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general description the max6791?ax6796 ultra-low-quiescent-current,single-/dual-output linear regulators are ideal for auto- motive applications. the devices offer a wide 5v to 72v operating input range, allowing them to withstand auto- motive load-dump conditions while consuming only 68?. the max6791?ax6794 are dual-output regula- tors capable of supplying up to 150ma per output. the max6795/max6796 offer a single output capable of delivering up to 300ma. these devices offer standard output-voltage options (5v, 3.3v, 2.5v, or 1.8v) and can be adjusted to any voltage from 1.8v to 11v. the max6791?ax6794 also offer a fixed 5v output. all devices feature a push-pull or open-drain, active-low reset output with a fixed output reset threshold that is 92.5%/87.5% of the regulator output out/out1. thereset output asserts low when out/out1 drops below the reset threshold and remains low for the fixed or capacitor-adjustable reset timeout period after out/out1 exceeds the reset threshold. the max6791?ax6796 provide a watchdog input that monitors a pulse train from the microprocessor (?) and generates reset pulses if the watchdog input remains high or low for a duration longer than the watchdog timeout period. all devices are available with either a fixed watchdog timeout period of 280ms (min) or a peri- od adjustable with an external capacitor. the max6791/max6792 feature a windowed watchdog timeout period with selectable window ratio. the watch- dog feature can be disabled. the max6791?ax6794 provide dual enable inputs (enable1 and enable2) that control each regulator independently. the single-output max6795/max6796 feature one enable input (enable). all devices include a hold input ( hold) that aids the implementation of a self-holding circuit without requir-ing external components. once the regulator is enabled, setting hold low forces the regulator to remain on even if enable/enable1 is subsequentlyset low. releasing hold shuts down the regulator. the max6791?ax6796 are available in a small, ther-mally enhanced tqfn package. the 5mm x 5mm package dissipates up to 2.7w, supporting continuous regulator operation during high ambient temperatures, high battery voltage, and high load-current conditions. the max6791?ax6796 are specified for a -40? to +125? operating temperature range. applications automotive features ? low 68 a quiescent current ? wide 5v to 72v supply voltage range ? output current single output up to 300ma dual outputs up to 150ma per output ? low dropout voltage 420mv (typ) at 100ma (single) 840mv (typ) at 100ma (dual) ? fixed output-voltage options: 5v, 3.3v, 2.5v, 1.8v, or adjustable output (from 1.8v to 11v) ? enable and hold functionality ? reset output: open drain or push-pull ? internally fixed (35 s, 3.125ms, 12.5ms, 50ms, or 200ms) or capacitor-adjustable reset timeout periods ? internally fixed or capacitor-adjustable watchdog timeout periods ? windowed (minimum/maximum) watchdog timer options (max6791/max6792) ? watchdog disable feature ? thermal, short-circuit, and output overvoltage protection ? fully specified from -40c to +125c ? small, thermally enhanced, 5mm x 5mm tqfn max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ _____________ maxim integrated products 1 ordering information 19-3875; rev 2; 10/11 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. + denotes lead-free package. for tape-and-reel, add a t after the ?.?tape-and-reel are offered in 2.5k increments. the first placeholder ??designates preset output-voltage option and preset reset threshold level; see table 1. the second placeholder ? ?designates the reset timeout period; see table 2. for example, the max6791tpsd3+ indicates a 3.3v output voltage with a reset threshold of 87.5% at nominal voltage and a 50ms reset timeout period. samples are generally held in stock. nonstandard versions require a 2.5k minimum order quantity. /v denotes an automotive-qualified part. *ep = exposed pad. evaluation kit available part temp range pin-package m a x6 7 9 1 tp _d _+ -40? to +125? 20 tqfn-ep* m a x6 7 9 2 tp _d _+ -40? to +125? 20 tqfn-ep* m a x6 7 9 3 tp _ d _+ -40? to +125? 20 tqfn-ep* m a x6 7 9 4 tp _ d _+ -40? to +125? 20 tqfn-ep* m a x6 7 9 5 tp _ d _+ -40? to +125? 20 tqfn-ep* m ax 6795tp _d _/v + -40? to +125? 20 tqfn-ep* m ax 6795tp s d 2/v + -40? to +125? 20 tqfn-ep* m a x6 7 9 6 tp _d _+ -40? to +125? 20 tqfn-ep* typical application circuit, pin configurations, and selector guide appear at end of data sheet. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 2 __________________________________________________ _____________________________________ absolute maximum ratings electrical characteristics (v in = 14v, c in = 1?, c out = 10?, t a = t j = -40? to +125?, unless otherwise noted. typical values are at t a = t j = +25?.) (note 1) stresses beyond those listed under ?bsolute 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. (all pins referenced to gnd, unless otherwise noted.) in to gnd ...............................................................-0.3v to +80v enable, enable1, enable2, pfi, gatep to gnd .........................................-0.3v to (v in + 0.3v) gatep to in ...........................................................-12v to +0.3v out, out1, out2, pfo , reset (open-drain versions), csrt, cswt .......................................................-0.3v to +12v hold , reset (push-pull versions), wdi, wds0, wds1, wd-dis, set, set1 ......................-0.3v to (v out/out1 + 0.3v) out, out1, out2 short circuit to gnd .....................continuous maximum current (all pins except in and out_)...............50ma continuous power dissipation (t a = +70?) 