View MIC23451_7812249.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

mic 23451 3mhz, 2a triple synchronous buck regulator with hyperlight load ? and power good hyperlight load is a registered trademark of micrel, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 (408) 944 - 0800 ? fax + 1 (408) 474 - 1000 ? http://www.micrel.com novem ber 5 , 2013 revision 1.2 general description the MIC23451 is a high - efficiency, 3mhz, triple 2a , synchronous buck regulator with hyperlight load ? mode. hyperlight load provides very - high efficiency at light loads and ultra - fast transient response, which is ideal for supplying processor core voltages. an additional benefit of this proprietary architecture is very low output ripple voltage throughout the entire load range with the use of small output capacitors. the 4mm x 4mm qfn package saves board space and requires only five external components for each channel. the MIC23451 is designed for use with a very small inductor, down to 0.47h, and an output capacitor as small as 2.2f that enables a total solution size that is less than 1mm height. the MIC23451 has a very - low quiescent current of 24a each channel and achieves as high as 81% efficiency at 1ma. at higher loads, the MIC23451 provides a constant switching fr equency around 3mhz while achieving peak efficiencies up to 93%. the MIC23451 is available in a 26 - pin 4mm x 4mm qfn package with an operating junction temperature range from C 40 c to +125 c. datasheets and support documentation are available on micrels w eb site at : www.micrel.com . features ? 2.7v to 5.5v i nput voltage ? three independent 2 a outputs ? up to 93% peak efficiency ? 81% typical efficiency at 1ma ? three independent p ower g ood i ndicators ? 24a typical quiescent cu rrent (per channel) ? 3mhz pwm operation in continuous mode ? ultra - fast transient response ? low voltage output ripple ? 30mv pp ripple in hyperlight load mode ? 5mv output voltage ripple in full pwm mode ? fully integrated mosfet switches ? 0.1 a shutdown current (per channel) ? thermal - shutdown and current - limit protection ? output voltage as low as 1v ? 26- pin 4mm 4mm qfn ? C 40 c to +125 c junction temperature range applications ? solid state drives (ssd) ? c/ p, fpga, and dsp power ? test and measurement systems ? set - top boxes and dtv ? high - performance servers ? security/surveillance cameras ? 5v pol applications typical application
micrel, inc. MIC23451 november 5 , 2013 2 revision 1.2 ordering information part number marking nominal output voltage junction temperature range ( 1 ) package (2,3 ) lead finish MIC23451 - aaayfl aaa adj./adj./adj. C 40 c to +125c 26- pin 4mm 4mm qfn pb - free note s : 1. other options are available. contact micrel for details. 2. qfn is a green, rohs - compliant package. lead finish is nipdau. mold compound is halogen free. 3. qfn ? = pin 1 identifier pin configuration 26- pin 4mm 4mm qfn (f l) ? adjustable (top view) pin description pin number pin name pin function 26, 4, 7 sw1, 2, 3 switch (output). internal power mosfet output switches for o utput 1/2/3. 21, 19, 15 en1, 2, 3 enable (input). logic high enables operation of regulator 1/2/3. logic low will shut down the device. do not leave floating. 22, 18, 12 sns1, 2, 3 sense. connect to v out1,2,3 as close to output capacitor as possible to sense output voltage. 23, 17, 14 fb1, 2, 3 feedback. connect a resistor d ivider from output 1/2/3 to ground to set the output voltage. 20, 16, 13 pg1, 2, 3 power good. open -d rain output for the power good indicator for output 1/2/3. place a resistor between this pin and a voltage source to detect a power good condition. ep1, 24, 11 agnd analog ground. connect to quiet ground point a way from high - current paths, for example, c out , for best operation. must be connected externally to pgnd. 25, 5, 8 pvin1, 2, 3 power input voltage. connect a capacitor to pgnd to localize loop currents and decouple switching noise. 3, 6, 9 avin1, 2, 3 analog input voltage. connect a capacitor to agnd to decouple noise. ep2, 10, 2, 1 pgnd power ground.
