microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division description description description description the lx8817 is a dual channel positive-voltage linear regulator. this dual regulator has one fixed output coupled with an adjustable output. each channel features low-dropout and high accuracy. the lx8817 utilizes dual inputs that can be used as separate sources for the control and power sections. this configuration reduces power dis- sipation by operating the regulator near dropout (v pwr -v out = v do = 0.6v @ 2.5a) while providing sufficient operating headroom for the control logic. the lx8817 provides designers with an efficient flexible power management solution, minimal printed circuit board area, and shorter design cycles. each channel can supply up to 2.5a independently with a regulator design optimized for system efficiency by consuming minimal ground current and directing quiescent current to the load. the lx8817 features on-chip trimming of the internal voltage refer- ence, enabling precise output voltages, typically 1% of it?s specified value. power sequencing logic ensures proper startup regardless of the level of v ctrl or v pwr . the lx8817 outputs remain off while v pwr < 2.4v. thermal and short circuit current protection are integrated on-chip and operate independently for each regulator output. the lx8817 regulator is stable with a low-value output capacitor, typically 10 f tantalum or ceramic on the outputs, allowing designers flexibility in external component selection. linfinity?s s-pak power package offers maximum power dissipation and ease of assembly using surface mount technology. important: for the most current data, consult microsemi ?s website: http://www.microsemi.com key features key features key features key features two independent regulated outputs accurate output voltages max. dropout of 0.6v at rated current independent thermal and current limit protection low profile 7 lead smt power package low tolerance line (0.2%) and load (0.4%) regulation wide dc supply voltage of 3.0v to 10.0v loop stability independent of output capacitor type applications/benefit applications/benefit applications/benefit applications/benefits s s s 3.3v to 2.5v/adj linear regulator low voltage logic supplies active scsi terminators battery charging circuits instrumentation pc peripherals product highlight product highlight product highlight product highlight 2 5 6 4 1 3 lx8817 v pwr v 1 v 2 v ctrl v ctrl v pwr v out1 v out2 adj v2 gnd package order info t a ( c) o utput v 1 o utput v 2 df plastic s-pak 7-pin 0 to 125 2.5v adj lx8817-25cdf note: available in tape & reel. append the letter ?t? to the part number. (i.e. LX8817-25CDFT) l l x x 8 8 8 8 1 1 7 7
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division absolute maximum rat absolute maximum rat absolute maximum rat absolute maximum ratings ings ings ings input voltage (v ctrl , v pwr ) ........................................................................ 13.5v load current (internally limited).................................................................. 3.0a power dissipation...................................................................... internally limited short-circuit protection...........................................................................indefinite operating junction temperature ..................................................................150 c storage temperature range .......................................................... -65 c to 150 c lead temperature (soldering 180 seconds) .................................................235 c note: exceeding these ratings could cause damage to the device. all voltages are with respect to ground. currents are positive into, negative out of specified terminal . package pin out package pin out package pin out package pin out df p ackage (top view) 1 v ctrl v out1 v pwr gnd v out2 2 3 4 5 tab is gnd adj v2 6 nc 7 thermal data thermal data thermal data thermal data df plastic s-pak 7-pin thermal resistance - junction to t ab , jt thermal resistance - junction to a mbient , ja 4.5 c/w 30 c/w junction temperature calculation: t j = t a + (p d x ja ). the ja numbers are guidelines for the thermal performance of the device/pc-board system. all of the above assume no ambient airflow. ja can vary significantly depending on mounting technique. (see application notes section: thermal considerations) functional pin descr functional pin descr functional pin descr functional pin description iption iption iption p in n ame d escription 1 v ctrl unregulated input voltage supply, provides bias for control circuitry, (v ctrl ? v out ) > 1v. 2 v out1 regulator #1 fixed output voltage. 3 v pwr unregulated input voltage supply for power section. for proper operation: (v pwr ? v out ) > v dropout . 4 gnd common terminal for ground reference, tab of package is internally connected to this pin. 5 v out2 regulator #2 adjustable output. 6 adj v2 regulator #2 voltage feedback. sets the output voltage for regulator #2 via an external resistor divider. 7 nc not used. p p a a c c k k a a g g e e d d a a t t a a
