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general description the max44285 dual-channel high-side current-sense amplifier has precision accuracy specifications of v os less than 12v (max) and gain error less than 0.1% (max). the max44285 features an input common-mode voltage range from 2.7v to 76v with 80khz of small-signal band - width, which makes it ideal for interfacing with a sar adc for multichannel multiplexed data acquisition systems. the max44285 operates over the -40c to +125c temperature range. the max44285 is offered in 8-bump wafer-level package (wlp) and 8-pin max m package. applications base stations and communication equipment power management systems server backplanes industrial control and automation beneits and features 2.7v to 76v input common mode low 12v (max) input offset voltage low 0.1% (max) gain error gain options ? g = 12.5v/v (max44285l) ? g = 20v/v (max44285t) ? g = 50v/v (max44285f) ? g = 100v/v (max44285h) 1mm x 2mm 8-bump wlp and 8-pin max packages ordering information appears at end of data sheet. max is a registered trademark of maxim integrated products, inc. max44285 dual-channel, high-precision, high-voltage, current-sense amplifier 19-6910; rev 4; 4/16 r sense2 r sense1 system load 2 system load 1 i sense2 i sense1 rs2- rs2+ rs1- rs1+ max44285 out2 out1 gnd v dd v dd = 2.7v to 5.5v v cm = 2.7v to 76v v cm = 2.7v to 76v typical operating circuit evaluation kit available downloaded from: http:///
v dd to gnd .........................................................-0.3v to +6.0v rs+, rs- to gnd ..................................................-0.3v to +80v rs+ to rs- max (1s maximum duration due to package thermal dissipation .......................................................................80v wlp (1s maximum duration due to package thermal dissipation .......................................................................50v continuous input current (any pin) .................................20ma continuous power dissipation (t a = +70c) wlp (derate 13.3mw/c above +70c) ....................1064mw max (derate 4.8mw/c above +70c) ...................387.8mw operating temperature range ......................... -40c to +125c junction temperature ......................................................+150c storage temperature range ............................ -65c to +150c lead temperature (soldering, 10s)(max only) ............. +300c soldering temperature (reflow) .......................................+260c wlp junction-to-ambient thermal resistance ( ja ) ..........75c/w max junction-to-ambient thermal resistance ( ja ) .....206.3c/w junction-to-case thermal resistance ( jc ) ............... 42 c/w (v rs+ = v rs- = +76v, v dd = +3.3v, v sense = v rs+ - v rs- = 1mv, t a = -40c to +125c, unless otherwise noted. typical values are at t a =+25c.) (note 2) parameter symbol conditions min typ max units dc characteristics supply voltage v dd guaranteed by psrr 2.7 5.5 v supply current i dd t a = +25c 1300 a -40c < t a < +125c 1500 power-supply rejection ratio psrr 2.7v v dd 5.5v 110 120 db input common-mode voltage range v cm guaranteed by cmrr 2.7 76 v input bias current at v rs+ and v rs- (note 3) i rs+ , i rs- 65 a input offset current (note 3) i rs+ - i rs- 1100 na input leakage current (note 3) i rs+ , i rs- v dd = 0v, v rs+ = 76v 6 a common-mode rejection ratio cmrr 4.5v < v rs+ < 76v 125 140 db input offset voltage (note 3) v os t a = +25c 12 v -40 c t a +125c 25 input offset voltage drift (note 3) tcv os 130 nv/c max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 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 . absolute maximum ratings stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. (note 1) package thermal characteristicselectrical characteristics downloaded from: http:///
(v rs+ = v rs- = +76v, v dd = +3.3v, v sense = v rs+ - v rs- = 1mv, t a = -40c to +125c, unless otherwise noted. typical values are at t a =+25c.) (note 2) note 2: all devices are 100% production tested at t a = +25c. all temperature limits are guaranteed by design. note 3: specifications are guaranteed by design, not production tested. note 4: gain and offset voltage are calculated based on two point measurements: v sense1 and v sense2 . v sense1 = 20% x full scale v sense . v sense2 = 80% x full scale v sense . note 5: output is high-z during power-up. parameter symbol conditions min typ max units input sense voltage v sense max44285l (g = 12.5v/v) 200 mv max44285t (g = 20v/v) 125 max44285f (g = 50v/v) 50 max44285h (g = 100v/v) 25 gain (note 4) g full-scale v sense = 200mv 12.5 v/v full-scale v sense = 125mv 20 full-scale v sense = 50mv 50 full-scale v sense = 25mv 100 gain error (note 3) ge t a = +25c 0.1 % -40c t a +85c 0.3 -40c t a +125c 0.5 output resistance r out 0.1 m ? output low voltage v ol sink 500 a 15 mv no load 4 output high voltage v oh source 500a v dd - 0.015 v ac characteristics signal bandwidth bw -3db all gain conigurations v sense > 5mv 80 khz ac power-supply rejection ratio ac psrr f = 200khz 40 db ac cmrr ac cmrr f = 200khz 1mv sine wave 54 db 20mv sine wave 47 output transient recovery time ?v out = 2v p-p , 14-bit settling with 400? and 1nf, 6nf adc sampling capacitor 2 s capacitive load stability c load with 250? isolation resistor 20 nf without any isolation resistor 200 pf input voltage-noise density e n f = 1khz 45 nv/ hz total harmonic distortion (up to 7th harmonics) thd f = 1khz, v out = 1v p-p 63 db power-up time (note 5) 200 s saturation recovery time 10 s max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 3 electrical characteristics (continued) downloaded from: http:///
