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mic2811/2821 digital power management ic 2mhz, 600ma dc/dc with triple 300ma ldos micro leadframe and mlf are registered trademarks of amkor technology, 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 april 2008 m9999-042208-a general description the mic2811/21 are high performance power management ics, supporting four output voltage rails with maximum efficiency. the four rails are generated by a single 600ma dc/dc converter and three 300ma ldos. ldo1 and ldo2 are capable of operating at a low input voltage down to 1.65v useful fo r post regulating the output voltage of the dc-dc conver ter. the mic2811 supports the use of a bypass cap fo r improved noise performance on ldo1 & ldo2 while the mic2821 offers a separate enable pin for ldo3. featuring an operating frequency of 2mhz, the dc to dc converter uses small values of l and c to reduce board space but still retains operati ng efficiencies up to 86% at load currents up to 600ma. the mic2811/21 feature a cap design, operating with very small ceramic output capacitors and inductors for stability, reducing requir ed board space and component cost and it is available in fi xed output voltages in the 16- pin 3mm 3mm mlf ? leadless package. data sheets and support doc umentation can be found on micrel?s web site at: www.micrel.com. applications ? mobile phones / pdas ? portable media players ? mobile television receivers features ? 2mhz dc/dc converter and 3 ldos ? tiny 16-pin 3mm x 3mm mlf ? package ? thermal shutdown protection ? 2% output voltage ac curacy on all outputs ? current limit protection dc/dc converter ? 2.7v to 5.5v input voltage range ? output current to 600ma ? 2mhz pwm operation ? up to 86% efficiency (1.2v output) ldo 1 & 2 ? 1.65v to 5.5v input voltage range ? 300ma output current ? fixed output voltage as low as 0.8v ? low 142mv dropout ? 70db psrr at 1khz ldo 3 ? 2.7v to 5.5v input voltage range ? 300ma output current ? fixed output voltage as low as 1.0v ____________________________________________________________________________________________________________ typical application 0 10 20 30 40 50 60 70 80 90 100 0 100 200 300 400 500 600 efficiency (%) output current (ma) 1.2vout efficiency l = 2.2 h c = 2.2 f 3v 3.6v 4.2v
micrel, inc. mic2811/2821 april 2008 2 m9999-042208-a ordering information part number marking code voltage (1) junction temperature range package (2) mic2811-4gjlyml yha4 1.2v/1.8v/2.5v/2.7v ?40c to +125c 16-pin 3x3 mlf ? MIC2811-4GMSYML yha3 1.2v/1.8v/2.8v /3.3v ?40c to +125c 16-pin 3x3 mlf ? mic2821-4gjlyml yja2 1.2v/1.8v/2.5v/2.7v ?40c to +125c 16-pin 3x3 mlf ? mic2821-4gmsyml yja3 1.2v/1.8v/2.8v /3.3v ?40c to +125c 16-pin 3x3 mlf ? note: 1. output voltage of dc/dc, ldo1, ldo2, ldo3 respectively for additional voltage options, contact micr el marketing. available fixed output voltage range for each output is as follows: min max dc/dc 1.0 2.0 (adjustable output also available) ldo1 0.8 3.6 ldo2 0.8 3.6 ldo3 1.0 3.9 2. mlf is a green rohs compliant package. lead finish is nipdau. mold compound is halogen free.
