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january 2010 1 m9999-012610 mic4684 micrel, inc. mic4684 2a high-effciency superswitcher? buck regulator general description the mic4684 is a high-effciency 200khz stepdown (buck) switching regulator. power conversion effciency of above 85% is easily obtainable for a wide variety of applications. the mic4684 achieves 2a of continuous current in an 8-lead so (small outline) package at 60c ambient temperature. high effciency is maintained over a wide output current range by utilizing a boost capacitor to increase the voltage available to saturate the internal power switch. as a result of this high effciency, no external heat sink is required. the mic4684, housed in an so-8, can replace larger to-220 and to-263 packages in many applications. the mic4684 allows for a high degree of safety. it has a wide input voltage range of 4v to 30v (34v transient), allowing it to be used in applications where input voltage transients may be present. built-in safety features include over-current protection, frequency-foldback short-circuit protection, and thermal shutdown. the mic4684 is available in an 8-lead so package with a junction temperature range of C40c to +125c. typical application bs vin 4 1 5 2, 6, 7 3 8 sw fb en gnd mic4684bm c bs 0.33f/50v c in 33f 35v 330f 6.3v 3a 40v r1 3.01k r2 3.01k 68h v in 6.5v to 25v v out 2.5v/1.5a adjustable buck converter features ? so-8 package with 2a continuous output current ? over 85% effciency ? fixed 200khz pwm operation ? wide 4v to 30v input voltage range ? output voltage adjustable to 1.235v ? all surface mount solution ? internally compensated with fast transient response ? over-current protection ? frequency foldback short-circuit protection ? thermal shutdown applications ? simple high-effciency step-down regulator ? 5v to 3.3v/1.7a converter (60c ambient) ? 12v to 1.8v/2a converter (60c ambient) ? on-card switching regulator ? dual-output 5v converter ? battery charger micrel, inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com 0 20 40 60 80 100 0 0. 5 1 1. 5 2 ) % ( y c n e i c i f f e output current (a) efficiency vs. output current v out = 1.8v v out = 2.5v v out = 3.3v v in = 5.0v effciency vs. output current ordering information part number voltage junction temp. range package standard pb-free mic4684bm MIC4684YM adj -40c to +125c sop-8 superswitcher is a trademark of micrel, inc.
micrel, inc. mic4684 january 2010 2 m9999-012610 pin description pin number pin name pin function 1 sw switch (output): emitter of npn output switch. connect to external storage inductor and shottky diode. 2, 6, 7 gnd ground 3 in supply (input): unregulated +4v to 30v supply voltage (34v transient) 4 bs booststrap voltage node (external component): connect to external boost capacitor. 5 fb feedback (input): outback voltage feedback to regulator. connect to output of supply for fxed versions. connect to 1.23v tap of resistive divider for adjustable versions. 8 en enable (input): logic high = enable; logic low = shutdown pin confguration 1 sw gnd vin bs 8 en gnd gnd fb 7 6 5 2 3 4 8-pin sop (m) detailed pin description switch (sw, pin 1) the switch pin is tied to the emitter of the main internal npn transistor. this pin is biased up to the input voltage minus the v sat of the main npn pass element. the emitter is also driven negative when the output inductors magnetic feld collapses at turn-off. during the off time the sw pin is clamped by the output schottky diode to a C0.5v typically. ground (gnd, pins 2,6,7) there are two main areas of concern when it comes to the ground pin, emi and ground current. in a buck regulator or any other non-isolated switching regulator the output capacitor(s) and diode(s) ground is referenced back to the switching regulators or controllers ground pin. any resistance between these reference points causes an offset voltage/ir drop proportional to load current and poor load regulation. this is why