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mic23051 4mhz pwm buck regulator with hyperlight load? and voltage scaling hyperlight load is a trademark of micrel, inc. mlf and micro leadframe are registered trademarks of amkor technology, inc. protected by us patent no. 7064531 micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel +1 ( 408 ) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micrel.com july 2009 m9999-070809-f general description the micrel mic23051 is a high efficiency 600ma pwm synchronous buck (step-down) regulator featuring hyperlight load?, a patent ed switching scheme that offers best in class light load efficiency and transient performance while providing very small external components and low output ripple at all loads. the mic23051 has an output vo ltage scaling feature that can toggles between two different voltage levels. the mic23051 also has a very low typical quiescent current draw of 20a and can achieve over 85% efficiency even at 1ma. the device allows operation with a tiny inductor ranging from 0.47h to 2.2h and uses a small output capacitor that enables a sub-1mm height solution. in contrast to traditional light load schemes hyperlight load? architecture does not need to trade off control speed to obtain low standby currents and in doing so the device only needs a small output capacitor to absorb the load transient as the powered device goes from light load to full load. at higher loads the mic23051 provides a constant switching frequency of greater than 4mhz while providing peak efficiencies greater than 93%. the mic23051 is available in fixed output voltage options from 0.72v to 3.3v eliminating external feedback components. the mic23051 is available in an 8-pin 2mm x 2mm mlf ? with a junction operating range from ?40 c to +125 c. data sheets and support documentation can be found on micrel?s web site at: www.micrel.com. features ? input voltage: 2.7v to 5.5v hyperlight load? ? 600ma output current ? fixed output voltage from 0.72v to 3.3v ? output voltage scaling option ? ultra fast transient response ? 20a typical quiescent current ? 4mhz in ccm pwm operation in normal mode ? 0.47h to 2.2h inductor ? low voltage output ripple ? 25mvpp in hyperlight load mode ? 3mv output voltage ripple in full pwm mode ? >93% efficiency ? ~85% at 1ma ? micropower shutdown ? available in 8-pin 2mm x 2mm mlf ? ? ?40 c to +125 c junction temperature range applications ? cellular phones ? digital cameras ? portable media players ? wireless lan cards ? wifi/wimax/wibro modules ? usb powered devices ____________________________________________________________________________________________________________ typical application 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency v out = 1.8v v out = 1.8v l = 1h v in = 3.3v v in = 2.7v v in = 3.6v
micrel, inc. mic23051 july 2009 2 m9999?070809-f ordering information part number marking voltage scaled to with vsc low nominal output voltage junction temp. range package lead finish mic23051-cgyml jcg 1.0v 1.8v ?40 to +125c 8-pin 2x2 mlf ? pb-free mic23051-c4yml jc4 1.0v 1.2v ?40 to +125c 8-pin 2x2 mlf ? pb-free MIC23051-16YML j16 1.15v 1.40v ?40 to +125c 8-pin 2x2 mlf ? pb-free mic23051-945yml 945 0.95v 1.25v ?40 to +125c 8-pin 2x2 mlf ? pb-free note 1. other output voltage combinations (0.72 to 3.3v) available, contact micrel marketing for details. 2. mlf ? is a green rohs compliant package. lead fini sh is nipdau. mold compound is halogen free. 3. over bar symbol ( ) may not be to scale. pin configuration 1 sw en vs c sns 8pgnd vin agnd cff 7 6 5 2 3 4 8-pin 2mm x 2mm mlf ? (top view) pin description pin number pin name pin name 1 sw switch (output): internal power mosfet output switches. 2 en enable (input). logic low will shut do wn the device, reducing the quiescent current to less than 4a. do not leave floating. 3 vsc voltage scaling pin (input): a low on this pin will scale the output voltage down to specified level. do not leave floating. 4 sns connect to v out to sense output voltage. 5 cff feed forward capacitor. connect a 560pf capacitor. 6 agnd analog ground. 7 vin supply voltage (input): r equires bypass capacitor to gnd. 8 pgnd power ground.
