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general description the MAX20021/ max20022 power-management ics (pmics) integrate four low-voltage, high-efficiency, step- down dc-dc converters. each of the four outputs is factory or resistor programmable between 1.0v to 4.0v and can deliver up to 1.0a of current. the pmics operate from 3.0v to 5.5v, making them ideal for automotive point- of-load and post-regulation applications. the pmics feature fixed-frequency pwm-mode operation with a switching frequency of 2.2mhz or 3.2mhz. high- frequency operation allows for an all-ceramic capacitor design and small-size external components. the low- resistance on-chip switches ensure high efficiency at heavy loads while minimizing critical inductances, making the layout a much simpler task with respect to discrete solutions. internal current sensing and loop compensation reduce board space and system cost. the pmics offer a spread-spectrum option to reduce radiated emissions. two of the four buck converters oper - ate 180o out-of-phase with the internal clock. this feature reduces the necessary input capacitance and improves emi as well. all four buck converters operate in constant- pwm mode outside the am band. the pmics offer a sync input to synchronize to an external clock. the pmics provide individual enable inputs and power- good/reset outputs, as well as factory-programmable reset times. the pmics offer several important protection features including: input overvoltage protection, input undervoltage monitoring, input undervoltage lockout, cycle-by-cycle current limiting, and overtemperature shutdown. the input undervoltage monitor indicates a brownout condition by driving pg_ low when the input falls below the uvm threshold. the MAX20021/ max20022 pmics are available in a 28-pin tqfn package with an exposed pad and are specified for operation over the -40oc to +125oc automo - tive temperature range. applications automotive industrial benefts and features quad step-down dc-dc converters with integrated fets operate from 3.0v to 5.5v supply voltage 1.0v to 4.0v fixed or adjustable output voltage 2.2mhz (max20022) or 3.2mhz (MAX20021) switching frequency four channels capable of delivering up to 1a each designed to improve automotive emi performance ? forced-pwm operation ? two channels 180o out-of-phase ? sync input ? spread-spectrum option soft-start and supply sequencing reduces inrush current individual enable inputs and power-good outputs to simplify sequencing ov/uv input-voltage monitoring overtemperature and short-circuit protection 28-pin (5mm x 5mm x 0.8mm) tqfn-ep package -40oc to +125oc operating temperature range 19-6628; rev 2; 12/13 ordering informatio n /selector guide appear at end of data sheet. for related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX20021.related . simplifed block diagram evaluation kit available pgnd_ lx_ sync outs_ ep control v out1 10f 1.5h 5v v out_ MAX20021 2.2f 1f en_ pg_ v a gnd sel step-down pwm out_ 1.0v to 4.0v up to 0.5a or 1a ss osc 4 channels pv_ en 5v 10k MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters
maxim integrated 2 electrical characteristics (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = t j = -40oc to +125oc, unless otherwise noted. typical values are at t a = +25oc under normal conditions, unless otherwise noted.) (note 2) 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.maximintegrated.com/thermal-tutorial . pv_ to pgnd_ ..................................................... -0.3v to +6.0v v a to gnd ............................................................ -0.3v to +6.0v outs_, en_, pg_, sync, sel to gnd ...... -0.3v to v a + 0.3v pv_ to pv_ ........................................................... -0.3v to +0.3v pgnd_ to gnd .................................................... -0.3v to +0.3v lx_ to pgnd ............................................... -1.0v to pv_ + 0.3v lx_ continuous rms current .............................................. 2.0a output short-circuit duration .................................... continuous continuous power dissipation (t a = +70oc) tqfn (derate 28.6mw/oc above +70oc) .................. 2285mw esd hb ................................................................................. 2kv esd mm .............................................................................. 