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general description the max1702b power-management ic supports arm powered devices such as the intel pxa210 and pxa250 microprocessors based on the intel xscale micro-architecture. these devices include pdas, third- generation smart cellular phones, internet appliances, automotive in-dash telematics systems, and other appli- cations requiring substantial computing and multimedia capability at low power. the max1702b integrates three ultra-high-performance power supplies with associated supervisory and man- agement functions. included is a step-down dc-dc con- verter to supply 3.3v i/o and peripherals, a step-down dc-dc converter to supply 0.7v to v in for the micro- processor core, and a step-down dc-dc converter to supply either 1.8v, 2.5v, or 3.3v to power the memory. management functions include automatic power-up sequencing, power-on-reset and manual reset with timer, and two levels of low-battery detection. the dc-dc converters use fast 1mhz pwm switching, allowing the use of small external components. they automatically switch from pwm mode under heavy loads to skip mode under light loads to reduce quiescent cur- rent and maximize battery life. the input voltage range is from 2.6v to 5.5v, allowing the use of three nimh cells, a single li+ cell, or a regulated 5v input. the max1702b is available in a tiny 6mm x 6mm, 36-pin qfn package and operates over the -40? to +85? temperature range. applications pda, palmtop, and wireless handhelds third generation smart cell phones internet appliances and web books automotive in-dash telematics systems features three regulators in one package peripherals and i/o supply: 3.3v at 900ma p core supply: 0.7v to v in at 400ma memory supply: 1.8/2.5/3.3v at 800ma supports intel pxa210 and pxa250 microprocessors power-on reset with manual reset input auto power-up sequencing 1mhz pwm switching allows small external components low 5a shutdown current tiny 6mm ? 6mm, 36-pin qfn package max1702b triple-output power-management ic for microprocessor-based systems ________________________________________________________________ maxim integrated products 1 max1702b 6mm x 6mm qfn top view 32 33 34 35 36 28 29 30 31 n.c. inp3 lx3 pg3 n.c. comp3 out3 11 13 15 14 16 12 10 in pg1 lx1 n.c. inp1 comp1 19 20 21 22 23 n.c. 24 25 26 27 n.c. inp2 lx2 pg2 outok comp2 out1 n.c. 2 3 4 5 6 7 8 gnd ref 9 n.c. gnd pgm3 on2 dbi lbi 1 n.c. fb2 18 17 n.c. rso mr lbo pin configuration ordering information 19-2448; rev 0; 4/02 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. typical operating circuit appears at end of data sheet. intel is a registered trademark of intel corporation. xscale is a trademark of intel corporation. arm and arm powered are registered trademarks of arm limited. part temp range pin-package max1702begx -40 c to +85 c 36 6mm x 6mm qfn
max1702b triple-output power-management ic for microprocessor-based systems 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v inp1 = v inp2 = v inp3 = v in = 3.6v, v lbi = 1.1v, v dbi = 1.35v, mr = on2 = in, pgm3 = gnd, circuit of figure 1, t a = -40 c to +85 c unless otherwise noted. typical values are at t a = +25 c.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, fb2, out3, comp1, comp2, comp3, pgm3, on2, lbo , outok, rso , mr , lbi, dbi, out1 to gnd .......................................................-0.3v to +6v ref to gnd ...................................................-0.3 to (v in + 0.3v) inp1, inp2, inp3 to in...........................................-0.3v to +0.3v pg1, pg2, pg3 to gnd.........................................-0.3v to +0.3v lx1, lx2, lx3 continuous current .......................-1.5a to +1.5a inp1 to pg1..............................................................-0.3v to +6v inp2 to pg2..............................................................-0.3v to +6v inp3 to pg3..............................................................-0.3v to +6v output short-circuit duration ............................................infinite continuous power dissipation (t a =+70 c) 36-pin qfn (derate 22.7 mw/ c)..............................1818mw operating temperature range.............................40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10sec) .............................