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division recommended max oper recommended max oper recommended max oper recommended max operating conditio ating conditio ating conditio ating condition n n n lx8817-25 parameter symbol min typ max units v ctrl 10 v input voltage v pwr 7.5 v load current (internally limited) i 1, i 2 3.0 a operating junction temperature t j 125 c electrical character electrical character electrical character electrical characteristics istics istics istics unless otherwise specified, the following specifications apply over the operating ambient temperature 0 c t a 125 c except where otherwise noted and the following test conditions: v ctrl = 5v, v pwr = 3.3v i out = 5ma, c 1, 2, 3, 4 = 10 f (tantalum), and t j = t a using low duty cycling methods. lx8817-25 parameter symbol test conditions min typ max units ! fixed output output voltage ? lx8817-2500 v 1 5ma < i 1 < 2.5a, 3.75v < v ctrl < 10v 3.3v < v pwr < 5.5v 2.438 2.500 2.538 v line regulation ? v 1 (v in ) 3.3v microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division characteristic curve characteristic curve characteristic curve characteristic curves s s s vout vs temperature 2.41 2.42 2.43 2.44 2.45 2.46 2.47 2.48 2.49 2.5 2.51 -85 -80 -70 -60 -40 -20 0 23 50 70 100 125 145 165 170 175 temperature (c) output voltage (v) 1.205 1.21 1.215 1.22 1.225 1.23 1.235 1.24 1.245 1.25 1.255 vo1: 2.5v fixed vo2: adjustable dropout voltage 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 -50 -25 0 25 50 75 100 125 150 temperature (c) vdd (v) iout=2.5a iout=1a iout=0.5a quiescent current 0 1 2 3 4 5 6 7 8 -50 -25 0 25 50 75 100 125 150 temperature (c) iground (ma) il1&il2=2.5a il1&il2=5ma supply ramp (vcntrl+vpwr) ch4 1 2 3 4 2.00v 1.00v 2.00v 2.00v 1.00ms ch1 800mv ch1 ch3 ma b w b w ch2 ch1 = v p = v c ch3 = v o2 ch2 = v o1 ch4 = i p 2a/div step load response with ceramic cap (10f) ch2 ch4 1 2 4 200mv 200mv 1.00a ? 10.0s ch4 360ma ch1 ma b w b w ch1 = v o1 ch2 = v p ch4 = i o1 (10ma to 2.5a step) step load response with tantalum cap (10f) ch2 ch4 1 2 4 100mv 200mv 10mv 4.00s ch4 13.2mv ch1 ma b w b w b w ch1 = v o1 ch2 = v p ch4 = i o1 (10ma to 2.5a step) c c h h a a r r t t s s
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division appl appl appl application circuit/bloc ication circuit/bloc ication circuit/bloc ication circuit/block diagram k diagram k diagram k diagram bias 1.25v v ref 3 4 v pwr gnd 2 5 6 + - v 1 v 2 c 1 10 f c 3 10 f r 1 r 2 c 4 10 f 1 2 1 1 25 . 1 2 r adj i r r v + ? ? ? ? ? ? ? ? + = (adjustable) input power sequencing (uvlo) 1 v ctrl c 2 10 f + - f igure ? block diagram / application circuit a a p p p p l l i i c c a a t t i i o o n n s s
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division application informat application informat application informat application information ion ion ion the lx8817 is part of a family of dual ldo (low drop-out) linear regulators in linfinity?s s-pak power package which offer maximum power dissipation in a low profile surface mount technology. the family includes combination fixed and adjustable versions. each channel can supply up to 2.5a independently with a regulator design optimized for system efficiency by consuming minimal ground current and directing quiescent current to the load. input capacitor to improve load transient response and noise rejection a input bypass capacitor is of at least 10uf is required. generally we recommend a 10uf ceramic or tantalum or 22uf electrolytic capacitor. output capacitor the regulator requires output capacitors connected between each output (v1, v2) to gnd to stabilize the internal control loop. many types of capacitors are available, with different capacitance values tolerances, temperature coefficients and equivalent series resistance. we recommend a minimum of 4.7uf. to ensure good transient response from the power supply system under rapidly changing current load conditions, designers generally use additional output capacitors connected in parallel. such an arrangement serves to minimize the effects of the parasitic resistance (esr) and inductance (esl) that are present in all capacitors. the regulator has been tested stable with capacitor esr?s in the range of 0.05 to 2 ohms. we have found it best to use the same type of capacitor for both input