micrel, inc. mic2811/2821 april 2008 3 m9999-042208-a pin configuration en1 bias sgnd pgnd vin1 ldo1 vin ldo3 fb byp en en2 ldo2 vin2 dvin sw en1 bias sgnd pgnd vin1 ldo1 vin ldo3 fb en3 en en2 ldo2 vin2 dvin sw mic2811 16-pin 3mm x 3mm mlf ? (ml) (top view) mic2821 16-pin 3mm x 3mm mlf ? (ml) (top view) pin description pin number mic2811 pin number mic2821 pin name pin name 1 1 en1 enable input (ldo 1). active high inpu t. logic high = on; logic low = off; do not leave floating. 2 2 bias internal circuit bias supply. it must be de-coupled to signal ground with a 0.1 f capacitor and should not be loaded. 3 3 sgnd signal ground. 4 4 pgnd power ground. 5 5 sw switch (output): internal power mosfet output switches. 6 6 dvin power supply for dc/dc converter. must be tied to vin. 7 7 vin2 power supply to ldo2. 8 8 ldo2 output of ldo2. 9 9 ldo3 output of ldo3. 10 10 vin supply to bias circuitry and power to ldo3, must be tied to dvin. 11 11 ldo1 output of ldo1. 12 12 vin1 power supply to ldo1. 13 13 fb feedback input to the error amplif ier of the dc/dc converter. adjust version: use external resistor divider from dc/dc output to set vout. fixed voltage version: connect directl y to vout of the dc/dc converter. 14 n/a byp reference bypass. connect external 0.1 f to gnd to reduce output noise. may be left open. do not connect directly to gnd. n/a 14 en3 enable input (ldo3). active high inpu t. logic high = on; logic low = off; do not leave floating. 15 n/a en enable input (dc/dc and ldo3). active high input. logic high = on; logic low = off; do not leave floating. n/a 15 en enable input (dc/dc). active high input. logic high = on; logic low = off; do not leave floating. 16 16 en2 enable input (ldo2). active high inpu t. logic high = on; logic low = off; do not leave floating.
micrel, inc. mic2811/2821 april 2008 4 m9999-042208-a absolute maximum ratings (1) supply voltage (dv in , v in , v in1 , v in2 ) ................... 0v to +6v enable voltage (v en , v en1 , v en2 , v en3 ) ................ 0v to +6v power dissipation ................................. internally limited (3) lead temperature (solde ring, 10 se c.) ..................... 260c storage temperature (t s )...................?65c t j +150c esd rating (4) ................................................................. 2kv operating ratings (2) supply voltage (dv in, v in ) ......................... +2.7v to +5.5v supply voltage (v in1, v in2 ) ............................+1.65v to v in enable input voltage (v en , v en1 , v en2 , v en3 ) ...... 0v to v in junction temperature range (t j ) .........?40c to +125c package thermal resistance 3mm x 3mm mlf-16 ( ja ) .............................56c/w electrical characteristics (5) dv in = v in = v in1 = v in2 = v outmax + 1v, l = 2.2 h; c outdc/dc = 2.2 f, c out1 = c out2 = c out3 = 2.2 f; i outdc/dc = 20ma; i outldo1 = i outldo2 = i outldo2 = 100 a; t j = 25c, bold values indicate ?40c < t j < +125c; unless noted. parameter conditions min typ max units uvlo threshold rising input voltage during turn-on (dvin & vin only) 2.45 2.55 2.65 v uvlo hysteresis 100 mv ground pin current v fb = 1.1*v fbnom (not switching); ldo2 or ldo1 only (v en = v en3 = gnd) ldo3 