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________________________________________________________________ _ maxim integrated products _ _ 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. automotive power-management ic with three step-down converters and linear regulator MAX16920 19-5718; rev 1; 8/11 general description the MAX16920 power-management ic integrates three high-voltage step-down dc-dc converters, one high-voltage linear regulator, and an overvoltage protection block. the three step-down converters deliver up to 150ma, 600ma, and 1.5a, while the linear regulator is capable of up to 150ma. the MAX16920 is designed to operate with input voltages between 5.5v to 28v and survive voltage transients to 45v, making it ideal for automotive applications. the MAX16920 is optimized for high efficiency and low standby current. the MAX16920a features 400khz switching frequency, while the MAX16920b features 2mhz switching frequency. the MAX16920 can be ordered with spread-spectrum frequency modulation. the dc-dc converters can also be synchronized to an external frequency reference using the sync input minimize emi. the MAX16920 includes power-good outputs (pg_) for dc-dc2, dc-dc3, ldoa, and a power-on reset ( por) for dc-dc1. all regulators other than dc-dc1 have an enable input (en_). dc-dc1 always operates when power is applied to the MAX16920. the MAX16920 operates over the -40c to +125c temperature range, and is available in a compact, thermally enhanced 32-pin tqfn package (7mm x 7mm). applications automotive radios automotive navigation systems features s _ 5.5v _ to _ 28v _ wide _ operating _ voltage _ range s _ tolerates _ input _ voltage _ transients _ up _ to _ 45v s _ three _ high-voltage _ buck _ converters _ with _ high _ efficiency s _ dc-dc1: _ 150ma _ (max), _ always-on, _ ultra-low _ quiescent _ current _ (25a) _ _ 3.3v _ fixed _ or _ adjustable _ from _ 1.22v _ to _ 5v s _ dc-dc2: _ 600ma _ (max), _ 5.0v _ fixed _ or _ adjustable _ output _ voltage _ from _ 1.22v _ to _ 5v _ s _ dc-dc3: _ 1.5a _ (max), _ 3.3v _ fixed _ or _ adjustable _ from _ 1.22v _ to _ 8.0v s _ one _ high-voltage _ 5v _ linear _ regulator _ (150ma) s _ pmos _ driver _ output _ with _ fixed _ overvoltage _ shutdown s _ 400khz _ (MAX16920a) _ or _ 2mhz _ (MAX16920b) _ switching _ frequency s _ frequency _ synchronization _ input _ s _ open-drain _ power-good _ outputs _ for _ dc-dc2, _ dc-dc3, _ ldoa, _ and _ power-on _ reset _ for _ dc-dc1 s _ enable _ inputs _ for _ dc-dc2, _ dc-dc3, _ and _ ldo s _ internal _ soft-start s _ 2% _ undervoltage _ comparator s _ overtemperature _ shutdown s _ -40c _ to _ +125c _ operating _ temperature _ range s _ compact _ 32-pin _ tqfn _ package _ (7mm _ x _ 7mm) ordering information /v denotes an automotive qualified part. + denotes a lead(pb)-free/rohs-compliant package. * future productcontact factory for availability. ** ep = exposed pad. ? contact the factory for other por options. evaluation _ kit available part temp _ range switching _ frequency por _ delay ? (ms) pin-package MAX16920aatj/v+* -40n c to +125nc 400khz 5.1 32 tqfn-ep** MAX16920aatjs/v+* -40n c to +125nc 400khz 5.1 32 tqfn-ep** MAX16920batj/v+ -40n c to +125nc 2.2mhz 7.5 32 tqfn-ep** MAX16920batjs/v+* -40n c to +125nc 2mhz 8 32 tqfn-ep**
automotive power-management ic with three step-down converters and linear regulator MAX16920 2 stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. out1, out2, fb1, fb2, fb3, por , pg2, pg3, pga, ot to gnd ......................................... -0.3v to +6v uvo , en2, en3, ena, outa, sync, v l to gnd ... -0.3v to +6v uvi, uvs to gnd .................................................. -0.3v to +20v uvi, uvs input current ................................................... 10ma out3 to gnd ........................................................ -0.3v to +10v v ina , v inb , odrv, lx1, lx2, lx3 to gnd (500ms)..-0.3v to +45v v ina to v inb ............................................................. -2v to +18v bst1, bst2, bst3 to pgnd_ (500ms) ................. -0.3v to +50v continuous power dissipation (t a = +70c) tqfn (derate 37mw/c above +70c) ..................... 2963mw operating temperature range ........................ -40c to +125c junction temperature ..................................................... +150c storage temperature range ............................ -65c to +150c lead temperature (soldering, 10s) ................................ +300c soldering temperature (reflow) ...................................... +260c electrical _ characteristics (v ina = v inb = 14v, t a = -40 c to +125 c , unless otherwise noted. typical values are at t a = +25c.) (note 2) absolute _ maximum _ ratings note _ 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations , refer to www.maxim-ic.com/thermal-tutorial. package _ thermal _ characteristics _ ( note _ 1) tqfn junction-to-ambient thermal resistance ( q ja ) .......... 27c/w junction-to-case thermal resistance ( q jc ) ................. 1c/w parameter symbol conditions min typ max units v ina /v inb operating supply range v in full performance 5.5 18 v dc-dc1 maintains regulation, i out1 = 100ma (note 2) 4 28 v ina /v inb supply current in operation i in en2 = en3 = ena = high, no switching 2 3 ma v ina /v inb supply current, standby mode i st only dc-dc1 operating, en2 = en3 = ena = low, i out1 = no load 25 50 fa v l undervoltage lockout v uvl v l rising 2.9 3.15 3.4 v v l undervoltage lockout hysteresis v uvh 0.4 v v l output voltage v l 5 v uvi threshold uvl v ina /v inb falling 1.181 (-2%) 1.205 1.229 (+2%) v uvi input current i uvi v uvi = 1.2v 1 fa uvi hysteresis uvh 10 20 30 mv uvs switch resistance r uvs 1100 1540 2100 i thermal shutdown temperature t s temperature rising, ot output asserted (note 3) 155 170 nc thermal shutdown hysteresis t h (note 3) 10 20 nc overvoltage _ gate _ driver overvoltage shutdown level v ov input voltage rising, odrv output turns off external pmosfet 18.7 19.2 19.7 v overvoltage shutdown level v ov,f input voltage falling 18.1 v