micrel, inc. mic23051 july 2009 3 m9999?070809-f absolute maximum ratings (1) supply voltage (v in ) .........................................................6v output switch voltage (v sw ) ............................................6v output switch current (i sw )..............................................2a logic input voltage (v en , v lq )........................... v in to ?0.3v storage temperature range (t s )..............?65c to +150c esd rating (3) .................................................................. 3kv operating ratings (2) supply voltage (v in )......................................... 2.7v to 5.5v logic input voltage (v en) .................................... -0.3v to v in junction temperature (t j ) ..................?40c t j +125c thermal resistance 2x2 mlf-8 ( ja ) .................................................90c/w electrical characteristics (4) t a = 25c with v in = v en = v sc = 3.6v; l = 1h; c ff = 560pf; c out = 4.7f; i out = 20ma unless otherwise specified. bold values indicate ?40c< t j < +125c. parameter condition min typ max units supply voltage range 2.7 5.5 v under-voltage lockout threshol d (turn-on) 2. 45 2.55 2.65 v uvlo hysteresis 100 mv quiescent current, hyper ll mode i out = 0ma , sns > 1.8v 20 35 a shutdown current v in = 5.5v; v en = 0v; 0.01 4 a vsc high, v in = 3.0v, i load = 20ma -2.5 +2.5 % % output voltage accuracy vsc low, v in = 3.0v, i load = 20ma -2.5 +2.5 % % sns pin input current v out = 1v 1 a current limit in pwm mode sns = 0.9*v nom 0.65 1 1.7 a output voltage line regulation v in = 3.0v to 5.5v, i load = 20ma, v sc = 3.6v 0.5 % output voltage load regulation 20ma < i load < 500ma, v sc = 3.6v 0.3 % output voltage line regulation v in = 3.0v to 5.5v, i load = 20ma, v sc = 0v 0.5 % output voltage load regulation 20ma < i load < 500ma, v sc = 0v 0.3 % maximum duty cycle sns v nom, v out = 1.8v 80 89 % pwm switch on-resistance** see design note i sw = 100ma pmos i sw = -100ma nmos 0.45 0.5 ? ? v sc = 3.6v, i load = 120ma 4 mhz frequency v sc = 0v, i load = 120ma 4 mhz softstart time v out = 90% 650 s vsc threshold voltage 0.5 1.2 v vsc hysteresis 20 mv vsc from low to high 800 s output transition time vsc from high to low 800 enable threshold (turn-on) 0.5 1.2 v enable hysteresis 35 mv enable input current 0.1 2 a over-temperature shutdown 165 c over-temperature shutdown hysteresis 20 c notes: 1. exceeding the absolute maxi mum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. handling precautions recommended. human body model, 1.5k ? in series with 100pf. 4. specification for packaged product only.
micrel, inc. mic23051 july 2009 4 m9999?070809-f typical characteristics 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency v out = 1.8v v out = 1.8v l = 1h v in = 3.3v v in = 2.7v v in = 3.6v 50 60 70 80 90 1 10 100 1000 output current (ma) efficiency v out = 1.2v v out = 1.2v l = 1h v in = 3.3v v in = 2.7v v in = 3.6v 50 60 70 80 90 1 10 100 1000 output current (ma) efficiency v out = 1v v out = 1v l = 1h v in = 3.3v v in = 2.7v v in = 3.6v 0 10 20 30 40 quiescent current vs. temperature 20 40 60 80 temperature (c) v in = 3.6v v out = 1.8v 0 5 10 15 20 25 30 35 40 45 50 2.7 input voltage (v) quiescent current vs. input voltage 3.2 3.7 4.2 4.7 5.2 v in = 3.6v v out = 1.8v no load 2.5 3.0 3.5 4.0 4.5 5.0 5.5 switching frequency vs. temperature 20 40 60 80 temperature (c) v in = 3.6v v out = 1.8v load = 150ma 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.7 input voltage (v) switching frequency vs. input voltage 3.2 3.7 4.2 4.7 5.2 v in = 3.6v v out = 1.8v load = 150ma 0.60 0.62 0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80 feedback voltage vs. temperature 20 40 60 80 temperature (c) v in = 3.6v v out = 1.8v no load 1.70 1.75 1.80 1.85 1.90 output voltage vs. temperature 20 40 60 80 temperature (c) v in = 3.6v v out = 1.8v no load 1.70 1.75 1.80 1.85 1.90 2.7 input voltage (v) input voltage (v) output voltage vs. input voltage 3.2 3.7 4.2 4.7 5.2 load = 20ma 1.75 1.8 1.85 0 100 200 300 400 500 600 load (ma) 1.70 1.90 output voltage vs. load v in = 3.6v
micrel, inc. mic23051 july 2009 5 m9999?070809-f functional characteristics
micrel, inc. mic23051 july 2009 6 m9999?070809-f functional characteristics (continued)
micrel, inc. mic23051 july 2009 7 m9999?070809-f functional diagram en vin sw pgnd cff control logic timer & softstart isense agnd uvlo reference gate drive sns error comparator current limit zero 1 r15 r17 vsc mic23051 simplified block diagram