only (v en = v en1 = v en2 = gnd / mic2821 only) all 3 ldos 800 55 40 120 1100 85 95 a a a a a ground pin current in shutdown all en = 0v 0.2 5 a over-temperature shutdown 160 c over-temperature shutdown hysteresis 23 c logic low 0.2 v enable input voltage logic high 1.1 v enable input current 0.1 1 a electrical characteristi cs - dc/dc converter dv in = v in = v en = v outdc/dc + 1v, l = 2.2 h; c outdc/dc = 2.2 f, c out1 = c out2 = c out3 = 2.2 f; i outdc/dc = 20ma; t j = 25c, bold values indicate ?40c to + 125c; unless noted. parameter conditions min typ max units output voltage accuracy fixed output voltages -2 -3 +2 +3 % % current limit in pwm mode v fb = 0.9*v fbnom 0.75 1.2 1.8 a fb pin input current (adj only) 1 na output voltage line regulation v out > 2.4v; v in = v out + 300mv to 5.5v, i load = 20ma v out < 2.4v; v in = 2.7v to 5.5v, i load = 20ma 0.2 %/v %/v output voltage load regulation 20ma < i load < 300ma 0.2 1.5 % maximum duty cycle v fb 0.4v 100 % switch on-resistance pmos (0.7*v fbnom ) nmos (1.1*v fbnom ) 0.5 0.55 ? ? oscillator frequency 1.8 2 2.2 mhz turn-on time turn-on time (dc/dc) i load = 300ma; c byp = 0.1 f 83 350 s
micrel, inc. mic2811/2821 april 2008 5 m9999-042208-a electrical characteris tics - ldo1 and ldo2 v in = dv in = v outmax + 1v, v in1 = v en1 = v ldo1 + 1v; v in2 = v en2 = v ldo2 + 1v ; c outldo1 = c outldo2 = 2.2 f, i ldo1 = i ldo2 = 100 a; t j = 25c, v en = v en3 = gnd, bold values indicate ?40c< t j < +125c; unless noted. parameter conditions min typ max units output voltage accuracy -2.0 -3.0 +2.0 +3.0 % % output current capability v in > 1.8v 300 ma load regulation i out = 100 a to 300ma 0.3 1.5 % line regulation v in1(2) = v ldo1(2) +1v to 5.5v 0.02 0.3 %/v dropout voltage i out = 300ma @ vout > 1.5v 142 300 mv current limit v out = 0v 350 650 900 ma ripple rejection f = up to 1khz; c out = 2.2 f; c byp = 0.1 f f = 20khz; c out = 2.2 f; c byp = 0.1 f 70 44 db db output voltage noise c out = 2.2 f; c byp = 0.1 f; 10hz to 100khz 30 v rms electrical characteristics ? ldo3 v in = dv in = v en3 = v ldo3 +1 v; c out3 = 2.2 f; i outldo3 = 100 a; t j = 25c, v en1 = v en2 = gnd bold values indicate ?40c< t j < +125c; unless noted. parameter conditions min typ max units output voltage accuracy -2.0 -3.0 +2.0 +3.0 % % line regulation v in = v out +1v to 5.5v; i out = 100 a 0.03 0.5 %/v load regulation i out = 100 a to 300ma @ 3.3v 0.50 1.5 % dropout voltage i out = 300ma @ vin = 2.7v 210 350 mv ripple rejection f = up to 1khz; c out = 2.2 f f = 20khz; c out = 2.2 f 45 20 db db current limit v out = 0v 350 600 980 ma output voltage noise c out = 2.2 f, 10hz to 100khz 470 v rms notes: 1. exceeding the absolute maximum rating may damage the device. 2. the device is not guaranteed to function outside its operating rating. 3. the maximum allowable power dissipation of any t a (ambient temperature) is p d(max) = (t j(max) ? t a ) / ja . exceeding the maximum allowable power dissipation will result in excessive die temperatur e, and the regulator will go into thermal shutdown. 4. devices are esd sensitive. handli ng precautions recommended. human body model, 1.5k in series with 100pf. 5. specification for packaged product only.