automotive power-management ic with three step-down converters and linear regulator MAX16920 3 electrical _ characteristics _ (continued) (v ina = v inb = 14v, t a = -40 c to +125 c , unless otherwise noted. typical values are at t a = +25c.) (note 2) parameter symbol conditions min typ max units odrv positive output drive resistance r drv+ turning off 2000 i odrv negative output drive resistance r drv- turning on 2000 i dc-dc _ converters free-running switching frequency range f switchi sync = gnd, MAX16920a 360 400 440 khz sync = gnd, MAX16920b 1980 2200 2420 sync input frequency range f sync MAX16920a: switching frequency is half of f sync (note 3) 600 1000 khz MAX16920b: switching frequency is equal to f sync (notes 3, 4) 1800 2400 fb_ voltage v fb_ output in regulation, 5.5v < v in _ < 18v 1.196 (-2%) 1.22 1.244 (+2%) v power-good threshold pgt output rising for out2 and out3 88.5 91.5 94.5 % of v out (nom) power-good threshold hysteresis pgth 3 % por threshold por out1 rising 88.5 91.5 94.5 % of v out (nom) por threshold hysteresis porh 3 % por output delay t por MAX16920a 4.6 5.1 5.6 ms MAX16920b spread-spectrum disabled 6.75 7.5 8.25 spread-spectrum enabled 7 8 9 dc-dc1 high-side switch r dson r 1h 3 i dc-dc1 low-side switch r dson r 1l 1.55 i dc-dc1 v out1 accuracy v1 i out1 < 150ma, fb1 connected to gnd, 6v < v ina < 18v -3% 3.3 +3% v dc-dc2 high-side switch r dson r 2h 1.7 i dc-dc2 low-side switch r dson r 2l 0.64 i dc-dc2 v out2 accuracy v2 6v < v inb < 18v, i out2 < 600ma, fb2 connected to gnd -3% 5 +3% v 5.5v < v inb < 18v, i out2 = 400ma dc-dc3 high-side switch r dson r 3h 0.7 i dc-dc3 low-side switch r dson r 3l 0.3 i dc-dc3 v out3 accuracy v3 4.5v < v inb < 18v; i out3 = 500ma -3% 3.3 +3% v 6v < v inb < 18v; i out3 p 1.5a dc-dc1 output current limit i lim1 peak current limit 240 300 360 ma dc-dc2 output current limit i lim2 peak current limit 960 1200 1440 ma dc-dc3 output current limit i lim3 peak current limit 1920 2400 2880 ma
automotive power-management ic with three step-down converters and linear regulator MAX16920 4 electrical _ characteristics _ (continued) (v ina = v inb = 14v, t a = -40 c to +125 c , unless otherwise noted. typical values are at t a = +25c.) (note 2) parameter symbol conditions min typ max units dc-dc load regulation loreg dc-dc1 (0 to 150ma) 1 % dc-dc2 (0 to 600ma) 1.5 dc-dc3 (0 to 1.5a) 2.5 dc-dc line regulation lireg dc-dc1, v ina , v inb = 6v to 18v, i out1 = 15ma 3 mv/v dc-dc2, v ina , v inb = 6v to 18v, i out2 = 60ma 5 dc-dc3, v ina , v inb = 6v to 18v, i out3 = 150ma 3 soft-start time t ss MAX16920a 8.5 10 11.5 ms MAX16920b spread-spectrum disabled 6.5 7.5 8.5 spread-spectrum enabled 6.75 8 9.25 duty-cycle range (note 3) dcr MAX16920a 3 97 % MAX16920b 11 96 input voltage to maintain constant switching with v out_ = 1.22v (note 3) v indcl MAX16920a, limited by minimum duty cycle, dc-dc2 and dc-dc3 only 18 v MAX16920b, limited by minimum duty cycle, dc-dc2 and dc-dc3 only 8 spread-spectrum range ss spread-spectrum option only 10 % linear _ regulator _ (ldo) output voltage v outa output in regulation, i outa < 100ma, v ina = 6v to 18v 4.85 5 5.15 v operating current i cca no load (excludes dc-dc_ operating current) 100 fa power-good threshold pgta output rising 88.5 91.5 94.5 % of v outa (nom) power-good threshold hysteresis pgtah 2 % output current limit i lima 200 300 ma dropout voltage v da v ina = 5v, i ldoa = 100ma (note 3) 0.5 v load regulation di i outa = 5ma to 100ma 30 mv line regulation dv v ina = 6v to 18v, i outa = 50ma 0.05 mv/v logic _ levels por , pg_, ot , and uvo output voltage low v ol sink current = 1ma 0.4 v
automotive power-management ic with three step-down converters and linear regulator MAX16920 5 electrical _ characteristics _ (continued) (v ina = v inb = 14v, t a = -40 c to +125 c , unless otherwise noted. typical values are at t a = +25c.) (note 2) note _ 2: operation at voltages outside the 5.5v to 18v range is guaranteed, but some parameters may be out of specification. note _ 3: not production tested. note _ 4: the MAX16920batj/v+ with spread-spectrum disabled has a typical switching frequency of 2.2mhz, while the MAX16920batjs/v+ is centered at 2.025mhz typically. typical operating characteristics (v ina = v inb = 14v, t a = +25c, unless otherwise noted. data measured on MAX16920b, see figure 5 for application circuit.) dc-dc2 line regulation MAX16920 toc06 v in_ (v) v out2 (v) 24 20 8 12 16 4 28 i out2 = 400ma 4.85 4.90 4.95 5.00 5.05 5.10 5.15 5.20 4.80 dc-dc2 output voltage vs. temperature MAX16920 toc05 temperature (c) v out2 (v) 110 95 -25 -10 5 35 50 65 20 80 4.85 4.90 4.95 5.00 5.05 5.10 5.15 5.20 4.80 -40 125 i out2 = 400ma MAX16920 toc04 i out1 200ms/div v out1 (ac-coupled) dc-dc1 load regulation (15ma to 150ma to 15ma) 200ma/div 50mv/div dc-dc1 line regulation MAX16920 toc03 v in_ (v) v out1 (v) 24 20 8 12 16 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.10 4 28 i out1 = 150ma dc-dc1 output voltage vs. temperature MAX16920 toc02 temperature (c) v out1 (v) 110 95 -25 -10 5 35 50 65 20 80 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.10 -40 125 i out1 = 100ma dc-dc1 skip mode operation (i out1 = 100ma) MAX16920 toc01 v lx1 v out1 1s/div 2v/div 10v/div 100ma/div 0v MAX16920a 0v 0a i out1 parameter symbol conditions min typ max units en2, en3, ena, sync input low voltage v il 0.4 v en2, en3, ena, sync input high voltage v ih 1.7 v en2, en3, ena, sync input hysteresis v h 200 mv sync input pulldown resistor rsync 100 200 360 k
