at fb pin (positive output) voltage at fb pin (negative output) l l 1.195 0 1.215 5 1.235 12 v mv current into fb pin (positive output) current into fb pin (negative output) l l 81 81 83.3 83.3 86 86.5 a a run pin threshold voltage run pin rising run pin falling 1.235 1.32 1.29 1.385 v v run pin current v run = 3v v run = 1.3v v run = 0 v 9.7 40 11.6 0 60 13.4 0.1 a a a ss sourcing current ss = 0v 5 8 13 a synchronization frequency range 200 2000 khz synchronization duty cycle 35 65 % sync input low threshold 0.4 v sync input high threshold 1.3 v full C55c to 125c internal operating temperature range. note that the maximum internal temperature is determined by specific operating conditions in conjunction with board layout, the rated package thermal resistance and other environmental factors. note 3: this module converter includes overtemperature protection that is intended to protect the device during momentary overload conditions. internal temperature will exceed 125c when overtemperature protection is active. continuous operation above the specified maximum internal operating junction temperature may impair device reliability.
ltm 8045 4 8045fa for more information www.linear.com/8045 typical performance characteristics efficiency 8v out sepic efficiency 12v out sepic efficiency 15v out sepic efficiency C2.5v out inverting converter efficiency C3.3v out inverting converter efficiency C5v out inverting converter efficiency 2.5v out sepic efficiency 3.3v out sepic efficiency 5v out sepic output current (ma) 0 50 70 30 40 80 60 20 10 8045 g01 efficiency (%) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g02 efficiency (%) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g03 efficiency (%) 0 300 400 100 200 500 600 700 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g04 efficiency (%) 0 300 400 100 200 500 600 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g05 efficiency (%) 0 300 400 100 200 500 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g06 efficiency (%) 0 300 400 100 200 500 5v in 12v in 18v in output current (ma) 0 50 70 30 40 80 60 20 10 8045 g07 efficiency (%) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g08 efficiency (%) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g09 efficiency (%) 0 300 400 100 200 500 600 700 3.3v in 5v in 12v in 18v in
ltm 8045 5 8045fa for more information www.linear.com/8045 typical performance characteristics input current vs output current, 2.5v out sepic efficiency C8v out inverting converter efficiency C12v out inverting converter efficiency C15v out inverting converter input current vs output current, 3.3v out sepic input current vs output current, 5v out sepic input current vs output current, 8v out sepic input current vs output current, 12v out sepic input current vs output current, 15v out sepic output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g10 efficiency (%) 0 300 400 100 200 500 600 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g11 efficiency (%) 0 300 400 100 200 500 3.3v in 5v in 12v in 18v in output current (ma) 0 50 70 30 40 90 80 60 20 10 8045 g12 efficiency (%) 0 300 400 100 200 500 5v in 12v in 18v in output current (ma) 0 500 300 400 600 200 100 8045 g13 input current (ma) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 700 600 200 100 8045 g14 input current (ma) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 800 700 600 200 100 8045 g15 input current (ma) 0 300 400 100 200 500 600 700 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 900 800 700 600 200 100 8045 g16 input current (ma) 0 300 400 100 200 500 600 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 1000 900 800 700 600 200 100 8045 g17 input current (ma) 0 300 400 100 200 500 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 900 800 700 600 200 100 8045 g18 input current (ma) 0 300 400 100 200 500 5v in 12v in 18v in