its important to keep the output grounds placed as close as possible to the switching regulators ground pin. to keep radiated emi to a minimum its necessary to place the input capacitor ground lead as close as possible to the switching regulators ground pin. input voltage (v in , pin 3) the v in pin is the collector of the main npn pass element. this pin is also connected to the internal regulator. the output diode or clamping diode should have its cathode as close as possible to this point to avoid voltage spikes adding to the voltage across the collector. bootstrap (bs, pin 4) the bootstrap pin in conjunction with the external bootstrap capacitor provides a bias voltage higher than the input volt - age to the mic4684s main npn pass element. the bootstrap capacitor sees the dv/dt of the switching action at the sw pin as an ac voltage. the bootstrap capacitor then couples the ac voltage back to the bs pin plus the dc offset of v in where it is rectifed and used to provide additional drive to the main switch, in this case a npn transistor. this additional drive reduces the npns saturation voltage and increases effciency, from a v sat of 1.8v, and 75% effciency to a v sat of 0.5v and 88% effciency respectively. feedback (fb, pin 5) the feedback pin is tied to the inverting side of a gm error amplifer. the noninverting side is tied to a 1.235v bandgap reference. fixed voltage versions have an internal voltage divider from the feedback pin. adjustable versions require an external resistor voltage divider from the output to ground, with the center tied to the feedback pin. enable (en, pin 8) the enable (en) input is used to turn on the regulator and is ttl compatible. note: connect the enable pin to the input if unused. a logic-high enables the regulator. a logic-low shuts down the regulator and reduces the stand-by quiescent input current to typically 150a. the enable pin has an up - per threshold of 2.0v minimum and lower threshold of 0.8v maximum. the hysterisis provided by the upper and lower thresholds acts as an uvlo and prevents unwanted turn on of the regulator due to noise.
january 2010 3 m9999-012610 mic4684 micrel, inc. electrical characteristics v in = v en = 12v, v out = 5v; i out = 500ma; t a = 25c, unless otherwise noted. bold values indicate C40c t j +125c. parameter condition min typ max units feedback voltage (2%) 1.210 1.235 1.260 v (3%) 1.198 1.272 v 8v v in 30v, 0.1a i load 1a, v out = 5v 1.186 1.235 1.284 v 1.173 1.297 v feedback bias current 50 na maximum duty cycle v fb = 1.0v 94 % output leakage current v in = 30v, v en = 0v, v sw = 0v 5 500 a v in = 30v, v en = 0v, v sw = C1v 1.4 20 ma quiescent current v fb = 1.5v 6 12 ma bootstrap drive current v fb = 1.5v, v sw = 0v 250 380 ma bootstrap voltage i bs = 10ma, v fb = 1.5v, v sw = 0v 5.5 6.2 v frequency fold back v fb = 0v 30 50 120 khz oscillator frequency 180 200 225 khz saturation voltage i out = 1a 0.59 v short circuit current limit v fb = 0v, see test circuit 2.2 a shutdown current v en = 0v 150 a enable input logic level regulator on 2 v regulator off 0.8 v enable pin input current v en = 0v (regulator off) 16 50 a v en = 12v (regulator on) C1 C0.83 ma thermal shutdown @ t j 160 c note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. devices are esd sensitive. handling precautions recommended. note 4. 2.5v of headroom is required between v in and v out . the headroom can be reduced by implementing a feed-forward diode a seen on the 5v to 3.3v circuit on page 1. note 5. measured on 1 square of 1 oz. copper fr4 printed circuit board connected to the device ground leads. absolute maximum ratings (note 1) supply voltage (v in ), note 3 ....................................... +34v enable voltage (v en ) ...................................... C0.3v to +v in steady-state output switch voltage (v sw ) ......... C1v to v in feedback voltage (v fb ) .............................................. +12v storage temperature (t s ) ........................ C65c to +150c esd rating ............................................................... note 3 operating ratings (note 2) supply voltage (v in ) note 4 ............................ +4v to +30v ambient temperature (t a ) .......................... C40c to +85c junction temperature (t j ) ........................ C40c to +125c package thermal resistance ja , note 5 .......................................................... 75c/w jc , note 5 .......................................................... 25c/w
micrel, inc. mic4684 january 2010 4 m9999-012610 test circuit sw 68h i vin bs fb en device under t est +12v sop-8 5 gnd 2,6,7 4 1 3 8 current limit test circuit shutdown input behavior on off guaranteed on typical on guaranteed off typical off 0.8v 1.25v 0v 1.4v v in(max) 2v enable hysteresis
january 2010 5 m9999-012610 mic4684 micrel, inc. typical characteristics (t a = 25c unless otherwise noted) 0 10 20 30 40 50 60 70 80 90 100 0 0.5 1 1.5 2 2.5 3 efficiency (%) output current (a) with feed forward diode 5v out 1.8v out 2.5v out 3.3v out v in = 12v efficiency vs. output current 0 50 100 150 200 250 300 350 0 10 12 14 16 18 20 bootstrap current (ma) input voltage (v) bootstrap drive current vs. input voltage v in = 12v v fb = 1.5v 2 4 6 8 10.3 10.4 10.5 10.6 10.7 10.8 10.9 0 10 15 20 25 30 35 40 duty cycle (%) input voltage (v) minimum duty cycle vs. input voltage v in = 12v v out = 5v v fb = 1.3v 5 1.225 1.230 1.235 1.240 1.245 1.250 1.255 0 10 15 20 25 30 35 40 reference voltage (v) input voltage (v) reference voltage vs. input voltage v in = 12v v out = v ref i out = 500ma 5 0 1 2 3 4 5 6 7 0 10 15 20 25 30 bootstrap voltage (v) input voltage (v) bootstrap voltage vs. input voltage v in = 12v v fb = 1.5v 5 0 20 40 60 80 100 120 140 160 180 200 10 15 20 25 30 35 40 input current (a) input voltage (v) shutdown current vs. input voltage v en = 0v 0 5 570 575 580 585 590 595 600 605 10 15 20 25 30 35 40 saturation voltage (mv) input voltage (v) saturation voltage vs. input voltage i out = 1a v out = 5v 0 5 48.5 49 49.5 50 50.5 51 51.5 10 15 20 25 30 35 40 frequency (khz) input voltage (v) foldback frequency vs. input voltage v fb = 0v 0 5 5.7 5.8 5.9 6 6.1 6.2 6.3 0 10 15 20 25 30 35 40 input current (ma) input voltage (v) quiescent current vs. input voltage v en = 5v 5 50 55 60 65 70 75 80 85 90 95 100 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 efficiecny (%) output current (a) 5v out efficiency without feed forward diode v out = 5v v in = 8v v in = 12v v in = 24v 50 55 60 65 70 75 80 85 90 95 100 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 efficiecny (%) output current (a) 3.3v out efficiency without feed forward diode v out = 3.3v v in = 8v v in = 12v v in = 24v 50 55 60 65 70 75 80 85 90 95 100 0 0.5 1 1.5 2 efficiency (%) output current (a) 5v in efficiency with feed forward diode v out = 1.8v v out = 2.5v v out = 3.3v v in = 5.0v
micrel, inc. mic4684 january 2010 6 m9999-012610 5.000 5.002 5.004 5.006 5.008 5.010 5.012 5.014 5.016 5.018 5.020 0 0.2 0.4 0.6 0.8 1 1.2 1.4 output voltage (v) output current (a) load regulation v in = 12v 4.98 4.99 5 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 10 15 20 25 30 35 40 output voltage (v) input voltage (v) line regulation i out = 500ma 0 5 1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 1.16 1.18 1.2 -60 -40 -20 0 20 40 60 80 100 120 140 threshold trip points temperature (c) enable threshold vs. temperature upper threshold lower threshold v in = 12v v out = 5v i out = 100ma 1.200 1.201 1.202 1.203 1.204 1.205 1.206 1.207 1.208 1.209 1.210 -60 -40 -20 0 20 40 60 80 100 120 140 feedback voltage (v) temperature (c) feedback voltage vs. temperature v in = 12v v out =v fb i out = 100ma -1 0 1 2 3 4 5 6 -50 0 50 100 150 200 output voltage (v) temperature (c) shutdown hysteresis vs. temperature on off