automotive power-management ic with three step-down converters and linear regulator MAX16920 6 typical operating characteristics (continued) (v ina = v inb = 14v, t a = +25c, unless otherwise noted. data measured on MAX16920b, see figure 5 for application circuit.) odrv threshold vs. temperature MAX16920 toc14 temperature (c) odrv threshold (v) 110 95 65 80 -10 5 20 35 50 -25 18.2 18.4 18.6 18.8 19.0 19.2 19.4 19.6 19.8 20.0 18.0 -40 125 v in rising v in falling uvi threshold vs. temperature MAX16920 toc13 temperature (c) uvi threshold (v) 110 95 -25 -10 5 35 50 65 20 80 1.185 1.190 1.195 1.200 1.205 1.210 1.215 1.220 1.180 -40 125 ldoa line regulation MAX16920 toc12 vin (v) v outa (v) 15 10 5 4.85 4.90 4.95 5.00 5.05 5.10 5.15 5.20 4.80 0 20 i outa = 100ma ldoa output voltage vs. temperature MAX16920 toc11 temperature (c) v outa (v) 110 95 -25 -10 5 35 50 65 20 80 4.85 4.90 4.95 5.00 5.05 5.10 5.15 5.20 4.80 -40 125 i outa = 100ma MAX16920 toc10 i out3 200ms/div v out3 (ac-coupled) dc-dc3 load regulation (150ma to 1.5a to 150ma) 1a/div 100ma/div dc-dc3 line regulation MAX16920 toc09 v in_ (v) v out3 (v) 24 20 8 12 16 4 28 i out3 = 1a 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.10 dc-dc3 output voltage vs. temperature MAX16920 toc08 temperature (c) v out3 (v) 110 95 -25 -10 5 35 50 65 20 80 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.10 -40 125 i out3 = 1a MAX16920 toc07 i out2 200ms/div v out2 (ac-coupled) dc-dc2 load regulation (60ma to 600ma to 60ma) 500ma/div 0a 100mv/div
automotive power-management ic with three step-down converters and linear regulator MAX16920 7 typical operating characteristics (continued) (v ina = v inb = 14v, t a = +25c, unless otherwise noted. data measured on MAX16920b, see figure 5 for application circuit.) dc-dc1 efficiency vs. load current MAX16920 toc16 i out1 (ma) efficiency (%) 100 10 1 10 20 30 40 50 60 70 80 90 100 0 0.1 1000 v in = 8v v in = 14v v in = 18v en2 = en3 = ena = gnd odrv switch on/off sb_out is the drain side of the external pmos connected at odrv MAX16920 toc15 v in_ v odrv v sb_out (100ki load at sb_out) 100ms/div 10v/div 10v/div 10v/div 0v 0v ldoa startup into full load MAX16920 toc22 v ena v outa i outa v pga 100s/div 5v/div 50ma/div 2v/div 5v/div dc-dc3 startup into full load MAX16920 toc21 v en3 v out3 i out3 v pg3 1ms/div 5v/div 1a/div 2v/div 5v/div dc-dc2 startup into full load MAX16920 toc20 v en2 v out2 i out2 v pg2 1ms/div 5v/div 200ma/div 2v/div 5v/div dc-dc1 startup into full load MAX16920 toc19 v in v out1 i out1 v por 2ms/div 10v/div 100ma/div 2v/div 2v/div dc-dc3 efficiency vs. load current MAX16920 toc18 i out3 (a) efficiency (%) 1.35 1.20 0.90 1.05 0.45 0.60 0.75 0.30 10 20 30 40 50 60 70 80 90 100 0 0.15 1.50 v in = 8v v in = 14v v in = 18v en2 = ena = gnd dc-dc2 efficiency vs. load current MAX16920 toc17 i out2 (ma) efficiency (%) 540 480 360 420 180 240 300 120 10 20 30 40 50 60 70 80 90 100 0 60 600 v in = 8v v in = 14v v in = 18v en3 = ena = gnd
automotive power-management ic with three step-down converters and linear regulator MAX16920 8 pin configuration pin description MAX16920 tqfn top view 29 30 28 27 12 11 13 v l out1 fb1 out2 fb2 14 ena uvi out3 fb3 en3 pgnda lx3 1 2 sync 4 5 6 7 2324 22 20 19 18 pg3 pg2 lx2 pgndb lx1 v ina gnd uvs 3 21 31 10 pga bst1 32 9 odrv ep* + *connect to gnd. 26 15 v inb 25 16 bst2 outa bst3 8 17 en2 0t uvo por pin name function 1 ena ldo enable input. drive ena high to enable the ldo (outa). drive low to disable the ldo. 2 v l internal regulator output. bypass v l to gnd with a 4.7 f f capacitor. 3 gnd ground 4 out1 dc-dc1 converter output. out1 supplies internal circuitry in standby mode reducing overall current consumption. connect a 0.1 f f capacitor from out1 to gnd as close as possible to the ic. if the dc-dc1 output is pulled below its power-on-reset threshold ( por ), dc-dc2 and dc-dc3 are automatically disabled. 5 fb1 dc-dc1 converter feedback input. connect fb1 to gnd for a fixed 3.3v output. connect to a resistive divider to adjust the output voltage between 1.22v and 5.5v. 6 out2 dc-dc2 converter output 7 fb2 dc-dc2 converter feedback input. connect fb2 to gnd for a fixed 5v output. connect to a resistive divider to adjust the output voltage between 1.22v and 5v. 8 outa 5v linear regulator output. connect an external capacitor of at least 4.7 f f from outa to gnd. 9 odrv external pmos output drive signal. odrv turns off the pmos during overvoltage events. if only dc-dc1 is running, the overvoltage circuit is disabled and the external pmos is turned off. 10 bst1 bootstrap capacitor connection for dc-dc1. connect a 0.47 f f capacitor from bst1 to lx1. 11 v ina battery supply-voltage input. v ina supplies power to the v l regulator, the ldo, and dc-dc1. 12 lx1 dc-dc1 converter switching node. connect an lc filter to lx1. use a capacitor with a maximum esr of 0.3 i . unless there is an undervoltage lockout, dc-dc1 is always on when power is applied.
