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general description the max4080/max4081 are high-side, current-sense amplifiers with an input voltage range that extends from 4.5v to 76v making them ideal for telecom, automotive, backplane, and other systems where high-voltage cur- rent monitoring is critical. the max4080 is designed for unidirectional current-sense applications and the max4081 allows bidirectional current sensing. the max4081 single output pin continuously monitors the transition from charge to discharge and avoids the need for a separate polarity output. the max4081 requires an external reference to set the zero-current output level (v sense = 0v). the charging current is rep- resented by an output voltage from v ref to v cc , while discharge current is given from v ref to gnd. for maximum versatility, the 76v input voltage range applies independently to both supply voltage (v cc ) and common-mode input voltage (v rs+ ). high-side current monitoring does not interfere with the ground path of the load being measured, making the max4080/max4081 particularly useful in a wide range of high-voltage systems. the combination of three gain versions (5v/v, 20v/v, 60v/v = f, t, s suffix) and a user-selectable, external sense resistor sets the full-scale current reading and its proportional output voltage. the max4080/max4081 offer a high level of integration, resulting in a simple, accurate, and compact current-sense solution. the max4080/max4081 operate from a 4.5v to 76v sin- gle supply and draw only 75? of supply current. these devices are specified over the automotive operating temperature range (-40? to +125?) and are available in a space-saving 8-pin ?ax or so package. applications automotive (12v, 24v, or 42v batteries) 48v telecom and backplane current measurement bidirectional motor control power-management systems avalanche photodiode and pin-diode current monitoring general system/board-level current sensing precision high-voltage current sources features wide 4.5v to 76v input common-mode range bidirectional or unidirectional i sense low-cost, compact, current-sense solution three gain versions available 5v/v (max4080f/max4081f) 20v/v (max4080t/max4081t) 60v/v (max4080s/max4081s) 0.1% full-scale accuracy low 100 v input offset voltage independent operating supply voltage 75 a supply current (max4080) reference input for bidirectional out (max4081) available in a space-saving, 8-pin max package max4080/max4081 76v, high-side, current-sense amplifiers with voltage output ________________________________________________________________ maxim integrated products 1 n.c. out gnd 1 + 2 8 7 rs- n.c. v cc n.c. rs+ max/so top view 3 4 6 5 max4080 ref1b out gnd 1 2 8 7 rs- ref1a v cc n.c. rs+ max/so 3 4 6 5 max4081 + pin configurations ordering information 19-2562; rev 4; 7/11 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package max4080 faua+ -40 c to +125 c 8 ?ax max4080faua/v+ -40 c to +125 c 8 ?ax max4080fasa+ -40 c to +125 c 8 so max4080taua+ -40 c to +125 c 8 ?ax max4080taua/v+ -40 c to +125 c 8 ?ax max4080tasa+ -40 c to +125 c 8 so max4080saua+ -40 c to +125 c 8 ?ax max4080saua/v+ -40 c to +125 c 8 ?ax max4080sasa+ -40 c to +125 c 8 so selector guide appears at end of data sheet. ordering information continued at end of data sheet. + denotes a lead(pb)-free/rohs-compliant package. /v denotes an automotive qualified part. ?ax is a registered trademark of maxim integrated products, inc.
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc to gnd ............................................................-0.3v to +80v rs+, rs- to gnd....................................................-0.3v to +80v out to gnd.............-0.3v to the lesser of +18v or (v cc + 0.3v) ref1a, ref1b to gnd (max4081 only)....-0.3v to the lesser of +18v or (v cc + 0.3v) output short circuit to gnd.......................................continuous differential input voltage (v rs + - v rs -) ...............................?0v current into any pin..........................................................?0ma continuous power dissipation (t a = +70?) 8-pin ?ax (derate 4.5mw/? above +70?) .............362mw 8-pin so (derate 5.88mw/? above +70?)................471mw operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? dc electrical characteristics (v cc = v rs+ = 4.5v to 76v, v ref1a = v ref1b = 5v (max4081 only), v sense = (v rs+ - v rs- ) = 0v, r load = 100k ? , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units operating voltage range v cc inferred from psrr test 4.5 76 v common-mode range c mvr inferred from cmrr test (note 3) 4.5 76 v max4080 75 190 supply current i cc v cc = v rs+ = 76v, no load max4081 103 190 ? leakage current i rs+ , i rs- v cc = 0v, v rs+ = 76v 0.01 2 a input bias current i rs+ , i rs- v cc = v rs+ = 76v 5 12 a max4080f/max4081f 1000 max4080t/max4081t 250 full-scale sense voltage (note 4) v sense max4080s/max4081s 100 mv max4080f/max4081f 5 max4080t/max4081t 20 gain a v max4080s/max4081s 60 v/v t a = +25 c 0.1 0.6 t a = -40 c to +85 c 1 gain accuracy ? a v v cc = v rs+ = 48v (note 5) t a = t min to t max 1.2 % t a = +25? 0.1 0.6 t a = -40 c to +85 c 1 input offset voltage v os v cc = v rs+ = 48v (note 6) t a = t min to t max 1.2 mv common-mode rejection ratio cmrr v cc = 48v, v rs+ = 4.5v to 76v 100 124 db power-supply rejection ratio psrr v rs+ = 48v, v cc = 4.5v to 76v 100 122 db max4080f/max4081f, v sense = 1000mv max4080t/max4081t, v sense = 250mv out high voltage (v cc - v oh ) v cc = 4.5v, v rs+ = 48v, v ref1a = v ref1b = 2.5v, i out (sourcing) = +500? (note 8) max4080s/max4081s, v sense = 100mv 0.15 0.27 v
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output _______________________________________________________________________________________ 3 dc electrical characteristics (continued) (v cc = v rs+ = 4.5v to 76v, v ref1a = v ref1b = 5v (max4081 only), v sense = (v rs+ - v rs- ) = 0v, r load = 100k ? , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units i out (sinking) = 10? 4 15 out low voltage v ol v cc = v rs+ = 48v, v ref1a = v ref1b = 2.5v, v sense = -1000mv (for max4081 only) i out (sinking) = 100? 23 55 mv ref1a = ref1b input voltage range (max4081 only) (v ref - v gnd ) inferred from ref1a rejection ratio, v ref1a = v ref1b 1.5 6 v ref1a input voltage range (max4081 only) (v ref1a - v gnd ) inferred from ref1a rejection ratio, v ref1b = v gnd 312v ref1a rejection ratio (max4081 only) v cc = v rs+ = 48v, v sense = 0v, v ref1a = v ref1b = 1.5v to 6v 80 108 db ref/ref1a ratio (max4081 only) v ref1a = 10v, v ref1b = v gnd , v cc = v rs+ = 48v (note 2) 0.497 0.500 0.503 ref1a input impedance (max4081 only) v ref1b = v gnd 250 k ?
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output 4 _______________________________________________________________________________________ ac electrical characteristics (v cc = v rs+ = 4.5v to 76v, v ref1a = v ref1b = 5v (max4081 only), v sense = (v rs+ - v rs- ) = 0v, r load = 100k ? , c load = 20pf, t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol condition min typ max units max4080f/t/s 250 bandwidth bw v cc = v rs+ = 48v, v out = 2.5v max4081f/t/s 150 khz v sense = 10mv to 100mv 20 out settling time to 1% of final value v sense = 100mv to 10mv 20 ? capacitive-load stability no sustained oscillations 500 pf output resistance r out v sense = 100mv 0.1 ? power-up time v c c = v rs + = 48v , v s e ns e = 100mv ( note 9) 50 ? saturation recovery time (notes 9,10) 50 ? note 1: all devices are 100% production tested at t a = +25?. all temperature limits are guaranteed by design. note 2: v ref is defined as the average voltage of v ref1a and v ref1b . ref1b is usually connected to ref1a or gnd. v sense is defined as v rs+ - v rs- . note 3: the common-mode range at the low end of 4.5v applies to the most positive potential at rs+ or rs-. depending on the polarity of v sense and the device? gain, either rs+ or rs- can extend below 4.5v by the device? typical full-scale value of v sense . note 4: negative v sense applies to max4081 only. note 5: v sense is: max4080f, 10mv to 1000mv max4080t, 10mv to 250mv max4080s, 10mv to 100mv max4081f, -500mv to +500mv max4081t, -125mv to +125mv max4081s, -50mv to +50mv note 6: v os is extrapolated from the gain accuracy test for the max4080 and measured as (v out - v ref )/a v at v sense = 0v, for the max4081. note 7: v sense is: max4080f, 500mv max4080t, 125mv max4080s, 50mv max4081f/t/s, 0v v ref1b = v ref1a = 2.5v note 8: output voltage is internally clamped not to exceed 18v. note 9: output settles to within 1% of final value. note 10: the device will not experience phase reversal when overdriven.
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output _______________________________________________________________________________________ 5 0 20 15 10 5 30 25 35 -125 -75 -50 -25 -100 0 25 50 75 100 125 input offset voltage histogram max4080 toc01 input offset voltage ( v) percentage (%) input offset voltage vs. temperature max4080 toc02 -300 -250 -150 -200 0 50 -50 -100 300 100 150 200 250 input offset voltage ( v) -50 25 50 0 -25 75 100 125 150 temperature ( c) -0.5 -0.2 -0.3 -0.4 0 -0.1 0.4 0.3 0.2 0.1 0.5 -50 -25 0 25 50 75 100 125 gain accuracy vs. temperature max4080 toc03 temperature ( c) gain accuracy (%) gain accuracy vs. v cc max4080 toc04 v cc (v) gain accuracy (%) 64 52 40 28 16 -0.15 -0.10 -0.05 0 -0.20 476 v rs+ = 48v s version t version f version max4080 toc05 frequency (hz) common-mode rejection ratio (db) 100k 10k 1k 100 10 -120 -100 -110 -90 -80 -60 -70 -50 -40 -20 -30 -10 0 -130 11m max4081f/t/s common-mode rejection ratio vs. frequency max4080 toc06 frequency (hz) power-supply rejection ratio (db) 100k 10k 1k 100 10 -120 -100 -110 -90 -80 -60 -70 -50 -40 -20 -30 -10 0 -130 11m max4081f/t/s power-supply rejection ratio vs. frequency max4080 toc07 frequency (hz) reference rejection ratio (db) -110 -90 -100 -80 -60 -70 -50 -40 -20 -30 -10 0 -120 max4081f/t/s reference rejection ratio vs. frequency 10k 1k 100 10 1 100k max4080 toc08 frequency (khz) gain (db) 100 10 1 5 10 15 20 25 30 35 40 45 50 0 0.1 1000 max4080f/t/s small-signal gain vs. frequency v sense = 10mv max4080s max4080t max4080f max4080 toc09 frequency (khz) gain (db) 100 10 1 5 10 15 20 25 30 35 40 45 50 0 0.1 1000 max4081f/t/s small-signal gain vs. frequency v out = 100mv p-p max4081s max4081t max4081f typical operating characteristics (v cc = v rs+ = 48v, v sense = 0v, c load = 20pf, r load = , t a = +25?, unless otherwise noted.)
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output 6 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = v rs+ = 48v, v sense = 0v, c load = 20pf, r load = , t a = +25?, unless otherwise noted.) 60 65 75 70 80 85 428 16 40 52 64 76 max4080 supply current vs. v cc max4080 toc10 v cc (v) supply current ( a) no load v sense = 0v max4080 toc11 v cc (v) supply current ( a) 64 52 16 28 40 85 90 95 100 105 110 115 120 125 476 max4081 supply current vs. v cc v ref = 2.5v no load v sense = 0v 65 80 75 70 90 85 110 105 100 95 115 -50 -25 0 25 50 75 100 125 max4080 supply current vs. temperature max4080 toc12 temperature ( c) supply current ( a) 65 80 75 70 90 85 110 105 100 95 115 -50 -25 0 25 50 75 100 125 max4081 supply current vs. temperature max4080 toc13 temperature ( c) supply current ( a) v ref1a = v ref1b = 2.5v max4080 toc14 i out (sourcing) (ma) v out high voltage (v cc - v oh ) (v) 0.9 0.8 0.6 0.7 0.2 0.3 0.4 0.5 0.1 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0 0 1.0 v out high voltage vs. i out (sourcing) v cc = 4.5v t a = +125 c t a = +85 c t a = +25 c t a = 0 c t a = -40 c 450 400 350 300 250 200 150 100 50 50 100 150 200 250 300 0 0500 v out low voltage vs. i out (sinking) max4080 toc15 i out (sinking) ( a) v out low voltage (mv) t a = +125 c t a = +85 c t a = +25 c t a = 0 c t a = -40 c v cc = 4.5v max4080 toc16 input 5mv/div output 25mv/div 20 s/div max4080f small-signal transient response max4080 toc17 input 5mv/div output 100mv/div 20 s/div max4080t small-signal transient response max4080 toc18 input 5mv/div output 300mv/div 20 s/div max4080s small-signal transient response
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output _______________________________________________________________________________________ 7 max4080 toc19 input 10mv/div output 50mv/div 20 s/div max4081f small-signal transient response max4080 toc20 input 2.5mv/div output 50mv/div 20 s/div max4081t small-signal transient response max4080 toc21 input 1mv/div output 50mv/div 20 s/div max4081s small-signal transient response max4080 toc22 input 400mv/div output 2v/div 20 s/div max4080f large-signal transient response max4080 toc23 input 100mv/div output 2v/div 20 s/div max4080t large-signal transient response max4080 toc24 input 33mv/div output 2v/div 20 s/div max4080s large-signal transient response max4080 toc25 input 400mv/div output 2v/div 20 s/div max4081f large-signal transient response max4080 toc26 input 100mv/div output 2v/div 20 s/div max4081t large-signal transient response max4080 toc27 input 33mv/div output 2v/div 20 s/div max4081s large-signal transient response typical operating characteristics (continued) (v cc = v rs+ = 48v, v sense = 0v, c load = 20pf, r load = , t a = +25?, unless otherwise noted.)
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output 8 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = v rs+ = 48v, v sense = 0v, c load = 20pf, r load = , t a = +25?, unless otherwise noted.) max4080 toc28 4 s/div v cc -transient response v cc 5v/div v out 1v/div v rs+ = 20v v cc = 20v step v ref1 = v ref2 = 2.5v v cc = 40v v cc = 20v max4080 toc29 input 500mv/div output 2v/div 20 s/div max4080f saturation recovery response (v cc = 4.5v) max4080 toc30 v cc (0 to 10v) 5v/div output 2.5v/div 100 s/div max4080t startup delay (v sense = 250mv)
detailed description the max4080/max4081 unidirectional and bidirectional high-side, current-sense amplifiers feature a 4.5v to 76v input common-mode range that is independent of supply voltage. this feature allows the monitoring of current out of a battery as low as 4.5v and also enables high-side current sensing at voltages greater than the supply voltage (v cc ). the max4080/max4081 monitors current through a current-sense resistor and amplifies the voltage across the resistor. the max4080 senses current unidirectionally, while the max4081 senses cur- rent bidirectionally. the 76v input voltage range of the max4080/max4081 applies independently to both supply voltage (v cc ) and common-mode, input-sense voltage (v rs+ ). high- side current monitoring does not interfere with the ground path of the load being measured, making the max4080/max4081 particularly useful in a wide range of high-voltage systems. battery-powered systems require a precise bidirectional current-sense amplifier to accurately monitor the bat- tery? charge and discharge. the max4081 charging current is represented by an output voltage from v ref to v cc , while discharge current is given from v ref to gnd. measurements of out with respect to v ref yield a positive and negative voltage during charge and dis- charge, as illustrated in figure 1 for the max4081t. current monitoring the max4080 operates as follows: current from the source flows through r sense to the load (figure 2), cre- ating a sense voltage, v sense . since the internal-sense amplifier? inverting input has high impedance, negligible current flows through rg2 (neglecting the input bias current). therefore, the sense amplifier? inverting input voltage equals v source - (i load )(r sense ). the ampli- fier? open-loop gain forces its noninverting input to the same voltage as the inverting input. therefore, the drop across rg1 equals v sense . the internal current mirror multiplies i rg1 by a current gain factor, , to give i a2 = irg1. amplifier a2 is used to convert the output current to a voltage and then sent through amplifier a3. total gain = 5v/v for max4080f, 20v/v for the max4080t, and 60v/v for the max4080s. the max4081 input stage differs slightly from the max4080 (figure 3). its topology allows for monitoring of bidirectional currents through the sense resistor. when current flows from rs+ to rs-, the max4081 matches the voltage drop across the external sense resistor, r sense , by increasing the current through the q1 and rg1. in this way, the voltages at the input ter- minals of the internal amplifier a1 are kept constant and an accurate measurement of the sense voltage is achieved. in the following amplifier stages of the max4081, the output signal of amplifier a2 is level- shifted to the reference voltage (v ref = v ref1a = v ref1b ), resulting in a voltage at the output pin (out) max4080/max4081 76v, high-side, current-sense amplifiers with voltage output _______________________________________________________________________________________ 9 pin description pin max4080 max4081 name function 1 1 rs+ power connection to the external-sense resistor. 22 v cc supply voltage input. decouple v cc to gnd with at least a 0.1? capacitor to bypass line transients. 3, 6, 7 3 n.c. no connection. no internal connection. leave open or connect to ground. 4 4 gnd ground 5 5 out voltage output. for the unidirectional max4080, v out is proportional to v sense . for the bidirectional max4081, the difference voltage (v out - v ref ) is proportional to v sense and indicates the correct polarity. 8 8 rs- load connection to the external sense resistor. 6 ref1b reference voltage input: connect ref1b to ref1a or to gnd (see the external reference section). 7 ref1a reference voltage input: connect ref1a and ref1b to a fixed reference voltage (v ref ). v out is equal to v ref when v sense is zero (see the external reference section).
max4080/max4081 that swings above v ref voltage for positive-sense volt- ages and below v ref for negative-sense voltages. v out is equal to v ref when v sense is equal to zero. set the full-scale output range by selecting r sense and the appropriate gain version of the max4080/ max4081. 76v, high-side, current-sense amplifiers with voltage output 10 ______________________________________________________________________________________ max4081t v sense i charge i load r sense v cc gnd rs+ rs- out ref1a ref1b 5v system load and charger battery v out = v gnd v out = 10v v ref1a = v ref1b = 5v discharge current 4.5v to 76v v out - v ref charge current 5v 10v -250mv 250mv -5v v sense figure 1. max4081t out transfer curve r sense v sense i load out r g1 r g2 rs- q1 rs+ current mirror a1 i a2 a3 a2 max4080 v sense r g1 r g2 v ref rs- ref1b out gnd ref1a q1 q2 rf 125k ? 125k ? rs+ current mirror current mirror a1 a2 max4081 figure 3. max4081 functional diagram figure 2. max4080 functional diagram note: for gain = 5 (f), r g1 = r g2 = 160k. for gain = 20 (t), r g1 = r g2 = 60k. for gain = 60 (s), r g1 = r g2 = 20k .
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output ______________________________________________________________________________________ 11 table 1. typical component values full-scale load current, i load (a) current-sense resistor (m ? ) gain (v/v) full-scale v sense (mv) max4081 full-scale output voltage (v out - v ref, v) 0.500 1000 5 ?00 ?.5 0.125 1000 20 ?25 ?.5 0.050 1000 60 ?0 ?.0 5.000 100 5 ?00 ?.5 1.250 100 20 ?25 ?.5 0.500 100 60 ?0 ?.0 50.000 10 5 ?00 ?.5 12.500 10 20 ?25 ?.5 5.000 10 60 ?0 ?.0 full-scale load current, i load (a) current-sense resistor (m ? ) gain (v/v) full-scale v sense (mv) max4080 full-scale output voltage (v) 1.000 1000 5 1000 5.0 0.250 1000 20 250 5.0 0.100 1000 60 100 6.0 10.000 100 5 1000 5.0 2.500 100 20 250 5.0 1.000 100 60 100 6.0 50.000 10 5 500 2.5 25.000 10 20 250 5.0 10.000 10 60 100 6.0 external references (max4081) for the bidirectional max4081, the v out reference level is controlled by ref1a and ref1b. v ref is defined as the average voltage of v ref1a and v ref1b . connect ref1a and ref1b to a low-noise, regulated voltage source to set the output reference level. in this mode, v out equals v ref1a when v sense equals zero (see figure 4). alternatively, connect ref1b to ground, and ref1a to a low-noise, regulated voltage source. in this case, the out- put reference level (v ref ) is equal to v ref1a divided by two. v out equals v ref1a /2 when v sense equals zero. in either mode, the output swings above the reference voltage for positive current-sensing (v rs+ > v rs- ). the output swings below the reference voltage for negative current-sensing (v rs+ < v rs- ). applications information recommended component values ideally, the maximum load current develops the full- scale sense voltage across the current-sense resistor. choose the gain needed to yield the maximum output voltage required for the application: v out = v sense a v where v sense is the full-scale sense voltage, 1000mv for gain of 5v/v, 250mv for gain of 20v/v, 100mv for gain of 60v/v, and a v is the gain of the device. in applications monitoring a high current, ensure that r sense is able to dissipate its own i 2 r loss. if the resis- tor? power dissipation is exceeded, its value may drift or it may fail altogether. the max4080/max4081 sense a wide variety of cur- rents with different sense-resistor values. table 1 lists common resistor values for typical operation.
max4080/max4081 the full-scale output voltage is v out = r sense i load (max) a v , for the max4080 and v out = v ref r sense i load(max) a v for the max4081. v sense(max) is 1000mv for the 5v/v gain version, 250mv for the 20v/v gain version, and 100mv for the 60v/v gain version. choosing the sense resistor choose r sense based on the following criteria: voltage loss: a high r sense value causes the power-source voltage to degrade through ir loss. for minimal voltage loss, use the lowest r sense value. accuracy: a high r sense value allows lower cur- rents to be measured more accurately. this is due to offsets becoming less significant when the sense voltage is larger. for best performance, select r sense to provide approximately 1000mv (gain of 5v/v), 250mv (gain of 20v/v), or 100mv (gain of 60v/v) of sense voltage for the full-scale current in each application. efficiency and power dissipation: at high current levels, the i 2 r losses in r sense can be significant. take this into consideration when choosing the resistor value and its power dissipation (wattage) rating. also, the sense resistor? value might drift if it is allowed to heat up excessively. inductance: keep inductance low if i sense has a large high-frequency component. wire-wound resis- tors have the highest inductance, while metal film is somewhat better. low-inductance, metal-film resis- tors are also available. instead of being spiral- wrapped around a core, as in metal-film or wire- wound resistors, they are a straight band of metal and are available in values under 1 ? . because of the high currents that flow through r sense , take care to eliminate parasitic trace resistance from causing errors in the sense voltage. either use a four- terminal current-sense resistor or use kelvin (force and sense) pc board layout techniques. dynamic range consideration although the max4081 have fully symmetrical bidirec- tional v sense input capability, the output voltage range is usually higher from ref to v cc and lower from ref to gnd (unless the supply voltage is at the lowest end of the operating range). therefore, the user must con- sider the dynamic range of current monitored in both directions and choose the supply voltage and the refer- ence voltage (ref) to make sure the output swing above and below ref is adequate to handle the swings without clipping or running out of headroom. power-supply bypassing and grounding for most applications, bypass v cc to gnd with a 0.1? ceramic capacitor. in many applications, v cc can be connected to one of the current monitor terminals (rs+ or rs-). because v cc is independent of the monitored voltage, v cc can be connected to a separate regulated supply. if v cc will be subject to fast-line transients, a series resistor can be added to the power-supply line of the max4080/max4081 to minimize output disturbance. this resistance and the decoupling capacitor reduce the rise time of the transient. for most applications, 1k ? in conjunction with a 0.1? bypass capacitor work well. the max4080/max4081 require no special considera- tions with respect to layout or grounding. consideration should be given to minimizing errors due to the large charge and discharge currents in the system. 76v, high-side, current-sense amplifiers with voltage output 12 ______________________________________________________________________________________ max4081 r sense i load = 0 load v cc gnd rs- rs+ out ref1a ref1b 5v 5v 10v max4081 r sense i load = 0 load v cc gnd rs- rs+ out ref1a ref1b 5v figure 4. max4081 reference inputs
power management the bidirectional capability of the max4081 makes it an excellent candidate for use in smart battery packs. in the application diagram (figure 5), the max4081 moni- tors the charging current into the battery as well as the discharge current out of the battery. the microcon- troller stores this information, allowing the system to query the battery's status as needed to make system power-management decisions. max4080/max4081 76v, high-side, current-sense amplifiers with voltage output ______________________________________________________________________________________ 13 max4080 v cc = 4.5v to 76v r sense i sense system load v cc gnd rs- rs+ out typical operating circuit chip information process: bipolar selector guide max4081 r sense v cc gnd rs- rs+ out ref1a ref1b system power management and charger circuitry c 1.8v serial interface battery max1243 adc figure 5. max4081 used in smart-battery application part gain (v/v) i sense max4080faua 5 unidirectional max4080fasa 5 unidirectional max4080taua 20 unidirectional max4080tasa 20 unidirectional max4080saua 60 unidirectional max4080sasa 60 unidirectional max4081faua 5 bidirectional max4081fasa 5 bidirectional max4081taua 20 bidirectional max4081tasa 20 bidirectional max4081saua 60 bidirectional max4081sasa 60 bidirectional package type package code outline no. land pattern no. 8 ?ax u8+1 21-0036 90-0092 8 so s8+2 21-0041 90-0096 ordering information (continued) part temp range pin-package max4081 faua+ -40 c to +125 c 8 ?ax max4081fasa+ -40 c to +125 c 8 so max4081taua+ -40 c to +125 c 8 ?ax max4081tasa+ -40 c to +125 c 8 so max4081saua+ -40 c to +125 c 8 ?ax max4081sasa+ -40 c to +125 c 8 so + denotes a lead(pb)-free/rohs-compliant package. 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.
max4080/max4081 76v, high-side, current-sense amplifiers with voltage output maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 14 ____________________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 10/02 initial release 1 11/08 added values for rg1 and rg2 10 2 5/09 added lead-free and automotive parts to ordering information 1 3 5/10 removed automotive part and added soldering temperature 1, 2 4 7/11 added automotive part designation 1

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