20-pin tqfn (derate 33.3mw/? above +70?) .....2666.7mw operating temperature range (t a ) ..................-40? to +125? junction temperature (t j ) .................................................150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? parameter smbol conditions min tp max units supply voltage range v in 5 72 v regulators on (i load = 0ma), v in = 8v 68 85 v in = 8v, i load = 300ma (max6795/max6796) 130 220 v in = 14v, i load = 100ma (max6795/max6796) 100 160 v in = 8v, i load1 = i load2 = 150ma (max6791Cmax6794) 130 220 regulators on, v out/out1 = v out2 = 5v v in = 14v, i load1 = i load2 = 50ma (max6791Cmax6794) 100 160 regulators on (i load = 0ma), v in = 42v 74 95 supply current i in regulators on (i load = 20ma, total) out1/out2/out = 5v, v in = 42v 100 170 a shutdown supply current i shdn regulators off, v in = 14v 27 45 a downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ____________________________________ 3 electrical characteristics (continued) (v in = 14v, c in = 1?, c out = 10?, t a = t j = -40? to +125?, unless otherwise noted. typical values are at t a = t j = +25?.) (note 1) parameter smbol conditions min tp max units l/m, i load = i load1 = 1ma 4.858 4.974 5.090 l/m, i load = 150ma (max6791Cmax6794), v in = 8v 4.811 4.945 5.078 l/m, i load = 300ma (max6795/max6796), v in = 8v 4.850 5 5.150 t/s, i load = i load1 = 1ma 3.206 3.282 3.360 t/s, i load = 150ma (max6791Cmax6794), v in = 6v 3.175 3.263 3.351 t/s, i load = 300ma (max6795/max6796), v in = 6v 3.201 3.3 3.399 z/y, i load = i load1 = 1ma 2.429 2.487 2.546 z/y, i load = 150ma (max6791Cmax6794), v in = 5.5v 2.405 2.472 2.539 z/y, i load = 300ma (max6795/max6796), v in = 5.5v 2.425 2.5 2.575 w/v, i load = i load1 = 1ma 1.748 1.791 1.832 w/v, i load = 150ma (max6791Cmax6794), v in = 5v 1.731 1.780 1.828 output voltage v out / v out1 w/v, i load = 300ma (max6795/max6796), v in = 5v 1.746 1.8 1.854 v i load2 = 1ma 4.858 4.974 5.090 output voltage (max6791Cmax6794) v out2 i load2 = 150ma 4.811 4.945 5.079 v set/set1 threshold voltage v set i load = i load1 = 1ma, v out/out1 = 5v 1.207 1.2315 1.256 v adjustable output voltage v out 1.8 11.0 v set/set1 rising 124 dual-mode? set threshold set/set1 falling 62 mv set/set1 input current set/set1 = 1v, v in = 11v -100 +100 na l/m, i load = 20ma (note 2) 84 130 l/m, i load = 300ma (note 2) 1200 1800 (max6795/ max6796) t/s, i load = 300ma (note 3) 1700 2400 l/m, i load = 150ma (note 2) 1000 1800 l/m, i load = 10ma (note 2) 84 130 dropout voltage v do (max6791C max6794) t/s, i load = 150ma (note 3) 1700 2400 mv max6795/max6796, inferred from dropout test 300 guaranteed output current (note 4) max6791Cmax6794, inferred from dropout test 150 ma dual mode is a trademark of maxim integrated products, inc. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 4 __________________________________________________ _____________________________________ electrical characteristics (continued) (v in = 14v, c in = 1?, c out = 10?, t a = t j = -40? to +125?, unless otherwise noted. typical values are at t a = t j = +25?.) (note 1) parameter smbol conditions min tp max units max6795/max6796, output shorted, v in = 6v 400 480 short-circuit output current limit (note 4) max6791Cmax6794, output shorted, v in = 6v 200 240 ma thermal-shutdown temperature +165 c thermal-shutdown hysteresis 20 c 8v v in 72v, i load = 1ma 1 line regulation 8v v in 72v, i load = 10ma 1 % of v out i out = 1ma to 300ma (max6795/max6796) 2 load regulation (note 5) i out = 1ma to 150ma (max6791Cmax6794) 1.5 % power-supply rejection ratio psrr i load = 10ma, f = 100hz, v in = 500mv p-p 69 db i load = 300ma, v out = 5v, v out = 90% of its nominal value 180 startup response time t start i load = 150ma, v out = 5v, v out1/out2 = 90% of its nominal value 360 s output overvoltage protection threshold ov th i sink = 1ma from out/out1/out2 1.05 x v out 1.1 x v out v output overvoltage protection sink current v out = v out (nominal) x 1.15 5 10 ma in to gatep clamp voltage i gatep = -100a, v in = 20v 13.8 16.3 18.8 v in to gatep drive voltage i gatep = 0a, v in = 20v 8 10 12 v enable/enable1/enable2/ hold input-voltage low v il 0.4 v enable/enable1/enable2/ hold input-voltage high v ih 1.4 v enable/enable1/enable2 input pulldown current enable is internally pulled down to gnd 0.5 a hold input pullup current hold is internally pulled to out/out1 2 a downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ____________________________________ 5 electrical characteristics (continued) (v in = 14v, c in = 1?, c out = 10?, t a = t j = -40? to +125?, unless otherwise noted. typical values are at t a = t j = +25?.) (note 1) parameter smbol conditions min tp max units reset output l 4.500 4.625 4.750 m 4.250 4.375 4.500 t 2.970 3.053 3.135 s 2.805 2.888 2.970 z 2.250 2.313 2.375 y 2.125 2.188 2.250 w 1.620 1.665 1.710 reset threshold (preset output voltage) set/set1 = gnd v 1.530 1.575 1.620 v l/t/z/w 0.90 x v out 0.925 x v out 0.95 x v out reset threshold (adjustable output voltage) m/s/y/v 0.85 x v out 0.875 x v out 0.90 x v out v out to reset delay v out1 /v out falling 35 s d0 35 s d1 2.187 3.125 4.063 d2 8.75 12.5 16.25 d3 35 50 65 reset timeout period (csrt = out/out1) t rp v out1 /v out rising d4 140 200 260 ms csrt ramp current 800 1000 1250 na csrt ramp threshold 1.185 1.218 1.255 v watchdog input cswt = out/out1 (fixed) 280.0 400.0 520.0 normal watchdog timeout period t wd2 cswt = 1500pf (adjustable) 170 236.2 290 ms cswt = out/out1 (fixed) 37.5 50.0 62.5 fast watchdog