automotive power-management ic with three step-down converters and linear regulator MAX16920 9 pin description (continued) pin name function 13 pgndb power ground for dc-dc1 and dc-dc2 14 lx2 dc-dc2 converter switching node. connect an lc filter to lx2. use a capacitor with a maximum esr of 0.3 i. 15 v inb battery supply-voltage input. v inb supplies power to dc-dc2 and dc-dc3. 16 bst2 bootstrap capacitor connection for dc-dc2. connect a 0.1 f f capacitor from bst2 to lx2. 17 bst3 bootstrap capacitor connection for dc-dc3. connect a 0.1 f f capacitor from bst3 to lx3. 18 lx3 dc-dc3 converter switching node. connect an lc filter to lx3. use a capacitor with a maximum esr of 0.3 i. 19 pgnda power ground for dc-dc3 20 fb3 dc-dc3 feedback input. connect fb3 to gnd for a fixed 3.3v output. connect to a resistive divider to adjust the output voltage between 1.22v and 8v. 21 out3 dc-dc3 converter output 22 uvs undervoltage switch. this switch connects the undervoltage resistor-divider to ground during normal operation. when only dc-dc1 is running, this switch is open to reduce current consumption, and the undervoltage circuit is not active. 23 uvi undervoltage lockout sense input. connect a resistor-divider between the battery, uvi, and uvs to set the undervoltage lockout level. the nominal threshold for uvi is 1.205v. 24 en3 dc-dc3 converter enable input. drive en3 high to enable the dc-dc3 converter. drive low to disable the dc-dc3 converter. 25 en2 dc-dc2 converter enable input. drive en2 high to enable the dc-dc2 converter. drive low to disable the dc-dc2 converter. 26 ot active-low open-drain overtemperature output. ot output low indicates that all converters except dc-dc1 are in shutdown due to an overtemperature condition. 27 uvo active-low open-drain undervoltage output. uvo asserts low when the voltage at uvi falls below 1.205v q 2%. the uvo output is high impedance when only dc-dc1 is operating (standby mode). 28 sync dc-dc converters synchronization input. for MAX16920a, the sync frequency is divided by 2, whereas for the MAX16920b the switching frequency is same as the sync frequency. connect sync to gnd if sync is not used. the sync input is a schmitt trigger type to accommodate a lowpass-filtered square-wave input. the duty-cycle range of the signal is 30% to 70%. the sync input has an internal 200k i pulldown resistor. 29 pg3 dc-dc3 open-drain power-good output. pg3 goes low when out3 is out of regulation. in standby mode, pg3 is high-impedance. 30 pg2 dc-dc2 open-drain power-good output. pg2 goes low when out2 is out of regulation. in standby mode, pg2 is high-impedance. 31 pga linear regulator open-drain power-good output. pga goes low when ldo is out of regulation. in standby mode, pga is high-impedance. 32 por active-low open-drain reset output from dc-dc1. por is low when dc-dc1 is out of regulation and has a delay time of 7.5ms to 8ms in the MAX16920b (2mhz) and 5.1ms in the MAX16920a (400khz). ep exposed pad. connect the exposed pad to ground.
