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microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? description the lx1684 is a monolithic, voltage- mode pulse-width modulator controller. it is designed to implement a flexible, low cost buck (step-down) regulator supply with a minimal of external components. the lx1684 has a synchronous driver for higher efficiency and is optimized to provide 12v to 3.3v or 12v to 2.5v regulation. it also can be used to convert 5v or 3.3v to voltages as low as 1.25v. switching frequency is fixed at 175khz for optimal cost and space. short-circuit current limiting can be implemented without expensive current sense resistors. similar to the lx1682 in function but with the positive side of the current sense comparator brought out (csp) to allow it to be referenced to the topside fet. current is sensed using the voltage drop across the r ds(on) of the mosfet this sensing is delayed for 1s to eliminate mosfet ringing errors. hiccup-mode fault protection reduces average power to th e power elements during short-circuit conditions. under-voltage lockout and soft-start are provided for optimal start-up performance. pulling the soft-start pin to ground can disable the lx1684. the small 14-pin soic packaging, combined with low profile, low esr capacitors, and to-252 packaged fets results in a high effi ciency converter in a small board area. in most cases pcb copper can accomplish necessary heat sinking and no bulky additional heat sinks are required. if a low profile design is not required small electrolytic capacitors can be used reducing the overall converter cost. important: for the most current data, consult microsemi ?s website: http://www.microsemi.com key features ? fixed 175khz switching frequency ? constant frequency voltage- mode control requires no external compensation ? hiccup-mode over-current protection ? high efficiency ? output voltage set by resistor divider ? under-voltage lockout ? soft-start and enable ? synchronous rectification ? small, 14-pin surface mount package applications ? 12v to 3.3v or less buck regulators ? 3.3/5v to 2.5v or less buck regulators ? hard disk drives ? computer add-on cards product highlight - typical 12v to 3.3v application fb nc ss csp gnd pgnd bdr tdr nc vc1 nc cs nc vcc css 0.1f r2 100 ohm r1 165 ohm c5 1f 5v 5% rset 3.3k l1 10h vout q2 sub45n05- 20l 4x 1500f 6.3v 3x 820f, 16v q1 sub45n 05-20l 12v 10% c1 0.1f 3.3v 10a c3 c4 l1 is a powdered iron toroid 1 2 3 4 5 6 7 14 13 12 11 10 9 8 d1 5817smt optional 12v only circuit 5v 12v to vcc lm78l05 or equivalent package order info d plastic soic 14-pin t a ( c) o utput rohs compliant / pb-free transition dc: 0440 0 to 70 synchronous lx1684cd note: available in tape & reel. append the letters ?tr? to the part number. (i.e. LX1684CD-TR) l l x x 1 1 6 6 8 8 4 4
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? absolute maximum ratings (note 1) supply voltage (v c1 ) ...................................................................................... 18v supply voltage (v cc )........................................................................................ 7v input voltage (csp pin) ................................................................................. 14v output drive peak current source (500ns) ................................................... 1.0a output drive peak current sink (500ns) ....................................................... 1.0a input voltage (ss/enab le pin) .......................................................... -0.3 to 6v operating junction temperature.................................................................. 150c storage temperature ................................................................... -65c to +150c peak package solder reflow temp. (40 second max. exposure) ...260c (+0, -5) note: exceeding these ratings could cause damage to the device. all voltages are with respect to ground. currents are positive into, ne gative out of specified terminal. package pin out 1 2 4 3 14 13 11 12 14-p in soic (top view) 5 6 10 7 9 8 tdrv n/c v c1 n/c cs n/c v cc fb n/c ss vcsp gnd pgnd bdrv rohs / pb-free 100% matte tin lead finish thermal data d p ackage thermal resistance - junction to ambient , ja 165 c/w junction temperature calculation: t j = t a + (p d x ja ). the ja numbers are guidelines for the ther mal performance of the device/pc-board system. all of the above assume no ambient