micrel, inc. MIC23451 november 5 , 2013 3 revision 1.2 absolute maximum ratings (1) supply voltage (pv in, av in ) .................................. ? 0.3 to 6v sense (v sns1 , v sns2 , v sns3 ). ................................. ? 0.3 to 6v power good (pg1, pg2, pg3) ............................ ? 0.3 to 6v output switch voltage (v sw1 , v sw2 , v sw3 ) ......... ? 0.3v to 6v enable input voltage (v en1 , v en2 , v en3 ) ............ ? 0.3v to v in storage temperature range .................... ? 65c to + 150 c esd rating (3) ................................................. esd sensitive operating ratings (2) supply voltage (v in ) ..................................... +2.7v to +5.5v enable input voltage (v en1 , v en2 , v en3 ) ................. 0v to v in output voltage range (v sns1 , v sns2 , v sns3 ) ... + 1v to + 3.3v junction voltage range (t j ) ............... ? 40 c t j + 125 c thermal resistance 26- pin 4mm 4mm qfn ( ja ) ......................... + 2 0c/w 26- pin 4mm 4mm qfn ( jc ) ........................ + 10c/w electrical characteristics (4) t a = + 25 c; v in = v en1 , v en2 , v en3 = 3.6v; l1 = l2 = l3 = 1 h; c out1 , c out2 , c out3 = 4.7 f, unless otherwise specified. bold values indicate C 40c t j +125 c, unless noted. parameter condition min . typ . max . units supply voltage range 2.7 5.5 v undervoltage lockout threshold turn - on 2.45 2.55 2.65 v undervoltage lockout hysteresis 75 mv quiescent current i out = 0ma, sns > 1.2 v outnom 65 120 a per channel shutdown current v en1 , v en2 , v en3 = 0v; v in = 5.5v 0.1 5 a output voltage accuracy v in = 3.6v if v out(nom) < 2.5v, i load = 20ma ? 2.5 + 2.5 % v in = 4.5v if v out(nom) 2.5v, i load = 20ma feedback voltage (v fb1 , v fb2 , v fb3 ) 0.604 0.62 0.635 v peak current limit i out1 , i out2 , i out3 sns1, sns2, sns3 = 0.9 v outnom 2.2 4.1 a foldback current limit 2.3 a output voltage line regulation (v out1 , v out2 , v out3 ) v in = 3.6v to 5.5v if v outnom1, 2, 3 < 2.5v, i load = 20ma 0.3 %/v v in = 4.5v to 5.5v if v outnom1, 2, 3 2.5v, i load = 20ma output voltage load regulation (v out1 , v out2 , v out3 ) dcm: 20ma < i load < 130ma, v in = 3.6v if v outnom < 2.5v 0.2 % dcm: 20ma < i load < 130ma, v in = 5.0v if v outnom > 2.5v 0.4 ccm: 200ma < i load < 500ma, v in = 3.6v if v outnom < 2.5v 0.6 ccm: 200ma < i load < 1a, v in = 5.0v if v outnom > 2.5v 0.3 pwm switch on - resistance (r sw1 , r sw2 , r sw3 ) i sw1 , i sw2 , i sw3 = + 100ma (pmos) 0.217 maximum frequency i out1 , i out2 , i out3 = 120ma 3 mhz soft - start time v out1 , v out2 , v out3 = 90% 150 s power good threshold % of v nom 83 90 96 % power good hysteresis 10 % power good pull down v sns = 90% v nom , i pg = 1ma 200 mv notes: 1. exceeding the absolute maximum ratings may damage the device. 2. the device is not guaranteed to function outside its operating ratings. 3. devices are esd sensitive. handling precautions are recommended. human body model, 1.5k in series with 100pf. 4. specification for packaged product only.