timeout period set ratio = 8 t wd1 cswt = 1500pf (adjustable) 21.95 29.52 36.90 ms cswt = out/out1 (fixed) 18.75 25.0 31.25 fast watchdog timeout period set ratio = 16 t wd1 cswt = 1500pf (adjustable) 10.80 14.76 18.45 ms cswt = out/out1 (fixed) 4.68 6.25 7.81 fast watchdog timeout period set ratio = 64 t wd1 cswt = 1500pf (adjustable) 2.52 3.69 4.62 ms fast watchdog minimum period t wd0 2000 ns cswt ramp current adjustable timeout 800 1000 1250 na cswt ramp threshold adjustable timeout 1.185 1.218 1.255 v undercurrent threshold for watchdog enable 7.0 10 13.8 ma undercurrent threshold for watchdog disable 3 5 7 ma downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 6 __________________________________________________ _____________________________________ electrical characteristics (continued) (v in = 14v, c in = 1?, c out = 10?, t a = t j = -40? to +125?, unless otherwise noted. typical values are at t a = t j = +25?.) (note 1) parameter smbol conditions min tp max units logic input (wds0, wds1, wd-dis, wdi) input-voltage low v il 0.4 v input-voltage high v ih 1.4 v input current inputs connected to out/out1 or gnd -100 +100 na power-fail comparator pfi threshold v pfi 1.199 1.231 1.263 v pfi hysteresis 0.5 % pfi input current v pfi = 14v -100 +100 na pfi to pfo delay (v pfi + 50mv) to (v pfi - 50mv) 35 s logic output ( reset , pfo ) i sink = 50a (output asserted) 0.3 output-voltage low (open drain or push-pull) v ol i sink = 3.2ma (output asserted) 0.4 v v out 1.0v, i source = 10a (output not asserted) 0.8 x v out v out 1.5v, i source = 100a (output not asserted) 0.8 x v out output-voltage high (push-pull) v oh v out 2.2v, i source = 500a (output not asserted) 0.8 x v out v open-drain leakage v reset = v pfo = 12v (output not asserted) 100 na note 1: all devices are 100% production tested at t j = +25? and +125?. limits at -40? are guaranteed by design. note 2: dropout voltage is defined as (v in - v out ) when v out is 98% of v out for v in = 8v. note 3: dropout voltage is defined as (v in - v out ) when v out is 98% of v out for v in = 6v. note 4: operation beyond the absolute maximum power dissipation is not guaranteed and may damage the part. note 5: test at v in = 8v (l/m), v in = 6v (t/s), v in = 5v (z/y/w/v). downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions _______________________________________________________________________________________ 7 40 5045 6055 65 70 75 80 53 5 4 5 15 25 55 65 75 supply current vs. supply voltage max6791-96 toc01 supply voltage (v) supply current ( a) max6791no load 50 60 8070 90 100 110 120 -40 -10 5 20 35 -25 50 65 80 110 95 125 supply current vs. temperature max6791 toc02 temperature ( c) supply current ( a) i load = 100ma i load = 50ma i load = 1ma i load = 0a max6791 10 2015 3025 35 40 53 5 4 5 15 25 55 65 75 shutdown supply current vs. supply voltage max6791-96toc03 supply voltage (v) supply current ( a) max6793/max6794 20 25 3530 40 -40 -10 5 20 35 -25 50 65 80 110 95 125 shutdown supply current vs. temperature max6791toc04 temperature ( c) shutdown supply current ( a) max6795v in = 14v 0.980 0.990 1.0101.000 1.020 -40 -10 5 20 35 -25 50 65 80 110 95 125 normalized reset threshold vs. temperature max6791toc05 temperature ( c) normalized reset threshold max6796 0 400 1200 800 1600 200 1000 600 1400 -40 -10 5 20 35 -25 50 65 80 110 95 125 dropout voltage vs. temperature max6791toc06 temperature ( c) dropout voltage (mv) max6792v out = 5v i load = 100ma i load = 150ma i load = 10ma 0 600 16001200 2000 200 800400 14001000 1800 -40 -10 5 20 35 -25 50 65 80 110 95 125 dropout voltage vs. temperature max6791toc07 temperature ( c) dropout voltage (mv) max6796 i load = 10ma i load = 150ma i load = 100ma i load = 300ma 4.980 4.9834.981 4.9874.985 4.9894.982 4.9864.984 4.988 4.990 53 5 4 5 15 25 55 65 75 output voltage vs. input voltage max6791-96toc08 input voltage (v) output voltage (v) max6795preset voltage, no load output voltage vs. load current max6791-96 toc09 load current (ma) v out (v) 250 200 50 100 150 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.02.0 03 0 0 max6796v in = 14v v out = 5v v out = 3.3v set externally typical operating characteristics (v in = v en = 14v, c in = 0.1?, c out = 10?, t j = t a = +25?, unless otherwise noted.) downloaded from: http:///
typical operating characteristics (continued) (v in = v en = 14v, c in = 0.1?, c out = 10?, t j = t a = +25?, unless otherwise noted.) max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 8 __________________________________________________ _____________________________________ 0.98 1.01 1.030.99 1.021.00 -40 -10 5 20 35 -25 50 65 80 110 95 125 normalized reset timeout period vs. temperature max6791toc10 temperature ( c) normalized reset timeout period max6796 -40-80 10 100 1k 100k psrr vs. frequency -75 -65 -55-70 -60 -50 -45 max6791toc11 frequency (hz) psrr (db) 10k v in = 6v v out = 1.8v i load = 10ma 0.980 0.995 1.0200.985 1.0000.990 1.0101.005 1.015 -40 -10 5 20 35 -25 50 65 80 110 95 125 normalized watchdog timeout period vs. temperature max6791toc12 temperature ( c) normalized watchdog timeout period max6796 0.995 0.998 1.0010.996 0.9990.997 1.000 -40 -10 5 20 35 -25 50 65 80 110 95 125 normalized pfi threshold vs. temperature max6791toc13 temperature ( c) normalized pfi threshold max6796 0 1.50.5 3.52.5 4.51.0 3.02.0 4.0 5.0 06 8 2 4 10 12 14 reset output vs. source current max6791-96toc14 source current (ma) reset output (v) max6796 reset output voltage vs. sink current max6791-96toc15 sink current (ma) reset output voltage (v) 9 8 6 7 2 3 4 5 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 01 0 max6796 downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions _______________________________________________________________________________________ 9 typical operating characteristics (continued) (v in = v en = 14v, c in = 0.1?, c out = 10?, t j = t a = +25?, unless otherwise noted.) 