airflow. functional pin description p in n ame d escription v fb voltage feedback. a 1.25v reference is connected to a resistor divider to set desired output voltage. ss soft-start and hiccup capacitor pin. during start up the voltage of this pin controls the output voltage. an internal 22k ? resistor and the external capacitor set the time constant for soft-startup. soft-start does not begin until the supply voltage exceeds the uvlo threshold. when over-current occurs, this capacitor is used for timing hiccup. the pwm can be disabled by pulling the ss pin below 0.3v vcsp positive over-cu rrent threshold input gnd analog ground for ss, fb, cs and vcc. pgnd mosfet driver power ground tdrv gate drive for upper mosfet. bdrv gate drive for lower mosfet. v c1 separate supply for mosfet gate driv es. connect to gat e drive voltage. cs over-current set. connect resistor between cs pin and th e source of the upper mosfet to set current-limit point. v cc ic supply voltage (nominal 5v). p p a a c c k k a a g g e e d d a a t t a a
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? electrical characteristics unless otherwise specified, the following specifications apply over the operating ambient temperature 0 c t a 70 c except where otherwise noted. test conditions: v cc =5v, v c1 =16v lx1684 parameter symbol test conditions min typ max units ` reference reference voltage v fb v out =v fb , t a =25c 1.237 1.25 1.262 v v out =v fb , 0c < t a < 70c 1.231 1.269 v ` oscillator frequency f osc 135 175 200 khz ramp amplitude v ramp 1.25 vpp ` error amplifier input resistance r in v out = v fb 20 k ? ` current sense current set i set v cs = v cc ?0.4v 40 45 a v trip 300 380 420 mv current sense delayed t csd 1.0 sec ` output drivers drive rise time, fall time t rf c l = 3000pf 50 ns drive high v dh i source = 20ma, v c1 =16v 13 14 v drive low v dl i sink = 20ma, v c1 =16v 0.1 0.2 v ` uvlo and soft-start (ss) v cc5 start-up threshold v st v c1 > 4.0v 4.0 4.25 4.5 v hysteresis 0.10 v ss resistor r ss 22 k ? ss output enable v en 0.25 0.3 0.35 v hiccup duty cycle dc hic c ss = 0.1f, f req =100hz 12 14 % ` supply current v c1 dynamic supply current i cd out freq = 175khz, c l =3000pf, synch., v ss > 0.3v 30 40 ma static supply current v c1 i vc1 v ss < 0.3v ; outputs low (disable), v c1 = 16v 7 9 ma 5v i vcc v ss > 0.3v ; outputs low (disable) 9 12 ma e e l l e e c c t t r r i i c c a a l l s s
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? block diagram cs comp + - amplifier/ compensation + - error comp + - i reset r s q q 8 v trip 12 320k 20k 1 r ss v ref hiccup ramp oscillator 7 6 uvlo 14 3 10 l r 1 esr c out r 2 c in +17.5v v in (+12v) +5v v core r set c ss v cc pgnd bdrv tdrv v c1 cs v fb ss/enable hiccup uvlo i set pw m set v reset i set 4 5 gnd vcsp b b l l o o c c k k d d i i a a g g r r a a m m
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? theory of operation general description the lx1684 is a voltage-mode pulse-width modulation controller integrated circuit. the internal oscillator and ramp generator frequency is fixed at 1 75khz. the devices have internal compensation, so that no external compensation is required. power up and initialization at power up, the lx1684 monitors the supply voltage to both the +5v and the v c1 pins (there is no special requirement for the sequence of the two supplies). before both supplies reach their under-voltage lock-out (uvlo) thres holds, the soft-start (ss) pin is held low to prevent soft-sta rt from beginning; the oscillator control is disabled and th e top mosfet is kept off. soft-start once the supplies are above the uvl o threshold, the soft-start capacitor begins to be charged up by the reference through a 20k internal resistor. the capacitor voltage at the ss pin rises as a simple rc circuit. the ss pin is connected to the amplifier's non- inverting input that controls the output voltage. the output voltage will follow the ss pin voltage if sufficient charging current is provided to the output capacitor. the simple rc soft-start allows the output to rise faster at the beginning and slower at the end of the soft-start interval. thus, the required charging current into the output capacitor is less at the end of the soft-start interval so decreasing the possibility of an over-current. a comparator monitors the ss pin voltage and indicates the end of soft-start when ss pin voltage reaches 95% of v ref . over-current protection (ocp) and hiccup the lx1684 uses the rds(on) of the upper mosfet, together with a resistor (rset) to set the actual current limit point. unlike the lx1681/2 controllers the lx1684 includes the positive current sense comparator input providing true kelvin sensing which is more accurate and offers more noise immunity. this kelvin sensing also simplifies th e pcb layout for current sense. the csp pin has a useful common m ode input range to about 14v. the comparator senses the current 1s after the top mosfet is switched on. experiments have shown that the mosfet drain voltage will ring for 200-500ns after the gate is turned on. in order to reduce inaccuracies due to ringing, a 1s blanking delay after gate turn-on is built into the current sense co mparator. this 1us delay reduces the effectiveness of the current sense comparator when the output pulse width is below 1us. this can be problem when the set application output voltage is less than 3.0v with a 12v input. under this condition the output current limit protection will not function properly. this is usually not true with a short circuit current condition, which causes the on time to be greater than the blanking delay. in this circumstance the current limit comparator would turn off the top fet driver. the comparator draws a current (iset), whose magnitude is 45a. the set resistor is selected to set the current limit for the application. when the sensed voltage across the rds(on) plus the set resistor exceeds the 400mv vtrip threshold, the ocp comparator outputs a signal to reset the pwm latch and to start hiccup mode. the soft-start capacitor (css) is discharged slowly (10 times slower than when being charged up by rss). when the voltage on the ss/enable pin reaches a 0.3v threshold, hiccup finishes and the circuit soft-starts again. during hiccup, the top mosfet is off and the bottom mosfet remains on. hiccup is disabled during the soft-start interval, allowing the circuit to start up with the maximum current. if the rise speed of the output voltage is too fast, the required charging current to the output capacitor may be higher than the limit-current. in this case, the peak mosfet current is regulate d to the limit-current by the current-sense comparator. if the mosfet current still reaches its limit after the soft-start finishes, the hiccup is triggered again. the hiccup ensures the average heat generation on both mosfet?s and the average current to be much less than that in normal operation, if the output has a short circuit. over-current protection can also be implemented using a sense resistor , instead of using the rds(on) of the upper mosfet, for greater set-point accuracy. see application information section. oscillator frequency an internal oscillator sets the switching frequency at about 175 khz. d d e e s s c c r r i i p p t t i i o o n n
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? application information output inductor the output inductor should be sele cted to meet the requirements of the output voltage ripple in steady-state operation and the inductor current slew-rate duri ng transient. the peak-to-peak output voltage ripple is: ripple ripple i esr v = where ( ) = l f sw i ripple is the inductor ripple current, l is the output inductor value and esr is the effective series resistance of the output capacitor. i ripple should typically be in the range of 20% to 40% of the maximum output current. higher inductance results in lower output voltage ripple, allowing s lightly higher esr to satisfy the transient specification. higher inductance also slows the inductor current slew rate in response to the load-current step change, ? i, resulting in more output-capacitor voltage droop. the inductor- current rise and fall times are: () out in v v ? ? = i l t rise and out v i l t fall ? = when using electrolyt ic capacitors, the ca pacitor voltage droop is usually negligible, due to the large capacitance. output capacitor the output capacitor is sized to meet ripple and transient performance specifications . effective series re sistance (esr) is a critical parameter. when a step load current occurs, the output voltage will have a step that equals the product of the esr and the current step, ? i. in an advanced microprocessor power supply, the output capacitor is us ually selected for esr instead of capacitance or rms current capability. a cap acitor that satisfies the esr requirement usually has a larger cap acitance and c urrent capability than strictly needed. the allowed esr can be found by: () ex v i esr < ? + ripple i where i ripple is the inductor ripple current, ? i is the maximum load current step change, and v ex is the allowed output voltage excursion in the transient. output capacitor (continued) electrolytic capacitors can be us ed for the output capacitor, but are less stable with age than tantalum capacitors. as they age, their esr degrades, reducing the system performance and increasing the risk of failure. it is recommended that multiple parallel capacitors be used, so that, as esr increases with age, overall performance will still meet the processor?s requirements. there is frequently strong pressure to use the least expensive components possible, however, this could lead to degraded long- term reliability, especially in the case of filter capacitors. linfinity?s demonstration bo ards use sanyo mv-gx filter capacitors, which are aluminum electrolytic, and have demonstrated reliability. the oscon series from sanyo generally provides the very best performance in terms of long term esr stability and general reliability, but at a substantial cost penalty. the mv-gx series provides exce llent esr performance at a reasonable cost. beware of off-brand, very low-cost filter capacitors, which have been shown to degrade in both esr and general electrolytic characteristics over time. input capacitor the input capacitor and the input inductor are to filter the pulsating current generated by the buck converter to reduce interference to other circuits connected to the same 12v rail. in addition, the input capacitor provides local de-coupling the buck converter. the capacitor should be rated to handle the rms current requirement. the rms current is: ) 1 ( d d i i l rms ? = where i l is the inductor current and the d is the duty cycle. the maximum value, when d = 50%, i rms = 0.5 i l . for 12v input and output in the range of 3v, the required rms current is very close to 0.43 i l . soft-start capacitor the value of the soft-start capacitor determines how fast the output voltage rises and how large the inductor current is required to charge the output capacitor. the output voltage will follow the voltage at ss pin if the required inductor current does not exceed the maximum current in the inductor. the ss pin voltage can be expressed as: ) 1 ( / ss ss c r t set ss e v v ? ? = where v set is the reference voltage. r ss and c ss are soft start resistor and capacitor. the required inductor current for the output capacitor to follow the ss-pin voltage equals the required capacitor current plus the load current. the soft-start capacitor should be selected so that the overall inductor current does not exceed its maximum. 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 integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 7 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? application information soft-start capacitor (continued) the capacitor current to follo w the ss-pin voltage is: () ss ss out c r t ss out out c e c c dt dv c i / ? = = where c out is the output capacitance. the typical value of c ss should be in the range of 0.1 to 0.2f. during the soft-start interval the load current from a microprocessor is negligible; ther efore, the capacitor current is approximately the required inductor current. over-current protection current limiting occurs at current level i cl , when the voltage detected by the current sense comp arator is greater than the current sense comparator threshold, v trip (400mv). trip set set on ds cl v r i r i = + ) ( so, a r i mv r i r i v r on ds cl set set on ds cl trip set 45 400 ) ( ) ( ? = ? = example: for 10a current limit, using sub45n05-20l mosfet (20m ? r ds(on) ): ? = ? = ? k r set 42 4 10 45 020 0 10 4 0 6 . . . current sensing using sense resistor the method of current sensing using the r ds(on) of the upper mosfet is economical, but can have a large tolerance, since the r ds(on) can vary with temperature, etc. a more accurate alternative is to use an external sense resistor (r sense ). the sense resistor could be a pcb trace (for construc tion details, s ee application note an-10 or lx1668 data sheet). the over-current trip point is calculated as in the equations above, replacing r ds(on) with r sense . example: for 10a current limit, using a 5m ? sense resistor: ? = ? = ? = ? k r i r i v r set set sense cl trip set 8 . 7 10 45 005 . 