ltm 8045 6 8045fa for more information www.linear.com/8045 typical performance characteristics input current vs output current, C2.5v out inverting converter input current vs input voltage, 5ma load input current vs input voltage, output shorted output current vs input voltage, output shorted input current vs output current, C3.3v out inverting converter input current vs output current, C5v out inverting converter input current vs output current, C8v out inverting converter input current vs output current, C12v out inverting converter input current vs output current, C15v out inverting converter output current (ma) 0 500 300 400 600 200 100 8045 g19 input current (ma) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 700 600 200 100 8045 g20 input current (ma) 0 300 400 100 200 500 600 700 800 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 800 700 600 200 100 8045 g21 input current (ma) 0 300 400 100 200 500 600 700 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 900 800 700 600 200 100 8045 g22 input current (ma) 0 300 400 100 200 500 600 3.3v in 5v in 12v in 18v in input voltage (v) 10 55 25 50 60 20 15 30 45 40 35 8045 g25 input current (ma) 2 8 10 4 6 12 14 16 18 15v out 12v out 8v out 5v out 3.3v out 2.5v out input voltage (v) 150 500 250 450 550 200 400 300 350 8045 g26 input current (ma) 2 8 10 4 6 12 14 16 18 input voltage (v) 1.2 2.0 2.2 1.8 1.4 1.6 8045 g27 output current (a) 2 8 10 4 6 12 14 16 18 output current (ma) 0 500 300 400 1000 600 800 700 900 200 100 8045 g23 input current (ma) 0 300 400 100 200 500 3.3v in 5v in 12v in 18v in output current (ma) 0 500 300 400 900 800 700 600 200 100 8045 g23 input current (ma) 0 300 400 100 200 500 5v in 12v in 18v in
ltm 8045 7 8045fa for more information www.linear.com/8045 typical performance characteristics minimum required input voltage vs output current maximum output current vs input voltage internal temperature rise vs output current, 2.5v out sepic internal temperature rise vs output current, 3.3v out sepic internal temperature rise vs output current, 5v out sepic internal temperature rise vs output current, 8v out sepic internal temperature rise vs output current, 12v out sepic internal temperature rise vs output current, 15v out sepic internal temperature rise vs output current, C2.5v out inverting converter output current (ma) 2 16 14 18 6 4 8 12 10 8045 g28 input voltage (v) 0 200 400 600 800 15v out 12v out 8v out 5v out 3.3v out 2.5v out input voltage (v) 100 700 600 800 200 300 500 400 8045 g29 output current (ma) 2 8 10 4 6 12 14 16 18 2.5v out 3.3v out 5v out 8v out 12v out 15v out output current (ma) 0 20 10 15 30 25 5 8045 g30 internal temperature rise (c) 0 300 400 100 200 500 600 700 800 18v in 12v in 5v in 3.3v in output current (ma) 0 20 10 15 35 30 25 5 8045 g31 internal temperature rise (c) 0 300 400 100 200 500 600 700 800 18v in 12v in 5v in 3.3v in output current (ma) 0 20 10 15 35 30 25 5 8045 g32 internal temperature rise (c) 0 300 400 100 200 500 600 700 18v in 12v in 5v in 3.3v in output current (ma) 0 20 10 15 45 40 35 30 25 5 8045 g34 internal temperature rise (c) 0 300 400 100 200 500 18v in 12v in 5v in 3.3v in output current (ma) 0 20 10 60 50 40 30 8045 g35 internal temperature rise (c) 0 300 400 100 200 500 18v in 12v in 5v in output current (ma) 0 20 25 15 10 5 8045 g36 internal temperature rise (c) 0 300 400 100 200 500 600 700 800 18v in 12v in 5v in 3.3v in output current (ma) 0 20 10 15 40 35 30 25 5 8045 g33 internal temperature rise (c) 0 300 400 100 200 600500 18v in 12v in 5v in 3.3v in
ltm 8045 8 8045fa for more information www.linear.com/8045 typical performance characteristics internal temperature rise vs output current, C3.3v out inverting converter internal temperature rise vs output current, C5v out inverting converter internal temperature rise vs output current, C8v out inverting converter internal temperature rise vs output current, C12v out inverting converter internal temperature rise vs output current, C15v out inverting converter output current (ma) 0 20 30 25 15 10 5 8045 g37 internal temperature rise (c) 0 300 400 100 200 500 600 700 800 18v in 12v in 5v in 3.3v in output current (ma) 0 20 35 30 25 15 10 5 8045 g38 internal temperature rise (c) 0 300 400 100 200 500 600 700 18v in 12v in 5v in 3.3v in output current (ma) 0 20 35 30 25 15 10 5 8045 g39 internal temperature rise (c) 0 300 400 100 200 500 600 18v in 12v in 5v in 3.3v in output current (ma) 0 20 45 35 40 30 25 15 10 5 8045 g40 internal temperature rise (c) 0 300 400 100 200 500 18v in 12v in 5v in 3.3v in output current (ma) 0 40 60 50 30 20 10 8045 g41 internal temperature rise (c) 0 300 400 100 200 500 18v in 12v in 5v in