micrel, inc. MIC23451 november 5 , 2013 4 revision 1.2 electrical characteristics (4) (continued) t a = + 25 c; v in = v en1 , v en2 , v en3 = 3.6v; l1 = l2 = l3 = 1 h; c out1 , c out2 , c out3 = 4.7 f, unless otherwise specified. bold values indicate C 40c t j +125 c, unless noted. parameter condition min. typ. max. units enable threshold turn - on 0.5 0.9 1.2 v enable input current 0.1 1 a overtemperature shutdown 160 c overtemperature shutdown hysteresis 20 c
micrel, inc. MIC23451 november 5 , 2013 5 revision 1.2 typical characteristics 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 2 3 4 5 6 peak current limit (a) input voltage (v) current limit vs. input voltage ch3 = 1.2v ch2 = 1.8v ch1 = 2.5v 0 20 40 60 80 100 120 140 160 180 2 3 4 5 6 supply current (na) input voltage (v) shutdown current vs. input voltage 1.70 1.75 1.80 1.85 1.90 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 output voltage (v) input voltage (v) line regulation (low loads) i out = 1ma i out = 20ma i out = 80ma 1.70 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.86 1.88 1.90 0 0.03 0.06 0.09 0.12 0.15 0.18 output voltage (v) load current (a) output voltage vs. output current (hll) v out = 1.8v v in = 3v v in = 3.6v v in = 5v 1.74 1.76 1.78 1.80 1.82 1.84 -60 -40 -20 0 20 40 60 80 100 120 140 output voltage (v) temperature ( c) output voltage vs. temperature v in = 5.5v v in = 3.6v v in = 2.7v
micrel, inc. MIC23451 november 5 , 2013 6 revision 1.2 typical characteristics (continued) 0 20 40 60 80 100 2 3 4 5 6 pg delay (s) input voltage (v) pg delay time vs. input voltage pg rising pg falling 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.90 0.91 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 pg threshold (% of vref) input voltage (v) pg thresholds vs. input voltage pg rising pg falling 2.47 2.49 2.51 2.53 2.55 2.57 -60 -40 -20 0 20 40 60 80 100 120 140 uvlo threshold (v) temperature ( c) uvlo threshold vs. temperature uvlo rising uvlo falling 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 enable threshold (v) input voltage (v) enable threshold vs. input voltage t amb = 25 c 0.5 0.6 0.7 0.8 0.9 1.0 -60 -40 -20 0 20 40 60 80 100 120 enable threshold (v) temperature ( c) enable threshold vs. temperature v in = 3.6v 0.1 1 10 100 1000 10000 0.0001 0.001 0.01 0.1 1 10 frequency (khz) output current (a) switching frequency vs. load current v out = 1.8v v in = 5v v in = 3v v in = 3.6v 0.600 0.605 0.610 0.615 0.620 0.625 0.630 0.635 0.640 -60 -40 -20 0 20 40 60 80 100 120 140 vfb (v) temperature ( c) vfb vs. temperature v in =2.7v v in = 5.5v v in = 3.6v
micrel, inc. MIC23451 november 5 , 2013 7 revision 1.2 typical characteristics (continued) 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 power dissipation (w) ambient temperature ( c) max package dissipation vs. ambient temperature
micrel, inc. MIC23451 november 5 , 2013 8 revision 1.2 functional characteristics
micrel, inc. MIC23451 november 5 , 2013 9 revision 1.2 functional characteristics (continued)
micrel, inc. MIC23451 november 5 , 2013 10 revision 1.2 functional characteristics (continued)
micrel, inc. MIC23451 november 5 , 2013 11 revision 1.2 functional diagram figure 1 . simplified MIC23451 adjustable functional block diagram
micrel, inc. MIC23451 november 5 , 2013 12 revision 1.2 functional description pvin the input supply (pv in ) provides power to the internal mosfets for the switch mode regulator. the v in operating range is 2.7v to 5.5v , so an input capacitor, with a minimum voltage rating of 6.3v is recommended. because of the high di/dt switching speeds, a minimum 2.2f or 4.7 f recommended bypass capacitor , placed close to pvin and the power ground (pgnd) pin , is required. refer to the pcb layout recommendations section for details. avin the input supply (av in ) provides power to the internal control circuitry. because the high di/ dt switching speeds on pvin cause small voltage spikes, a 50? rc filter and a minimum 100nf decoupling capacitor , placed close to the avin and signal ground (agnd) pin , is required. en a logic high signal on the enable pin (en) activates the output voltage of the device. a logic low signal on the enable pin deactivates the output and reduces supply current to 0.01a. the MIC23451 features internal soft - start circuitry that reduces in rush current and prevents the output voltage f rom overshooting at start - up. do not leave the en pin floating. sw the switch (sw) connects directly to one end of the inductor and provides the current path during switching cycles. the other end of the inductor is