10,000 1000 100 10 1 0.1 0.0001 0.01 0.1 0.001 1 reset timeout period vs. c csrt max6791-96toc16 c csrt ( f) reset timeout period (ms) watchdog timeout period vs. c cswt max6791-96toc17 c cswt ( f) watchdog timeout period 0.01 0.001 10 100 1000 10,000 100,000 1 0.0001 0.1 load-transient response max6791-96toc18 out1 i out1 100ma/div1ma 1v/div 400 s/div max6796 c out = 10 f v out = 5v v in = 14v v out ac- coupled load-transient response max6791-96toc19 i out out 100ma/div1ma 500mv/div 400 s/div out ac-coupled max6796v in = 14v v out = 5v line-transient response max6791-96toc20 v in out 10v/div(ac-coupled) 20mv/div 1ms/div out ac-coupled max6796i load = 10ma downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 10 _________________________________________________ _____________________________________ pin description typical operating characteristics (continued) (v in = v en = 14v, c in = 0.1?, c out = 10?, t j = t a = +25?, unless otherwise noted.) load-transient response max6791-96toc21 out1 ac-coupled i out1 100ma/div1ma 500mv/div 1ms/div max6792v out1 = 5v c out = 10 f load-transient response max6791-96toc22 i out1 out1 ac-coupled 100ma/div20ma 500mv/div 1ms/div max6792v out1 = 5v c out = 10 f pin max6791/ max6792 max6793/ max6794 max6795/ max6796 name function 1, 2 1, 2 out1 regulator 1 output. fixed (+1.8v, +2.5v, +3.3v, or +5v) or adjustable (+1. 8v to +11v). v out1 = 150ma (max). connect a 10f (min) capacitor from out1 to gnd. 3 3 set1 feedback input for setting the out1 voltage. connect set1 to gnd to select the preset output voltage. connect to an external resistive divider f or adjustable output operation. 4 4 4 pfo active-low, open-drain, power-fail comparator output. pfo asserts low when pfi is below the internal 1.231v threshold. pfo deasserts when pfi is above the internal 1.231v threshold. 5 5 5 cswt watchdog timeout period adjust input. connect cswt to out1/out for the internally fixed watchdog timeout period. for adjustable watchdog timeout period, connect a capacitor from cswt to gnd. see the selecting watchdog timeot period section for more details. 6 6 6 csrt reset timeout period adjust input. connect csrt to out1/out for the internally fixed timeout period. for adjustable timeout, connect a capaci tor from csrt to gnd. see the reset otpt section for more details. 7 7 7 gnd ground 8 8 8 reset active-low reset output. reset remains low while out1/out is below the reset threshold. reset remains low for the duration of the reset timeout period after the reset conditions end. reset is available in push-pull and open-drain options. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 11 pin description (continued) pin max6791/ max6792 max6793/ max6794 max6795/ max6796 name function 9 wds1 10 wds0 min/max watchdog logic-select input. wds0 and wds1 select the watchdog window ratio or disable the watchdog timer. drive wds0 and wds1 high or low to select the desired ratio, see table 4. 11 11 11 wdi watchdog input. max6793Cmax6796: a falling or rising transition must occur on wdi within the selected watchdog timeout period or a reset pulse occurs. the watchdog timer clears when a transition occurs on wdi or whenever reset is asserted. max6791/max6792: wdi falling and rising transitions within periods shor ter than t wd1 or longer than t wd2 force reset to assert low for the reset timeout period. the watchdog timer begins to count after reset is deasserted. the watchdog timer clears when a valid transition occurs on wdi or whenever reset is asserted. connect wds0 high and wds1 low to disable the watchdog timer function. see the watchdog timer section. 12 12 12 hold active-low regulator hold input. when hold is forced low, out1/out remains on even if enable1/enable is pulled low. to shut down t he output of the regulator (out/out1), release hold after enable1/enable is pulled low. connect hold to out1/out or leave unconnected if unused. hold is internally connected to out/out1 through a 2a current source. 13, 14 13, 14 out2 regulator 2 output. out2 is a fixed +5v output. connect a 10f (min) capacitor from out2 to gnd. 15 15 enable2 active-high enable input 2. drive enable2 high to turn on out2. enabl e2 is internally connected to ground through a 0.5a current sink. 16 16 16 pfi adjustable power-fail comparator input. connect pfi to a resistive-divide r to set the desired pfi threshold. the pfi input is referenced to an accurate 1.231v threshold. 17, 18 17, 18 17, 18 in regulator inputs. bypass in with a 1f capacitor to gnd. 19 19 19 gatep pfet gate drive. connect gatep to the gate of a p-channel mosfet t o provide low drop reverse-battery voltage protection. 20 20 enable1 active-high enable input 1. drive enable1 high to turn on out1. enabl e1 is internally connected to ground through a 0.5a current sink. 9 9 wd-dis watchdog disable input. drive wd-dis low to disable the watchdog timer. drive wd-dis high or connect to out/out1 to enable the watchdog timer. the watchdog timer clears when reset asserts. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 12 _________________________________________________ _____________________________________ detailed description the max6791?ax6796 ultra-low-quiescent-current,single-/dual-output, high-input-voltage linear regulators operate from 5v to 72v. the max6791?ax6794 fea- ture dual regulators that deliver up to 150ma of load current per output. one output is available with preset output-voltage options (+1.8v, +2.5v, +3.3v, and +5.0v) and can be adjusted to any voltage between +1.8v to +11v using an external resistive-divider at set1. the other output provides a fixed 5v output volt- age. the max6795/max6796 feature a single regulator that delivers up to 300ma of current with preset output- voltage options (+1.8v, +2.5v, +3.3v, and +5.0v) or can be adjusted to any voltage between +1.8v to +11v. all devices include an integrated ? reset circuit with a fixed/adjustable reset and watchdog timeout period. the max6791?ax6796 monitor out/out1 and assert a reset output when the output falls below the reset threshold. regulators the single and dual regulators accept an input voltagefrom 5v to 72v. the max6791?ax6796 offer fixed preset output voltages of +1.8v, +2.5v, +3.3v, and +5v, or an adjustable output voltage of +1.8v to +11v, selected using an external resistive-divider network connected between out1/out, set1/set, and gnd (see figure 1). in addition to an adjustable output, the max6791?ax6794 feature a fixed 5v output voltage. reset output the reset output is typically connected to the resetinput of a ?. a ?? reset input starts or restarts the ? in a known state. the max6791?ax6796 supervisory circuits provide the reset logic output to prevent code- execution errors during power-up, power-down, and brownout conditions (see the typical application circuit ). reset changes from high to low whenever the monitored output voltage drops below the reset thresh-old voltage or the watchdog timeout expires. once the monitored voltage exceeds its respective reset thresh- old voltage, reset remains low for the reset timeout period, then goes high. pin description (continued) pin max6791/ max6792 max6793/ max6794 max6795/ max6796 name function 10 10, 13, 14, 15 n.c. not internally connected 1, 2 out regulator output. fixed +5v, +3.3v, +2.5v, +1.8v, or adjustab le output (+1.8v to +11v). connect a 10f (min) capacitor from out to gnd. 3 set feedback input for setting the out voltage. connect set to gnd to select the preset output voltage. connect to an external resistive-divider for adjustable output operation. 20 enable active-high enable input. drive enable high to turn on the regulator. enable is internally connected to gr ound through a 0.5a current sink. ep exposed pad. ep is internally connected to gnd. connect ep to the gr ound plane to provide a low thermal-resistance path from the ic junction to the pc board. do not use as the electrical connection to gnd. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 13 functional diagrams max6791/max6792 thermal protection control logic 1.23v 124mv out2out1 set1 reset csrt wdi cswt wds0 wds1 pfo gnd pfi 1.138v or 1.076v overcurrent protection reset timeout reset enable2 in gatep enable1 hold watchdog timeout downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 14 _________________________________________________ _____________________________________ functional diagrams (continued) max6793/max6794 thermal protection control logic 1.23v 124mv out2out1 set1 reset csrt wdi cswt wd-dis pfo gnd pfi 1.138v or 1.076v overcurrent protection reset timeout reset enable2 in gatep enable1 hold watchdog timeout downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 15 functional diagrams (continued) max6795/max6796 thermal protection control logic 1.23v 124mv outset reset csrt wdi cswt wd-dis pfo gnd pfi 1.138v or 1.076v overcurrent protection reset timeout reset in gatep enable hold watchdog timeout downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 16 _________________________________________________ _____________________________________ watchdog timer the max6791?ax6796 include a watchdog timerthat asserts reset if the watchdog input (wdi) does not toggle high to low or low to high within the watch-dog timeout period t wd (280ms min or externally adjustable). reset remains low for the fixed or user- adjustable reset timeout period, t rp . if the watchdog is not updated for lengthy periods of time, the reset out-put appears as a pulse train, asserted for t rp , deasserted for t wd , until wdi is toggled again. once reset asserts, it stays low for the entire reset timeout period ignoring any wdi transitions that may occur. toprevent the watchdog from asserting reset , toggle wdi with a valid rising or falling edge before t wd from the last edge. the watchdog counter clears when wditoggles prior to t wd from the last edge or when reset asserts. the watchdog resumes counting after reset deasserts.the max6791/max6792 have a windowed watchdog timer that asserts reset for the adjusted reset timeout period when the watchdog recognizes a fast watchdogfault (t wdi < t wd1 ), or a slow watchdog fault (t wdi > t wd2 ). the reset timeout period is adjusted indepen- dently of the watchdog timeout period. enable and hold inputs the max6791?ax6796 support two logic inputs,enable1/enable and hold , making these devices suitable for automotive applications. for example, whenthe ignition key signal drives enable1/enable high, the regulator turns on and remains on even if enable1/enable goes low, as long as hold is forced low and stays low after initial regulator power-up. in thisstate, releasing hold turns the regulator output (out/out1) off. this feature makes it possible to imple-ment a self-holding circuit without external components. forcing enable1/enable low and hold high or unconnected places the max6791?ax6796 into shut-down mode in which the max6791?ax6796 draw less than 27? of supply