ltm 8045 9 8045fa for more information www.linear.com/8045 pin functions v out C (bank 1): v out C is the negative output of the ltm8045. apply an external capacitor between v out + and v out C . tie this net to gnd to configure the ltm8045 as a positive output sepic regulator. v out + (bank 2): v out + is the positive output of the ltm8045. apply an external capacitor between v out + and v out C . tie this net to gnd to configure the ltm8045 as a negative output inverting regulator. gnd (bank 3): tie these gnd pins to a local ground plane below the ltm8045 and the circuit components. gnd must be connected either to v out + or v out C for proper operation . in most applications, the bulk of the heat flow out of the ltm8045 is through these pads, so the printed circuit design has a large impact on the thermal performance of the part. see the pcb layout and thermal considerations sections for more details. return the feedback divider (r fb ) to this net. v in ( bank 4): the v in pin supplies current to the ltm8045 s internal regulator and to the internal power switch. this pin must be locally bypassed with an external, low esr capacitor. fb (pin a3): if configured as a sepic, the ltm8045 regulates its fb pin to 1.215v. apply a resistor between fb and v out + . its value should be r fb = [(v out C 1.215)/ 0.0833]k. if the ltm8045 is configured as an inverting converter , the ltm 8045 regulates the fb pin to 5 mv . apply a resistor between fb and v out C of value r fb = [(| v out | + 0.005)/0.0833]k. sync (pin e1): to synchronize the switching frequency to an outside clock, simply drive this pin with a clock. the high voltage level of the clock needs to exceed 1.3v, and the low level should be less than 0.4v. drive this pin to less than 0.4v to revert to the internal free running clock. ground this pin if the sync function is not used. see the applications information section for more information. ss ( pin f 1): place a soft - start capacitor here . upon start - up, the ss pin will be charged by a (nominally) 275k resistor to about 2.2v. rt (pin g1): the rt pin is used to program the switching frequency of the ltm8045 by connecting a resistor from this pin to ground. the necessary resistor value for the ltm 8045 is determined by the equation r t = (91.9/ f osc ) C 1, where f osc is the typical switching frequency in mhz and r t is in k. do not leave this pin open. run (pin g3): this pin is used to enable/disable the chip and restart the soft-start sequence. drive below 1.235v to disable the chip. drive above 1.385v to activate chip and restart the soft-start sequence. do not float this pin .
ltm 8045 10 8045fa for more information www.linear.com/8045 block diagram current mode controller 1f v in v out ? v out + run ss sync gnd 8045 bd 0.1f ? ? 2f 10h 10h rt fb
ltm 8045 11 8045fa for more information www.linear.com/8045 operation the ltm8045 is a stand-alone switching dc/dc converter that may be configured either as a sepic (single-ended primary inductance converter) or inverting power supply simply by tying v out C or v out + to gnd, respectively. it accepts an input voltage up to 18vdc. the output is adjustable between 2.5v and 15v for the sepic, and between C2.5v and C15v for the inverting configuration. the ltm8045 can provide 700ma at v in = 12v when v out = 2.5v or C2.5v. as shown in the block diagram, the ltm8045 contains a current mode controller, power switching element, power coupled inductor, power schottky diode and a modest amount of input and output capacitance. the ltm8045 is a fixed frequency pwm converter. the ltm8045 switching can free run by applying a resis- tor to the rt pin or synchronize to an external source at a frequency between 200khz and 2mhz. to synchronize to an external source , drive a valid signal source into the sync pin. an r t resistor is required whether or not a sync signal is applied. see the applications information section for more details. the ltm8045 also features run and ss pins to control the start-up behavior of the device. the run pin may also be used to implement an accurate undervoltage lockout function by applying just one or two resistors. the ltm8045 is equipped with a thermal shutdown to protect the device during momentary overload conditions. it is set above the 125c absolute maximum internal tem- perature rating to avoid interfering with normal specified operation, so internal device temperatures will exceed the absolute maximum rating when the overtemperature protection is active. therefore, continuous or repeated activation of the thermal shutdown may impair device reliability.