micrel, inc. mic23051 july 2009 8 m9999?070809-f functional description vin vin provides power to the mosfets for the switch mode regulator section and to the analog supply circuitry. due to the high switching speeds, a 2.2f or greater capacitor is recommended close to vin and the power ground (pgnd) pin for bypassing. refer to the layout recommendations for details. en the enable pin (en) controls the on and off state of the device. a logic high on the enable pin activates the regulator, while a logic low deactivates it. mic23051 features built-in soft-start circuitry that reduces in-rush current and prevents the output voltage from overshooting at start up. do not leave floating. sw the switch (sw) pin connects directly to the inductor and provides the switching current necessary to operate in pwm mode. due to the high speed switching on this pin, the switch node should be rout ed away from sensitive nodes such as the cff pin. sns an inductor is connected from the sw pin to the sns pin. the sns pin is the output pin of the device and a minimum of 2.2f bypass capacitor should be connected in shunt. in order to reduce parasitic i nductance it is good practice to place the output bypass capacitor as close to the inductor as possible. cff the cff pin is connected to the sns pin of mic23051 with a feed-forward capacitor of 560pf. the cff pin itself is compared with the internal reference voltage (v ref ) of the device and provides the co ntrol path to control the output. v ref is equal to 0.72v. the cff pin is sensitive to noise and should be place away from the sw pin. refer to the layout recommendations for details. vsc the voltage scaling pin (vsc) is used to switch between two different voltage levels. a logic high on the vsc pin will set the output voltage to the higher voltage. a logic low on the vsc pin will set the output voltage to the lower voltage. do not leave floating. pgnd power ground (pgnd) is the ground path for the high current pwm mode. the current loop for the power ground should be as small as possible and separate from the analog ground (agnd) loop. refer to the layout recommendations for more details. agnd signal ground (agnd) is the ground 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 layout recommendations for more details.
micrel, inc. mic23051 july 2009 9 m9999?070809-f applications information input capacitor a minimum of 2.2f ceramic capacitor should be placed close to the vin pin and pgnd pin for bypassing. x5r or x7r dielectrics are recommended for the input capacitor. y5v dielectrics, aside from losing most of their capacitance over temperature, they also become resistive at high frequencies. this redu ces their ability to filter out high frequency noise. output capacitor the mic23051 was designed for use with a 2.2f or greater ceramic output capacito r. a low equivalent series resistance (esr) ceramic output capacitor either x7r or x5r is recommended. y5v and z5u dielectric capacitors, aside from the undesirable effect of their wide variation in capacitance over temperature, become resistive at high frequencies. inductor selection inductor selection will be determined by the following (not necessarily in the order of importance); ? inductance ? rated current value ? size requirements ? dc resistance (dcr) the mic23051 was designed for use with an inductance range from 0.47h to 2.2h. typically, a 1h inductor is recommended for a balance of transient response, efficiency and output ripple. for faster transient response a 0.47h inductor may be used. for lower output ripple, a 2.2h is recommended. maximum current ratings of the inductor are generally given in two methods; permissible dc current and saturation current. permissible dc current can be rated either for a 40c temperature rise or a 10% to 20% loss in inductance. ensure the inductor selected can handle the maximum operating current. when saturation current is specified, make sure that t here is enough margin so that the peak current of the induct or does not cause it to saturate. peak current can be calculated as follows: i pk = i out + v out (1-v out /v in )/2fl as shown by the previous ca lculation, the peak inductor current is inversely proportional to the switching frequency and the inductance; the lower the switching frequency or the inductance the higher 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 application circuit and bill of material for details. dc resistance (dcr) is al so important. while dcr is inversely proportional to size, dcr can represent a significant efficiency loss. refer to the efficiency considerations. compensation the mic23051 is designed to be stable with a 0.47h to 2.2h inductor with a 2. 2f ceramic (x5r) output capacitor. efficiency considerations efficiency is defined as the am ount of useful output power, divided by the amount of power supplied. 100 i v i v _% efficiency in in out out ? ? ? ? ? ? ? ? = maintaining high efficiency serves two purposes. it reduces power dissipation in the power supply, reducing the need for heat sinks and ther mal design considerations and it reduces consumption of current for battery powered applications. reduced current draw from a battery increases the devices operating 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 simply the power 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 switch current 2 . during the off cycle, the low side n-channel mosfet conducts, also dissipating power. device operating current also reduces efficiency. the product of the quiescent (operating) current and the supply voltage is another dc loss. the current re quired driving the gates on and off at a constant 4mhz frequency and the switching transitions make up the switching losses. 50 60 70 80 90 100 1 10 100 1000 output current (ma) efficiency v out = 1.8v v out = 1.8v l = 1h v in = 3.3v v in = 2.7v v in = 3.6v the figure above 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 mic23051 is able to 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 gate to sour ce threshold on the internal
micrel, inc. mic23051 july 2009 10 m9999?070809-f mosfets, reducing the internal r dson . this improves efficiency by reducing dc losses in the device. all but the inductor losses are inherent to the device. in which case, inductor selection becomes increasingly critical in efficiency calculations. as the inductors are reduced in size, the dc resistance (dcr) can become quite significant. the dcr losses can be calculated as follows; l_pd = i out 2 dcr from that, the loss in efficiency due to inductor resistance can be calculated as follows; 100 l_pd i v i v 1 _loss efficiency out out out out ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = efficiency loss due to 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. hyperlight load mode? mic23051 uses a minimum on and off time proprietary control loop. 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 minimu m-on-time. when the output voltage is over the regulation threshold, the error comparator turns the pmos off for a minimum-off-time. the nmos acts as an ideal rectifier that conducts when the pmos is off. using a 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 control loop to work in discontinuous mode for light load operations. in discontinuous mode mic23051 works in pulse frequency modulation (pfm) to regulate the output. as the output current increases, the switching frequency increases. this improves the efficiency of mic23051 during light load currents. as the load current increases, the mic23051 goes into continuous conduction mode (ccm) at a constant frequency of 4mhz. the equation to calculate the load when the mic23051 goes into continuous conduction mode may be approximated by the following formula: ? ? ? ? ? ? ? = f 2l d ) v (v i out in load
micrel, inc. mic23051 july 2009 11 m9999?070809-f mic23051 typical application circuit bill of materials item part number manufacturer description qty c1, c2 c1608x5r0j476k tdk (1) 4.7f ceramic capacitor, 6.3v, x5r, size 0603 2 c3 c1608c0g1h561j tdk (1) 560pf ceramic capacitor, 50v, npo, size 0603 1 lqm21pn1r0mc0d murata (2) 1h, 0.8a, 190m ? , l2mm x w1.25mm x h0.5mm lqh32cn1r0m33 murata (2) 1h, 1a, 60m ? , l3.2mm x w2.5mm x h2.0mm lqm31pn1r0m00 murata (2) 1h, 1.2a, 120m ? , l3.2mm x w1.6mm x h0.95mm cpl2512t1r0m tdk (1) 1h, 1.5a, 100m ? , l2.5mm x w1.5mm x h1.2mm lqm31pnr47m00 murata (2) 0.47h, 1.4a, 80m ? , l3.2mm x w1.6mm x h0.85mm l1 mipf2520d1r5 fdk (3) 1.5h, 1.5a, 70m ? , l2.5mm x w2mm x h1.0mm 1 u1 mic23051-xxyml micrel, inc. (4) 4mhz pwm buck regulator with hyperlight load mode 1 notes: 1. tdk: www.tdk.com 2. murata: www.murata.com 3. fdk: www.fdk.co.jp 4. micrel, inc: www.micrel.com
micrel, inc. mic23051 july 2009 12 m9999?070809-f pcb layout recommendations top layer bottom layer
micrel, inc. mic23051 july 2009 13 m9999?070809-f package information 8-pin 2mm x 2mm mlf ? (ml) 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 the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specific ations at any time without notification to the customer. micrel products are not designed or authorized for use as components in life suppor t appliances, devices or systems where malfu nction of a product can reasonably be expected to result in pers onal injury. life support devices or system s are devices or systems that (a) are in tended 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 significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, 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. ? 2007 micrel, incorporated.

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