+300 c parameter conditions min typ max units inp1, inp2, inp3, in supply voltage range inp1, inp2, inp3, in must be connected together externally 2.6 5.5 v v in rising 2.25 2.40 2.55 undervoltage lockout threshold v in falling 2.2 2.35 2.525 v on2 = in, no load 485 on2 = gnd, no load 335 quiescent current (i inp1 + i inp2 + i inp3 + i in ) v dbi < 1.2 v (shutdown) lx1-3 = gnd 520 a synchronous buck pwm regulator 1 (reg1) out1 voltage accuracy 3.6v v inp1 5.5v, load = 0 to 900ma 3.234 3.3 3.366 v out1 input resistance 200 400 k ? error-amp transconductance 55 95 135 s dropout voltage load = 800ma (note 1) 250 425 mv i lx1 = 180ma 0.25 0.4 p-channel on-resistance i lx1 = 180ma, v inp1 = 2.6v 0.3 0.5 ? n-channel on-resistance i lx1 = 180ma 0.2 0.35 ? current-sense transresistance 0.40 0.47 0.54 v/a p-channel current-limit threshold 1.15 1.275 1.45 a p-channel pulse-skipping current threshold 0.115 0.140 0.160 a n-channel zero-crossing comparator 25 55 75 ma out1 maximum output current 2.6v v inp1 5.5v (note 2) 0.9 a lx1 leakage current v inp1 = 5.5v, lx1= gnd or inp1, v out1 = 3.6v -20 0.1 +20 a lx1 duty-cycle range v inp2 = 4.2v 0 100 %
max1702b triple-output power-management ic for microprocessor-based systems _______________________________________________________________________________________ 3 electrical characteristics (continued) (v inp1 = v inp2 = v inp3 = v in = 3.6v, v lbi = 1.1v, v dbi = 1.35v, mr = on2 = in, pgm3 = gnd, circuit of figure 1, t a = -40 c to +85 c unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units out1 discharge resistance v out1 = 3.3v, v dbi = 1v 300 (note 3) ? synchronous buck regulator 2 (reg2) fb2 regulation voltage 2.6v v inp2 5.5v, load = 0 to 400ma 0.686 0.7 0.714 v fb input current v fb = 0.7v 1 150 na error-amp transconductance 150 250 350 s dropout voltage load = 400ma (note 1) 150 250 mv i lx2 = 180ma 0.25 0.4 p-channel on-resistance i lx2 = 180ma, v inp2 = 2.6v 0.3 0.5 ? n-channel on-resistance i lx2 = 180ma 0.2 0.35 ? current-sense transresistance 0.40 0.47 0.54 v/a p-channel current-limit threshold 1.15 1.275 1.45 a p-channel pulse-skipping current threshold 0.115 0.140 0.160 ma n-channel zero-crossing comparator 25 55 75 ma out2 maximum output current 2.6v v inp2 _ 5.5v (note 2) 0.4 a lx2 leakage current v inp2 = 5.5v, lx2 = gnd or inp2, v fb2 = 1v -20 0.1 +20 a lx2 duty-cycle range v inp _ = 4.2v 0 100 % lx2 discharge resistance v lx2 = v dbi = 1v 300 ? synchronous buck regulator 3 (reg3) pgm3 = gnd, 3.6v v inp3 _ 5.5v, load = 0 to 800ma 1.764 1.8 1.836 pgm3 = ref, 3.6v v inp3 _ 5.5v, load = 0 to 800ma 2.45 2.5 2.55 out3 voltage accuracy pgm3 = in, 3.6v v inp3 _ 5.5v, load = 0 to 800ma 3.234 3.3 3.366 v pgm3 = gnd 340 650 pgm3 = ref 200 400 out3 input resistance pgm3 = in 160 320 k ? pgm3 = gnd 105 175 245 pgm3 = ref 75 125 175 error-amp transconductance pgm3 = in 55 95 135 s dropout voltage load = 800ma (note 1) 220 400 mv i lx3 = 180ma 0.25 0.4 p-channel on-resistance i lx3 = 180ma, v inp3 = 2.6v 0.3 0.5 ? n-channel on-resistance i lx3 = 180ma 0.2 0.35 ?
max1702b triple-output power-management ic for microprocessor-based systems 4 _______________________________________________________________________________________ electrical characteristics (continued) (v inp1 = v inp2 = v inp3 = v in = 3.6v, v lbi = 1.1v, v dbi = 1.35v, mr = on2 = in, pgm3 = gnd, circuit of figure 1, t a = -40 c to +85 c unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units current-sense transresistance 0.40 0.47 0.54 v/a p-channel current-limit threshold 1.15 1.275 1.45 a p-channel pulse-skipping current threshold 0.115 0.140 0.160 a n-channel zero-crossing comparator 25 55 75 ma out3 maximum output current 2.6v v inp3 _ 5.5v (note 2) 0.8 a lx3 leakage current v inp3 = 5.5v, lx3 = gnd or inp3, v out3 = 3.6v -20 0.1 +20 a lx3 duty-cycle range v inp3 = 4.2v 0 100 % out3 discharge resistance v out3 = 3.3v, v dbi = 1v 300 (note 3) ? reference ref output voltage 1.225 1.25 1.275 v ref load regulation 10a < i ref < 100a 2.5 6.25 mv ref line regulation 2.6v < v batt < 5.5v 0.6 5 mv oscillator switching frequency 0.85 1 1.15 mhz thermal shutdown thermal shutdown temperature t j rising 160 c thermal shutdown hysteresis 15 c supervisory/management functions reset timeout mr rising to rso rising 55 65.5 75 ms v fb2 rising 94 95.5 97.5 outok trip threshold v fb2 falling 91 92.5 94 % outok, lbo minimum assertion time 107 126 145 s v lbi falling 0.98 1.000 1.02 lbi input threshold v lbi rising 1.00 1.020 1.04 v lbi input bias current v lbi = 0.95v 0.02 0.1 a v dbi falling, t a = 0 c to +85 c 1.2103 1.235 1.2597 v dbi rising, t a = 0 c to +85 c 1.2345 1.2597 1.2849 v dbi falling, t a = -40 c to +85 c 1.198 1.235 1.273 dbi input threshold v dbi rising, t a = -40 c to +85 c 1.221 1.260 1.298 v dbi input bias current v dbi = 1.25v 0.01 0.1 a