connected to the load, sns pin , and outp ut capacitor. because of the high - speed switching on this pin, the switch node should be routed away from sensitive nodes. sns the sense (sns) pin is connected to the output of the device to provide feedback to the control circuitry. the sns connection sho uld be placed close to the output capacitor. refer to the pcb layout recommendations section for more details. agnd the analog ground (agnd) is the g round path for the biasing and control circuitry. the current loop for the signal ground should be separate from the power ground (pgnd) loop. refer to the pcb layout recommendations section for more details . pgnd the power ground pin is the ground path for the high current in pwm mode. the current loop for the power ground should be as short and wide as possible and separate from the analog ground (ag nd) loop as applicable. refer to the pcb layout recommendations section for more details . pg the power good (pg) pin is an open - drain output that indicates logic high when the output voltage is typically above 90% of its steady state voltage. a pull - up r esistor of more than 5k ? should be connected from pg to v out . fb the feedback (fb) pin is the control input for programming the output voltage. a resistor divider network is connected to this pin from the output and is compared to the internal 0.62v refere nce within the regulation loop. the output voltage can be programmed between 1v and 3.3v using equation 1: ? ? ? ? ? ? + = r2 r1 1 v v ref out eq. 1 w here: r1 is the top, v out connected resistor r2 is the bottom, agnd connected resistor table 1 shows example feedback resistor values. table 1 . feedback resistor values v out r1 r2 1.2v 274k 294k 1.5v 316k 221k 1.8v 301k 158k 2.5v 324k 107k 3.3v 309k 71.5k
micrel, inc. MIC23451 november 5 , 2013 13 revision 1.2 application information the MIC23451 is a triple high performance dc - to - dc step down regulator offering a small solution size. supporting three outputs with currents up to 2 a inside a 4mm 4mm qfn package, the ic requires only five external components per channel while meeting todays miniature portable electronic device needs. using the hyperlight load switching scheme, the MIC23451 can maintain high efficiency throughout the entire load range whi le providing ultra - fast load transient response. the following sections provide additional device application information. input capacitor a 2.2f or greater ceramic capacitor should be placed close to the p vin pin for each channel and it s corresponding pg nd pin for bypassing. for example, the murata grm188r60j475me19d, size 0603, 4.7f ceramic capacitor is ideal, b ased on performance, size , and cost. a n x5r or x7r temperature rating is recommended for the input capacitor. y5v temperature rating capacitors, in addition to losing most of their capacitance over temperature, can also become resistive at high frequencies. this reduces t heir ability to filter out high - frequency noise. output capacitor the MIC23451 is designed for use with a 2.2f or greater ceramic output capacitor. increasing the output capacitance lower s output ripple and improve s load transient response , but could also increase solution size or cost. a low equivalent series resistance (esr) ceramic output capacitor , such as the murata grm1 88r60j475me84d, size 0603, 4.7f ceramic capacitor , is recommended based on performance, size , and cost. both the x7r or x5r temperature rating capacitors are recommended. the y5v and z5u temperature rating capacitors are not recommended due to their wide variation in capacitance over temperature and increased resistance at high frequencies. inductor selection when selecting an inductor, it is important to consider the following factors (not necessarily in order of importance): ? inductance ? rated current valu e ? size requirements ? dc resistance (dcr) the MIC23451 is designed for use with a 0.47h to 2.2h inductor. for faster transient response, a 0.47h inductor yield s the best result. on the other hand, a 2.2h inductor yield s lower output voltage ripple. for t he best compromise of these, a 1 h is generally recommended. maximum current ratings of the inductor are generally given in two forms: permissible dc current and saturation current. permissible dc current can be rated either for a 40 c temperature rise or a 1 0% to 20% loss in inductance. make sure the inductor selected can handle the maximum operating current. when saturation current is specified, make sure that there is enough margin , so that the peak current does not cause the inductor to