automotive power-management ic with three step-down converters and linear regulator MAX16920 10 functional diagram voltage sense v inb v ina fet drive dc-dc1 lx1 out1 fb1 bst2 lx2 fb2 en2 control oscillator internal regulator overtemperature sensor v l odrv v ina bst1 pgndb uvi uvs 30v en2 dc-dc2 divide by 2* v inb pgndb pgnda out2 bst3 lx3 fb3 out3 por dc-dc3 v inb ldo v ina outa uvo pg2 pg3 pga ena *divide by 2 is only for MAX16920a. en3 sync ot gnd pgnda pgndb MAX16920
automotive power-management ic with three step-down converters and linear regulator MAX16920 11 detailed description the MAX16920 power-management ic integrates three high-voltage step-down dc-dc converters, one high- voltage linear regulator, and an overvoltage protection block. the three step-down converters deliver up to 150ma, 600ma, and 1.5a, while the linear regulator is capable of up to 150ma. the MAX16920 is designed to operate with input voltages between 5.5v to 28v and survive voltage transients to 45v, making it ideal for automotive applications. the MAX16920 is optimized for high efficiency and low standby current. the MAX16920a features 400khz switching frequency, while the MAX16920b features 2mhz switching frequency. the dc-dc converters can also be synchronized to an external frequency reference to ensure low emi. the MAX16920 includes power-good outputs (pg_) for dc-dc2, dc-dc3, ldoa, and a power-on-reset ( por) output for dc-dc1. all regulators other than dc-dc1 have an enable input (en_). dc-dc1 dc-dc1 is an always-on, high-efficiency, step-down converter that outputs up to 150ma. the dc-dc1 has a 5.5v to 28v wide input voltage range and provides a fixed 3.3v output, or provides an adjustable output between 1.22v to 5.5v. dc-dc1 operates in pwm mode or in skip mode. soft-start dc-dc1 features an internal soft-start timer. the out - put voltage soft-start ramp time is 10ms (typ) for the MAX16920a, and 7.5ms to 8ms (typ) for the MAX16920b. if a short circuit is encountered, after the soft-start timer has expired, the device is disabled for 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b) and then reattempts soft-start. this pattern repeats until the short circuit has been removed. adjusting output voltage dc-dc1 provides a fixed 3.3v output or an adjustable output between 1.22v to 5.5v. connect fb1 to gnd to set the out1 voltage to a fixed 3.3v voltage. connect a resistive divider between out1, fb1, and gnd to adjust the output voltage. when out1 is set to a voltage greater than 3.3v, additional resistors are needed between the converter output, out1 and gnd. see the setting the output voltage (dc-dc1, dc-dc2, dc-dc3) section for more information. overcurrent protection dc-dc1 limits the peak output current to 300ma (typ). the accuracy of the current limit is 20%, which makes selection of external components very easy. to protect against short-circuit events, the MAX16920 shuts off if the current limit is exceeded and out1 is below 1.5v. dc-dc1 attempts a soft- start restart every 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b) and stays off if the short circuit has not been removed. when the short circuit is no longer present, normal operation resumes with the output voltage following the normal soft-start sequence. if the MAX16920 die reaches the thermal limit of +170?c (typ), all outputs except out1 are immediately shut off. power-on reset dc-dc1 features an open-drain reset output ( por). if out1 exceeds 91.5% of its nominal output voltage, the por output goes high after a delay time of 5.1ms (typ) for the MAX16920a, or 7.5ms to 8ms (typ) for the MAX16920b. contact the factory for other por delay options. standby and skip mode when en2, en3, and ena are all logic-low, the MAX16920 consumes a standby current of 25a (typ) with no load on out1. if i out1 < 170ma (typ), dc-dc1 operates in skip mode. also, the power-good outputs (pg_) are high impedance and the undervoltage circuit is inactive in standby mode. when any other channel (dc-dc2, dc-dc3, or ldoa) is enabled, dc-dc1 operates in con - stant pwm mode to improve emi performance. holding up the out1 during input undervoltage events it is possible to make dc-dc1 more immune to input voltage dropouts by adding extra capacitance buff - ered by means of a diode on the v ina pin as shown in figure 1. this is useful if out1 powers the main system processor, which needs to remain powered for as long as possible. estimate the size of the hold-up capacitor needed on v ina using the following formula: c vina = (i in1 x t h )/v where i in1 is the estimated input current to dc-dc1, t h is the hold-up time, and v is the drop-in voltage on c vina that can be tolerated. to prolong the hold-up time, the ldo should be disabled during undervoltage events. if this is not possible, the supply and load current of the ldo should be taken into account in the calculation. dc-dc2 dc-dc2 is a high-efficiency step-down converter that outputs up to 600ma. dc-dc2 has a 5.5v to 28v input voltage range and provides a fixed 5v output or
automotive power-management ic with three step-down converters and linear regulator MAX16920 12 an adjustable output between 1.22v to 5.5v. dc-dc2 operates in pwm mode only. dc-dc2 is activated by driving en2 high. soft-start dc-dc2 features an internal soft-start timer with a ramp time of 10ms (typ) for the MAX16920a, and 7.5ms to 8ms (typ) for the MAX16920b. the soft-start at out2 is initiated when out1 reaches a power-good condition and en2 is high. if a short circuit is encountered, after the soft-start timer has expired, dc-dc2 is disabled for 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b) and it reattempts soft-start. this pattern repeats until the short circuit has been removed. adjusting output voltage dc-dc2 provides a fixed 5v output or an adjustable output between 1.22v to 5.5v. connect fb2 to gnd to set the out2 voltage to a fixed 5v. connect a resistive divider between out2, fb2, and gnd to adjust the output voltage. see the setting the output voltage (dc- dc1, dc-dc2, dc-dc3) section for more information. overcurrent protection dc-dc2 limits the peak output current to 1.2a (typ). the accuracy of the current limit is 20%, which makes selection of external components very easy. to protect against short-circuit events, the MAX16920 shuts off dc-dc2 if out2 is below 1.5v and one overcurrent event is detected. dc-dc2 attempts a soft-start restart every 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b)) and stays off if the short circuit has not been removed. when the short-circuit is no longer present, normal operation resumes with the output voltage following the normal soft-start sequence. if the MAX16920 die reaches the thermal limit of +170?c (typ) (temperature rising) out2 is immediately