max1702b triple-output power-management ic for microprocessor-based systems _______________________________________________________________________________________ 5 electrical characteristics (continued) (v inp1 = v inp2 = v inp3 = v in = 3.6v, v lbi = 1.1v, v dbi = 1.35v, mr = on2 = in, pgm3 = gnd, circuit of figure 1, t a = -40 c to +85 c unless otherwise noted. typical values are at t a = +25 c.) parameter conditions min typ max units 2.6v v in _ 5.5v, sinking 1ma rso , lbo , outok output low level v in_ = 1v, sinking 100a 0.4 v rso , lbo , outok output high leakage current v r s o = v l b o = v outok = 5.5v 0.1 a on2, mr , input high level 2.6v v in _ 5.5v 1.6 v on2, mr , input low level 2.6v v in _ 5.5v 0.4 v on2, mr , pgm3, input leakage current v on2 = v mr = v pgm3 = gnd, 5.5v -1 +1 a reg3 target = 1.8v, in = 2.6v to 5.5v 0.4 reg3 target = 2.5v, in = 2.6v to 5.5v 1.1 ref 1.4 pgm3 selection threshold reg3 target = 3.3v, in = 2.6v to 5.5v v in_ - 0.25 v note 1: dropout voltage is not tested. guaranteed by p-channel switch resistance and assumes a 72m ? (reg1 and reg3) or 162m ? (reg2) maximum esr of inductor. note 2: the maximum output current is guaranteed by the following equation: where: and: r n = n-channel synchronous rectifier r dson r p = p-channel power switch r dson r l = external inductor esr i out(max) = maximum required load current ? = operating frequency minimum l = external inductor value note 3: specified resistance is in series with an internal diode to lx2. note 4: specifications to -40 c are guaranteed by design and not production tested. d vi rr vi rr out out max n l in out max n p = ++ ++ () () () () i i vd l rr d l out max lim out nl () () () () = ? ? ++ ? 1 2 1 1 2 ? ?
max1702b triple-output power-management ic for microprocessor-based systems 6 _______________________________________________________________________________________ typical operating characteristics (circuit of figure 1, t a = +25 c, unless otherwise noted.) max1702b toc09 load current (ma) 400 350 300 250 200 150 100 50 3.275 3.285 3.295 3.305 3.315 3.325 3.265 0 450 reg3 output voltage vs. load current (v out3 = 3.3v) output voltage (v) t a = -40 c t a = +85 c t a = 0 c t a = +40 c max1702b toc08 load current (ma) output voltage (v) 250 200 150 100 50 1.095 1.097 1.099 1.101 1.103 1.105 1.107 0 300 reg2 output voltage vs. load current t a = -40 c t a = +85 c t a = 0 c t a = +40 c reg1 output voltage vs. load current max1702b toc07 load current (ma) output voltage (v) 600 500 400 300 200 100 3.23 3.25 3.27 3.29 3.31 3.33 3.21 0 700 t a = +85 c t a = -40 c t a = 0 c t a = +40 c max1702b toc06 load current (ma) dropout voltage (mv) 400 350 50 100 150 250 200 300 20 40 60 80 100 120 140 160 0 0 450 reg3 dropout voltage vs. load current (v in = 3.3v) v out3 = 3.3v max1702b toc05 load current (ma) dropout voltage (mv) 900 800 700 600 500 400 300 200 100 50 100 150 200 250 300 350 0 0 1000 reg1 dropout voltage vs. load current (v in = 3.3v) max1702b toc04 supply voltage (v) quiescent current (ma) 5.5 5.0 4.5 4.0 3.5 3.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 2.5 6.0 no load quiesecnt current vs. supply voltage max1702b toc03 load current (ma) efficiency (%) 100 10 10 20 30 40 50 60 70 80 90 100 0 1 1000 reg2 incremental efficiency vs. load current v out2 = 1v v out2 = 1.3v note: incremental efficiency is reg2 output power over additional input power. reg1 and reg3 quiescent current is reflected in reg1 s efficiency graph. v out2 = 1.1v max1702b toc02 load current (ma) efficiency (%) 100 10 10 20 30 40 50 60 70 80 90 100 0 1 1000 reg3 incremental efficiency vs. load current v out3 = 2.5v v out3 = 3.3v v out3 = 1.8v note: incremental efficiency is reg3 output power over additional input power. reg1 and reg3 quiescent current is reflected in reg1 s efficiency graph. max1702b toc01 load current (ma) efficiency (%) 100 10 10 20 30 40 50 60 70 80 90 100 0 1 1000 reg1 efficiency vs. load current
max1702b triple-output power-management ic for microprocessor-based systems _______________________________________________________________________________________ 7 typical operating characteristics (continued) (circuit of figure 1, t a = +25 c, unless otherwise noted.) reg2 heavy-load switching waveform load = 400ma, v in = 4v 400ns/div v out2 ac-coupled 20mv/div i l2 500ma/div max1702b toc15 v lx2 2v/div 0 0 0 reg1 heavy-load switching waveform load = 800ma, v in = 4v 400ns/div v out1 ac-coupled 20mv/div i l1 500ma/div max1702b toc14 v lx1 2v/div 0 0 0 i/o core max1702b toc13 temperature ( c) reference voltage (v) 60 35 10 -15 1.21 1.22 1.23 1.24 1.25 1.26 1.27 1.28 1.29 1.30 1.20 -40 85 internal reference vs. temperature max1702b toc12 supply voltage (v) frequency (khz) 5.0 4.5 4.0 3.5 3.0 920 940 960 980 1000 1020 1040 900 2.5 5.5 internal oscillator frequency vs. supply voltage t a = -40 c t a = +25 c t a = +85 c max1702b toc11 load current (ma) 400 350 300 250 200 150 100 50 1.787 1.792 1.797 1.802 1.807 1.812 1.782 0 450 reg3 output voltage vs. load current (v out3 = 1.8v) output voltage (v) t a = +85 c t a = +40 c t a = -40 c t a = 0 c max1702b toc10 load current (ma) 400 350 50 100 150 250 200 300 2.480 2.485 2.490 2.495 2.500 2.505 2.510 2.515 2.475 0 450 reg3 output voltage vs. load current (v out3 = 2.5v) output voltage (v) t a = +85 c t a = +40 c t a = -40 c t a = 0 c
max1702b triple-output power-management ic for microprocessor-based systems 8 _______________________________________________________________________________________ typical operating characteristics (continued) reg3 medium-load switching waveform load = 100ma, v in = 4v 2 s/div v out3 ac-coupled 20mv/div i l3 500ma/div max1702b toc18 v lx3 2v/div 0 0 0 reg1 medium-load switching waveform load = 100ma, v in = 4v 400ns/div v out1 ac-coupled 20mv/div i l1 500ma/div max1702b toc17 v lx1 2v/div 0 0 0 reg3 heavy-load switching waveform load = 700ma, v in = 4v 400ns/div v out3 ac-coupled 20mv/div i l3 500ma/div max1702b toc16 v lx3 2v/div 0 0 0 reg1 light-load switching waveform load = 10ma, v in = 4v 10 s/div v out1 ac-coupled 20mv/div i l1 500ma/div max1702b toc19 v lx1 2v/div 0 0 0 reg2 light-load switching waveform load = 10ma, v in = 4v 10 s/div v out2 ac-coupled 20mv/div i l2 500ma/div max1702b toc20 v lx2 2v/div 0 0 0 reg3 light-load switching waveform load = 10ma, v in = 4v 10 s/div v out3 ac-coupled 20mv/div i l3 500ma/div max1702b toc21 v lx3 2v/div 0 0 0
max1702b triple-output power-management ic for microprocessor-based systems _______________________________________________________________________________________ 9 typical operating characteristics (continued) (circuit of figure 1, t a = +25 c, unless otherwise noted.) reg1 load transient waveform load = 100ma to 500ma, v in = 4v 40 s/div i lx1 500ma/div i load1 500ma/div max1702b toc25 v out1 ac-coupled 200mv/div 0 0 turn-on delay i load1 = 250ma, i load2 = 100ma, i load3 = 200ma 40 s/div i in 200ma/div max1702b toc24 v out2 1v/div v on2 2v/div 0 0 0 turn-off sequence i load1 = 250ma, i load2 = 100ma, i load3 = 200ma 200 s/div i in 500ma/div max1702b toc23 v out1 5v/div v out3 5v/div v out2 2v/div v in 5v/div 0 0 0 0 0 0 v rso 5v/div turn-on sequence from power application i load1 = 250ma, i load2 = 100ma, i load3 = 200ma 20ms/div i in 500ma/div max1702b toc22 v out1 5v/div v out3 5v/div v out2 2v/div v in 5v/div 0 0 0 0 0 0 v rso 5v/div
max1702b triple-output power-management ic for microprocessor-based systems 10 ______________________________________________________________________________________ typical operating characteristics (continued) (circuit of figure 1, t a = +25 c, unless otherwise noted.) reg3 load transient waveform load = 75ma to 400ma, v in = 4v 40 s/div i lx3 200ma/div i load3 200ma/div max1702b toc27 v out3 ac-coupled 200mv/div 0 0 0 reg2 load transient waveform load = 20ma to 200ma, v in = 4v 40 s/div i lx2 200ma/div i load2 100ma/div max1702b toc26 v out2 ac-coupled 100mv/div 0 0 0 entering and exiting dropout waveform v in = 2.75v to 4v, i load1 = 250ma, i load2 = 100ma, i load3 = 200ma 20ms/div max1702b toc29 v out1 ac-coupled 500mv/div v out3 ac-coupled 500mv/div 0 0 0 v in ac-coupled 500mv/div line transient response waveform v in = 4v to 5v, i load1 = 250ma, i load2 = 100ma, i load3 = 200ma 400 s/div max1702b toc28 v out1 ac-coupled 50mv/div v out2 ac-coupled 50mv/div 0 0 0 0 v in 2v/div v out3 ac-coupled 20mv/div
max1702b triple-output power-management ic for microprocessor-based systems ______________________________________________________________________________________ 11 pin description pin name function 1, 9, 13, 18, 19, 26, 27, 31, 35 n.c. no connection. these pins are not internally connected. 2 lbi low-battery input. connect a resistive voltage-divider from the battery voltage to lbi to set the low- battery threshold. lbi threshold voltage is 1.235v. 3 dbi dead-battery input. connect a resistive voltage-divider from the battery voltage to dbi to set the dead-battery voltage threshold. when the voltage at dbi is below the 1.25v threshold, the max1702b is turned off and draws only 5a from the battery. 4 on2 reg2 on/off input. drive on2 high to turn on reg2, drive it low to turn it off. when enabled, the max1702b soft-starts reg2, when disabled, the output of reg2 is internally discharged to pg2. 5 pgm3 reg3 regulation voltage-control input. connect pgm3 to in, ref, or gnd to set the reg3 output regulation voltage. connect pgm3 to gnd for 1.8v, ref for 2.5v, and in for 3.3v. 6 gnd connect pin 6 to pin 8 7 ref reference output. output of the 1.25v reference. bypass ref to gnd with a 0.1f or greater capacitor. 