0 10 4 . 0 ) ( 6 output enable the lx1684 fet driver outputs ar e driven to ground by pulling the soft-start pin below 0.3v. programming the output voltage the output voltage is sensed by the feedback pin (v fb ) which has a 1.25v reference. the output voltage can be set to any voltage above 1.25v (and lower than the input voltage) by means of a resistor divider (see product highlight). ) 1 ( 2 1 r r v v ref out + = note: keep r 1 and r 2 close to 100 ? (order of magnitude). fet selection to insure reliable operation, the operating junction temperature of the fet switches must be kept below certain limits. the intel specification states that 115c maximum junction temperature should be maintained with an ambient of 50c. this is achieved by properly derating the part, and by adequate heat sinking. one of the most critical parameters for fet selection is the r ds(on) resistance. this parameter directly contribu tes to the power dissipation of the fet devices, and thus impacts heat sink design, mechanical layout, and reliability. in general, the larger the current handling capability of the fet, the lower the r ds(on) will be, since more die area is available. table 1 - fet selection guide this table gives selection of suitable fets from vishay device v ds (v) r ds(on) @4.5v (m ? ) r ds(on) @10v (m ? ) gate charge typ(nc) d 2 pak and to-220 sub70n03-09bp 30 13 9 15.5 sub45n03-13l 30 20 13 45 sub45n05-20l 40 20 18 43 sub70n04-10 40 14 10 50 so-8 si4810dy 30 20 13.5 20 si4812dy 30 28 18 16 heat dissipated in upper mosfet the heat dissipated in the top mosfet will be: ) 5 . 0 ( ) ( ) ( 2 s sw in on ds d f t v i cycle duty r i p + = where t sw is switching transition line for body diode (~100ns) and f s is the switching frequency. for the sub70n03-09bp (13m ? r ds(on) ), converting 12v to 3.3v at 15a will result in typi cal heat dissipation of 2.6w. 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 integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 8 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? application information fet selection (continued) synchronous rectification ? lower mosfet the lower pass element can be either a mosfet or a schottky diode. the use of a mosfet (synchronous rectification) will result in higher efficiency, but at higher cost than using a schottky diode (non-synchronous). power di ssipated in the bottom mosfet will be: [] w cycle duty r i p on ds d 26 3 1 2 . ) ( = ? = [sub45n03-13l or 2.12w for the sub70n03-09bp] non-synchronous operation - schottky diode a typical schottky diode, with a forward drop of 0.6v will dissipate 0.6 * 15 * [1 ? 3.3/12] = 6.5w (compared to the 2.1 to 4.2w dissipated by a mosfet unde r the same conditions). this power loss becomes much more si gnificant at lower duty cycles. the use of a dual schottky diode in a single to-220 package (e.g. the mbr2535) helps improve thermal dissipation. boost operation the lx1684 needs a seconda ry supply voltage (v c1 ) to provide sufficient drive to the upper mosfet. the top fet must be a logic level power mosfet such as sub45n03-13l . it must be able to turn on to a low r ds(on) with v gs of 4.5v or higher. v c1 can be generated using a bootstrap (charge pump) circuit, as shown in the product highlight on page 1. the capacitor, (c 1 ) is alternatively charged up from 5v via the schottky diode, (d 1 ), and then boosted up when the fet is turned on. under any circumstance the voltage at v c1 should not be more than 18v for more than 300ns and must not be greater than 19v for more than 50ns. lab evaluation and module production test should be the final arbiter to verify the proper operation. for applicati on with a large mosfet, the maximum voltage at v c1 should be kept lower due to thermal dissipation in the fet driver section. it is inherent in a higher current power supply that the pa rasitic inductance and capacitance on pcb board and power mosfet device induces ringing at the gate drive. the extra thermal dissipation and the higher peak voltage generated by gate ringing should be taken in account during final design. the temperature rise due to gate drive thermal dissipation can be reduced by extr a heat sinking. a resistor in series with the gate in order of 10ohm or snubber circuitry can reduce the gate ringing. the volta ge must provide sufficient gate drive to the external mosfet in order to get a low r ds(on) and must be lower than maximum voltage rating of 18v. note that using the bootstrap circ uit in synchronous rectification mode is likely to result in faster turn-on than in non-synchronous mode. layout guidelines - thermal design a great deal of time and eff ort were spent optimizing the thermal design of the demonstration boards. any user who intends to implement an embedded mothe rboard would be well advised to carefully read and follow these guidelines. if the fet switches have been carefully selected, external heatsinking is generally not required. however, this means that copper trace on the pc board must now be used. this is a potential trouble spot; as much copper area as possible must be dedicated to heatsinking the fet switches , and the diode as well if a non- synchronous solution is used.. lx1684 +12v input output gnd figure 2 ? key power pcb traces general notes as always, be sure to provide local capacitive decoupling close to the chip. be sure use ground plane construction for all high- frequency work. use low esr capac itors where justified, but be alert for damping and ringing problems. high-frequency designs demand careful routing and layout, and may require several iterations to achieve desired performance levels. power traces to reduce power losses due to ohmic resistance, careful consid- eration should be given to the layout of traces that carry high currents. the main paths to consider are: ? input power from 12v supply to drain of top mosfet. ? trace between top mosfet and lower mosfet or schottky diode. ? trace between lower mosfet or schottky diode and ground. ? trace between source of top mosfet and inductor and load. all of these traces should be made as wide and thick as possible, in order to minimize resistance and hence power losses. it is also recommended that, whenever possible, the ground, input and output power signals should be on separate planes (pcb layers). see figure 2 ? bold traces are power traces. 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 integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 9 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? typical application fb nc ss csp gnd pgnd bdr tdr nc vc1 nc cs nc vcc css 0.1f r2 100 ohm r1 300 ohm c5 1f 5v rset 2k l1 is powder iron toroid vout q1 4x 1500 f c6 1f 2x 820f, 16v 10.8v - 13.2v mbr2545 l1 10h figure 3 ? 12v to 5v with p-mosfet. no charge pump is needed. fb nc ss csp gnd pgnd bdr tdr nc vc1 nc cs nc vcc css 0.1f r2 50k ohm r1 150 ohm c5 1f 5v 5% rset 3.9k l1 5h vout q2 sub45n05- 20l 2x 270f 2v 2x 150f, 6.3v q1 sub45n 05-20l 3.3v 10% c1 0.1f c3 panasonic eef-ue0d271r 270uf 3a 15mohm esr c4 panasonic eef-ue0j151r 150uf 3a 18mohm esr 1.25v 10a 5817smt c3 c4 l1 is a powdered iron toroid 1 2 3 4 5 6 7 14 13 12 11 10 9 8 d1 figure 4 ? 3.3v to 1.25v with charge pump. 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 integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 10 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? characterization charts see product highlight schematic typical 12v to 3.3v application efficency vs. output current 0.70 0.75 0.80 0.85 0.90 0.95 1.00 012345678910 output current (a) efficieny output voltage vs. load 3.300 3.305 3.310 3.315 3.320 024681012 output current (a) output voltage (v) output voltage vs. temperature 3.28 3.29 3.30 3.31 3.32 3.33 3.34 20 30 40 50 60 70 80 90 temperature (c) output voltage(v) output startup 1ms / div v out = 3.3v v cc = 5v dc 2v / div 2v / div output voltage vs. temperature 100s / div v out = 2vdc i out = 5a 100mv / div 25a / div output voltage vs. temperature 10s / div 100mv / div i out = 10a c c h h a a r r t t s s
microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 11 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? package dimensions d 14-pin plastic soic b g f k l a p c d j m 123 m illimeters i nches dim min max min max a 8.54 8.74 0.336 0.344 b 3.81 3.94 0.150 0.155 c 1.35 1.75 0.053 0.069 d 0.33 0.51 0.013 0.020 f 0.77 0.030 g 1.27 bsc 0.050 bsc j 0.19 0.25 0.007 0.010 k 0.10 0.25 0.004 0.010 l 4.82 5.21 0.189 0.205 m 0 8 0 8 p 5.79 6.20 0.228 0.244 *lc 0.10 0.004 *lead coplanarity 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 integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 12 copyright ? 2000 rev. 1.0c, 2005-03-08 www. microsemi . com lx1684 v olta g e-mode pwm controller p roduction d ata s heet tm ? 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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