january 2010 7 m9999-012610 mic4684 micrel, inc. 0 0.5 1 1.5 2 2.5 0 5 10 15 20 25 30 35 continuous output current (a) inpu t vo l t age (v) t ypical 5v out so a with standard configuration v out = 5v t a = 60 c t j = 125 c t a = 25 c soa measured on the mic4684 evaluation board. soa measured on the mic4684 evaluation board. 0 0.5 1 1.5 2 2.5 0 10 15 20 output current (a) input voltage (v) v out = 3. 3v t a = 60 c t j = 12 5c 5 t ypical 3.3v out so a with feed forward diode soa measured on the mic4684 evaluation board. 0 0.5 1 1.5 2 2.5 0 10 15 20 output current (a) input voltage (v) v out = 2. 5v t a = 60 c t j = 12 5c 5 t ypical 2.5v out so a with feed forward diode soa measured on the mic4684 evaluation board. 0 0.5 1 1.5 2 2.5 0 10 15 20 output current (a) input voltage (v) v out = 1. 8v t a = 60 c t j = 12 5c 5 t ypical 1.8v out so a with feed forward diode
micrel, inc. mic4684 january 2010 8 m9999-012610 functional characteristics switching frequency foldback time normal operatio n shor t circui t operatio n v sw (shor ted) 12v in, 0v out v sw (normal) 12v in, 5v/1a out 200khz 70khz frequency foldback the mic4684 folds the switching frequency back during a hard short circuit condition to reduce the energy per cycle and protect the device. load t ransient v in = 12v v out = 5v i out = 1.0a to 0.1a time (100ms/di v. ) i out (500ma/di v. ) v out (100mv/di v. ) 5.1v 5v 1a 0a
january 2010 9 m9999-012610 mic4684 micrel, inc. block diagrams sw fb r1 r2 c out v in in v out mic4684 internal regulator bootstrap charger enable 200khz oscillator thermal shutdown reset current limit com- parator error amp driver 1.235v bandgap reference v v r1 r2 1 r1 r2 v v 1 v 1.235v out ref out ref ref = + = - = ( ) ( ) adjustable regulator functional description the mic4684 is a variable duty cycle switch-mode regula - tor with an internal power switch. refer to the above block diagram. supply voltage the mic4684 operates from a +4v to +30v (34v transient) unregulated input. highest effciency operation is from a supply voltage around +12v. see the effciency curves on page 5. enable/shutdown the enable ( en ) input is ttl compatible. tie the input high if unused. a logic-high enables the regulator. a logic-low shuts down the internal regulator which reduces the current to typically 150a when v en = 0v. feedback fixed-voltage versions of the regulator have an internal resis - tive divider from the feedback ( fb ) pin. connect fb directly to the output voltage. adjustable versions require an external resistive voltage divider from the output voltage to ground, center tapped to the fb pin. see table 1 and table 2 for recommended resis - tor values. duty cycle control a fxed-gain error amplifer compares the feedback signal with a 1.235v bandgap voltage reference. the resulting error amplifer output voltage is compared to a 200khz sawtooth waveform to produce a voltage controlled variable duty cycle output. a higher feedback voltage increases the error amplifer output voltage. a higher error amplifer voltage (comparator invert - ing input) causes the comparator to detect only the peaks of the sawtooth, reducing the duty cycle of the comparator output. a lower feedback voltage increases the duty cycle. the mic4684 uses a voltage-mode control architecture. output switching when the internal switch is on, an increasing current fows from the supply v in, through external storage inductor l1, to output capacitor c out and the load. energy is stored in the inductor as the current increases with time. when the internal switch is turned off, the collapse of the magnetic feld in l1 forces current to fow through fast recovery diode d1, charging c out . output capacitor external output capacitor c out provides stabilization and reduces ripple. return paths during the on portion of the cycle, the output capacitor and load currents return to the supply ground. during the off portion of the cycle, current is being supplied to the output capacitor and load by storage inductor l1, which means that d1 is part of the high-current return path.