shut off. power-good output (pg2) dc-dc2 provides an open-drain power-good output (pg2). pg2 is an active-high output that pulls high when the output voltage (out2) is above 91.5% of its nominal value. in standby mode pg2 is high impedance. dc-dc3 dc-dc3 is a high-efficiency step-down converter that outputs up to 1.5a. dc-dc3 has a 5.5v to 28v input volt - age range and provides a fixed 3.3v output or provides an adjustable output between 1.22v to 8v. dc-dc3 operates in pwm mode only. dc-dc3 is activated by driving en3 high. soft-start dc-d3 features an internal soft-start timer. the out3 soft-start ramp time is 10ms (typ) for the MAX16920a, and 7.5ms to 8ms (typ) for the MAX16920b. a soft-start at out3 is initiated when out1 reaches the power- good condition and en3 is taken high. if a short circuit is encountered, after the soft-start timer has expired, dc-dc3 is disabled for 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b) and it reattempts soft- start. this pattern repeats until the short circuit has been removed. adjusting output voltage dc-dc3 provides a fixed 3.3v output or provides an adjustable output between 1.22v to 8v. connect fb3 to gnd to set the out3 voltage to 3.3v. connect a resistive divider between out3, fb3, and gnd to adjust the out - put voltage. when out3 is set to a voltage greater than 3.3v, additional resistors are needed between the con - verter output, out3 and gnd. see the setting the output voltage (dc-dc1, dc-dc2, dc-dc3) section for more information. overcurrent protection the dc-dc3 limits the peak output current to 2.4a (typ). the accuracy of the current limit is 20%, which makes the selection of external components very easy. to protect against short-circuit events, the MAX16920 shuts off if out3 is below 1.5v and one overcurrent event is detected. the dc-dc3 attempts a soft-start restart every 40ms (typ) (for MAX16920a) or 28ms (typ) (for MAX16920b) and stays off if the short circuit has not been removed. when the short circuit is no longer present, normal operation resumes with the output figure 1. holding up out1 during input undervoltage events 10f 0.1f 10h battery input v ina v inb odrv p MAX16920
automotive power-management ic with three step-down converters and linear regulator MAX16920 13 voltage following the normal soft-start sequence. if the MAX16920 die reaches the thermal limit of +170?c (typ) (temperature rising), out3 is immediately shut off. power-good output (pg3) dc-dc3 provides an open-drain power-good output (pg3). pg3 is an active-high output that pulls high when the output voltage (out3) is above 91.5% of its nominal value. in standby mode, pg3 is high impedance. linear regulator (outa) the MAX16920 features a fixed 5v output linear regulator (outa). outa provides up to 150ma load current. connect an external capacitor of at least 4.7 f from outa to gnd. outa is activated by driving ena high. power-good output (pga) outa provides an open-drain power-good output (pga). pga is an active-high output that pulls high when the output voltage (outa) is above 91.5% of its nominal value. in standby mode, pga is high impedance. overcurrent protection the outa output current is limited to 200ma (min). if the output current exceeds the current limit, outa drops out of regulation. excess power dissipation in the device can cause the device to turn off due to thermal shutdown. dropout the dropout voltage for the linear regulator (outa) is 500mv (max) at 100ma load. to avoid dropout, make sure the input supply voltage is greater than the output voltage plus the dropout voltage based on the application output current requirements. switching frequency the MAX16920aatj/v+ provides a fixed 400khz switch - ing frequency, whereas the MAX16920batj/v+ pro - vides a fixed 2.2mhz switching frequency. connect sync to gnd when using the internal switching fre - quency. for external synchronization, see the dc-dc synchronization (sync) section. spread-spectrum option the MAX16920aatjs/v+ and MAX16920batjs/v+ have a built-in spread-spectrum oscillator. the inter - nal operating frequency varies by +10% relative to the internally generated operating frequency of 400khz (typ) for MAX16920aatjs/v+ and 2.025mhz (typ) for MAX16920batjs/v+. spread spectrum improves the emi performance of the MAX16920 in some applications. by varying the frequency 10% only in the positive direction, the switching frequency of MAX16920batjs/v+ never drops below the am radio band upper limit of 1.8mhz. the internal spread spectrum does not interfere with the external clock applied on the sync pin. it is active only when generating the switching frequency internally. dc-dc synchronization (sync) the sync input provides for synchronization of the dc-dc converters. the MAX16920 defaults to the internal switching frequency during startup or when a sync input signal is not provided. for external synchronization, provide a signal between 600khz and 1000khz for the MAX16920a and between 1800khz and 2400khz for the MAX16920b. the MAX16920a divides the sync frequency by a factor of 2 before feeding to the dc-dc converters, whereas the MAX16920b feeds the sync frequency as it is to the dc-dc converters. the duty cycle of the sync signal should be in the 30% to 70% range. the sync input has an internal 200k? pulldown resistor. controlled emi with forced-fixed frequency under normal operating conditions, the MAX16920 attempts to operate at a constant switching frequency for all load currents (dc-dc1 enters skip mode below its skip-mode threshold). for tightest frequency control, apply the operating frequency to sync. the advantage of this is a more accurate switching frequency and more predictable emi characteristics. extremes of input voltage in some cases, especially at high switching frequen - cies, the MAX16920 is forced to deviate from its operat - ing frequency independent of the state of sync. for input voltages above 18v, the required duty cycle to regulate the output can be lower than the minimum on- time of the high-side switch (90ns typ). in this event, the MAX16920 is forced to lower its switching frequency by skipping pulses. in an analogous fashion when the input voltage is reduced and the MAX16920 approaches dropout, the device attempts to turn on the high-side fet continuously. however, to maintain gate charge on the high-side fet, the bst capacitor must be peri - odically recharged. to ensure proper charge on the bst capacitor when in dropout, the high-side fet is turned off every 5.5s for the MAX16920b and the low-side fet is turned on for about 150ns. this gives an effective duty cycle of > 97% and a switching frequency of 180khz when in dropout. (the MAX16920a refreshes the bst capacitor every 7.5 s for 150ns and switches at 133khz when in dropout.)