8 gnd analog ground. connect gnd to a local analog ground plane with no high-current paths. gnd should be connected to the main ground plane at a single point as close to the ic and the in bypass capacitor as possible. connect the ground of the low-noise components, such as resistive voltage- dividers and reference bypass capacitor to the analog ground plane. 10 in analog supply input. bypass in to gnd with a 1f or greater low-esr capacitor. 11 rso reset output. rso is low (sinks current to gnd) during initial startup or while the manual reset input, mr , is asserted. rso remains low for 65.5ms after all regulators are in regulation or after mr is deasserted. rso is an open-drain output. rso remains high when reg2 is turned off. the rso line maintains a valid low output for in as low as 1v. 12 pg1 reg1 power ground. connect pg1 directly to a power ground plane. connect pg1, pg2, pg3 and gnd together at a single point as close to the ic as possible. 14 lx1 reg1 power-switching node. connect the external inductor of the reg1 output lc filter from lx1 to out1 (see the inductor selection section). 15 inp1 reg1 power input. bypass inp1 to pg1 with a 1.0f or greater low-esr capacitor. inp1, inp2, inp3, and in must be connected together externally. a single 4.7f capacitor can be used for inp1, inp2, and inp3. 16 mr manual reset input. a momentary low on mr forces rso to go low. rso remains low as long as mr is low, and returns high 65.5ms after mr returns high and all output voltages are in regulation. 17 comp1 reg1 compensation node. connect a series resistor and capacitor from comp1 to gnd in parallel with a 33pf capacitor to compensate reg1 (see the compensation and stability section).
max1702b triple-output power-management ic for microprocessor-based systems 12 ______________________________________________________________________________________ pin description (continued) pin name function 20 out1 reg1 output-voltage sense input. bypass out1 to pg1 with a 10f or greater low-esr capacitor (see the output capacitor selection section). 21 comp2 reg2 compensation node. connect a series resistor and capacitor from comp2 to gnd in parallel with a 33pf capacitor to compensate reg2 (see the compensation and stability section). 22 outok output-ok output. outok sinks current to gnd when the voltage at reg2 is below the regulation threshold. when the output is in regulation, outok is high impedance. outok is used by the processor to indicate when it is safe for the processor to exit sleep mode. outok is an open-drain output. outok maintains a valid low output for in as low as 1v. 23 pg2 reg2 power ground. connect pg2 directly to a power ground plane. connect pg1, pg2, pg3, and gnd together at a single point as close to the ic as possible. 24 lx2 reg2 power-switching node. connect the external inductor of the reg2 output lc filter from lx2 to out2. lx2 discharges out2 when reg2 is disabled (see the inductor selection section). 25 inp2 reg2 power input. bypass inp2 to pg2 with a 1.0f or greater low-esr capacitor. inp1, inp2, inp3, and in must be connected together externally. a single 4.7f capacitor can be used for inp1, inp2, and inp3. 28 fb2 reg2 feedback-sense input. set the reg2 output voltage with a resistive voltage-divider from the reg2 output voltage to fb2. the fb2 regulation threshold is 0.7v. connect fb2 directly to out2 for an output voltage of 0.7v. 29 out3 reg3 output-voltage sense input. bypass out3 to gnd with a 10f or greater low-esr capacitor (see the output capacitor selection section). 30 comp3 reg3 compensation node. connect a series resistor and capacitor from comp3 to gnd in parallel with a 33pf capacitor to compensate reg3 (see the compensation and stability section). 32 pg3 reg3 power ground. connect pg3 directly to a power ground plane. connect pg1, pg2, pg3, and gnd together at a single point as close to the ic as possible. 33 lx3 reg3 power-switching node. connect the external inductor of the reg3 output lc filter from lx3 to out3 (see the inductor selection section). 34 inp3 reg3 power input. bypass inp3 to pg3 with a 1.0f or greater low-esr capacitor. inp1, inp2, inp3, and in must be connected together externally. a single 4.7f capacitor can be used for inp1, inp2, and inp3. 36 lbo low-battery output. lbo sinks current to gnd when the voltage at lbi is below the lbi threshold voltage; lbo is high impedance when lbi is above the threshold. lbo is an open-drain output. lbo maintains a valid low output level for in as low as 1v.