saturate. peak current can be calculated as shown in equation 2: ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + = l f 2 /v v 1 v i i in out out out peak eq. 2 as equation 2 shows , the peak inductor current is inversely proportional to the switching frequency and the inductance; the lower the switching frequency or the inductance the h igher the peak current. as input voltage increases, the peak current also increases. the size of the inductor depends on the requirements of the application. refer to the typical application schematic and bill of materials sections for details. dc resistance (dcr) is also important. while dcr is inversely proportional to size, dcr can represent a significant efficiency loss. refer to the efficiency considerations section . the transition betw een high loads (ccm) to hyperlight load (hll) mode is determined by the inductor ripple current and the load curr ent , as shown in figure 2 . figure 2 . transition between ccm mode and hll mode the diagram shows the signals for high - side switch drive (hsd) for t on control, the i nductor current , and the l ow - side switch drive (lsd) for t off control. in hll mode, the inductor is charged with a fixed t on pulse on the high - side switch (hsd). after this, the lsd is switched on and current falls at a rate of v out /l. the controller remains in hll mode while the i nductor falling
micrel, inc. MIC23451 november 5 , 2013 14 revision 1.2 current is detected to cross approximately C 50ma. when the lsd (or t off ) time reaches its minimum and the inductor falling current is no longer able to reach this ? 50ma threshold, the part is in ccm mode and switching at a virtually constan t frequency. once in ccm mode, the t off time does not vary. therefore, it is important to note that if l is large enough, the hll transition level will not be triggered. that inductor is: 50ma 2 135ns v l out max = eq. 3 compensation the MIC23451 is designed to be stable with a 0.47h to 2.2h inductor with a 4.7f ceramic (x5r) output capacitor. duty cycle the typical maximum duty cycle of the MIC23451 is 80%. efficiency considerations efficiency is defined as the amount of useful output power, divided by the amount of power supplied. 100 i v i v % efficiency in in out out ? ? ? ? ? ? ? ? = eq. 4 maintaining high efficiency serves two purposes. it reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design considerations , and it reduces current consumptio n for battery - powered applications. reduced current draw from a battery increases the device s operati ng time and is critical in hand - held devices. there are two types of losses in switching converters : dc losses and switching losses. dc losses are the pow er dissipation of i 2 r. power is dissipated in the high - side switch during the on cycle. power loss is equal to the high - side mosfet r dson multiplied by the s witch c urrent squared . during the off cycle, the low - side n - channel mosfet conducts, also dissipati ng power. device operating current also reduces efficiency. the product of the quiescent (operating) current and the supply voltage represents another dc loss. the current required to driv e the gates on and off at a constant 4mhz frequency , and the switchi ng transitions , make up the switching losses. figure 3 . efficiency under load figure 3 shows an efficiency curve. from no load to 100ma, efficiency losses are dominated by quiescent current losses, gate drive , and transition losses. by using the hyperlight load mode, the mic234 51 can maintain high efficiency at low output currents. over 100ma, efficiency loss is dominated by mosfet r dson and inductor losses. higher input supply voltages will increase the g ate - to - s ource voltage on the internal mosfets, thereby reducing the intern al r dson . this improves efficiency by reducing dc losses in the device. all but the inductor losses are inherent to the device. because of this , inductor selection becomes increasingly critical in efficiency calculations. as the inductors are reduced in si ze, the dc resistance (dcr) can become very significant. the dcr losses can be calculated as shown in equation 5. dcr i p 2 out dcr = eq. 5 from that, the loss in efficiency caused by inductor resistance can be calculated as shown in equation 6. 100 p i v i v 1 loss efficiency dcr out out out out ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = eq. 6 efficiency loss caused by dcr is minimal at light loads and gains significance as the load is increased. inductor selection becomes a trade - off between efficiency and size in this case.