200v operating temperature range .......................... -40oc to +125oc junction temperature ...................................................... +150oc storage temperature range ............................. -65oc to +150oc lead temperature (soldering, 10s) ................................. +300oc soldering temperature (reflow) ....................................... +260oc 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 ab solute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics (note 1) tqfn junction-to-ambient thermal resistance ( ja ) .............. 35c/w junction-to-case thermal resistance ( jc ) ..................... 3c/w absolute maximum ratings parameter symbol conditions min typ max unit general supply voltage range v pv_ fully operational 3.0 5.5 v supply current i pv0 no load, no switching, v en1 = v en2 = v en3 = v en4 = v pv_ 2.5 3.8 5 ma shut-off current i vpsd v en1 = v en2 = v en3 = v en4 = v gnd t a = +25c 0.1 2 a t a = +125c 2 overvoltage threshold rising 5.6 5.8 6 v hysteresis 0.1 undervoltage monitor threshold uvm option enabled v pv_ falling 4.15 4.3 4.45 v v pv_ hysteresis 0.1 uvlo threshold v pv_ falling 2.68 v v pv_ rising 3.0 pwm switching frequency f sw switching frequency = 2.2mhz (see the selector guid e ) 2.0 2.2 2.4 mhz switching frequency = 3.2mhz (see the selector guide ) 3.0 3.2 3.4 spread spectrum df/f spread-spectrum option = enabled (see the selector guide) +3 % MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 3 electrical characteristics (continued) (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = t j = -40oc to +125oc, unless otherwise noted. typical values are at t a = +25oc under normal conditions, unless otherwise noted.) (note 2) parameter symbol conditions min typ max unit sync input frequency range f sync pwm switching frequency = 2.2mhz (see the selector guide ) 1.7 2.5 mhz pwm switching frequency = 3.2mhz (see the selector guide ) 2.8 3.5 out1, out2, out3, out4synchronous step-down dc-dc converters fixed dc output accuracy i load = 0ma +1.5 % i load = 0ma to i max -3 +3 fb dc set-point accuracy v sfb_ max20022 i load = 0ma 1015 mv i load = 0ma to i max 970 1030 load regulation i load = i max -1.5 -2.5 % line regulation i load = i max /2, v pv_ = 4.5v to 5.5v +0.3 % pmos on-resistance v pv_ = 5.0v, i lx_ = 0.2a 125 250 m nmos on-resistance v pv_ = 5.0v, i lx_ = 0.2a 100 200 m pmos current-limit threshold i lim 1.0a channel output (see the selector guide ) 1.4 1.65 2 a 0.5a channel output (see the selector guide ) 0.8 1.1 1.5 soft-start ramp time 3272 cycles outs leakage current i b_outs_ externally adjustable output 20 na lx leakage current v pv_ = 5.0v, lx_ = v pgnd_ or v pv_ 0.1 a minimum on-time 45 66 ns lx rise/fall time 4 ns duty cycle range 100 % outs_ discharge resistance v en_ = v gnd 35 out1, out2 phasing (note 3) 0 degrees out3, out4 phasing (note 3) 180 degrees thermal overload thermal-shutdown temperature t j rising (note 4) +185 oc hysteresis (note 4) 15 oc output power-good indicators (pg_) output overvoltage threshold v out rising (percentage of nominal output) 106 110 114 % output undervoltage threshold v out falling (percentage of nominal output) 92.5 94 96 % v out rising (percentage of nominal output) 93.5 95 97 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 4 note 2: all units are 100% production tested at +25oc. all temperature limits are guaranteed by design. note 3: phase measurement is in relation to the rising edge of v lx_ . note 4: guaranteed by design. not production tested. electrical characteristics (continued) (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = t j = -40oc to +125oc, unless otherwise noted. typical values are at t a = +25oc under normal conditions, unless otherwise noted.) (note 2) parameter symbol conditions min typ max unit uv/ov propagation delay 15 s pg_ output high leakage current 0.1 a pg_ output low level v pv_ = 3.0v, sinking 3ma 0.22 v enable inputs (en_) input high level v pv_ = 5.0v, v en_ rising 0.7 1.0 1.3 v hysteresis v pv_ = 5.0v, v en_ falling 50 mv pulldown resistance 100 k digital interface (sync, sel) input voltage high v inh 1.5 v input voltage low v inl 0.5 v input voltage hysteresis 70 mv pulldown resistance 100 k MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 5 typical operating characteristics (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = +25oc, unless otherwise noted.) buck efficiency (3.2mhz) vs. load current MAX20021 toc01 load current (a) efficiency (%) 0.1000 0.0100 0.0010 0.0001 1.0000 10 20 30 40 50 60 70 80 90 100 0 v out2 = 1.2v v out4 = 1.8v v out1 = 3.3v v out3 = 2.65v f sw = 3.2mhz, v pv_ = 5v lx leakage current vs. temperature MAX20021 toc04 temperature (oc) lx leakage current (na) 80 100 120 40 60 -40 -20 200 0 100 200 300 400 500 600 700 800 -100 -60 140 lx_ to pv_ lx_ to pgnd_ buck efficiency (2.2mhz) vs. load current MAX20021 toc02 load current (a) efficiency (%) 0.1000 0.0100 0.0010 0.0001 1.0000 10 20 30 40 50 60 70 80 90 100 0 f sw = 2.2mhz, v pv_ = 5v v out2 = 1.2v v out4 = 1.8v v out1 = 3.3v v out3 = 2.65v load regulation (buck 1) MAX20021 toc05 i out1 (a) v out1 (v) 0.80.7 0.9 0.60.5 0.20.1 0.40.3 3.22 3.24 3.26 3.28 3.32 3.30 3.34 3.36 3.20 0 1.0 supply current vs. supply voltage MAX20021 toc03 supply voltage (v) supply current (ma) 5.2 4.7 4.2 3.7 3.2 5 10 15 20 25 30 0 2.7 5.7 t a = -40oc t a = +25oc t a = +125oc v pv_ = v a = v en_ line regulation (buck 2) MAX20021 toc06 v pv2 (v) v out2 (% nominal) 5.2 4.7 4.2 3.7 3.2 99.8 100.0 100.2 100.4 100.6 100.8 101.0 99.6 2.7 5.7 t a = +125oc t a = +25oc t a = -40oc startup sequence MAX20021 toc07 2ms/div v out1 v out2 v out3 v out4 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 6 typical operating characteristics (continued) (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = +25oc, unless otherwise noted.) short-circuit behavior MAX20021 toc08 400ns/div v out3 2v/div v lx3 2v/div i out3 1a/div line transient, (v out1 = 3.3v) MAX20021 toc10 10ms/div v pv1 1v/div v out1 50mv/div v pv1 = 3.8v v pv1 = 5.2v v pv1 = 3.8v load transient, (v out1 = 3.3v) MAX20021 toc09 10s/div i out1 500ma/div v out1 100mv/div p-channel switch resistance vs. supply voltage MAX20021 toc13 v pv_ (v) p-channel switch resistance () 5.7 5.2 4.7 4.2 3.7 3.2 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0 2.7 t a = +125oc t a = -40oc t a = +25oc switching frequency vs. temperature MAX20021 toc11 f sw (% nominal) 98 99 100 101 102 103 97 80 100 120 40 temperature (c) 60 -40 -20 200 -60 140 dropout voltage vs. load current (buck 1) MAX20021 toc12 v pv1 - v out1 (mv) 50 100 150 200 250 300 350 0 i out1 (a) 0.80.7 0.9 0.60.5 0.20.1 0.40.3 0 1.0 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 7 typical operating characteristics (continued) (v a = v pv1 = v pv2 = v pv3 = v pv4 = 5.0v; t a = +25oc, unless otherwise noted.) psrr vs. frequency MAX20021 toc16 frequency (khz) psrr (db) 100.000 10.000 1.000 0.1000.010 -60 -50 -40 -30 -20 -10 0 -70 0.001 1000.000 no load 150ma load small-signal gain vs. frequency MAX20021 toc14 frequency (hz) magnitude (db) 1e+5 1e+4 1e+3 0 45 90 -45 1e+2 1e+6 output voltage-noise density vs. frequency MAX20021 toc17 rf frequency (mhz) output voltage-noise density (nv/hz) 3000 3500 1500 2000 2500 1000500 10 100 1000 10,000 1 0 4000 v pv_ = 5v v out_ = 1.2v i out_ = 0ma phase margin vs. frequency MAX20021 toc15 frequency (hz) phase margin () 1e+5 1e+4 1e+3 -50 0 50 100 150 200 -100 1e+2 1e+6 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 8 pin description pin confguration pin name function 1 en1 active-high digital enable input for buck 1. driving en1 high enables buck 1. 2 pv1 buck 1 voltage input. connect a 2.2f or larger ceramic capacitor from pv1 to pgnd1 as close as possible to the device. 3 lx1 buck 1 switching node. lx1 is high impedance when the device is off. 4 pgnd1 power ground for buck 1 5 pgnd2 power ground for buck 2 6 lx2 buck 2 switching node. lx2 is high impedance when the device is off. 7 pv2 buck 2 voltage input. connect a 2.2f or larger ceramic capacitor from pv2 to pgnd2 as close as possible to the device. 8 outs2 buck 2 voltage sense input 9 en2 active-high digital enable input for buck 2. driving en2 high enables buck 2. 10 pg2 open-drain, active-high, power-good output for buck 2. to obtain a logic signal, pull up pg2 with an external resistor connected to a positive voltage equal to or lower than v a . 11 sel buck 3 output-voltage select input. connect sel to pgnd_ for a 1.8v output. connect sel to pv_ for a 2.65v output. do not toggle during normal operation. 12 pg3 open-drain, active-high, power-good output for buck 3. to obtain a logic signal, pull up pg3 with an external resistor connected to a positive voltage equal to or lower than v a . 13 en3 active-high digital enable input for buck 3. driving en3 high enables buck 3. 14 outs3 buck 3 voltage sense input 26 27 25 24 10 9 11 pv1 pgnd 1 pgnd 2 lx 2 pv2 12 en1 pv4 pgnd 4 pgnd 3 en4 lx 3 pv3 12 ep = gnd sync 45 67 2021 19 17 16 15 v a pg1 pg3 sel pg2 en2 MAX20021 lx 1 lx 4 3 18 28 8 outs1 outs2 + gnd 23 13 en3 pg4 22 14 outs3 outs4 tqfn top view MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 9 pin description (continued) pin name function 15 pv3 buck 3 voltage input. connect a 2.2f or larger ceramic capacitor from pv3 to pgnd3 as close as possible to the device. 16 lx3 buck 3 switching node. lx3 is high impedance when the device is off. 17 pgnd3 power ground for buck 3 18 pgnd4 power ground for buck 4 19 lx4 buck 4 switching node. lx4 is high impedance when the device is off. 20 pv4 buck 4 voltage input. connect a 2.2f or larger ceramic capacitor from pv4 to pgnd4 as close as possible to the device. 21 en4 active-high digital enable input for buck 4. driving en4 high enables buck 4. 22 outs4 buck 4 voltage sense input 23 pg4 open-drain, active-high, power-good output for buck 4. to obtain a logic signal, pull up pg4 with an external resistor connected to a positive voltage equal to or lower than v a . 24 gnd analog ground 25 sync sync input. supply an external clock to control the switching frequency. connect sync to pgnd_ to use the default switching frequency. 26 v a analog voltage supply. connect a 1f or larger ceramic capacitor from v a to gnd as close as possible to the device. connect to the same supply as pv_ inputs. 27 pg1 open-drain, active-high, power-good output for buck 1. to obtain a logic signal, pull up pg1 with an external resistor connected to a positive voltage equal to or lower than v a . 28 outs1 buck 1 voltage sense input ep exposed pad. connect the exposed pad to ground. connecting the exposed pad to ground does not remove the requirement for proper ground connections to pgnd1Cpgnd4 and gnd. the exposed pad is attached with epoxy to the substrate of the die, making it an excellent path to remove heat from the ic. MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 10 figure 1. internal block diagram control logic peak current comp pv1 pgnd1 current-sense amp pv1pv4 lx1lx4 pgnd1 pgnd4 pg1 v a pg2 pg3 pg4 gnd outs1 outs4 sync en1 en2 en3 en4 sel clk clk180 pwm comp clk180 clk soft -start generato r feedback select osc MAX20021 p1-ok v ref v ref sel p-ok[1:4] va lley current lim comp ramp generato r v ref pv1 pgnd1 v ref uvlo volta ge reference trimbits otp main control logic v a MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 11 detailed description the MAX20021/max20022 pmics offer four, high- efficiency, synchronous step-down converters that oper - ate with a 3.0v to 5.5v input voltage range and provide a 1.0v to 4.0v output voltage range. the pmics deliver up to 1.0a of load current per output. the pmics achieve 3% output error over load, line, and temperature ranges. the pmics feature fixed-frequency pwm-mode operation with a 2.2mhz or 3.2mhz switching frequency. an optional spread-spectrum frequency modulation minimizes radiated electromagnetic emissions due to the switching frequency, while a factory-programmable synchronization input (sync) allows the device to synchronize to an external clock. integrated low r dson switches help minimize efficien - cy losses at heavy loads and reduce critical/parasitic inductance, making the layout a much simpler task with respect to discrete solutions. the pmics are offered in factory-preset output voltages to allow customers to achieve 3% output-voltage accuracy, without using expensive 0.1% resistors. in addition, adjust - able output-voltage versions can be set to any desired values between 1.0v and 4.0v using an external resistive divider. see the selector guide for available options. additionally, each converter features soft-start, pg_ output, overcurrent, and overtemperature protections (see figure 1). control scheme the pmics use peak current-mode control. the devices feature internal slope compensation and internal loop compensation, both of which reduce board space and allow a very compact solution. hybrid load-line architecture t he pmics feature hybrid load-line architecture to reduce the output capacitance needed, potentially saving system cost and size. this results in a measurable load transient response. input overvoltage monitoring (ov) the pmics feature an input overvoltage-monitoring circuit on the input supply. when the input exceeds 5.8v (typ) all power-good indicators (pg_) go low. when the input supply returns to within the operating range of 5.7v (typ) or less during the timeout period, the power-good indica - tors go high. input undervoltage monitoring (uvm) the MAX20021 features an input undervoltage monitor - ing circuit on the input supply. when the input drops below 4.3v (typ), all power-good indicators (pg_) go low to indi - cate a potential brownout condition. the device remains operational down to the uvlo threshold. when the input voltage exceeds the uv threshold above 4.4v (typ), pg_ remains low for the factory-trimmed active timeout period. uvm is a factory-selectable option. input undervoltage lockout (uvlo) the pmics feature an undervoltage lockout on the pv_ inputs set at 2.77v (typ) falling. this prevents loss of con - trol of the device by shutting down all outputs. this circuit is only active when at least one buck converter is enabled. power-good outputs (pg_) the pmics feature an open-drain power-good output for each of the four buck regulators. pg_ asserts low when the output voltage drops 6% below the regulated voltage or 10% above the regulated voltage for approximately 15s. pg_ remains asserted for a fixed 20,480 switching cycles after the output returns to its regulated voltage. pg_ asserts low during soft-start and in shutdown. pg_ becomes high impedance when buck_ is in regulation. connect pg_ to a logic supply with a 10k resistor. soft-start the pmics include a 3272 switching cycle fixed-duration soft-start time. the soft-start time limits startup inrush current by forcing the output voltage to ramp up towards its regulation point. during soft-start, the converters oper - ate in skip mode to prevent the outputs from discharging. when the pmics exit uvlo or thermal shutdown, there is a fixed blanking time for en2Cen4 to prevent all four outputs from going through soft-start at the same time. after 24,576 switching cycles with uvlo high and at least one buck converter enabled, there is no blanking time between en2Cen4 high and the start of soft-start. figure 2. load transient response +5.0% +1.5% 0% -1.0% -3.5% 1.0a 0a 4s 1 s1 s 4s MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 12 output 3 voltage select (sel) the MAX20021 offers a sel input to allow selection of the out3 voltage. for fixed output versions, connect sel to pgnd_ for a 1.8v output or to pv_ for a 2.65v output. there is no soft transition between the two output-voltage settings, so sel should not be toggled during normal operation. for the max20022, connect sel to pgnd_ or leave unconnected. spread-spectrum option the pmics feature a linear spread-spectrum (ss) opera - tion, which varies the internal operating frequency between f sw and (f sw + 3%). the internal oscillator is frequency modulated at a rate of 1.5khz with a frequency deviation of 3% (see figure 4). this function does not apply to an oscillation frequency applied externally through the sync pin. spread spectrum is a factory-selectable option. see the selector guide for available options. synchronization (sync) the pmics feature a sync input to allow the internal oscillator to synchronize with an external clock. sync accepts signal frequencies in the range of 1.7mhz < f sync < 2.5mhz (2.2mhz option), or 2.7mhz < f sync < 3.5mhz (3.2mhz option). connect to pgnd_ if the sync feature is not used. current limit /short-circuit protection the pmics offer a current-limit feature that protects the devices against short-circuit and overload conditions on each output. in the event of a short-circuit or overload condition at an output, the high-side mosfet remains on until the inductor current reaches the high-side mosfets current-limit threshold. the converter then turns on the low-side mosfet and the inductor current ramps down. the converter allows the high-side mosfet to turn on only when the inductor current ramps down to the low- side mosfets current threshold. this cycle repeats until the short or overload condition is removed. overtemperature protection thermal-overload protection limits the total power dissipa - tion in the pmics. when the junction temperature exceeds 185oc (typ), an internal thermal sensor shuts down the step-down converters, allowing the ic to cool. the thermal sensor turns on the ic again after the junction temperature cools by 15oc. the ic goes through a standard power-up sequence as defined in the soft-start section. applications information adjustable output-voltage option the max20022 features adjustable output voltages (see the selector guide for more details), which allows the cus - tomer to set the outputs to any voltage between 1.0v and v pv_ - 0.5v (up to 4.0v). connect a resistive divider from output (v out_ ) to outs_ to gnd to set the output volt - age (see figure 5). select r2 (outs_ to the gnd resis - tor) less than or equal to 100k. calculate r1 (v out_ to the outs_ resistor) with the following equation: out_ outs_ v r1 r2 1 v ?? ?? ?? ?? = ? ?? ?? ?? ?? where v outs_ = 1000mv (see the electrical characteristics table). the output voltage is nominal at 50% load current. figure 3. power-up soft-start delays figure 4. effect of spread-spectrum on internal oscillator uvlo en1?en4 out1 out2 out3 out4 8192 cycles 16,384 cycles 24,576 cycles 3272 cycles 3272 cycles 3272 cycles f sw + 3% f sw tt + 667s time t + 1.334ms internal oscilla to r frequency MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 13 the external feedback resistive divider must be frequency compensated for proper operation. place a capacitor across r1 in the resistive divider network. use the follow - ing equation to dete rmine the value of the capacitor: r2 r2 i f 1, c 1 c r1 r1 else c1 c, where c 15pf ?? >= ?? ?? = = connect outs_ to v out_ for a fixed 1.0v output voltage. inductor selection the pmic s are optimized for use with a 1.5h inductor for 2.2mhz and 3.2mhz opera tion. chip inductors can be used for additional board-space savings. input capacitor the pmics are designed to operate with a single 2.2f ceramic bypass capacitor on each pv_ input. phase interleaving of the four buck converters contributes to a lower required input capacitance by canceling input ripple currents. place the bypass capacitors as close as possible to their corresponding pv_ input to ensure the best emi and jitter performance. output capacitor all outputs of the pmics are optimiz ed for use with a 10 ff x7r ceramic capacitor. additional output capacitance can be used if better voltage ripple or load transient response is required. due to the soft-start sequence, the device is unable to drive arbitrarily large output ca pacitors. thermal considerations how much power the package can dissipate strongly depends on the mounting method of the ic to the pcb and the copper area for cooling. using the jedec test standard, the maximum power dissipation allowed is 2285mw in the tqfn package. more power dissipation can be handled by the package if great attention is given during pcb layout. for example, using the top and bottom copper as a heatsink and connecting the thermal vias to one of the middle layers (gnd) transfers the heat from the package into the board more efficiently, resulting in lower junction temperature at high power dissipation in some pmic applications. furthermore, the solder mask around the ic area on both top and bottom layers can be removed to radiate the heat directly into the air. the maximum allowable power dissipation in the ic is as follows: ( ) ? = + where t j(max) is the maximum junction temperature (+150oc), t a is the ambient air temperature, b jc (3oc/w for the 28-pin tqfn) is the thermal resistance from the junction to the case, and ca is the thermal resistance from the case to the surrounding air through the pcb, copper traces, and the package materials. ca is directly related to system-level variables and can be modified to increase the maximum power dissipation. the tqfn package has an exposed thermal pad on its underside. this pad provides a low thermal-resistance path for heat transfer into the pcb. this low thermally resistive path carries a majority of the heat away from the ic. the pcb is effectively a heatsink for the ic. the exposed pad should be connected to a large ground plane for proper thermal and electrical performance. the minimum size of the ground plane is dependent upon many system vari - ables. to create an efficient path, the exposed pad should be soldered to a thermal landing, which is connected to the ground plane by thermal vias. the thermal landing should be at least as large as the exposed pad and can be made larger depending on the amount of free space from the exposed pad to the other pin landings. a sample lay - out is available on the max20022 evaluation kit to speed designs. pcb layout guidelines careful pcb layout is critical to achieve low switching losses and clean, stable operation. use a multilayer board whenever possible for better noise immunity and power dissipation. follow these guidelines for good pcb layout: 1) use a large contiguous copper plane under the pmic packages. ensure that all heat-dissipating components have adequate cooling. 2) keep the high-current paths short, especially at the ground terminals. this practice is essential for stable, jitterCfree operation. the high current path comprising of input capacitor, inductor, and the output capacitor should be as short as possible. figure 5. adjustable output-voltage configuration max20022 v out_ r1 c1 outs_ r2 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 14 3) keep the power traces and load connections short. this practice is essential for high efficiency. use thick copper pcbs (2oz vs. 1oz) to enhance full-load efficiency. 4) use a single ground plane to reduce the chance of ground potential differences. with a single ground plane, enough isolation between analog return signals and high-power signals must be main tained. typical operating circuit pgnd1 lx1 outs1 control 10f 1.5h 5v 3.3v MAX20021 2.2f step-down pwm out1 1.0v to 4.0v 1.0a sync ss osc pv1 en en4 sel en3 en2 en1 pg1 pg2 pg3 pg4 v out1 10k? v out1 10k? 1f v a gnd 5v pgnd2 lx2 outs2 10f 1.5h 5v 1.25v 2.2f step-down pwm out2 1.0v to 4.0v 500ma pv2 en pgnd4 lx4 outs4 10f 1.5h 5v 1.8v 2.2f step-down pwm out4 1.0v to 4.0v 1.0a pv4 en pgnd3 lx3 outs3 10f 1.5h 5v 2.2f step-down pwm out3 1.0v to 4.0v 500ma pv3 en ep 2.65v or 1.8v MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
maxim integrated 15 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. note: insert the desired suffix letter (from the selector guide ) into the blank area "_" to indicate factory-selectable features. /v denotes an automotive qualified part that conforms to aec-q100. + denotes a lead(pb)-free/rohs-compliant package. *ep = exposed pad. ordering information selector guide* * contact factory for options that are not included. factory-selectable features include: dc-dc voltages in 100mv steps between 1.0v and 4.0v. spread spectrum enabled or disabled. uvm enabled or disabled. number of cycles in active timeout period independent current limit for each channel up to 1a. part frequency temp range pin-package MAX20021 ati_ / v+ 3.2mhz -40oc to +125oc 28 tqfn-ep* max20022 ati_ / v+ 2.2mhz -40oc to +125oc 28 tqfn-ep* package type package code outline no. land pattern no. 28 tqfn-ep t2855+5 21-0140 90-0025 part current configuration dc-dc1 dc-dc2 dc-dc3 dc-dc4 spread spectrum frequency (mhz) uvm active timeout period (cycles) ch1 ch2 ch3 ch4 v out (v) MAX20021 MAX20021atia/v+ 1.0a 0.5a 0.5a 1.0a 3.30 1.25 2.65/1.80 1.80 disabled 3.2mhz enabled 20,480 MAX20021atib/v+ 1.0a 0.5a 0.5a 1.0a 3.30 1.25 2.65/1.80 1.80 enabled 3.2mhz enabled 20,480 max20022 max20022atia+ 1.0a 1.0a 1.0a 1.0a adjustable adjustable adjustable adjustable disabled 2.2mhz disabled 256 max20022atia/v+ 1.0a 1.0a 1.0a 1.0a adjustable adjustable adjustable adjustable disabled 2.2mhz disabled 256 max20022atib+ 1.0a 1.0a 1.0a 1.0a adjustable adjustable adjustable adjustable enabled 2.2mhz disabled 256 max20022atib/v+ 1.0a 1.0a 1.0a 1.0a adjustable adjustable adjustable adjustable enabled 2.2mhz disabled 256 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters www.maximintegrated.com
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. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 16 ? 2013 maxim integrated products, inc. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. revision history revision number revision date description pages changed 0 3/13 initial release 1 4/13 removed future product reference for the max20022 15 2 12/13 added aec-q100 reference to ordering information 15 MAX20021/max20022 automotive quad, low-voltage step-down dc-dc converters

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