automotive power-management ic with three step-down converters and linear regulator MAX16920 14 undervoltage output (uvo) the MAX16920 features an active-low undervoltage output ( uvo ) to monitor the input voltage. uvo is pulled low when the voltage at uvi falls below 1.205v. to monitor battery voltage, connect a resistive divider between the battery, uvi, and uvs. an undervoltage condition asserts the uvo flag only and does not effect the regulator outputs. in case only dc-dc1 is running, uvo is high impedance. for more details, see the setting the undervoltage output ( uvo ) level section. overvoltage output (odrv) the MAX16920 features an overvoltage output (odrv) that can be used to create an overvoltage-protected battery output with the addition of an external pmos transistor. if v ina exceeds 19.2v (typ), the odrv out - put is driven high, which turns off the external pmos. an overvoltage condition does not affect any of the other MAX16920 converters. choose an external pmos transistor with a low-enough r dson so that voltage loss and power dissipation at the nominal output current are acceptable. very low r dson pmos transistors have larger effective input capacitance and thus are switched more slowly by the odrv output. when only dc-dc1 is running, odrv is high and the external pmos is off. overtemperature protection (ot) the MAX16920 features an active-low overtemperature output ( ot ). the MAX16920 pulls the ot output low and disables all the regulators except dc-dc1, if the die temperature exceeds the thermal shutdown temperature (t s ). applications information inductor selection three key inductor parameters must be specified for operation with the MAX16920: inductance value (l), peak inductor current (i peak ), and inductor satura - tion current (i sat ). the minimum required inductance is a function of operating frequency, input-to-output voltage differential, and the peak-to-peak inductor current (i p-p ). higher i p-p allows for a lower inductor value, while a lower i p-p requires a higher inductor value. a lower inductor value minimizes size and cost, improves large-signal and transient response, but reduces efficiency due to higher peak currents and higher peak-to-peak output-voltage ripple for the same output capacitor. on the other hand, higher inductance increases efficiency by reducing the ripple current. resistive losses due to extra wire turns can exceed the benefit gained from lower ripple current levels, especial - ly when the inductance is increased without also allow - ing for larger inductor dimensions. a good compromise is to choose i p-p equal to 30% of the full load current. use the following equation to calculate the inductance: l = v out (v in C v out )/(v in x f sw x i p-p ) v in and v out are typical values so that efficiency is optimum for typical conditions. the peak-to-peak inductor current, which reflects the peak-to-peak output ripple, is larger at the maximum input voltage. see the output capacitor selection section to verify that the worst-case output ripple is acceptable. the inductor saturation current is also impor - tant to avoid runaway current during continuous output short circuit. choose an inductor with a saturation cur - rent of greater than the maximum current limit _ to ensure proper operation and avoid runaway. input capacitor selection the discontinuous input current of the buck converter causes large input ripple current. the switching fre - quency, peak inductor current, and the allowable peak- to-peak input-voltage ripple dictate the input capaci - tance requirement. increasing the switching frequency or the inductor value lowers the peak-to-average current ratio, yielding a lower input capacitance requirement. the input ripple consists mainly of v q (caused by the capacitor discharge) and v esr (caused by the esr of the input capacitor). the total voltage ripple is the sum of v q and v esr . assume the input voltage ripple from the esr and the capacitor discharge is equal to 50% each. the following equations show the esr and capaci - tor requirement for a target voltage ripple at the input: esr pCp out out in q sw v esr i i 2 i x d(1C d) c v x f ? = ? ? ? + ? ? ? ? = ? where: ( ) ( ) in out out pCp in sw v C v x v i v x f x l ? =
automotive power-management ic with three step-down converters and linear regulator MAX16920 15 and: out in v d v = where i out is the output current, d is the duty cycle, and f sw is the switching frequency. use additional input capacitance at lower input voltages to avoid possible undershoot below the uvlo threshold during transient loading. output capacitor selection the allowable output voltage ripple and the maximum deviation of the output voltage during step load currents determine the output capacitance and its esr. the output ripple is composed of v q (caused by the capacitor discharge) and v esr (caused by the esr of the output capacitor). use low-esr ceramic or alumi - num electrolytic capacitors at the output. for aluminum electrolytic capacitors, the entire output ripple is contributed by v esr . use the esr out equation to cal - culate the esr requirement and choose the capacitor accordingly. if using ceramic capacitors, assume the contribution to the output ripple voltage from the esr and the capacitor discharge to be equal. the following equations show the output capacitance and esr requirement for a specified output voltage ripple. esr = v esr /i p-p c out = i p-p /(8 x v q x f sw ) where: i p-p = (v in - v out ) x v out /(v in x f sw x l) v out_ripple ~ v esr + v q i p-p is the peak-to-peak inductor current as calculated above, and f sw is the converters switching frequency. the allowable deviation of the output voltage during fast transient loads also determines the output capacitance and its esr. the output capacitor supplies the load- step current until the converter responds with a greater duty cycle. the response time (t response ) depends on the closed-loop bandwidth of the converter. the high switching frequency of the MAX16920 allows for a higher closed-loop bandwidth, thus reducing t response and the output capacitance requirement. the resistive drop across the output capacitors esr and the capacitor discharge causes a voltage droop during a load step. use low-esr ceramic capacitors for better transient load and ripple/noise performance. keep the maximum output voltage deviations below the tolerable limits of the electronics being powered. when using a ceramic capacitor, assume an 80% and 20% contribution from the output capacitance discharge and the esr drop, respectively. use the following equations to calculate the required esr and capacitance value: esr out = v esr /i step c out = (i step x t response )/v q where i step is the load step, and t response is the response time of the converter. the converter response time depends on the control-loop bandwidth. electrolytic output capacitors can be used if a 2.2 f ceramic capacitor is connected in parallel. at output currents lower than the maximum, smaller capacitors can be used. use a 4.7 f or larger ceramic capacitor on the output of the linear regulator, outa. setting the output voltage (dc-dc1, dc-dc2, dc-dc3) the output voltage for any of the dc-dc converters is set by selecting resistor r1 according to the formula: r1 = r2 x ((v out_ /1.22) - 1) where v out_ is the desired output voltage, and r2 is the value of the ground connected resistor (a good starting value is 30k ? ). see figure 2. when setting dc-dc1 or dc-dc3 to output voltages higher than 3.3v , it is neces - sary to add an additional resistive divider between the converter output and the out1 or out3 pins. resistor values of 100k ? and 50k ? work well in all applications. see figure 3 for the exact configuration. figure 2. setting the output voltage out_ fb_ gnd r1 r2 MAX16920