micrel, inc. mic4684 january 2010 10 m9999-012610 applications information adjustable regulators adjustable regulators require a 1.23v feedback signal. rec - ommended voltage-divider resistor values for common output voltages are included in table 1. for other voltages, the resistor values can be determined using the following formulas: vv r1 r2 1 r1 r2 v v 1 v1 .235v out ref out ref ref =+ ? ? ? ? ? ? =? ? ? ? ? ? ? = minimum pulse width the minimum duty cycle of the mic4684 is approximately 10%. see minimum duty cycle graph . if this input-to-output voltage characteristic is exceeded, the mic4684 will skip cycles to maintain a regulated v out . 0 5 10 15 20 25 30 35 40 0 1 2 34 5 6 ) v ( e g a t l o v t u p n i . x a m output voltage (v) max. v in for a given v out for constant-frequency switchin g figure 1. minimum pulse width characteristic thermal considerations the mic4684 superswitcher? features the power-sop-8. this package has a standard 8-lead small-outline package profle, but with much higher power dissipation than a standard sop - 8. micrels mic4684 superswitcher? family are the frst dc-to-dc converters to take full advantage of this package. the reason that the power sop-8 has higher power dissipa - tion (lower thermal resistance) is that pins 2, 6, and 7 and the die-attach paddle are a single piece of metal. the die is attached to the paddle with thermally conductive adhesive. this provides a low thermal resistance path from the junction of the die to the ground pins. this design signifcantly improves package power dissipation by allowing excellent heat transfer through the ground leads to the printed circuit board. one limitation of the maximum output current on any mic4684 design is the junction-to-ambient thermal resistance ( ja ) of the design (package and ground plane). examining ja in more detail: ja = ( jc + ca ) where: jc = junction-to-case thermal resistance ca = case-to-ambient thermal resistance jc is a relatively constant 25c/w for a power sop-8. ca is dependent on layout and is primarily governed by the connection of pins 2, 6, and 7 to the ground plane. the pur - pose of the ground plane is to function as a heat sink. ja is ideally 75c/w, but will vary depending on the size of the ground plane to which the power sop-8 is attached. determining ground-plane heat-sink area make sure that mic4684 pins 2, 6, and 7 are connected to a ground plane with a minimum area of 6cm 2 . this ground plane should be as close to the mic4684 as possible. the area may be distributed in any shape around the package or on any pcb layer as long as there is good thermal contact to pins 2, 6, and 7 . this ground plane area is more than suf - fcient for most designs. ja jc ca ambient printed circuit board ground plane heat sink area sop-8 figure 2. power sop-8 cross section when designing with the mic4684, it is a good practice to connect pins 2, 6, and 7 to the largest ground plane that is practical for the specifc design. checking the maximum junction temperature: for this example, with an output power (p out ) of 5w, (5v output at 1a with v in = 12v) and 60c maximum ambient temperature, what is the junction temperature? referring to the typical characteristics: 5v output effciency graph, read the effciency ( ) for 1a output current at v in = 12v or perform you own measurement. = 84% the effciency is used to determine how much of the output power (p out ) is dissipated in the regulator circuit (p d ). p= p p d out out ? p= 5w 0.84 5w d ? p d = 0.95w
january 2010 11 m9999-012610 mic4684 micrel, inc. a worst-case rule of thumb is to assume that 80% of the total output power dissipation is in the mic4684 (p d(ic) ) and 20% is in the diode-inductor-capacitor circuit. p d(ic) = 0.8 p d p d(ic) = 0.8 0.95w p d(ic) = 0.76w calculate the worst-case junction temperature: t j = p d(ic) jc + (t c C t a ) + t a(max) where: t j = mic4684 junction temperature p d(ic) = mic4684 power dissipation jc = junction-to-case thermal resistance. the jc for the mic4684s power-sop-8 is approximately 25c/w. t c = pin temperature measurement taken at the entry point of pins 2, 6 or 7 t a = ambient temperature t a(max) = maximum ambient operating temperature for the specifc design. calculating the maximum junction temperature given a maximum ambient temperature of 60c: t j = 0.76 25c/w + (41c C 25c) + 60c t j = 95c this value is within the allowable maximum operating junction temperature of 125c as listed in operating ratings. typical thermal shutdown is 160c and is listed in electrical charac - teristics . also see soa curves on pages 7 through 8. layout considerations layout is very important when designing any switching regu - lator. rapidly changing currents through the printed circuit board traces and stray inductance can generate voltage transients which can cause problems. to minimize stray inductance and ground loops, keep trace lengths as short as possible. for example, keep d1 close to pin 1 and pins 2, 6, and 7, keep l1 away from sensitive node fb, and keep c in close to pin 3 and pins 2, 6, and 7. see applications information: thermal considerations for ground plane layout. the feedback pin should be kept as far way from the switch - ing elements (usually l1 and d1) as possible. a circuit with sample layouts are provided. see figure 7. gerber fles are available upon request. feed forward diode the ff diode (feed forward) provides an external bias source directly to the main pass element, this reduces v sat thus allowing the mic4684 to be used in very low head-room ap - plications i.e. 5v in to 3.3v out. load bs l1 68h in fb gnd c out r1 r2 d1 v out mic4684bm gnd c in v in +4v to +30v (34v transient) power sop-8 2 6 7 5 4 3 sw en 1 8 figure 5. critical traces for layout
micrel, inc. mic4684 january 2010 12 m9999-012610 v in = 4v to 16v (in feed-forward confguration) v out i out r1 r2 v in c in d1 d2 l1 c out 5.0v 1.6a 3.01k 976k 6.5vC16v 47f, 20v 2a, 30v 1a, 20v 27h 120f, 6.3v vishay-dale schottky schottky sumida vishay-dale 595d476x0020d2t ss23 mbrx120 cdh74-270mc 594d127x06r3c2t 3.3v 1.7a 3.01k 1.78k 4.85vC16v 47f, 20v 2a, 30v 1a, 20v 27h 220f, 6.3v vishay-dale schottky schottky sumida vishay-dale 595d476x0020d2t ss23 mbrx120 cdh74-270mc 594d227x06r3c2t 2.5v 1.8a 3.01k 2.94k 4.5vC16v 47f, 20v 2a, 30v 1a, 20v 27h 330f, 6.3v vishay-dale schottky schottky sumida vishay-dale 595d476x0020d2t ss23 mbrx120 cdh74-270mc 594d337x06r3d2t 1.8v 2a 3.01k 6.49k 4.2vC16v 47f, 20v 2a, 30v 1a, 20v 27h 330f, 6.3v vishay-dale schottky schottky sumida vishay-dale 595d476x0020d2t ss23 mbrx120 cdh74-270mc 594d337x06r3d2t note 1. this bill of materials assumes the use of feedforward schotty diode from v in to the bootstrap pin. table 1. recommended components for common ouput voltages (v in = 4v to 16v) recommended components for a given output voltage (feed-forward confguration) sw l1 47h vin fb gnd en d1 b340a or ss34 j2 v out 2a j4 gnd u1 mic4684bm c2 0.1f 50v c1 15f 35v j1 v in 4v to +16v d2 mbrx120 1a/20v j3 gnd sop-8 2, 6, 7 5 bs 4 1 3 8 on off c4 330f 6.3v c3* optional c5 0.1f 50v c6 0.33f 50v r1 3.01k r2 6.49k jp1a 1.8v r3 2.94k r4 1.78k r5 976? jp1b 2.5v jp1c 3.3v jp1d 5.0v 1 2 3 4 5 6 7 8 * c3 can be used to provide additional stability and improved transient response. note: optimized for 5v out figure 6. 4v - 16v input evaluation board schematic diagram
january 2010 13 m9999-012610 mic4684 micrel, inc. abbreviated bill of material (critical components) reference part number manufacturer description qty c1 594d156x0035d2t vishay sprague (1) 15f 35v 1 c2, c5 vj0805y104kxaab vitramon 0.1f 50v 2 c6 grm426x7r334k50 murata 0.33f, 50v ceramic capacitor c3 optional 1800pf, 50v ceramic (1) c4 594d337x06r3d2t vishay sprague (2) 330f, 6.3v, tantalum 1 d1 b340a diode inc (3) schottky 3a, 40v 1 d2 mbrx120 micro com. components (5) schottky 1a, 20v 1 l1 cdrh104r-470mc sumida (4) 47h, 2.1a i sat 1 u1 mic4684bm micrel, inc. (6) 1a 200khz power-so-8 buck regulator 1 notes: 1. vishay dale, inc., tel: 1 402-644-4218, http://www.vishay.com 2. vishay sprague, inc., tel: 1 207-490-7256, http://www.vishay.com 3. diodes inc, tel: (805) 446-4800, http://www.diodes.com 4. sumida, tel: (408) 982-9960, http://www.sumida.co m 5. micro commercial components, tel: (800) 346-3371 6. micrel, inc. tel: (408) 944-0800, http://www.micrel.com figure 7a. bottom side copper figure 7c. bottom side silk screen figure 7b. top side copper figure 7d. top side silk screen printed circuit board evaluation board optimized for low input voltage by using feed-forward diode confguration (v in = 4v to 16v)
micrel, inc. mic4684 january 2010 14 m9999-012610 v in = 4v to 30v v out i out r1 r2 v in c in d1 l1 c out 5.0v 1.7a 3.01k 976k 8vC30v 33f, 35v 3a, 40v 68h 120f, 6.3v vishay-dale schotty sumida vishay-dale 595d336x0035r2t ss34 cdrh104r-680mc 594d127x06r3c2t 3.3v 1.5a 3.01k 1.78k 7vC28v 33f, 35v 3a, 40v 68h 220f, 6.3v vishay-dale schotty sumida vishay-dale 595d336x0035r2t ss34 cdrh104r-680mc 594d227x06r3c2t 2.5v 1.5a 3.01k 2.94k 6.5vC23v 33f, 35v 3a, 40v 68h 330f, 6.3v vishay-dale schotty sumida vishay-dale 595d336x0035r2t ss334 cdrh104r-680mc 594d337x06r3d2t 1.8v 1.5a 3.01k 6.49k 6vC17v 47f, 25v 3a, 40v 68h 330f, 6.3v vishay-dale schotty sumida vishay-dale 595d476x0025d2t ss334 cdrh104r-680mc 594d337x06r3d2t table 2. recommended components for common ouput voltages (v in = 4v to 30v) recommended components for a given output voltage (standard confguration) sw l1 47h vin fb gnd en d1 b340a or ss34 j2 v out 2a j4 gnd u1 mic4684bm c2 0.1f 50v c1 15f 35v j1 v in 4v to +30v (34v transient) j3 gnd sop-8 2, 6, 7 5 bs 4 1 3 8 on off c4 330f 6.3v c3* optional c5 0.1f 50v c6 0.33f 50v r1 3.01k r2 6.49k jp1a 1.8v r3 2.94k r4 1.78k r5 976? jp1b 2.5v jp1c 3.3v jp1d 5.0v 1 2 3 4 5 6 7 8 * c3 can be used to provide additional stability and improved transient response. note: optimized for 5v out figure 8. 4v - 30v input evaluation board schematic diagram
january 2010 15 m9999-012610 mic4684 micrel, inc. abbreviated bill of material (critical components) reference part number manufacturer description qty c1 594d156x0035d2t vishay sprague (1) 15f 35v 1 c2, c5 vj0805y104kxaab vitramon 0.1f 50v 2 c6 grm426x7r334k50 murata 0.33f, 50v ceramic capacitor c3 optional 1800pf, 50v ceramic (1) c4 594d337x06r3d2t vishay sprague (2) 330f, 6.3v, tantalum 1 d1 b340a diode inc (3) schottky 3a 40v 1 l1 cdrh104r-470mc sumida (4) 47h, 2.1a i sat 1 u1 mic4684bm micrel, inc. (5) 1a 200khz power-so-8 buck regulator 1 notes: 1. vishay dale, inc., tel: 1 402-644-4218, http://www.vishay.com 2. vishay sprague, inc., tel: 1 207-490-7256, http://www.vishay.com 3. diodes inc, tel: (805) 446-4800, http://www.diodes.com 4. sumida, tel: (408) 982-9960, http://www.sumida.co m 5. micrel, inc. tel: (408) 944-0800, http://www.micrel.com printed circuit board general purpose evaluation board (v in = 4v to 30v) figure 9a. bottom side copper figure 9c. bottom side silk screen figure 9b. top side copper figure 9d. top side silk screen
micrel, inc. mic4684 january 2010 16 m9999-012610 package information 8-lead sop (m) micrel inc. 2180 fortune drive san jose, ca 95131 usa t e l + 1 (408) 944-0800 fa x + 1 (408) 474-1000 w e b http://www.micrel.com this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and specifcations at any time without notifcation to the customer . micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a signifcant injury to the user . a purchaser's use or sale of micrel products for use in life support appliances, devices or systems is a purchaser's own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2001 micrel incorporated

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