current. table 3 shows the state of the regulator output with respect to the voltage level at enable1/enable and hold . connect hold to out1/out or leave it uncon- nected to allow the enable1/enable input to act as astandard on/off switch for the regulator output (out/out1). power-fail comparator pfi is the noninverting input to a comparator. if pfi isless than v pfi (1.231v), pfo goes low. common uses for the power-fail comparator include monitoring the preregulated input of the power supply (such as a bat-tery) or providing an early power-fail warning so soft- ware can conduct an orderly system shutdown. set the power-fail threshold with a resistive-divider, as shown in figure 5. the typical comparator delay is 35? from pfi to pfo . connect pfi to gnd or in if unused. reverse-battery protection circuitry the max6791?ax6796 include an overvoltage pro-tection circuit that is capable of driving a p-channel mosfet to protect against reverse-battery conditions. this mosfet eliminates the need for external diodes, thus minimizing the input voltage drop. see the typical application circuit . the low p-channel mosfet on- resistance of 30m ? or less yields a forward-voltage drop of only a few millivolts versus hundreds of milli-volts for a diode, thus improving efficiency in battery- operated devices. connecting a positive battery voltage to the drain of q1 (see the typical application circuit ) forward biases its body diode. when the source voltage exceeds q1? threshold voltage, q1 turns on.once the fet is on, the battery is fully connected to the system and can deliver power to the device and the load. an incorrectly inserted battery reverse-biases the fet? body diode. the gate remains at the ground potential. the fet remains off and disconnects the reversed battery from the system. the internal zener diode and resistor combination at gatep prevent dam- age to the p-channel mosfet during an overvoltage condition. see the functional diagrams . thermal protection when the junction temperature exceeds t j = +165?, the internal protection circuit turns off the internal passtransistor and allows the ic to cool. the thermal sensor turns the pass transistor on again after the junction tem- perature drops to +145?, resulting in a cycled output during continuous thermal-overload conditions. thermal protection protects the max6791?ax6796 in the event of fault conditions. for continuous operation, do not exceed the absolute maximum junction temper- ature rating of +150?. proper soldering of package heatsink the max6791?ax6796 package features an exposedthermal pad on its underside that should be used as a heatsink. this pad lowers the package? thermal resis- tance by providing a direct heat-conduction path from the die to the pc board. connect the exposed pad and gnd to the system ground using a large pad or ground plane, or multiple vias to the ground plane layer. downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 17 applications information output voltage selection the max6791?ax6796 feature dual-mode operation:these devices operate in either a preset voltage mode or an adjustable mode. in preset voltage mode, internal trimmed feedback resistors set the internal linear regula- tor to +1.8v, +2.5v, +3.3v, or +5v (see the selector guide ). select preset voltage mode by connecting set1 (max6791?ax6794)/set(max6795/max6796) tognd. in adjustable mode, select an output voltage between +1.8v and +11v using two external resistors connected as a voltage-divider to set1/set (see figure 1). set the output voltage using the following equation: where v set = 1.2315v and r1, r2 200k ? . available output-current calculation the max6791?ax6794 provide up to 150ma per out-put, and the max6795/max6796 provide up to 300ma of load current. since the input voltage can be as high as +72v, package power dissipation limits the amount of output current available for a given input/output volt- age and ambient temperature. figure 2 shows the max- imum power-dissipation curve for the max6791 max6796. the graph assumes that the exposed metal pad of the device package is soldered to a solid 1in 2 section of pc board copper. use figure 2 to determinethe allowable package dissipation for a given ambient temperature. alternately, use the following formula to calculate the allowable package dissipation: pd max = maximum power dissipation pd max = 2.666w, for t a +70? pd max = [2.666w - 0.0333w x (t a - 70?)], for +70? < t a +125? where 0.0333w is the max6791?ax6796 packagethermal derating in w/? and t a is the ambient temper- ature in ?.after determining the allowable package dissipation, calculate the maximum output current using the follow- ing formula: pd = power dissipation pd < pd max where pd = [(in - out1) x i out1 ] + [(in - out2) x i out2 ], for max6791?ax6794. also, i out1 should be 150ma and i out2 should be 150ma in any case. pd < pd max where pd = [(in - out) x i out ], for max6795/max6796.also, i out should be 300ma in any case. selecting reset timeout period the reset timeout period is adjustable to accommodatea variety of ? applications. adjust the reset timeout period by connecting a capacitor between csrt and gnd. use the following formula to set the reset timeout period: where t rp is in seconds and c csrt is in farads. connect csrt to out1 (max6791?ax6794) or toout (max6795/max6796) to select an internally fixed timeout period. connect csrt to gnd to force reset low. c csrt must be a low-leakage (< 10na) type capacitor. ceramic capacitors are recommended; donot use capacitors lower than 100pf to avoid the influ- ence of parasitic capacitances. tc v a rp csrt . = ? ? ? ? ? ? 1 218 10 6 vv r r out set =+ ? ? ? ? ? ? 1 1 2 max6791?ax6796 v in r1r2 out1/out set1/set in gnd figure 1. setting the output voltage using a resistive-divider i out vs. (v in - v out ) (v in - v out ) (v) i out (ma) 70 75 60 50 40 30 20 10 50 100 150 200 250 300 350 0 0 +70 c +85 c +125 c v out = 1.8v safe operation region for each temperature point is under the curve figure 2. maximum power dissipation for max6791?ax6796 downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 18 _________________________________________________ _____________________________________ selecting watchdog timeout period the watchdog timeout period is adjustable to accommo-date a variety of ? applications. with this feature, the watchdog timeout can be optimized for software execu- tion. the programmer can determine how often the watchdog timer should be serviced. adjust the watch- dog timeout period (t wd ) by connecting a capacitor between cswt and gnd. for normal-mode operation,calculate the watchdog timeout capacitor as follows: where t wd is in seconds and c cswt is in farads. to select the internally fixed watchdog timeout periodfor the max6791?ax6794, connect cswt to out1. to select the internally fixed watchdog timeout period for the max6795/max6796, connect cswt to out. c cswt must be a low-leakage (< 10na) type capacitor. ceramic capacitors are recommended; do not usecapacitors lower than 100pf to avoid the influence of parasitic capacitances. the max6791/max6792 have a windowed watchdog timer that asserts reset for t rp when the watchdog recognizes a fast watchdog fault (time between transi-tions < t wd1 ), or a slow watchdog fault (time between transitions > t wd2 ). the reset timeout period is adjust- ed independently of the watchdog timeout period. theslow watchdog period, t wd2 , is calculated as follows: where t wd2 is in seconds and c cswt is in farads. the fast watchdog period, t wd1 , is selectable as a ratio from the slow watchdog fault period (t wd2 ). select the fast watchdog period by connecting wds0 and wds1 toout/out1 or gnd according to table 4, which illus- trates the settings for the 8, 16, and 64 window ratios (t wd2 /t wd1 ). for example, if c cswt is 2000pf, and wds0 and wds1 are low, then t wd2 is 318ms (typ) and t wd1 is 40ms (typ). reset asserts if the watchdog input has two edges too close to each other (faster than t wd1 ); or has edges that are too far apart (slower than t wd2 ). all wdi inputs are ignored while reset is asserted. the watchdog timer begins to count after reset is deasserted. if the time difference between two transi-tions on wdi is shorter than t wd1 or longer than t wd2 , reset is forced to assert low for the reset timeout peri- od. if the time difference between two transitions on wdiis between t wd1 (min) and t wd1 (max) or t wd2 (min) and t wd2 (max), reset is not guaranteed to assert or deassert; see figure 3. to guarantee that the windowwatchdog does not assert reset , strobe wdi between t wd1 (max) and t wd2 (min). the watchdog timer is cleared when reset is asserted. disable the watchdog timer by connecting wds0 high and wds1 low.there are several options available to disable the watchdog timer (for system development or test pur- poses or when the ? is in a low-power sleep mode). one way to disable the watchdog timer is to drive wd-dis low for the max6793?ax6796 and drive wds0 high and wds1 low for the max6791/max6792. this prevents the capacitor from ramping up. finally, reducing the out/out1 regulator current below the specified regulator current watchdog-disable threshold (3ma min) also disables the watchdog timer. the tc v a wd cswt 2 6 155 10 = ? ? ? ? ? ? tc v a wd cswt 2 6 155 10 = ? ? ? ? ? ? t wd1 t wd2 t wd0 min guaranteed to assert undetermined undetermined guaranteed to not assert guaranteed to assert fastfault normal operation slow fault reset:wdi input: max min max figure 3. windowed watchdog timing diagram downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 19 watchdog re-enables immediately when any of theseconditions are removed (as long as the reset is not asserted). note that the output current threshold limitincludes hysteresis so that output current must exceed 13.8ma (max) to reenable the watchdog timer. capacitor selection and regulator stability for stable operation over the full temperature rangeand with load currents up to 150ma, use a 10? (min) output capacitor with an esr < 0.5 ? . to reduce noise and improve load-transient response and power-supplyrejection, use larger output-capacitor values. some ceramic dielectrics exhibit large capacitance and esr variation with temperature. for these types of capaci- tors (such as z5u and y5v), much higher-value capaci- tors are required to maintain stability over the temperaure range. with x7r dielectrics, a 10? capaci- tor should be sufficient at all operating temperatures. to improve power-supply rejection and transient response, increase the capacitor between in and gnd. ensuring a valid reset output down to v in = 0v when v in falls below 1v, reset current-sinking capa- bilities decline drastically. high-impedance cmos-logic inputs connected to reset can drift to undetermined voltages. this presents no problems inmost applications, since most ?s and other circuitry do not operate with a supply voltage below 1v. in those applications where reset must be valid down to 0v, adding a pulldown resistor between reset and gnd sinks any stray leakage currents, holding reset low (figure 4). the value of the pulldown resistor is not criti-cal; 100k ? is large enough not to load reset and small enough to pull reset to