automotive power-management ic with three step-down converters and linear regulator MAX16920 16 setting the undervoltage output (uvo) level the uvo level is set by using two resistors connected between the input (before the reverse-polarity protection diode if used) and the uvi and between uvi and uvs. the uvs switch has a 1540 ? typical resistance that must be taken into account when calculating the external resistor values to maintain accuracy. use the following equation to calculate the value of the upper resistor, r1: r1 = (v bt C 1.205)/(1.205/(r2 + r uvs )) where v bt is the desired undervoltage level at the battery, and r2 is the value of the lower resistor (a good starting value is 100k ? ). r uvs is 1540 ? . see the typical operating circuits in figures 4 and 5. pcb layout guidelines grounding establish a quiet ground for all analog ground (gnd) connections. sources of switching current and other noisy signals should be connected to their respective power grounds (pgnda and pgndb). gnd, pgnda, and pgndb should be connected together at the gnd pin of the MAX16920. if needed, use multiple vias to connect ground planes between different board layers to keep the ground impedance low. the following should be connected to analog gnd: 1) the gnd pin of the MAX16920. 2) the ground connection of the v l capacitor. 3) the grounds for any feedback resistor-dividers used. 4) the ground side of the outa output capacitor. all other ground connections should be to their respec - tive pgnda and pgndb grounds. general guidelines 1) minimize the area of high-current loops by placing each dc-dc converters inductor and output capaci - tors near its input capacitors and its lx_ and pgnd_ pins. out1 and out2 converters share pgndb for ground return, while out3 has pgnda for ground return. 2) keep the power traces and load connections as short and wide as possible, especially at the ground terminals. this practice is essential for high efficiency and jitter-free operation. 3) use thick copper pcbs (2oz. vs. 1oz.) if possible to enhance efficiency. 4) keep the lx_ connections short and wide and place the inductors as close as possible to the associated lx pin. figure 3. typical application circuit for setting out1 or out3 above 3.3v ri1 = 212ki ri2 = 121ki fbi v fb_ = 1.21v ~750mv use internal r1 = 100ki out1/out3 dc-dc3 output 7.4v fb1/fb3 r2 = 50ki r top r bot
automotive power-management ic with three step-down converters and linear regulator MAX16920 17 5) route high-speed switching nodes (bst_ and lx_) away from sensitive analog areas (sync and fb_) and keep their area as small as possible. 6) place the v ina , v inb , and v l bypass capacitors as close as possible to the device. if using multiple bypass capacitors, place the lowest value capacitor closest to the pin. the ground connection of the v l bypass capacitor should be connected directly to the gnd pin with a wide trace. 7) keep any feedback traces as short and small as possible to prevent noise pickup. make feedback connections directly to the positive terminal of the output capacitor to ensure good regulation. thermal considerations the power dissipation of the MAX16920 is made up of three components: power dissipation due to the dc-dc converters, power dissipation due to the linear regulator, and internal power dissipation. the dc-dc converter power dissipation can be estimated as follows: p dcdc = p resistive + p switching p resistive = d x i out 2 x r h + (1 - d) x i out 2 x r l where d is the duty cycle (approximately v out /v in ), i out is the output current, r h is the resistance of the high-side switch, and r l is the resistance of the low-side switch. p switching = f sw x (0.25 x v in x i out x t rise + 0.25 x v in x i out x t fall ) where v in is the input voltage, t rise is the rise time of the lx node (approximately 5ms (MAX16920b) and 10ms (MAX16920a)), and t fall is the fall time of the lx node (approximately 5ms (MAX16920b) and 10ms (MAX16920a)). the linear regulator power dissipation is: p lin = (v in - 5v) x i lin the internal power dissipation can be approximately calculated as v in_ x 35ma during normal operation. in many applications, the power dissipation of the linear regulator (ldoa) is a large contributor to the overall power dissipation. note that although the linear regula - tor can provide up to 150ma of output current, in most cases the permitted output current is lower due to power dissipation limitations. the total power dissipation leads to an increase in the chip temperature, which is dependent on the thermal resistance of the board upon which the MAX16920 is mounted. the maximum permitted junction temperature is +150c and a junction temperature above this eventu - ally leads to overtemperature shutdown of the chip.
automotive power-management ic with three step-down converters and linear regulator MAX16920 18 typical operating circuits figure 4. typical operating circuit for MAX16920a operating at 400khz 0.47f 4.7f 0.1f 47h bst1 lx1 out1 fb1 47f 3.3v/150ma 0.1f 22h bst2 lx2 out2 47f 5v/600ma fb2 0.1f 4.7f 10h bst3 lx3 out3 outa 150f 3.3v/1.5a 5v/150ma fb3 10f uvi uvs sync en2 10h battery input sb_out r1 100ki r2 19.1ki v ina v inb odrv p v l gnd pgnda pgndb MAX16920a en3 ena uvo ot por out1 pg2 pg3 pga
automotive power-management ic with three step-down converters and linear regulator MAX16920 19 package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package_ type package_ code outline_ no. land_ pattern _ no. 32 tqfn-ep t3277+2 21-0144 90-0125 chip information process: bicmos typical operating circuits (continued) figure 5. typical operating circuit for MAX16920batj/v+ operating at 2.2mhz 0.47f 4.7f 0.1f 8.2h bst1 lx1 out1 fb1 10f 3.3v/150ma 0.1f 4.7h bst2 lx2 out2 22f 5v/600ma fb2 0.1f 4.7f 2.2h bst3 lx3 out3 outa 100f 3.3v/1.5a 5v/150ma fb3 10f uvi uvs sync 10h battery input r1 100ki r2 19.1ki v ina v inb odrv p v l gnd pgnda pgndb en2 sb_out MAX16920b en3 ena uvo ot por out1 pg2 pg3 pga
automotive power-management ic with three step-down converters and linear regulator MAX16920 maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 _ ___________________ _ ________ maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision_ date description pages_ changed 0 12/10 initial release 1 8/11 added the spread-spectrum option; updated the electrical characteristics table and added note 4; included output voltage setting application instructions; added the spread-spectrum option section; added new figure 3 (typical application circuit for setting out1 or out3 above 3.3v) 1, 3, 4, 5, 8, 9, 11, 12, 13, 15, 16

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