and output bypass. adjustable output voltage the lx8817x develops a 1.25v reference voltage between the output and the adjust terminal (see figure 2). by placing a resistor, r1, between these two terminals, a constant current is caused to flow through r1 and down through r2 to set the overall output voltage.. because i adj is very small and constant when compared with the current through r1, it represents a small error and can usually be ignored. lx8817-25 r1 r2 v in adj v 2 figure 2 - basic adjustable regulator v ref 1 2 1 1 2 r i r r v v adj ref + ? ? ? ? ? ? ? + = i adj 1a v 1 minimum load requirement the lx8817 has a minimum load is requirement for proper output regulation. this typical current is specified at 0ma for the fixed output and 1ma for the adjustable output regulators. temperature protection the thermal protection shuts the lx8817 down when the junction temperature exceeds 160 0 c. each output has independent thermal shutdown capability. exposure to absolute maximum rated conditions for extended periods may affect device reliability, see thermal considerations below. current limit protection the lx8817 includes over current protection, when the output load current exceeds typically 3a the circuit forces the regulator decrease in output. thermal considerations thermal shutdown protects the integrated circuit from thermal overload caused from a rise in junction temperature during power dissipation. this means of protection is intended for fault protection only and not as a means of current or power limiting during normal application usage. proper thermal evaluation should be done to ensure that the junction temperature dose not exceed it?s maximum rating. operating at the maximum t j of 150c can impact reliability . due to variation in individual device electrical characteristics and thermal resistance , the built in thermal overload protection may be activated at power levels slightly above or below the rated dissipation. also peak output power should be considered for each individual output. power dissipation for regulator can be calculated using the following equation: 2 2 in(max) 1 1 in(max) d i ) v (v i ) v (v p ? + ? = (note: power dissipation resulting from quiescent (ground) current is negligible) for the s-pak package, thermal resistance, tab-amb is 25- 45 0 c/w depending on mounting technique when mounted on a fr4 copper clad pcb. junction temperature of the integrated circuit can be calculated using: amb rise amb tab rise tab junction junction t t t t + + = ? ? jt dmax tab p t = ; pcb 2 dreg 1 dreg amb tab ) p (p t + = ? an example: given conditions: t a = 50c, v in = 5.0v, v 1 = 2.5v, i 1 = 210ma, v 2 = 3.3v i 2 = 1a. calculated values: c c/w c/w 2.4 4.5 (0.525) 4.5 2.5v) (5v t reg1 tab j = = ? = ? c c/w c/w v v 7.7 4.5 (1.7) 4.5 (1a) ) 3.3 (5 t reg2 tab j = = ? = ? c 66.8 c/w 30 1.7w) (0.525w t ambrise tab = + = ? c 124.5 c 50 c 66.8 c 7.7 t junction = + + = it is important to note that although each output of the regulator will produce up to 2.5a in current, the individual or total power dissipation may limit the useful total current draw. the junction temperature should be calculated for each individual output as well as the combined outputs to insure the maximum junction temperature in not exceeded. a a p p p p l l i i c c a a t t i i o o n n s s
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 7 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division mechanical diminesio mechanical diminesio mechanical diminesio mechanical diminesions ns ns ns a b k f g i d c h j e m illimeters i nches dim min max min max a 9.27 9.52 .365 .375 b 8.89 9.14 .350 .360 c 1.77 2.03 .070 .080 d 7.49 7.74 .295 .305 e 0.12 0.38 .005 .015 f 0.58 0.84 .023 .033 g 1.27 bsc 0.050 bsc h 0.79 1.04 .031 .041 i 4.31 6.86 .170 .270 j 0.03 0.13 .001 .005 k 10.41 10.67 .410 .420 note: 1. dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006?) on any side. lead dimension shal l not include solder coverage. m m e e c c h h a a n n i i c c a a l l s s
microsemi linfinity microelectronics division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 8 copyright ? 2000 rev. 0.3d, 2002-01-08 www. microsemi . com lx8817 dual channel 2.5a low dropout regulato r p roduction d ata s heet linfinity division notes notes notes notes production data ? information contained in this document is proprietary to microsemi and is current as of publication date. this document may not be modified in any way without the express written consent of microsemi. product processing does not necessarily include testing of all parameters. microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. n n o o t t e e s s
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