micrel, inc. mic2811/2821 april 2008 6 m9999-042208-a typical characteristics (dc/dc converter) 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 -40 -20 0 20 40 60 80 100 120 frquency (mhz) temperature (c) sw frequency vs. temperature v in = 4v v out = 1.2v i out = 300ma 1.17 1.18 1.19 1.2 1.21 1.22 1.23 -40 -20 0 20 40 60 80 100 120 output voltage (v) temperature (c) output voltage vs. temperature v in = 4v c out = 4.7 f i out = 300ma 0 10 20 30 40 50 60 70 80 90 100 0 100 200 300 400 500 600 efficiency (%) output current (ma) 1.2vout efficiency l = 2.2 h c = 2.2 f 3v 3.6v 4.2v 700 720 740 760 780 800 820 840 860 880 2.73.44.14.85.5 enable threshold (mv) supply voltage (v) dc/dc enable threshold vs. supply voltage i load = 100ma l = 2.2 h c out = 2.2 f enable disable 1.2015 1.2018 1.2021 1.2024 1.2027 1.203 1.2033 1.2036 1.2039 2.7 3.4 4.1 4.8 5.5 output voltage (v) input voltage (v) line regulation i out = 300ma l = 2.2 h c out = 2.2 f 1.2 1.2005 1.201 1.2015 1.202 1.2025 1.203 1.2035 1.204 1.2045 1.205 0 100 200 300 400 500 600 output voltage (v) output current (ma) load regulation v in = 3.6v l = 2.2 h c = 2.2 f 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 2.73.44.14.85.5 switching frequency (mhz) input voltage (v) switching frequency vs. input voltage i out = 300ma l = 2.2 h c = 2.2 f 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5 2.73.44.14.85.5 current limit (a) input voltage (v) current limit vs. input voltage l = 2.2 h c = 2.2 f
micrel, inc. mic2811/2821 april 2008 7 m9999-042208-a typical characteristics (ldo) 0 10 20 30 40 50 60 70 80 90 1e+1 1e+2 1e+3 1e+4 1e+5 1e+6 psrr (db) frequency (hz) mic2811 ldo1 psrr 10ma 150ma 300ma 10 100 1k 10k 100k 1m 0 10 20 30 40 50 60 70 80 90 100 1e+1 1e+2 1e+3 1e+4 1e+5 1e+6 psrr (db) frequency (hz) mic2811 ldo2 psrr 10ma 150ma 300ma 10 100 1k 10k 100k 1m 0 10 20 30 40 50 60 70 80 1e+1 1e+2 1e+3 1e+4 1e+5 1e+6 psrr (db) frequency (hz) mic2811 ldo3 psrr 10ma 150ma 300ma 10 100 1k 10k 100k 1m 0.001 0.01 0.1 1 10 mic2811 ldo1 output noise spectral density v in = 4v c out = 2.2 f c byp = 0.1 f v out = 1.8v noise(10hz to 100khz) = 35.88 v rms 10 100 1k 10k 100k 1m 10m frequency (hz) 0.001 0.01 0.1 1 10 mic2811 ldo2 output noise spectral density v in = 4v c out = 2.2 f c byp = 0.1 f v out = 2.5v noise(10hz to 100khz) = 46.75 v rms 10 100 1k 10k 100k 1m 10m frequency (hz) 0.001 0.01 0.1 1 10 mic2811 ldo3 output noise spectral density v in = 4v c out = 2.2 f c byp = 0.1 f v out = 2.7v noise(10hz to 100khz) = 91.93 v rms 10 100 1k 10k 100k 1m 10m frequency (hz) 1.7 1.72 1.74 1.76 1.78 1.8 1.82 1.84 1.86 1.88 1.9 -40 -20 0 20 40 60 80 100 120 ldo1 out (v) temperature (c) ldo1 vs. temperature v in = 4v c out = 2.2 f 2.35 2.4 2.45 2.5 2.55 2.6 2.65 -40 -20 0 20 40 60 80 100 120 ldo2 out (v) temperature (c) ldo2 vs. temperature v in = 4v c out = 2.2 f i out = 150ma 2.55 2.6 2.65 2.7 2.75 2.8 2.85 -40 -20 0 20 40 60 80 100 120 ldo3 out (v) temperature (c) ldo3 vs. temperature v in = 4v c out = 2.2 f i out = 150ma 1.75 1.76 1.77 1.78 1.79 1.8 1.81 1.82 1.83 1.84 1.85 0 50 100 150 200 250 300 output voltage (v) output current (ma) ldo1 load regulation v in = 5.5v v in1 = 3.6v c = 2.2 f 1.75 1.76 1.77 1.78 1.79 1.8 1.81 1.82 1.83 1.84 1.85 22.533.544.555.5 output voltage (v) vin1 input voltage (v) ldo1 line regulation v in = 5.5v i load = 150ma c = 2.2 f 2.48 2.485 2.49 2.495 2.5 2.505 2.51 2.515 2.52 2.525 2.53 2.8 3.1 3.4 3.7 4.0 4.3 4.6 4.9 5.2 5.5 output voltage (v) vin2 input voltage (v) ldo2 line regulation i load = 150ma c = 2.2 f
micrel, inc. mic2811/2821 april 2008 8 m9999-042208-a typical characteristics (ldo cont.) 0 20 40 60 80 100 120 140 0 50 100 150 200 250 300 dropout voltage (mv) output current (ma) ldo2 dropout voltage vs. load current v in = 5.5v v out = 1.2v c = 2.2 f 2.4975 2.498 2.4985 2.499 2.4995 2.5 2.5005 2.501 2.5015 2.502 2.5025 0 50 100 150 200 250 300 output voltage (v) output current (ma) ldo2 load regulation v in = 5.5v v in2 = 3.6v c = 2.2 f 2.65 2.66 2.67 2.68 2.69 2.7 2.71 2.72 2.73 2.74 2.75 3.13.74.34.95.5 output voltage (v) vin3 input voltage (v) ldo3 line regulation i load = 150ma c = 2.2 f 2.69 2.692 2.694 2.696 2.698 2.7 2.702 2.704 2.706 2.708 2.71 0 50 100 150 200 250 300 output voltage (mv) output current (ma) ldo3 load regulation v in = 3.6v c = 2.2 f 55 56 57 58 59 60 61 62 63 64 65 0 50 100 150 200 250 300 gnd current ( a) output current (ma) ldo2 gnd current vs. output current v in = 3.6v c = 2.2 f
micrel, inc. mic2811/2821 april 2008 9 m9999-042208-a functional characteristics (dc/dc converter)
micrel, inc. mic2811/2821 april 2008 10 m9999-042208-a functional characteristics (ldo)
micrel, inc. mic2811/2821 april 2008 11 m9999-042208-a functional diagram dvin vin bias c bias en sw r1 r2 v out c out fb ldo3 enable and control logic pwm control anti-shoot through p-channel current limit 6 ldo current limit sgnd 1.0v soft start bias, uvlo, thermal shutdown hsd lsd n-channel current limit ea ea c ldo3 ldo1 ldo current limit ea vin1 ldo2 ldo current limit ea vin2 en1 en2 ldo1 & 2 quick start byp c byp (mic2811) c ldo1 c ldo2 ref voltage bias 0.8v 750k internal for fixed output options connect v out directly to fb bias en3 (mic2821) bias pgnd 0.8v block diagram
micrel, inc. mic2811/2821 april 2008 12 m9999-042208-a applications information the mic2811 and mic2821 are power management ics with a single integrated step-down regulator and three low dropout regulators. ldo1, ldo2, and ldo3 are 300ma low dropout regulators supplied by their own independent input voltage pins. the supply to ldo3 (v in ) also powers the bias circuitry and must be available for any output to be operational. this supply requires an external connection to dvin . the step-down regulator is a 2mhz 600ma pwm power supply, using small values of l and c operating at over 90% efficiency. dvin/vin/vin1/vin2 all four regulators, the switch mode regulator, ldo1, ldo2, and ldo3 have their own unique input voltage supply pin. vin provides power to ldo3 and internal circuitry shared by all the r egulators and therefore must be available for any of the r egulators to operate properly. dvin and vin must be tied together and have a minimum input voltage of 2.7v . inputs to ldo1 (vin1) and ldo2 (vin2) can go as low as 1.65v, but should never exceed the vin and dvin input voltage. due to the high switching speeds, a 1 f input capacitor is recommended close to the dvin, decoupled to the pgnd pin. ldo1 regulated output voltage of ldo1. power is provided by vin1 and enabled through en1. recommended output capacitance is 2.2 f, decoupled to the sgnd pin. ldo2 regulated output voltage of ldo2. power is provided by vin2 and enabled through en2. recommended output capacitance is 2.2 f, decoupled to the sgnd pin. ldo3 regulated output voltage of ldo3. power is provided by vin and enabled through en (mic2811) or en3 (mic2821). recommended output capacitance is 2.2 f, decoupled to the sgnd pin. 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 routed away from sensitive nodes. dc/dc output capacitor the dc/dc regulator requires an output capacitor for proper operation. values of greater than 2.2 f improve transient response and noise reduction at high frequency. x7r/x5r dielectr ic-type ceramic capacitors are recommended because of their superior temperature performance. x7r-type capacitors change capacitance by 15% over their operat ing temperature range and are the most stable type of ceramic capacitors. z5u and y5v dielectric capacitors change value by as much as 50% to 60% respectively over their operating temperature ranges and for that reason are not recommended. larger output capacitances can be achieved by placing tantalum or aluminum electrolytics in parallel with the ceramic capacitor. for example, a 100 f electrolytic in parallel with a 10 f ceramic can provide the transient and high frequency noise performance of a 100 f ceramic at a significantly lower cost. specific undershoot/o vershoot perfo rmance will depend on both the values and esr/esl of the capacitors. inductor selection inductor selection will be det ermined by the following (not necessarily in the order of importance); ? inductance ? rated current value ? size requirements ? dc resistance (dcr) the mic2811 and mic2821 are designed for use with a 2.2 h inductor. 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 there is enough margin that the peak cu rrent will not saturate the inductor. peak inductor current can be calculated as follows: l f v i i in out v v out out pk ? + = 2 ) 1 ( the size requirements refer to the area and height requirements that are necessary to fit a particular design. please refer to the inductor dimensions on their datasheet. dc resistance is also important. while dcr is inversely proportional to size, dcr can represent a significant efficiency loss. efficiency considerations efficiency is defined as the amount of useful output power, divided by the amount of power supplied. 100 % _ ? ? ? ? ? ? = iin vin iout vout efficiency maintaining high efficiency serves two purposes. it reduces power dissipation in the power supply, reducing the need for heat sinks and thermal design