micrel, inc. MIC23451 november 5 , 2013 15 revision 1.2 thermal considerations m ost applications will not require 2 a continuous current from all outputs at all times, so it is useful to know what the thermal limits are for various loading profiles. the allowable overall package dissipation is limited by the intrinsic thermal resistanc e of the package (r (j -c) ) and the area of copper used to spread heat from the package case to the ambient surrounding temperature (r (c-a) ). the composite of these two thermal resistances is r (j-a) , which represents the package thermal resistance with at least 1 square inch of copper ground plane. from this figure, which for the MIC23451 is 2 0c/w , we can calculate maximum internal power dissipation , as shown in equation 7: a) (j amb jmax max r t t pd ? ? = eq. 7 where: t jmax = maximum junction temp (125c) t amb = ambient temperature r (j-a) = 2 0c/w t he allowable dissipation tends towards zero as the ambient temperature increases towards the maximum operating junction temperature. the graph of pd max vs. a mbient temperature could be drawn quite simply using this equation. however, a more useful measure is the maximum output current per regulator vs. ambient temperature. this requires creating an exchange rate between power dissipation per regulator (p diss ) and its output current (i out ). an accurate measure of th is function can use the efficiency curve, as illustrated in equation 8: ( ) 1 p p p p p out loss loss out out ? = + = eq. 8 where: = efficiency p out = i out .v out to arrive at the internal package dissipation p diss , remove the inductor loss p dcr , which is not dissipated within the package. this do es not give a worst case figure because efficiency is typically measured on a nominal part at nominal temperatures. the i out to p diss function used in this case is a synthesized p diss , which accounts for worst case values at maximum operating temp erature, as shown in equation 9. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + = in out dson_n in out dson_p 2 out diss v v 1 r v v r i p eq. 9 where: r dson_p = maximum r dson of the high - side, p - channel switch at t jmax r dson_n = maximum r dson of the low - side, n - channel switch at t jmax v out = output v oltage v in = input v oltage because ripple current and switching losses are small with respect to resistive losses at maximum output current, they can be considered negligible for the purpose of this method, but could be included if required. usi ng the function describing p diss in terms of i out , substitute p diss with equation 7 to form the function of maximum output current i outmax vs. ambient temperature t amb (equation 10) : ? ? ? ? ? ? ? ? ? + ? = ? in out dson_n in out dson_p a) (j amb jmax outmax v v 1 r v v r r t t i eq. 10 the curves shown in the typical characteristics section are plots of this function adjusted to account for 1, 2 , or 3 regulators running simultaneously. hyperlight load mode each regulator in the MIC23451 uses a minimum on and off time proprietary control loop (patented by micrel). when the output voltage falls below the regulation threshold, the error comparator begins a switching cycle that turns the pmos on and keeps it on for the duration of the minimum - on- time. this increases the output voltage. if the output voltage is over the regulation threshold, then the error comparator turns the pmos off for a minimum - off - time until the output drops below the threshold. the nmos act s as an ideal rectifier that conducts when the pmos is off. using a n nmos switch instead of a diode allows for lower voltage drop across the switching device when it is on. the asynchronous switching combination between the pmos and the nmos allows the con trol loop to work in discontinuous mode for light load operations. in discontinuous mode, the MIC23451 works in pulse - frequency modulation (pfm) to regulate the output. as the output current increases, the off - time decreases, which provides more energy to the output. this switching scheme improves the efficiency of MIC23451 during light load currents by switching only when it is needed. as the load current