ltm 8045 12 8045fa for more information www.linear.com/8045 applications information for most applications, the design process is straight forward , summarized as follows: 1. look at table 1 and find the row that has the desired input range and output voltage. 2. apply the recommended c in , c out , r fb and r t values. while these component combinations have been tested for proper operation, it is incumbent upon the user to verify proper operation over the intended systems line, load and environmental conditions. bear in mind that the maximum output current is limited by junction tempera- ture, the relationship between the input and output voltage magnitudes, polarity and other factors. please refer to the graphs in the typical performance characteristics section for guidance. the maximum frequency ( and attendant r t value ) at which the ltm8045 should be allowed to switch is given in table 1 in the f max column, while the recommended fre- quency (and r t value) for optimal efficiency over the given input condition is given in the f optimal column. table 1. recommended component values and configuration (t a = 25c. see the typical performance characteristics for load conditions) sepic topology v in (v) v out (v) c in c out r adj (k) f optimal r t( optimal) (k) f max (mhz) r t(min) (k) 2.8 to 18 2.5 4.7f, 25v, 1206 100f, 6.3v, 1210 15.4 600khz 154 1.3 69.8 2.8 to 18 3.3 4.7f, 25v, 1206 100f, 6.3v, 1210 24.9 700khz 130 1.5 60.4 2.8 to 18 5 4.7f, 25v, 1206 100f, 6.3v, 1210 45.3 800khz 115 2 45.3 2.8 to 18 8 4.7f, 25v, 1206 47f, 10v, 1210 80.6 1mhz 90.9 2 45.3 2.8 to 18 12 4.7f, 25v, 1206 22f, 16v, 1210 130 1.2mhz 75.0 2 45.3 4.5 to 18 15 4.7f, 25v, 1206 22f, 25v, 1210 165 1.5mhz 60.4 2 45.3 inverting topology v in (v) v out (v) c in c out r adj (k) f optimal r t( optimal) (k) f max (mhz) r t(min) (k) 2.8 to 18 C2.5 4.7f, 25v, 0805 47f, 6.3v, 1206 30.1 600khz 154 1.3 69.8 2.8 to 18 C3.3 4.7f, 25v, 0805 47f, 6.3v, 1206 39.2 650khz 140 1.5 60.4 2.8 to 18 C5 4.7f, 25v, 0805 22f, 6.3v, 1206 60.4 700khz 130 2 45.3 2.8 to 18 C8 4.7f, 25v, 1206 22f, 10v, 1206 95.3 1mhz 90.9 2 45.3 2.8 to 18 C12 4.7f, 25v, 1206 10f, 16v, 1206 143 1.2mhz 75.0 2 45.3 4.5 to 18 C15 4.7f, 25v, 1206 4.7f, 25v, 1206 178 1.5mhz 60.4 2 45.3
ltm 8045 13 8045fa for more information www.linear.com/8045 applications information setting output voltage the output voltage is set by connecting a resistor (r fb ) from v out + to the fb pin for a sepic and from v out C to the fb pin for an inverting converter. r fb is determined from the equation r fb = [(v out C 1.215)/0.0833]k? for a sepic and from r fb = [(|v out | + 0.005)/0.0833]k? for an inverting converter. capacitor selection considerations the c in and c out capacitor values in table 1 are the minimum recommended values for the associated oper - ating conditions. applying capacitor values below those indicated in table 1 is not recommended, and may result in undesirable operation. using larger values is generally acceptable, and can yield improved dynamic response, if it is necessary . again, it is incumbent upon the user to verify proper operation over the intended systems line, load and environmental conditions. ceramic capacitors are small, robust and have very low esr. however, not all ceramic capacitors are suitable. x5r and x7r types are stable over temperature and ap- plied voltage and give dependable service . other types, including y5v and z5u have very large temperature and voltage coefficients of capacitance. in an application cir - cuit they may have only a small fraction of their nominal capacitance resulting in much higher output voltage ripple than expected. a final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the ltm8045. a ceramic input capacitor combined with trace or cable inductance forms a high q (under damped) tank circuit . if the ltm8045 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possi- bly exceeding the devices rating. this situation is easily avoided; see the hot-plugging safely section. programming switching frequency the ltm8045 has an operational switching frequency range between 200khz and 2mhz. the free running frequency is programmed with an external resistor from the rt pin to ground . do not leave this pin open under any circumstance . when the sync pin is driven low (< 0.4 v), the frequency of operation is set by the resistor from rt to ground. the r t value is calculated by the following equation: r t = 91.9 f osc ? 1 where f osc is the typical switching frequency in mhz and r t is in k?. switching frequency trade-offs it is recommended that the user apply the optimal r t value given in table 1 for the corresponding input and output operating condition. system level or other considerations, however, may necessitate another operating frequency. while the ltm8045 is flexible enough to accommodate a wide range of operating frequencies , a haphazardly chosen one may result in undesirable operation under certain op- erating or fault conditions. a frequency that is too high can reduce efficiency , generate excessive heat or even damage the ltm8045 in some fault conditions. a frequency that is too low can result in a final design that has too much output ripple or too large of an output capacitor. switching frequency synchronization the switching frequency can be synchronized to an external clock source . to synchronize to the external source , simply provide a digital clock signal at the sync pin. switching will occur at the sync clock frequency. drive sync low and the switching frequency will revert to the internal free-running oscillator after a few clock periods. switching will stop if sync is driven high. the duty cycle of sync must be between 35% and 65% for proper operation. also, the frequency of the sync signal must meet the following two criteria: 1. sync may not toggle outside the frequency range of 200khz to 2mhz unless it is stopped low to enable the free-running oscillator. 2. the sync frequency can always be higher than the free-running oscillator frequency, f osc , but should not be less than 25% below f osc (f osc is set by r t ).