ground. open-drain reset versions are not recommended for applications requiring valid logic for v in down to 0v. adding hysteresis to pfi the power-fail comparator has a typical input hystere-sis of 0.5% (of v th ). this is sufficient for most applica- tions where a power-supply line is being monitoredthrough an external resistive-divider (figure 5). figure 6 shows how to add hysteresis to the power-fail com- parator. select the ratio of r5 and r6 so pfi sees 1.23v when v in falls to the desired trip point (v trip ). since pfo is an open-drain output, resistors r7 and r8 add hysteresis. r7 typically is an order of magnitudegreater than r5 or r6. the current through r5 and r6 should be at least 10? to ensure that the 100na (max) pfi input current does not shift the trip point. r7 should be larger than 50k ? to prevent it from loading down the pfo . max6792max6794 max6796 v in reset in gnd figure 4. ensuring reset valid to v in = 0v max6791 v in v term r5r6 pfo pfi in gnd figure 5. setting power-fail comparator to monitor v in max6791 v in v term r5 r7 r8 r6 pfo pfi in gnd figure 6. adding hysteresis power-fail comparator downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 20 _________________________________________________ _____________________________________ use the following formulas to determine the high/lowthreshold levels and the hysteresis: v l-h = v pfi x (1 + r5 / r6 +r5 / r7) v h-l = v pfi x (1 + r5 / r6 ) + (v pfi - v term ) [r5 / (r7 + r8)]v hys = v pfi x (r5 / r7 ) - (v pfi - v term ) [r5 / (r7 + r8)]where v l-h is the threshold level for the monitored volt- age rising and v h-l is the threshold level for the moni- tored voltage falling. chip information process: bicmos table 2. preset timeout period part suffix (_) reset timeout period (nominal) d0 35? d1 3.125ms d2 12.5ms d3 50ms d4 200ms table 1. preset output voltage and reset threshold part suffix (_) output voltage (v) reset threshold (nominal) l 5.0 4.625 m 5.0 4.375 t 3.3 3.053 s 3.3 2.888 z 2.5 2.313 y 2.5 2.188 w 1.8 1.665 v 1.8 1.575 operating state enable1/ enable hold regulator 1 output comment initial state low don? care off enable/enable1 is pulled to gnd through internal pulldown.out/out1 is disabled. turn-on state high don? care on enable/enable1 is externally driven high turning out/out1on. hold is pulled up to out/out1. hold setup state high low on hold is externally pulled low while enable/enable1 remains high, and the regulator latches on. hold state low low on enable/enable1 is driven low (or allowed to float low by aninternal pulldown). hold remains externally pulled low keeping out/out1 on. off state low high off hold is driven high (or pulled high by the internal pullup) while enable/enable1 is low. out/out1 is turned off andenable/enable1 and hold logic returns to the initial state. table 3. enable/enable1 and hold truth table/state table downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 21 table 4. min/max watchdog setting wds0 wds1 ratio 00 8 01 1 6 1 0 watchdog disabled 11 6 4 part number output voltage (v) reset timeout period (ms) (nominal) reset threshold (v) (nominal) max6791tpld2+ 5.0 12.5 4.625 max6791tpsd2+ 3.3 12.5 2.888 max6792tpld2+ 5.0 12.5 4.625 max6792tpsd2+ 3.3 12.5 2.888 max6793tpld2+ 5.0 12.5 4.625 max6793tpsd2+ 3.3 12.5 2.888 max6794tpld2+ 5.0 12.5 4.625 max6794tpsd2+ 3.3 12.5 2.888 max6795tpld2+ 5.0 12.5 4.625 max6795tpsd2+ 3.3 12.5 2.888 max6796tpld2+ 5.0 12.5 4.625 max6796tpsd2+ 3.3 12.5 2.888 table 5. standard version part number part reset output number of outputs windowed watchdog timeout enable inputs watchdog disable input max6791tp_d_ open drain 2 ? dual ? max6792tp_d_ push-pull 2 ? dual ? max6793tp_d_ open drain 2 dual ? max6794tp_d_ push-pull 2 dual ? max6795tp_d_ open drain 1 single ? max6796tp_d_ push-pull 1 single ? + denotes lead-free package. selector guide downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 22 _________________________________________________ _____________________________________ typical application circuit max6791/max6792 in i/o c reset i/o enable1 12v batt pfi enable2 to other circuitry out2 wdi out1set1 int v cc cswtpfo in gatep hold wds1 wds0 xcvr txd v cc inh batt rxd canhcanl reset gnd csrt 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 per tains to the package regardless of rohs status. package type package code outline no. land pattern no. 20 tqfn-ep t2055+4 21-0140 90-0009 downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions ___________________________________________________ ___________________________________ 23 max6791/max6792 thin qfn 5mm x 5mm top view 1920 18 17 76 8 out1 pfo cswt 9 out1 out2hold wdi enable2 1 + 2 in 45 15 14 12 11 gatep enable1 wds1reset gnd csrt set1 out2 3 13 in 16 10 wds0 pfi top view top view max6793/max6794 thin qfn 5mm x 5mm 1920 18 17 76 8 out1 pfo cswt 9 out1 out2hold wdi enable2 1 + 2 in 45 15 14 12 11 gatep enable1 wd-disreset gnd csrt set1 out2 3 13 in 16 10 n.c. pfi max6795/max6796 thin qfn 5mm x 5mm 1920 18 17 76 8 out pfo cswt 9 out n.c.hold wdi n.c. 1 + 2 in 45 15 14 12 11 gatep enable wd-disreset gnd csrt set n.c. 3 13 in 16 10 n.c. pfi pin configurations downloaded from: http:///
max6791?ax6796 high-voltage, micropower, single/dual linear regulators with supervisory functions 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. 24 ____________________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 10/05 initial release 1 8/06 correct text in data sheet. 10, 11, 18, 19 2 10/11 added /v automotive-qualified part to data sheet 1 downloaded from: http:///

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