micrel, inc. MIC23451 november 5 , 2013 16 revision 1.2 increases, the MIC23451 goes into continuous conduction mode (ccm) and switches at a frequency centere d at 3mhz. the equation to calculate the load when the MIC23451 goes into continuous conduction mode is approximated in equation 11 . ? ? ? ? ? ? ? ? ? > f 2l d ) v (v i out in load eq. 11 as shown in equation 11, the load at which the MIC23451 transitions from hyperlight load mode to pwm mode is a function of the input voltage (v in ), output voltage (v out ), duty cycle (d), inductance (l) , and frequency (f). figure 4 sho ws that as the o utput c urrent increases, the switching frequency also increases until the MIC23451 goes from hyperlight load mode to pwm mode at approximately 120ma. the MIC23451 will switch at a relatively constant frequency around 3mhz after the output c urrent is over 120ma. 0.1 1 10 100 1000 10000 0.0001 0.001 0.01 0.1 1 10 frequency (khz) output current (a) switching frequency vs. load current v out = 1.8v v in = 5v v in = 3v v in = 3.6v figure 4 . sw frequency vs. output current multiple sources the MIC23451 provides all the pins necessary to operate the three regulators from independent sources. this can be useful in partitioning power within a multi - rail system. for example, two supplies may be available within a system: 3.3v and 5v. the MIC23451 can be connected to use the 3.3v supply to provide two, low - vol tage outputs ( for example, 1.2v and 1.8v) and use the 5v rail to provide a higher output ( for example, 2.5v), resulting in the power blocks shown in figure 5 . figure 5 . multi - source power block diagram
micrel, inc. MIC23451 november 5 , 2013 17 revision 1.2 typical application schematic bill of materials item part number manufacturer description qty. c1, c2, c3 grm188r60j106ke19d murata (1) capacitor, 10 f, size 0603 3 c4, c5, c6, c7 c1608x5r0j475k tdk (2) capacitor, 4.7 f, size 0603 4 grm188r60j475ke19d murata c8 eeufr1a221 panasonic (3) electrolytic capacitor, 220 f, 10v, size 6.3mm r1, r2, r3, r4, r5, r6 crcw060310k0fkea vishay (4) resistor, 10k ? , size 0603 6 r7 crcw0603301k0fkea vishay resistor, 301k ? , size 0603 1 r8 crcw0603158k0fkea vishay resistor, 158k ? , size 0603 1 r9 crcw0603316k0fkea vishay resistor, 316 ? , size 0603 1 r10 crcw0603331k0fkea vishay resistor, 331k ? , size 0603 1 r11 crcw0603294k0fkea vishay resistor, 294k ? , size 0603 1 r12 crcw0603274k0fkea vishay resistor, 274k ? , size 0603 1 l1, l2, l3 vls3012st - 1r0n1r9 tdk 1 h, 2a, 60m ? , l3.0mm x w3.0mm x h1.0mm 3 lqh44pn1r0nj0 murata 1 h, 2.8a, 50m ? , l4.0mm x w4.0mm x h1.2mm u1 MIC23451 - aaayfl micrel, inc. (5) 3mhz pwm 2 a buck regulator with hyperlight ? load 1 notes: 1. tdk: www.tdk.com . 2. murata tel: www.murata.com . 3. panasonic: www.panasonic.com . 4. vishay tel: www.vishay.com . 5. micrel , inc.: www.micrel.com .
micrel, inc. MIC23451 november 5 , 2013 18 revision 1.2 pcb layout recommendations top layer mid layer 1
micrel, inc. MIC23451 november 5 , 2013 19 revision 1.2 mid layer 2 bottom layer
micrel, inc. MIC23451 november 5 , 2013 20 revision 1.2 package information (1) 26- pin 4mm 4mm qfn (f l) note: 1. package information is correct as of the publication date. for updates and most current information, go to www.micrel.com . micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944 - 0800 fax +1 (408) 474 - 1000 web http://www.micrel.com micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. this information is not intended as a warranty and micrel does not assume responsibility for its use. micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. no license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. except as provided in micrel s terms and conditions of sale for such products, micrel assumes no liability whatsoever, and micrel disclaims any express or implied warranty relating to the sale and/or use of micrel products including liability or warranties relating to fitness for a pa rticular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right . micrel products are not designed or authorized for use as components in life support appliances, devices or systems where mal function of a pr oduct 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 ex pected to result in a significant injury to the user. a purchasers use or sale of micrel products for use in life support appliances, devices or systems is a purchasers own risk a nd purchaser agrees to fully indemnify micrel for any damages resulting fro m such use or sale. ? 20 13 micrel, incorporated.

▲Up To Search▲

Price & Availability of MIC23451

	To Download MIC23451 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .