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mic2800 digital power management ic 2mhz, 600ma dc/dc w/dual 300ma/300ma low v in ldos lowq is a trademark of micrel, inc. mlf and micro leadframe 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 june 2006 m9999-061406 (408) 955-1690 general description the mic2800 is a high performance power management ic, giving three output voltages with maximum efficiency. integrating a 2mhz dc/dc converter with an ldo post regulator, the mic2800 gives two high efficiency outputs with a second, 300ma ldo fo r maximum flexibility. the mic2800 features a lowq? mode, reducing the total current draw while in this mode to less than 30a. in lowq? mode, the output noise of the dc to dc converter is 75v rms , significantly lower than other converters which use a pfm light load mode that can interfere with sensitive rf circuitry. the dc to dc converter uses small values of l and c to reduce board space but still re tains efficiencies over 90% at load currents up to 600ma. the mic2800 is a cap design, operating with very small ceramic output capacitors and inductors for stability, reducing required board spac e and component cost and it is available in fixed output voltages in the 16-pin 3mm x 3mm mlf ? leadless package. data sheets and support doc umentation can be found on micrel?s web site at www.micrel.com. features ? 2.7v to 5.5v input voltage range ? 2mhz dc/dc converter and two stand-alone ldos ? ldo1: low input voltage is powered directly from dc/dc converter for highest efficiency ? integrated power-on reset (or function for all outputs) ? adjustable delay time ? lowq? mode ? 30a total i q when in lowq? mode ? tiny 16-pin 3mm x 3mm mlf ? package dc to dc converter ? output current to 600ma in pwm mode ? lowq? mode: no noise light load mode ? 75v rms output noise in lowq? mode ? 2mhz pwm operation in normal mode ? >90% efficiency ldos ? ldo1 input voltage directly connected to dc/dc converter output voltage for maximum efficiency ? ideal for 1.8v to 1.5v conversion ? 300ma output current from 1.8v input ? output voltage down to 0.8v ? ldo2 ? 300ma output current capable ? thermal shutdown protection ? current limit protection applications ? mobile phones ? pdas ? gps receivers ? digital still cameras ? portable media players typical application ldo vin vin sw fb ldo1 ldo2 por c set lowq en2 c byp c bias en1 mic2800-xxxyml baseband memory/dsp pgnd sgnd v in 2.7v to 5.5v 4.7f/ 6.3v c byp 0.01f c out2 2.2f ceramic c out1 2.2f ceramic c set 0.01f c bias 0.1f 2.2f ceramic v out 2.2h gnd gnd 100 200 300 400 500 600 output current (ma) 50 55 60 65 70 75 80 85 90 95 100 dc/dc 1.8v out efficiency 0 3v 3.6v 4.2v l = 2.2h c out = 2.2f /lowq = v in
micrel, inc. mic2800 june 2006 2 m9999-061406 (408) 955-1690 ordering information part number manufacturing part number voltage junction temperature range package mic2800-1.8/1.2/2.8yml mic 2800-g4myml 1.8v/1.2v/2.8v ?40c to +125c 16-pin 3x3 mlf ? mic2800-1.87/1.2/2.8yml mic 2800-d24myml 1.87v/1.2v/2.8v ?40c to +125c 16-pin 3x3 mlf ? mic2800-1.8/1.5/2.8yml mic 2800-gfmyml 1.8v/1.5v/2.8v ?40c to +125c 16-pin 3x3 mlf ? mic2800-adj/1.2/3.3yml mic2800-a4syml ad j/1.2v/3.3v ?40c to +125c 16-pin 3x3 mlf ? notes: other voltage options available. pl ease contact micrel for details. dc/dc ? fixed output voltages (range of 1.0v to 2.0v). adjustable output voltage is available upon request. ldo1 ? output voltage range of 0.8v to v dc/dc - v do. ldo2 ? output voltage range of 0.8v to 3.6v.
micrel, inc. mic2800 june 2006 3 m9999-061406 (408) 955-1690 pin configuration 3mm x 3mm mlf ? (ml) fixed dc/dc converter output voltage pin description pin number pin name pin function 1 _____ lowq lowq mode. active low input. logic high = full power mode; logic low = lowq mode; do not leave floating. 2 bias internal circuit bias supply. it must be de-coupled to signal ground with a 0.1f capacitor and should not be loaded. 3 sgnd signal ground. 4 pgnd power ground. 5 sw switch (output): internal power mosfet output switches. 6 v in supply input ? dc/dc. must be tied to pin7 externally. 7 v in supply input ? ldo2. must be tied to pin6 externally. 8 ldo2 output of regulator 2 9 fb feedback. input to the error amplifier for dc to dc converter. adjust version, co for fixed output voltages connect to v out and an internal resistor network sets the output voltage 10 ldo ldo output: connect to v out of the dc/dc for lowq mode operation. 11 ldo1 output of regulator 1 12 por power-on reset output: open-drain output. active low indicates an output undervoltage condition on either one of the three regulated outputs. 13 c set delay set input: connect external capacitor to gnd to set the internal delay for the por output. when left open, there is minimu m delay. this pin cannot be grounded. 14 c byp reference bypass: connect external 0.1f to gnd to reduce output noise. may be left open. 15 en1 enable input (dc/dc and ldo1). active high input. logic high = on; logic low = off; do not leave floating. 16 en2 enable input (ldo 2). active high input. logic high = on; logic low = off; do not leave floating
micrel, inc. mic2800 june 2006 4 m9999-061406 (408) 955-1690 absolute maximum ratings (1) supply voltage (v in ) ............................................. 0v to +6v enable input voltage (v en )................................... 0v to +6v power dissipation, internally limited (3) lead temperature (solde ring, 10 se c.)...................... 260c storage temperature (t s ) .........................?65c to +150c eds rating (4) .................................................................. 2kv operating ratings (2) supply voltage (v in ) ..................................... +2.7v to +5.5v enable input voltage (v en )..................................... 0v to v in junction temperature (t j ) ........................ ?40c to +125c junction thermal resistance mlf-16 ( ja ) ......................................................45c/w electrical characteristics (5) v in = en1 = en2 = lowq = v out (6) + 1v; c outdc/dc = 2.2f, c out1 = c out2 = 2.2f; i outdc/dc = 100ma; i outldo1 = i outldo2 = 100a; 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 2.45 2.55 2.65 v uvlo hysteresis 100 mv ground pin current v fb = gnd (not switching); ldo2 only (en1 = low) 800 55 1100 85 95 a a a ground pin current in shutdown all en = 0v 0.2 5 a ground pin current (lowq mode) i dc/dc < i ldo1 < i ldo2 < 10ma dc/dc and ldo1 off; i ldo2 < 10ma 30 20 60 80 70 a a a over-temperature shutdown 160 q c over-temperature shutdown hysteresis 23 q c enable inputs (en1; en2; / lowq ) logic low 0.2 v enable input voltage logic high 1.0 v v il < 0.2v 0.1 1 a enable input current v ih > 1.0v 0.1 1 a turn-on time (see timing diagram) turn-on time (ldo1 and ldo2) en2=v in en1=v in 240 120 500 350 s s turn-on time (dc/dc) en2=v in ; i load = 300ma; c byp = 0.1f 83 350 s por output low threshold, % of nominal (v dc/dc or v ldo1 or v ldo2 ) (flag on) 90 91 % vth high threshold, % of nominal (v dc/dc and v ldo1 and v ldo2 ) (flag off) 96 99 % vol por output logic low voltage; il = 250a 10 100 mv ipor flag leakage current, flag off 0.01 1 a set input set pin current source vset = 0v 0.75 1.25 1.75 a set pin threshold voltage por = high 1.25 v
micrel, inc. mic2800 june 2006 5 m9999-061406 (408) 955-1690 electrical characteristi cs - dc/dc converter v in = v outdc/dc + 1; en1 = v in ; en2 = gnd; i outdc/dc = 100ma ;l = 2.2h; c outdc/dc = 2.2f; t j = 25c, bold values indicate ?40c to + 125c; unless noted. parameter conditions min typ max units lowq = high (full power mode) fixed output voltages nominal v out tolerance -2 -3 +2 +3 % % current limit in pwm mode v fb = 0.9*v nom 0.75 1 1.6 a fb pin input current (adj only) 1 5 na output voltage line regulation v out > 2.4v; v in = v out + 300mv to 5.5v, i load = 100ma v out < 2.4v; v in = 2.7v to 5.5v, i load = 100ma 0.2 %/v %/v output voltage load regulation 20ma < i load < 300ma 0.2 1.5 % maximum duty cycle v fb 0.4v 100 % pwm switch on-resistance i sw = 150ma v fb = 0.7v fb_nom i sw = -150ma v fb = 1.1v fb_nom 0.6 0.8 ? ? oscillator frequency 1.8 2 2.2 mhz output voltage noise c out = 2.2f; c byp = 0.1f; 10hz to 100khz 60 v rms lowq = low (light load mode) variation from nominal v out -2.0 +2.0 % output voltage accuracy variation from nominal v out ; -40c to +125c -3.0 +3.0 % output voltage temp. coefficient 40 ppm/c line regulation v in = v out + 1v to 5.5v; i out = 100a 0.02 0.3 0.6 %/v %/v load regulation i out = 100a to 50ma 0.2 1.5 % ripple rejection f = up to 1khz; c out = 2.2f; c byp = 0.1f f = 20khz; c out = 2.2f; c byp = 0.1f 55 45 db db current limit v out = 0v 80 120 190 ma
micrel, inc. mic2800 june 2006 6 m9999-061406 (408) 955-1690 electrical characteristics - ldo1 v in = v outdc/dc ; en1 = v in ; en2 = gnd; c out1 = 2.2f, i out1 = 100a; t j = 25c, bold values indicate ?40c< t j < +125c; unless noted. parameter conditions min typ max units lowq = high (full power mode) variation from nominal v out -2.0 +2.0 % output voltage accuracy variation from nominal v out ; -40c to +125c -3.0 +3.0 % output current capability v in > 1.8v v in > 1.5v 300 120 ma ma load regulation i out = 100a to 150ma i out = 100a to 300ma 0.17 0.3 1.5 % % current limit v out = 0v 350 500 700 ma ripple rejection f = up to 1khz; c out = 2.2f; c byp = 0.1f f = 20khz; c out = 2.2f; c byp = 0.1f 70 44 db db output voltage noise c out = 2.2f; c byp = 0.1f; 10hz to 100khz 30 v rms lowq = low (light load mode) variation from nominal v out -3.0 +3.0 % output voltage accuracy variation from nominal v out ; -40c to +125c -4.0 +4.0 % load regulation i out = 100a to 10ma 0.2 0.5 1.0 % % current limit v out = 0v 50 85 125 ma ripple rejection f = up to 1khz; c out = 2.2f; c byp = 0.1f f = 20khz; c out = 2.2f; c byp = 0.1f 70 42 db db
micrel, inc. mic2800 june 2006 7 m9999-061406 (408) 955-1690 electrical characteristics - ldo2 v in = v outldo2 + 1.0v; en1 = gnd; en2 = v in ; c out2 = 2.2f; i outldo2 = 100a; t j = 25c, bold values indicate ?40c< t j < +125c; unless noted. parameter conditions min typ max units lowq = high (full power mode) variation from nominal v out -2.0 +2.0 % output voltage accuracy variation from nominal v out ; -40c to +125c -3.0 +3.0 % line regulation v in = v out +1v to 5.5v; i out = 100a 0.02 0.3 0.6 %/v load regulation i out = 100a to 150ma i out = 100a to 200ma i out = 100a to 300ma 0.20 0.25 0.40 1.5 % % % dropout voltage i out = 150ma i out = 200ma i out = 300ma 70 94 142 300 mv mv mv ripple rejection f = up to 1khz; c out = 2.2f; c byp = 0.1f f = 20khz; c out = 2.2f; c byp = 0.1f 75 40 db db current limit v out = 0v 400 550 850 ma output voltage noise c out = 2.2f, c byp =0.1f, 10hz to 100khz 25 v rms lowq = low (light load mode) variation from nominal v out -3.0 +3.0 % output voltage accuracy variation from nominal v out ; -40c to +125c -4.0 +4.0 % line regulation v in = v out +1v to 5.5v 0.02 0.3 0.6 %/v load regulation i out = 100a to 10ma 0.2 1.0 % dropout voltage i out = 10ma 22 35 50 mv mv ripple rejection f = up to 1khz; c out = 2.2f; c byp = 0.1f f = 20khz; c out = 2.2f; c byp = 0.1f 75 55 db db current limit v in = 2.7v; v out = 0v 50 85 125 ma 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 temper ature, and the regulator will go into thermal shutdown. 4. devices are esd sensitive. handling precautions re commended. human body model, 1.5k in series with 100pf. 5. specification for packaged product only. 6. v out denotes the highest of the three output voltage plus one volt.
micrel, inc. mic2800 june 2006 8 m9999-061406 (408) 955-1690 typical characterist ics (dc/dc pwm mode) 50 55 60 65 70 75 80 85 90 95 100 100 200 300 400 500 600 output current (ma) dc/dc 1.87v out efficiency 0 3v 3.6v 4.2v l = 2.2h c out = 2.2f /lowq = v in 100 200 300 400 500 600 output current (ma) 50 55 60 65 70 75 80 85 90 95 100 dc/dc 1.8v out efficiency 0 3v 3.6v 4.2v l = 2.2h c out = 2.2f /lowq = v in 0 200 400 600 800 1000 1200 1400 20 40 60 80 temperature (c) dc/dc current limit c byp = 0.1f c out = 2.2f /lowq = v in en1 = en2 = v in vs. temperature 500 550 600 650 700 750 800 850 900 950 1000 2.7 supply voltage (v) dc/dc enable threshold 5.5 3.4 4.1 4.8 on off c out = 2.2f /lowq = v in vs. supply voltage 50 55 60 65 70 75 80 85 90 95 100 2.7 supply voltage (v) dc/dc turn-on delay 5.2 3.2 4.2 4.7 3.7 vs. supply voltage c out = 2.2f /lowq = v in
micrel, inc. mic2800 june 2006 9 m9999-061406 (408) 955-1690 typical characteristi cs (dc/dc lowq mode) 0 10 20 30 40 50 60 power supply rejection ratio (input voltage) 1 frequency (khz) 0.1 0.01 10 100 1,000 4.2v 3.6v i out = 50ma v out = 1.8v c out = 2.2f /lowq = gnd 0 10 20 30 40 50 60 70 80 power supply rejection ratio (output current) 1 frequency (khz) 0.1 0.01 10 100 1,000 100a 0a 50ma v in = 3.6v v out = 1.8v c out = 2.2f /lowq = gnd 0 20 60 80 100 2.7 supply voltage (v) 2.7 ldo current limit 3.4 4.8 5.5 4.1 vs. supply voltage /lowq = gnd c out = 2.2f 40 1.84 1.85 1.86 1.87 1.88 1.89 1.90 10 20 30 40 50 60 70 80 90 output current (ma) ldo output voltage v in = 3.6v v out = 1.87v /lowq = gnd c out = 2.2f vs. output current 0.001 0.01 0.1 1 10 dc/dc lowq mode output noise spectral density 1 frequency (khz) 0.1 0.01 10 100 1,000 10,000 v in = 4.2v v out = 1.87v c out = 2.2f /lowq = gnd
micrel, inc. mic2800 june 2006 10 m9999-061406 (408) 955-1690 typical characteristics (ldo1, ldo2) 0 10 20 30 40 50 60 70 80 90 100 power supply rejection ratio (ldo1 lowq mode) 1 frequency (khz) 0.1 0.01 10 100 1,000 50ma 100a v in = 4.2v v out = 1.2v /lowq = gnd c out = 2.2f c byp = 0.1f 0 10 20 30 40 50 60 70 80 power supply rejection ratio (ldo1 normal mode) 1 frequency (khz) 0.1 0.01 10 100 1,000 50ma 100a v in = 4.2v v out = 1.2v /lowq = v in c out = 2.2f c byp = 0.1f 150ma 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 1 frequency (khz) 0.1 0.01 10 100 1,000 power supply rejection ratio (ldo2 lowq mode) 50ma 100a v in = 4.2v v out = 2.8v /lowq = v in c out = 2.2f c byp = 0.01f 10ma 0 10 20 30 40 50 60 70 80 90 100 power supply rejection ratio (ldo2 normal mode) 1 frequency (khz) 0.1 0.01 10 100 1,000 50ma 150ma 300ma 100a v in = 4.2v v out = 1.2v /lowq = v in c out = 2.2f c byp = 0.01f 2.50 2.55 2.60 2.65 2.70 2.75 2.85 2.90 2.95 3.00 (ldo2) output voltage 20 40 60 80 temperature (c) v in = v out + 1v v out = 2.8v c byp = 0.1f c out = 2.2f en1 = gnd en2 = v in 2.80 vs. temperature 30 35 40 50 55 60 65 70 ground current 20 40 60 80 temperature (c) 45 v in = v out + 1v v out = 2.8v c byp = 0.1f c out = 2.2f /lowq = v in en1 = gnd en2 = v in 100ma 300ma 100a vs. temperature 30 40 50 60 70 0 50 100 150 200 250 300 output current (ma) ground current v in = 2.8v v out = 2.8v c byp = 0.1f c out = 2.2f vs. output current 0 20 40 60 80 100 120 140 0 50 100 150 200 250 300 output current (ma) (ldo2) dropout voltage v out = 2.8v c byp = 0.1f c out = 2.2f /lowq = v in vs. output current 0.00 0.12 0.14 0.16 0.18 0.20 (ldo2) dropout voltage 20 40 60 80 temperature (c) 0.02 0.04 0.06 0.08 0.10 150ma 100ma 50ma 300ma 20ma vs. temperature v out = 2.8v c out = 2.2f c byp = 0.1f /lowq = v in 2.0 2.5 3.0 1.5 2.0 2.5 3.0 3.5 supply voltage (v) dropout chararcteristics 150ma 300ma 100ma c out = 2.2f c byp = 0.1f /lowq = v in 0.001 0.01 0.1 1 10 ldo1 output noise spectral density 1 frequency (khz) 0.1 0.01 10 100 1,000 10,000 v in = 4.2v v out = 1.2v c byp = 0.1f c out = 2.2f /lowq = v in 0.001 0.01 0.1 1 10 ldo2 output noise spectral density 1 frequency (khz) 0.1 0.01 10 100 1,000 10,000 v in = 4.2v v out = 2.8v c byp = 0.1f c out = 2.2f /lowq = v in
micrel, inc. mic2800 june 2006 11 m9999-061406 (408) 955-1690 functional characteristics dc/dc load transient pwm mode output current (100ma/div) time (20s/div) ac coupled (100mv/div) output volta g e v in = v out + 1v v out = 1.8v c out = 2.2f c byp = 0.01f /lowq = v in 400ma 10ma dc/dc line transient pwm mode input voltage (1v/div) time (20s/div) ac coupled (100mv/div) output volta g e v in = v out + 1v v out = 1.87v c out = 2.2f c byp = 0.01f /lowq = v in i out = 100ma enable transient pwm mode enable volta g e (500mv/div) time (40s/div) output volta g e (500mv/div) v in = 3.6v v out = 1.8v c out = 2.2f c byp = 0.01f /lowq = v in i out = 300ma
micrel, inc. mic2800 june 2006 12 m9999-061406 (408) 955-1690 functional characteristics dc/dc load transient lowq mode output current (20ma/div) time (10s/div) ac coupled (20mv/div) output volta g e v in = v out + 1v v out = 1.8v c out = 2.2f c byp = 0.01f /lowq = gnd 50ma 100a dc/dc line transient lowq mode input voltage (1v/div) time (20s/div) ac coupled (50mv/div) output voltage v in = v out + 1v v out = 1.87v c out = 2.2f c byp = 0.01f /lowq = gnd i out = 10ma enable transient lowq mode time (20s/div) output voltage (500mv/div) v in = en1 = 3.8v v out = 1.8v c out = 2.2f c byp = 0.01f /lowq = gnd i out = 100a enable voltage (2v/div) supply voltage &
micrel, inc. mic2800 june 2006 13 m9999-061406 (408) 955-1690 functional characteristics ldo2 load transient normal mode output current (100ma/div) time (4s/div) ac coupled (100mv/div) output volta g e v in = 3.6v v out = 2.8v c out = 2.2f c byp = 0.01f /lowq = v in 300ma 100a ldo2 load transient lowq mode output current (25ma/div) time (200s/div) ac coupled (50mv/div) output volta g e v in = v out + 1v v out = 2.8v c out = 2.2f c byp = 0.01f /lowq = gnd 50ma 100a ldo2 line transient normal mode input voltage (1v/div) time (20s/div) ac coupled (50mv/div) outpu t volta g e v in = v out + 1v v out = 1.87v c out = 2.2f c byp = 0.01f /lowq = v in i out = 100ma 4v 5.5v ldo2 line transient lowq mode input voltage (1v/div) time (40s/div) ac coupled (50mv/div) output volta g e v in = v out + 1v v out = 1.87v c out = 2.2f c byp = 0.01f /lowq = gnd i out = 10ma 4v 5.5v
micrel, inc. mic2800 june 2006 14 m9999-061406 (408) 955-1690 functional characteristics dc/dc lowq mode to pwm mode transition lowq voltage (1v/div) time (100s/div) v in = v out + 1v v out = 1.8v c out = 2.2f c byp = 0.01f i out = 100a ac coupled (50mv/div) outpu t volta g e dc/dc pwm mode to lowq mode transition lowq voltage (1v/div) time (100s/div) v in = v out + 1v v out = 1.8v c out = 2.2f c byp = 0.01f i out = 50ma ac coupled (50mv/div) output volta g e dc/dc pwm wavefo r m lowq voltage (2v/div) time (400s/div) v in = 4v v out = 1.8v c out = 2.2f ac coupled (10mv/div) output volta g e c byp = 0.01f /lowq = v in l = 2.2h
micrel, inc. mic2800 june 2006 15 m9999-061406 (408) 955-1690 functional characteristics 0.1 1 10 100 0 50 100 150 output current (ma) esr vs. load ldo stable area 0.1 1 10 100 0 50 100 150 output current (ma) esr vs. load ldo1 stable area 0.1 1 10 100 0 50 100 150 output current (ma) esr vs. load ldo2 stable area
micrel, inc. mic2800 june 2006 16 m9999-061406 (408) 955-1690 functional diagram mic2800 fixed block diagram ldo sw cset vin _ ___ _ lowq en1 pgnd fb sgnd en2 dc to dc ldo2 ldo1 por reference and quick start cbyp vout1 vout2 por vin cbias
micrel, inc. mic2800 june 2006 17 m9999-061406 (408) 955-1690 application notes the mic2800 is a digital power management ic with a single integrated buck regulator and two independent low dropout regulators. ldo1 is a 300ma low dropout regulator that is using power supplied by the on board buck regulator. ldo2 is a 300ma low dropout regulator using the supply from the input pin. the buck regulator is a 600ma pwm power supply t hat utilizes a /lowq light load mode to maximize battery efficiency in light load conditions. this is achieved with a /lowq control pin that when pulled low, shuts down all the biasing and drive current for the pwm regulator, drawing only 20a of operating current. this allows the output to be regulated through the ldo output, capable of providing 60ma of output current. this method has the advantage of producing a clean, low current, ultra low noise output in /lowq mode. during /lowq mode, the sw node becomes high impedance, blocking current flow. other methods of reducing quiesc ent current, such as pulse frequency modulation (pfm) or bursting techniques create large amplitude, low frequency ripple voltages that can be detrimental to system operation. when more than 60ma is required, the /lowq pin can be forced high, causing the mic2800 to enter pwm mode. in this case, the ldo output makes a "hand-off" to the pwm regulator with virt ually no variation in output voltage. the ldo output then turns off allowing up to 600ma of current to be efficiently supplied through the pwm output to the load. vin two input voltage pins provide power to the switch mode regular and ldo2 separately. the ldo1 input voltage is provided by the dc/dc ldo pi n. vin provides power to the ldo section and the bias through an internal 6 ? resistor. both vin pins must be tied together. for the switch mode regulator vin provides power to the mosfet along with current limiting sensing. due to the high switching speeds, a 4.7f capacitor is recommended close to vin and the power ground (pgnd) pin for bypassing. please refer to layout recommendations. ldo the ldo pin is the output of the linear regulator and should be connected to the output. in /lowq mode (/lowq <0.2v), the ldo provid es the output voltage. in pwm mode (/lowq >1v) the ldo pin provides power to ldo1. ldo1 regulated output voltage of ldo1. power is provided by the dcdc switching regulator. recommended output capacitance is 2.2f. ldo2 regulated output voltage of ldo2. power is provided by vin. recommended output capacitance is 2.2f. en both enable inputs are active high, requiring 1.0v for guaranteed operation. en1 prov ides logic control of both the dcdc regulator and ldo1. en2 provides logic control for ldo2 only. the enable inputs are cmos logic and cannot be left floating. the enable pins provide logic level control of the specified outputs. when both enable pins are in the off state, supply current of the device is greatly reduced (typically <1a). when the dcdc regulator is in the off state, the output drive is placed in a "tri-stated" condition, where both the high side p-channel mosfet and the low-side n-channel are in an ?off? or non-conducting state. do not drive either of the enable pins above the supply voltage. power-on reset (por) the power-on reset output is an open-drain n-channel device, requiring a pull-up resistor to either the input voltage or output voltage for proper voltage levels. the por output has a delay time that is programmable with a capacitor from the cset pin to ground. the delay time can be programmed to be as long as 1 second. /lowq the /lowq pin provides a logic level control between the internal pwm mode and the low noise linear regulator mode. with /lowq pulled low (<0.2v), quiescent current of the device is greatly reduced by switching to a low noise linear regulator mode that has a typical iq of 20a. in linear (ldo) mode the output can deliver 60ma of current to the output. by placing /lowq high (>1v), the device transitions into a constant frequency pwm buck regulator mode. this allows the device the ability to efficient ly deliver up to 600ma of output current at the same output voltage. /lowq mode also limits t he output load of both ldo1 and ldo2 to 10ma. bias the bias pin supplies the power to the internal control and reference circuitry. the bias is powered from avin through an internal 6 ? resistor. a small 0.1f capacitor is recommended for bypassing.
micrel, inc. mic2800 june 2006 18 m9999-061406 (408) 955-1690 fb connect the feedback pin to vout. 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. 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. refer to the layout considerations for more details. 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. refer to the layout considerations for more details. cset the set pin is a current source output that charges a capacitor that sets the delay time for the power-on reset output from low to high. the delay for por high to low (detecting an undervoltage on any of the outputs) is always minimal. the current source of 1.25a charges a capacitor up from 0v. when the capacitor reaches 1.25v, the output of the por is allowed to go high. the delay time in micro seconds is equal to the cset in picofarads. por delay (s) = cset (pf) cbyp the internal reference voltage can be bypassed with a capacitor to ground to reduce output noise and increase power supply rejection (psr r). a quick-start feature allows for quick turn-on of the output voltage. the recommended nominal bypass c apacitor is 0.1f, but it can be increased, which will also result in an increase to the start-up time. output capacitor ldo1 and ldo2 outputs require a 2.2f ceramic output capacitor for stability. the dc/dc switch mode regulator requires a 2.2f ceramic output capacitor to be stable. all output capacitor values can be increased to improve transient response, but performance has been optimized for a 2.2f ceramic on the ldos and the dc/dc. x7r/x5r dielectric-type ceramic capacitors are recommended because of their 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. input capacitor a minimum 1f ceramic is recommended on the vin pin for bypassing. x5r or x7r dielectrics are recommended for the input capacitor. y5v dielectrics lose most of their capacitance over temperatur e and are therefore, not recommended. a minimum 1f is recommended close to the vin and pgnd pins for high frequency filtering. smaller case size capacitors are recommended due to their lower esr and esl. please refer to layout recommendations for proper layout of the input capacitor. inductor selection the mic2800 is designed for use with a 2.2h inductor. proper selection should ensure the inductor can handle the maximum average and peak currents required by the load. maximum current rati ngs 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 t hat the inductor selected can handle the maximum operating current. when saturation current is specified, make sure that there is enough margin that the peak current will not saturate the inductor. peak inductor current can be calculated as follows: l f 2 v v 1 v i i in out out out pk ? ? ? ? ? ? ? ? ? + =
micrel, inc. mic2800 june 2006 19 m9999-061406 (408) 955-1690 pcb layout top layer
micrel, inc. mic2800 june 2006 20 m9999-061406 (408) 955-1690 bottom layer
micrel, inc. mic2800 june 2006 21 m9999-061406 (408) 955-1690 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. ? 2006 micrel, incorporated.

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