max1702b triple-output power-management ic for microprocessor-based systems ______________________________________________________________________________________ 13 functional diagram detailed description the max1702b triple-output step-down dc-dc convert- er is ideal for powering pda, palmtop, and subnotebook computers. normally, these devices require separate power supplies for the processor core, memory, and the peripheral circuitry. the max1702b s reg1 provides a fixed 3.3v output designed to power the microprocessor i/o and other peripheral circuitry. reg1 delivers up to 900ma output current. the microprocessor core is pow- ered from reg2, which has an adjustable 0.7v to v in output, providing up to 400ma output current. the third output, reg3, is designed to power memory. reg3 out- put voltage is set to one of 3 voltages; 3.3v (pgm3 = in), 2.5v (pgm3 = ref), or 1.8v (pgm3 = gnd) and delivers up to 800ma of output current. all three regula- tors utilize a proprietary regulation scheme allowing pwm operation at medium to heavy loads, and automat- ically switch to pulse skipping at light loads for improved efficiency. under low-battery conditions, the max1702b issues a warning ( lbo output). the max1702b employs pwm control at medium and heavy loads, and skip mode at light loads (below approximately 80ma) to improve efficiency and reduce quiescent current to 485a. during skip operation, the max1702b switches only as needed to service the load, reducing the switching frequency and associated losses in the internal switch, the synchronous rectifier, and the external inductor. there are three steady-state operating conditions for the max1702b. the device performs in continuous conduc- tion for heavy loads. the inductor current becomes dis- continuous at light loads, requiring the synchronous rectifier to be turned off before the end of a cycle as the inductor current reaches zero. the device enters into skip mode when the converter output voltage exceeds its regulation limit before the inductor current reaches the pulse-skip threshold. during skip mode, a switching cycle initiates when the output voltage drops below the regulation voltage. the p-channel mosfet switch turns on and conducts cur- rent to the output-filter capacitor and load until the inductor current reaches the pulse-skip current thresh- old. then the main switch turns off, and the current flows through the synchronous rectifier to the output-filter capacitor and the load. the synchronous rectifier is turned off when the inductor current approaches zero. the max1702b waits until the output voltage drops below the regulation voltage again to initiate the next cycle. 100% duty-cycle operation if the inductor current does not rise sufficiently to sup- ply the load during the on-time, the switch remains on, allowing operation up to 100% duty cycle. this allows the output voltage to maintain regulation while the input voltage approaches the regulation voltage. dropout voltage is the output current multiplied by the on-resis- tance of the internal switch and inductor, approximately 220mv for an 800ma load for reg1 and reg3 and 150mv for a 400ma load on reg2. near dropout, the on-time may exceed one pwm clock cycle; therefore, small amplitude subharmonic ripple can occur in the output voltage. during dropout, the bandgap reference dead- battery detector reset timer low- battery detector on/off control logic dc-dc buck with skip 1mhz pwm reg1 en ref dc-dc buck with skip 1mhz pwm reg2 pok en ref dc-dc buck with skip 1mhz pwm reg3 en ref dbo dbi lbi lbo outok on2 in inp1 lx1 pg1 out1 comp1 inp2 lx2 pg2 fb2 comp2 inp3 lx3 pg3 out3 comp3 pgm3 rso mr gnd ref max1702b
max1702b triple-output power-management ic for microprocessor-based systems 14 ______________________________________________________________________________________ high-side p-channel mosfet turns on, and the con- troller enters a low-current consumption mode. the device remains in this mode until the max1702b is no longer in dropout. synchronous rectification an n-channel synchronous rectifier eliminates the need for an external schottky diode and improves efficiency. the synchronous rectifier turns on during the second half of each cycle (off-time). during this time, the volt- age across the inductor is reversed, and the inductor current falls. the synchronous rectifier is turned off at the end of the cycle (at which time another on-time begins) or when the inductor current approaches zero. battery monitoring and undervoltage lockout the max1702b does not operate with input voltages below the undervoltage lockout (uvlo) threshold of 2.35v (typ). the inputs remain high impedance until the supply voltage exceeds the uvlo threshold, reducing battery load under this condition. the max1702b provides a low-battery comparator that compares the voltage on lbi to the reference voltage. an open-drain output ( lbo ) goes low when the lbi volt- age is below 1v. use a resistive voltage-divider network as shown in figure 1 to set the trip voltage to the desired level. lbo is high impedance in shutdown mode. the max1702b also provides a dead-battery compara- tor that turns off the ic when the battery has excessive- ly discharged. when the voltage at dbi is below the 1.235v threshold, the max1702b is turned off and draws only 5a from the battery. use a resistive volt- age-divider network as shown in figure 1 to set the trip voltage to the desired level. power-on sequencing the max1702b starts when the input voltage rises above the uvlo threshold and the voltage at dbi is greater than the dbi threshold. when power is initially applied, reg1 starts in soft-start mode. once out1 reaches its regulation voltage, reg3 ramps to its target in soft-start mode. finally, once out3 reaches its regu- lation voltage, reg2 ramps to its target in soft-start mode. the rso output holds low during this time and remains low until 65.5ms after reg2 reaches its target output voltage. once all the regulators are running, on2 turns reg2 on and off. during