micrel, inc. mic2811/2821 april 2008 13 m9999-042208-a 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. 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 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: dcr iout pd l = 2 _ from that, the loss in efficiency due to inductor resistance can be calculated as follows; 100 _ 1 _ ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? = pd l iout vout iout vout loss efficiency efficiency loss due to dcr is minimal at light loads and gains significance as the l oad is increased. inductor selection becomes a trade-off between efficiency and size in this case. pgnd power ground (pgnd) is t he ground path for the high current pwm mode. the current loop area for the power ground should be as small as possible. sgnd signal ground (sgnd) is the ground path for the biasing and control circuitry. the current loop for the signal ground should be as small as possible. byp (mic2811 only) for enhanced noise and psrr performance on ldo1 & ldo2, the internal reference of the mic2811 can be bypassed with a capacitor to ground. a quick-start feature allows for quick turn-on of the output voltage. the recommended nominal bypass capacitor is 0.1 f, but it can be increased, which will also result in an increase to the start-up time. mic2811 layout recommendations a poor layout of the mic2811 may cause unwanted voltage and current spikes. this can lead to noise on dc voltages and emi radiating to nearby devices. the following are recommendations for the mic2811/21 layout. the evaluation board layout is included as an example. 1. place the mic2811/21 wi th the pad size designated in the ?recommended land patterns? page of the micrel website. 2. when laying out the components, keep the mic2811, inductor, and filter capacitors physically close to keep traces as short as possible . the traces between these components carry relatively high switching currents and can affect adjacent signals. 3. the input capacitor between dvin and pgnd should be placed right next to the mic2811/21. this will eliminate trace inductance effects and reduce internal noise for the mic2811/21 cont rol circuitry. the trace from the dvin filter capacito r to the mic2811/21 device should not be routed through any vias. this lessens the chance of noise coupling by the effective antenna of the via. 4. monitoring the path of the switching currents will help minimize the radiated noise. in the first half of the switching cycle, current flows from the input filter capacitor through the high side switch within the mic2811, then through the inductor to the output filter capacitor and lastly through ground. in the second half of the switching cycle, current is pulled up from ground through the low side synchronous switch within the mic2807 by the inductor, to the output filter capacitor and then back through ground, forming a second current loop. route these loops to ensure the current curls in the same direction, preventing magnetic field reversal between the switching cycles. 5. connect the bypass capacitor (mic2811 only) to the byp pin and the agnd pin. agnd and pgnd should be connected close to the chip at a single point in order to minimize undesirable behavior due to ground bounce. input and output filter capaci tors should be connected to pgnd. 6. connections between power components and the mic2811 should have wide traces. it is good practice to use a minimum of 30mils (0.762mm) per ampere for 1oz copper weight. 7. route noise sensitive tr aces such as feedback (fb), bias, and byp away from the switching traces and the inductor. noise coupled into these pins can affect the accuracy of the output. the feedback pin should be connected at point of load for an accurate load regulation.
micrel, inc. mic2811/2821 april 2008 14 m9999-042208-a mic2811/2821-yml schematic c1 4.7 f/6.3v dvin vin1 vin2 7 vin 10 en2 16 bias 2 vin1 12 ldo2 8 ldo1 11 sgnd 3 pgnd 4 en 15 dvin 6 en1 1 sw 5 fb 13 byp/en3 14 ldo3 9 u1 mic2811/2821-yml j1 dvin c2 4.7 f/6.3v dvin c3 4.7 f/6.3v vin1 c4 4.7 f/6.3v vin2 j2 gnd j3 vin1 j4 vin2 j6 en j7 en1 j8 en2 r5 10k vin2 r4 10k c5 0.1 f (for mic2811 only) j6 en r5 10k (for mic2821 only) c6 0.1 f/10v r2 option r1 option vo j13 vout j14 gnd c10 4.7 f/6.3v l1 2.2 h c9 2.2 f/6.3v j10 vo_ldo3 vo-ldo3 c8 2.2 f/6.3v j11 vo_ldo2 vo-ldo2 c7 2.2 f/6.3v j12 vo_ldo1 j5 gnd
micrel, inc. mic2811/2821 april 2008 15 m9999-042208-a bill of materials item part number manufacturer description qty. 06036d475kat2a avx (1) jmk107bj475ma-t taiyo yuden (5) c1608x5r0j475k tdk (3) c1, c2, c3, c4, c10 grm188r60j475ke19d murata (2) 4.7 f, 6.3v, 0603, x5r ceramic capacitor 5 c1608x5r0j225k tdk (3) 06036d225kat2a avx (1) grm188r60j225ke19d murata (2) c7, c8, c9 vj0603g225kxyat vishay (4) 2.2 f, 6.3v, 0603, x5r ceramic capacitor 3 c1005x7r1a104k tdk (3) c5, c6 vj0603y104kxqcw1bc vishay (4) 0.1 f, 10v, x5r ceramic capacitor (c5 for mic2811 ev board only) 2 cdrh2d11hpnp sumida (6) 2.2 h, 1.1a, 3.2x3.2x1.2mm inductor l1 me3220-222-ml coilcraft (7) 2.2 h, 1.1a, 2.5x3.2x2mm inductor 1 r1 crcw06030r00frt1 vishay (4) 0 ? , 0603, 1% resistor 1 r2 open 0 r3, r4, r5 crcw06031002frt1 vishay (4) 10k ? , 0603, 1% resistor 3 u1 mic2811/21 micrel, inc. (8) 16-pin 3mm x 3mm mlf ? 1 notes: 1. avx: www.avx.com 2. murata: www.murata.com 3. tdk: www.tdk.com 4. vishay: www.vishay.com 5. taiyo yuden: www.t-yuden.com 6. sumida: www.sumida.com 7. coilcraft: www.coilcraft.com 8. micrel, inc.: www.micrel.com
micrel, inc. mic2811/2821 april 2008 16 m9999-042208-a pcb layout recommendations top layer bottom layer
micrel, inc. mic2811/2821 april 2008 17 m9999-042208-a package information 16-pin 3mm x 3mm 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 specifications at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life suppo rt devices or systems 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. ? 2008 micrel, incorporated.

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