ltm 8045 14 8045fa for more information www.linear.com/8045 applications information soft-start the ltm8045 soft-start function controls the slew rate of the power supply output voltage during start-up. a controlled output voltage ramp minimizes output voltage overshoot, reduces inrush current from the v in supply, and facilitates supply sequencing. a capacitor connected from the ss pin to gnd programs the slew rate. in the event of a commanded shutdown or lockout (run pin), internal undervoltage lockout or a thermal shutdown, the soft-start capacitor is automatically discharged before charging resumes, thus assuring that the soft-start occurs when the ltm8045 restarts. the soft-start time is given by the equation: t ss = c ss / 5.45, where c ss is in f and t ss is in seconds. configurable undervoltage lockout figure 1 shows how to configure an undervoltage lock- out (uvlo) for the ltm8045. typically , uvlo is used in situations where the input supply is current-limited, has a relatively high source resistance, or ramps up/down slowly. a switching regulator draws constant power from the source , so source current increases as source voltage drops. this looks like a negative resistance load to the source and can cause the source to current-limit or latch low under low source voltage conditions. uvlo prevents the regulator from operating at source voltages where these problems might occur. the run pin has a voltage hysteresis with typical thresh- olds of 1.32v (rising) and 1.29v (falling) and an internal circuit that draws typically 11.6a at the run threshold. this makes r uvlo2 optional, allowing uvlo implemen- tation with a single resistor. resistor r uvlo2 is optional. r uvlo2 can be included to reduce the overall uvlo voltage variation caused by variations in the run pin current (see the electrical characteristics section). a good choice for r uvlo2 is 10k 1%. after choosing a value for r uvlo2 , r uvlo1 can be determined from either of the following: r uvlo1 = v in(rising) ? 1.32v 1.32v r uvlo2 + 11.6a or r uvlo1 = v in(falling) ? 1.29v 1.29v r uvlo2 + 11.6a where v in(rising) and v in( falling) are the v in threshold voltages when rising or falling, respectively. for example, to disable the ltm8045 for v in voltages below 3.5v using the single resistor configuration , choose : r uvlo1 = 3.5v ? 1.29v 1.29v + 11.6a = 191k to activate the ltm8045 for v in voltage greater than 4.5v using the two resistor configuration, choose r uvlo2 = 10k and: r uvlo1 = 4.5v ? 1.32v 1.32v 10k + 11.6a = 22.1k internal undervoltage lockout the ltm8045 monitors the v in supply voltage in case v in drops below a minimum operating level (typically about 2.3v). when v in is detected low, the power switch is deactivated, and while sufficient v in voltage persists, the soft- start capacitor is discharged . after v in is detected high, the ltm8045 will reactivate and the soft-start capacitor will begin charging. ltm8045 gnd v in run r uvlo1 r uvlo2 v in 8045 f01 figure 1. the run pin may be used to implement an accurate uvlo
ltm 8045 15 8045fa for more information www.linear.com/8045 applications information thermal shutdown if the part is too hot, the ltm8045 engages its thermal shutdown, terminates switching and discharges the soft- start capacitor . when the part has cooled , the part automati - cally restarts. this thermal shutdown is set to engage at temperatures above the 125 c absolute maximum internal operating rating to ensure that it does not interfere with functionality in the specified operating range. this means that internal temperatures will exceed the 125c absolute maximum rating when the overtemperature protection is active, possibly impairing the devices reliability. pcb layout most of the headaches associated with pcb layout have been alleviated or even eliminated by the high level of integration of the ltm8045. the ltm8045 is neverthe- less a switching power supply, and care must be taken to minimize emi and ensure proper operation. even with the high level of integration, you may fail to achieve specified operation with a haphazard or poor layout. see figure 2 for the suggested layout of the inverting topology applica- tion and figure 3 for the suggested layout of the sepic topology application. ensure that the grounding and heat sinking are acceptable. a few rules to keep in mind are: 1. place the r fb and r t resistors as close as possible to their respective pins. 2. place the c in capacitor as close as possible to the v in and gnd connection of the ltm8045. 3. place the cout capacitor as close as possible to the v out + and v out C connections of the ltm8045. 4. place the c in and c out capacitors such that their ground currents flow directly adjacent or underneath the ltm8045. 5. connect all of the gnd connections to as large a copper pour or plane area as possible on the top layer. avoid breaking the ground connection between the external components and the ltm8045. 6. use vias to connect the gnd copper area to the boards internal ground planes. liberally distribute these gnd vias to provide both a good ground connection and thermal path to the internal planes of the printed circuit board. pay attention to the location and density of the thermal vias in figures 2 and 3. the ltm8045 can benefit from the heat sinking afforded by vias that con- nect to internal gnd planes at these locations, due to their proximity to internal power handling components. the optimum number of thermal vias depends upon the printed circuit board design. for example, a board might use very small via holes. it should employ more thermal vias than a board that uses larger holes. figure 2. layout showing suggested external components, gnd plane and thermal vias for the inverting topology application 8045 f02 ground, thermal vias v in c in r t r fb v out ? gnd gnd fb run rt gnd c out figure 3. layout showing suggested external components, gnd plane and thermal vias for the sepic topology application 8045 f03 ground, thermal vias v in c in r t r fb v out + gnd gnd c out fb run rt
ltm 8045 16 8045fa for more information www.linear.com/8045 applications information hot-plugging safely the small size, robustness and low impedance of ceramic capacitors make them an attractive option for the input bypass capacitor of the ltm8045. however, these capaci- tors can cause problems if the ltm8045 is plugged into a live input supply (see application note 88 for a complete discussion ). the low loss ceramic capacitor combined with stray inductance in series with the power source forms an underdamped tank circuit , and the voltage at the v in pin of the ltm8045 can ring to more than twice the nominal input voltage, possibly exceeding the ltm8045s rating and damaging the part. if the input supply is poorly con- trolled or the user will be plugging the ltm8045 into an energized supply, the input network should be designed to prevent this overshoot. this can be accomplished by installing a small resistor in series with v in , but the most popular method of controlling input voltage overshoot is to add an electrolytic bulk capacitor to the v in net. this capacitors relatively high equivalent series resistance damps the circuit and eliminates the voltage overshoot. the extra capacitor improves low frequency ripple filter - ing and can slightly improve the efficiency of the circuit , though it is physically large. thermal considerations the ltm8045 output current may need to be derated if it is required to operate in a high ambient temperature or deliver a large amount of continuous power. the amount of current derating is dependent upon the input voltage, output power and ambient temperature. the temperature rise curves given in the typical performance character - istics section can be used as a guide. these curves were generated by a ltm8045 mounted to a 25.8cm 2 4-layer fr4 printed circuit board with a copper thickness of 2oz for the top and bottom layer and 1oz for the inner layers. boards of other sizes and layer count can exhibit differ - ent thermal behavior, so it is incumbent upon the user to verify proper operation over the intended systems line, load and environmental operating conditions. the thermal resistance numbers listed in the pin configura - tion section of the data sheet are based on modeling the module package mounted on a test board specified per jesd 51-9 ( test boards for area array surface mount package thermal measurements ). the thermal coefficients provided in this page are based on jesd 51-12 (guide- lines for reporting and using electronic package thermal information). for increased accuracy and fidelity to the actual application , many designers use fea to predict thermal performance . to that end, the pin configuration section of the data sheet typically gives four thermal coefficients: ? ja C thermal resistance from junction to ambient ? jcbottom C thermal resistance from junction to the bottom of the product case ? jctop C thermal resistance from junction to top of the product case ? jb C thermal resistance from junction to the printed circuit board. while the meaning of each of these coefficients may seem to be intuitive, jedec has defined each to avoid confusion and inconsistency. these definitions are given in jesd 51-12, and are quoted or paraphrased below: ? ja is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclosure . this environment is sometimes referred to as still air although natural convection causes the air to move . this value is determined with the part mounted to a jesd 51-9 defined test board, which does not reflect an actual application or viable operating condition. ? jcbottom is the thermal resistance between the junction and bottom of the package with all of the component power dissipation flowing through the bottom of the package. in the typical module converter, the bulk of the heat flows out the bottom of the package, but there is always heat flow out into the ambient environment. as a result, this thermal resistance value may be useful for comparing packages but the test conditions dont generally match the users application.
ltm 8045 17 8045fa for more information www.linear.com/8045 ? jctop is determined with nearly all of the component power dissipation flowing through the top of the pack- age . as the electrical connections of the typical module converter are on the bottom of the package, it is rare for an application to operate such that most of the heat flows from the junction to the top of the part. as in the case of jcbottom , this value may be useful for comparing packages but the test conditions dont generally match the users application. ? jb is the junction-to-board thermal resistance where almost all of the heat flows through the bottom of the module converter and into the board, and is really the sum of the jcbottom and the thermal resistance of the bottom of the part through the solder joints and through a portion of the board . the board temperature is measured a specified distance from the package, using a two-sided, two layer board. this board is described in jesd 51-9. given these definitions , it should now be apparent that none of these thermal coefficients reflects an actual physical operating condition of a module converter. thus, none of them can be individually used to accurately predict the applications information thermal performance of the product. likewise, it would be inappropriate to attempt to use any one coefficient to correlate to the junction temperature vs load graphs given in the products data sheet. the only appropriate way to use the coefficients is when running a detailed thermal analysis, such as fea, which considers all of the thermal resistances simultaneously. a graphical representation of these thermal resistances is given in figure 4. the blue resistances are contained within the module converter, and the green are outside. the die temperature of the ltm8045 must be lower than the maximum rating of 125c, so care should be taken in the layout of the circuit to ensure good heat sinking of the ltm8045. the bulk of the heat flow out of the ltm8045 is through the bottom of the module converter and the bga pads into the printed circuit board. consequently a poor printed circuit board design can cause excessive heating, resulting in impaired performance or reliability. please refer to the pcb layout section for printed circuit board design suggestions. 8045 f04 module device junction-to-case (top) resistance junction-to-board resistance junction-to-ambient resistance (jesd 51-9 defined board) case (top)-to-ambient resistance board-to-ambient resistance junction-to-case (bottom) resistance junction ambient case (bottom)-to-board resistance figure 4.
ltm 8045 18 8045fa for more information www.linear.com/8045 typical applications C5v inverting converter with added output filter output ripple and noise 500ns/div measured per an70, using hp461a amplifier, 150mhz bw 200v/div 8045 ta03b 4.7f v in 12vdc ? ? v in v out ? v out ?5v 580ma fb 8045 ta03 v out + run ltm8045 ss rt sync gnd 60.4k 22f 10f 130k mpz1608s601a ferrite bead 4.7f v in 2.8vdc to 18vdc ? ? v in v out ? v out ?12v fb 8045 ta04 v out + run ltm8045 ss rt sync gnd 143k 10f 75.0k C12 v inverting converter maximum output current vs input voltage C5v out inverting converter C5v inverting converter 4.7f v in 2.8vdc to 18vdc ? ? v in v out ? v out ?5v fb 8045 ta02 v out + run ltm8045 ss rt sync gnd 60.4k 22f 130k input voltage (v) 300 500 600 400 450 650 550 350 8045 ta02b output current (ma) 2 8 10 4 6 12 14 16 18
ltm 8045 19 8045fa for more information www.linear.com/8045 package description table 2. pin assignment table (arranged by pin number) pin number function pin number function pin number function pin number function a1 v out + b1 v out + c1 gnd d1 gnd a2 v out + b2 v out + c2 gnd d2 gnd a3 fb b3 gnd c3 gnd d3 gnd a4 v out C b4 v out C c4 gnd d4 gnd a5 v out C b5 v out C c5 gnd d5 gnd e1 sync f1 ss g1 rt h1 gnd e2 gnd f2 gnd g2 gnd h2 gnd e3 gnd f3 gnd g3 run h3 gnd e4 gnd f4 gnd g4 v in h4 v in e5 gnd f5 gnd g5 v in h5 v in package photo
ltm 8045 20 8045fa for more information www.linear.com/8045 package description please refer to http://www .linear.com/designtools/packaging/ for the most recent package drawings. 5. primary datum -z- is seating plane 6. solder ball composition is 96.5% sn/3.0% ag/0.5% cu 7 package row and column labeling may vary among module products. review each package layout carefully ! package top view 4 pin ?a1? corner y x aaa z aaa z detail a package bottom view 3 see notes suggested pcb layout top view 0.000 0.635 1.905 0.635 3.175 1.905 4.445 3.175 4.445 2.540 1.270 2.540 1.270 0.3175 0.3175 0.000 h g f e d c b a 12345 pin 1 2.8575 3.4925 bga 40 1212 rev a ltmxxxxxx module tray pin 1 bevel package in tray loading orientation component pin ?a1? notes: 1. dimensioning and tolerancing per asme y14.5m-1994 2. all dimensions are in millimeters ball designation per jesd ms-028 and jep95 4 3 details of pin #1 identifier are optional, but must be located within the zone indicated. the pin #1 identifier may be either a mold or marked feature detail a ?b (40 places) detail b substrate 0.27 ? 0.37 3.95 ? 4.05 // bbb z a a1 b1 ccc z detail b package side view mold cap z m x yzddd m zeee symbol a a1 a2 b b1 d e e f g aaa bbb ccc ddd eee min 4.72 0.50 4.22 0.71 0.60 nom 4.92 0.60 4.32 0.78 0.63 11.25 6.25 1.27 8.89 5.08 max 5.12 0.70 4.42 0.85 0.66 0.15 0.10 0.20 0.30 0.15 notes dimensions total number of balls: 40 a2 d e e b f g bga package 40-lead (11.25mm 6.25mm 4.92mm) (reference ltc dwg # 05-08-1867 rev a) 7 see notes
ltm 8045 21 8045fa for more information www.linear.com/8045 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 02/13 output voltage maximum: changed from 16v and C16v to 15v and C15v, respectively 1
ltm 8045 22 8045fa for more information www.linear.com/8045 ? linear technology corporation 2013 lt 0213 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/8045 related parts typical application maximum output current vs input voltage 12v out sepic part number description comments ltm8047 1.5w, 725vdc isolated module regulator 1.5w output power, 3.1v v in 32v, 2.5v v out 12v, 9mm 11.25mm 4.92mm bga package ltm8048 1.5w, 725vdc isolated module regulator with integrated low noise post regulator 1.5w output power, 3.1v v in 32v, 1.2v v out 12v, 1mv p-p output ripple, 9mm 11.25mm 4.92mm bga package ltm8025 36v in , 3a step-down module regulator 3.6v v in 36v, 0.8v v out 24v, synchronizable, 9mm 15mm 4.32mm lga package ltm8033 36v, 3a en55022 class b certified dc/dc step-down module regulator 3.6v v in 36v, 0.8v v out 24v, synchronizable, 11.25mm 15mm 4.3mm lga ltm8026 36v in , 5a step-down module regulator with adjustable current limit 6v v in 36v, 1.2v v out 24v, adjustable current limit, synchronizable , 11.25mm 15mm 2.82mm lga ltm8027 60v in , 4a dc/dc step-down module regulator 4.5v v in 60v, 2.5v v out 24v, synchronizable, 15mm 15mm 4.3mm lga ltm4613 36v in , 8a en55022 class b certified dc/dc step-down module regulator 3.3v v out 15v, 5v v in 36v, pll input, v out tracking and margining, 15mm 15mm 4.3mm lga ltm8061 32v, 2a step- down module battery charger with programmable input current limit suitable for cc-cv charging single and dual cell li-ion or li-poly batteries, 4.95v v in 32v, c/10 or adjustable timer charge termination, ntc resistor monitor input, 9mm 15mm 4.32mm lga ltm8062a 32v, 2a step-down module battery charger with integrated maximum peak power tracking ( mppt) for solar applications suitable for cc-cv charging method battery chemistries (li-ion, li-poly, lead-acid, lifepo 4 ), user adjustable mppt servo voltage, 4.95v v in 32v, 3.3v v batt 18.8v adjustable, c/10 or adjustable timer charge termination , ntc resistor monitor input, 9mm 15mm 4.32mm lga LTC2978 octal digital power supply manager with eeprom i 2 c/pmbus interface, configuration eeprom, fault logging, 16-bit adc with 0.25% tue, 3.3v to 15v operation ltc2974 quad digital power supply manager with eeprom i 2 c/pmbus interface, configuration eeprom, fault logging, per channel voltage , current and temperature measurements ltc3880 dual output polyphase ? step-down dc/dc controller with digital power system management i 2 c/pmbus interface, configuration eeprom, fault logging, 0.5% output voltage , accuracy, mosfet gate drivers 12v sepic converter 4.7f v in 2.8vdc to 18vdc v out 12v ? ? v in v out ? fb 8045 ta05 v out + run ltm8045 ss rt sync gnd 130k 22f 75.0k input voltage (v) 150 350 450 250 300 500 400 200 8045 ta05b output current (ma) 2 8 10 4 6 12 14 16 18

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