startup (before the end of the reset peri- od) reg2 is enabled and can only be turned off once the rso output goes high. when turned off, the reg2 output voltage is discharged to pg2 through lx2. reg1 and reg3 step-down converters reg1 and reg3 are 1mhz pwm, current-mode step- down converters and generate 3.3v at up to 900ma (reg1), and 3.3v, 2.5v, or 1.8v at up to 800ma (reg3). internal switches and synchronous rectifiers are integrated for small size and improved efficiency. both regulators remain on while the input voltage is above the uvlo threshold and dbi is above the dbi threshold. reg1 and reg3 cannot be independently turned on or off. to turn both regulators off, pull dbi below the dbi threshold (1.235v typ). the reg3 output voltage is set through the pgm3 pin. connect pgm3 to in to set the output voltage to 3.3v, connect it to ref to set it to 2.5v, and connect it to gnd to set the voltage to 1.8v. reg2 step-down converter reg2 is a 1mhz, current-mode step-down converter and generates a 0.7v to v in output delivering up to 400ma. an internal switch and synchronous rectifier are used for small size and improved efficiency. reg2 is turned on and off through the on2 input. drive on2 low to turn off the regulator, and high to turn it on. outok goes low when the reg2 output voltage drops below 92.5% of the regulation voltage. outok is an open-drain output. outok can be used to signal the processor that the reg2 voltage is in, allowing the processor to exit from sleep mode into run mode. reset output max1702b features an active-low, open-drain reset out- put ( rso ), rso holds low during startup or when the manual reset input mr is held low. rso goes high impedance 65.5ms after reg2 reaches its target value and the mr input goes high. (see the power-on sequencing section). note that rso remains high when reg2 is turned off. applications information setting the output voltages the reg1 output voltage is fixed at 3.3v and cannot be changed. the reg3 output voltage can be set by the pgm3 input to either 3.3v (connect pgm3 to in), 2.5v (connect pgm3 to ref), or 1.8v (connect pgm3 to gnd). the reg2 output voltage is set between 0.70v and v in through a resistive voltage-divider from the reg2 output voltage to fb2 (figure 1). select feedback resistor r5 to be less than 14k ? . r4 is then given by: where v fb2 = 0.70v and v out is the reg2 output voltage. rr v v out fb 45 1 2 =? ? ? ? ? ? ?
max1702b triple-output power-management ic for microprocessor-based systems ______________________________________________________________________________________ 15 compensation and stability compensate each regulator by placing a resistor and a capacitor in series, from comp_ to gnd and connect a 33pf capacitor from comp_ to gnd for improved noise immunity (figure 1). the capacitor integrates the current from the transconductance amplifier, averaging output-voltage ripple. this sets the device speed for transient responses and allows the use of small ceram- ic output capacitors. the resistor sets the proportional gain of the output error voltage by a factor g m ? r c . increasing this resistor also increases the sensitivity of the control loop to the output-voltage ripple. this resistor and capacitor set a compensation zero that defines the system s transient response. the load pole is a dynamic pole, shifting frequency with changes in load. as the load decreases, the pole frequency shifts lower. system stability requires that the compen- sation zero must be placed properly to ensure ade- quate phase margin (at least 30 ). the following is a design procedure for the compensation network: 1) select an appropriate converter bandwidth (f c ) to stabilize the system while maximizing transient response. this bandwidth should not exceed 1/5 of the switching frequency. use 100khz as a reason- able starting point. 2) calculate the compensation capacitor, comp_, based on this bandwidth. calculate comp1 and comp3 with the following equation: where rcs is the regulator s current-sense transre- sistance and gm is the regulators error amplifier transconductance. calculate comp2 with the fol- lowing equation: where r cs is reg2 s current-sense transresistance and g m is reg2 s error-amplifier transconductance. calculate the equivalent load impedance, r l , by: where v out(min) equals the minimum output voltage. i out(max) equals the maximum load current. choose the output capacitor, c out (see the output capacitor selection section). calculate the compensation resis- tance (r c ) value to cancel out the dominant pole creat- ed by the output load and the output capacitance: solving for r c gives: to find c comphf_ , calculate the high-frequency com- pensation pole to cancel the zero created by the output capacitor s equivalent series resistance (esr): solving for c comphf_ gives: if low-esr ceramic capacitors are used, the c comphf_ equation can yield a very small capacitance value. in such cases, do not use less than 33pf to maintain noise immunity. inductor selection a 4.7h inductor with a saturation current of at least 1.5a is recommended for most applications. for best efficiency, use an inductor with low esr. see table 1 for recommended inductors and manufacturers. for most designs, a reasonable inductor value (l ideal ) can be derived from the following equation: where lir is the inductor current ripple as a percent- age of the load current. lir should be kept between 20% and 40% of the maxi- mum load current for best performance and stability. the maximum inductor current is: i lir i lmax out max =+ ? ? ? ? ? ? 1 2 () l vvv v lir i f ideal out in out in out max osc = ? () () c rc r but not less than pf comphf esr out c _ , = 33 1 2 1 2 = rc rc esr out c comphf_ r rc c c l out comp = _ 1 2 1 2 = r c rc c l out comp_ r v i l out min out max = () () c v irf g r rr comp out max out max cs m 2 11 2 5 45 = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + ? ? ? ? ? ? () () c v irf g comp out max out max cs m 13 11 2 / () () = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
max1702b triple-output power-management ic for microprocessor-based systems 16 ______________________________________________________________________________________ the inductor current becomes discontinuous if i out decreases to lir/2 from the output current value used to determine l ideal . input capacitor selection the input capacitor reduces the current peaks drawn from the battery or input power source and reduces switching noise in the ic. the impedance of the input capacitor at the switching frequency should be less than that of the input source so high-frequency switch- ing currents do not pass through the input source but instead are shunted through the input capacitor. the input capacitor must meet the ripple-current require- ment (i rms ) imposed by the switching currents. the input capacitor rms current is: output capacitor selection the output capacitor is required to keep the output-volt- age ripple small and to ensure regulation control-loop stability. the output capacitor must have low impedance at the switching frequency. ceramic capacitors are rec- ommended. the output ripple is approximately: see the compensation and stability section for a dis- cussion of the influence of output capacitance and esr on regulation control-loop stability. the capacitor voltage rating must exceed the maximum applied capacitor voltage. consult the manufacturer s specifications for proper capacitor derating. avoid y5v and z5u dielectric types due to their huge voltage and temperature coefficients of capacitance and esr. x7r and x5r dielectric types are recommended. setting the battery detectors the low-battery and dead-battery detector trip points can be set by adjusting the resistor values of the divider string (r1, r2, and r3) in figure 1 according to the following: 1) choose r3 to be less than 250k ? 2) r1 = r3 ? v bl ? (1 - v th /v bd ) 3) r2 = r3 ? (v th ? v bl /v bd - 1) where v bl is the low-battery voltage, v bd is the dead- battery voltage, and v th = 1.235v. pc board layout and routing high switching frequencies and large peak currents make pc board layout a very important part of design. good design minimizes excessive emi on the feedback paths and voltage gradients in the ground plane, both of which can result in instability or regulation errors. connect the inductor, input filter capacitor, and output filter capacitor as close together as possible, and keep their traces short, direct, and wide. connect their ground pins to a single common power ground plane. the external voltage-feedback network should be very close to the fb pin, within 0.2in (5mm). keep noisy traces (from the lx pin, for example) away from the voltage-feedback network; also, keep them separate, using grounded copper. connect gnd and pg_ pins together at a single point, as close as possible to the max1702b. refer to the max1702b evaluation kit for a pc board layout example. chip information transistor count: 10,890 process: bicmos v lir i esr fc ripple out max osc out ? + ? ? ? ? ? ? () 1 2 ii rms load vvv v out in out in = ? ? ? ? ? ? ? ? ? () table 1. suggested inductors manufacturer part number inductance (h) esr (mw) saturation current (a) dimensions (mm) coilcraft do1606 4.7 120 1.2 5.3 x 5.3 x 2 coilcraft lpt1606-472 4.7 240 (max) 1.2 6.5 x 5.3 x 2.0 sumida cdrh4d28-4r7 4.7 56 1.32 4.6 x 5 x 3 sumida cdrh5d18-4r1 4.1 57 1.95 5.5 x 5.5 x 2 sumida cr43 4.7 108.7 1.15 4.5 x 4 x 3.5
max1702b triple-output power-management ic for microprocessor-based systems ______________________________________________________________________________________ 17 typical operating circuit max1702b v out1 3.3v at 900ma 4.7 h c out1 10 f c comp1 1000pf r comp1 33k ? c comphf1 33pf lx1 pg1 out1 comp1 v out2 1.1v at 400ma 4.7 h c out2 10 f c comp2 680pf r comp2 18k ? 8.06k ? 14k ? c comphf2 33pf lx2 pg2 fb2 comp2 v out3 3.3v/2.5v/1.8v at 800ma 4.7 h c out3 10 f c comp3 1000pf r comp3 22k ? c comphf3 33pf lx3 pg3 out3 comp3 gnd ref pgm3 r1 162k ? r2 53.6k ? r3 86.6k ? dbi lbi inp2 in inp1 inp3 4.7 f 4.7 f input 2.6v to 5.5v 100k ? 100k ? out1 lbo outok 100k ? rso out1 on2 mr figure 1. typical operating circuit
max1702b triple-output power-management ic for microprocessor-based systems 18 ______________________________________________________________________________________ package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) 36l,40l, qfn.eps
max1702b triple-output power-management ic for microprocessor-based systems maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 19 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs max1702b part number table notes: see the max1702b quickview data sheet for further information on this product family or download the max1702b full data sheet (pdf, 828kb). 1. other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 2. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 3. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 4. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 5. part number free sample buy direct package: type pins size drawing code/var * temp rohs/lead-free? materials analysis max1702begx qfn;36 pin;6x6x0.9mm dwg: 21-0105f (pdf) use pkgcode/variation: g3666-1 * -40c to +85c rohs/lead-free: no materials analysis max1702begx-t qfn;36 pin;6x6x0.9mm dwg: 21-0105f (pdf) use pkgcode/variation: g3666-1 * -40c to +85c rohs/lead-free: no materials analysis MAX1702BETX thin qfn;36 pin;6x6x0.8mm dwg: 21-0141h (pdf) use pkgcode/variation: t3666-3 * -40c to +85c rohs/lead-free: no materials analysis MAX1702BETX-t thin qfn;36 pin;6x6x0.8mm dwg: 21-0141h (pdf) use pkgcode/variation: t3666-3 * -40c to +85c rohs/lead-free: no materials analysis MAX1702BETX+ thin qfn;36 pin;6x6x0.8mm dwg: 21-0141h (pdf) use pkgcode/variation: t3666+3 * -40c to +85c rohs/lead-free: yes materials analysis MAX1702BETX+t thin qfn;36 pin;6x6x0.8mm dwg: 21-0141h (pdf) use pkgcode/variation: t3666+3 * -40c to +85c rohs/lead-free: yes materials analysis didn't find what you need?
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