(v rs+ = v rs- = 76v, v dd = 3.3v, v sense = v rs+ - v rs- = 1mv, t a = +25c, unless otherwise noted.) (note 2) 0 2 4 6 8 10 12 14 16 -4 -3 -2 -1 0 1 2 3 4 o ccurr e nc e n (%) input o ff se t voltage (v) input o ff se t vo lt age hist og ra m toc 0 1 -6 -4 -2 0 2 4 6 8 10 12 0 20 40 60 80 input - referred offset (v) common - mode voltage (v) input - referred offset vs. common - mode voltage toc03 v dd = 3.3v g = 12.5v/v g = 20v/v g = 50v/v g = 100v/v -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0 20 40 60 80 gain error (%) common - mode voltage (v) gain error vs. common - mode voltage toc05 v dd = 3.3v g = 12.5v/v g = 20v/v g = 50v/v g =100v/v -10 -8 -6 -4 -2 0 2 4 6 8 10 -50 0 50 100 150 input - referred offset (v) temperature (c?) input - referred offset vs. temperature toc02 v dd = 3.3v g =12.5v/v g = 20v/v g = 50v/v g = 100v/v -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 -50 0 50 100 150 gain error (%) temperature ( c) gain error vs. temperature toc04 g = 12.5v/v g = 20v/v g = 50v/v g = 100v/v 0 10 20 30 40 50 60 70 80 90 100 110 120 10 100 1000 10000 100000 1000000 ac cmrr (db) frequency (hz) ac cmrr vs. frequency toc06 maxim integrated 4 www.maximintegrated.com max44285 dual-channel, high-precision, high-voltage, current-sense ampliier typical operating characteristics downloaded from: http:///
(v rs+ = v rs- = 76v, v dd = 3.3v, v sense = v rs+ - v rs- = 1mv, t a = +25c, unless otherwise noted.) (note 2) 20 40 60 80 100 120 140 1 100 10000 1000000 ac psrr (db) frequency (hz) ac psrr vs. frequency toc07 600 650 700 750 800 850 900 950 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 supply current ( a) supply voltage (v) supply current vs. supply voltage toc9 g = 12.5v/v g = 20v/v g = 50v/v g = 100v/v 0 50 100 150 200 250 0 2 4 6 8 10 output voltage high (mv) source current (ma) output voltage high vs. source current toc11 g = 20v/v 0 5 10 15 20 25 30 35 40 45 1 100 10000 magnitude (db) frequency (hz) gain vs. frequency toc08 g = 12.5v/v g = 20v/v g = 50v/v g = 100v/v 820 840 860 880 900 920 940 -45 -20 5 30 55 80 105 130 supple current ( a) temperature ( ? c) supply current vs. temperature toc10 g = 12.5v/v g = 20v/v g = 50v/v g = 100v/v v dd = 3.3v 0 20 40 60 80 100 120 140 160 0 2 4 6 8 10 output voltage low (mv) sink current (ma) output voltage low vs. sink current toc12 g = 20v/v maxim integrated 5 www.maximintegrated.com max44285 dual-channel, high-precision, high-voltage, current-sense ampliier typical operating characteristics (continued) downloaded from: http:///
(v rs+ = v rs- = 76v, v dd = 3.3v, v sense = v rs+ - v rs- = 1mv, t a = +25c, unless otherwise noted.) (note 2) small - signal step response toc14 400 s/div v outn v inside toc13 v in 20mv 10mv/div v out 200mv/div saturation recovery response toc15 400 s/div v outn v inside v backup no load v in 200mv 100mv/div v out 1v/div -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 100 1000 10000 100000 total harmonic distortion (db) frequency (hz) total harmonic distortion vs. frequency 1v p-p output toc17 g = 20v/v large - signal step response toc14 400 s/div v outn v inside v backup 10k ? load v in 120mv 50mv/div v out 1v/div 0 100 200 300 400 500 600 10 1000 100000 input voltage - noise density (nv/ hz ) frequency (hz) input voltage - noise density vs. frequency toc16 maxim integrated 6 www.maximintegrated.com max44285 dual-channel, high-precision, high-voltage, current-sense ampliier typical operating characteristics (continued) downloaded from: http:///
12 34 8 7 6 5 v dd v dd out1 out1 out2 gnd rs1+ rs1- rs2+ rs2- out2gnd rs2- rs2+ rs1- rs1+ max top view + b 1 2 3 4 a + bottom view wlp max44285 pin name function wlp max a1 1 rs1+ channel 1 external resistor power-side connection a2 2 rs1- channel 1 external resistor load-side connection a3 3 rs2+ channel 2 external resistor power-side connection a4 4 rs2- channel 2 external resistor load-side connection b1 8 v dd supply voltage b2 7 out1 output channel 1 b3 6 out2 output channel 2 b4 5 gnd ground max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 7 pin description pin coniguration downloaded from: http:///
detailed description the max44285 high-side, current-sense amplifier fea - tures a 2.7v 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 2.7v and enables high-side current sensing at voltages greater than the supply voltage (v dd ). the max44285 monitors current through a current-sense resistor and amplifies the voltage across the resistor. high-side current monitoring does not interfere with the ground path of the load being measured, making the max44285 particularly useful in a wide range of high- voltage systems. the max44285 operates as follows: current from the source flows through r sense to the load (see functional diagram ), creating a sense voltage, v sense . the internal op amp a1 is used to force the current through an internal gain resistor r g11 at rs1+ pin, such that its voltage drop equals the voltage drop (v sense ) across the external sense resistor (r sense ). the internal resistor at rs1- pin (r g12 ) has the same value as r g11 to minimize error. the current through r g11 is sourced by a high-voltage p-channel fet. its source current is the same as the drain current which flows through a second gain resistor, r 01, producing a voltage v r01 = v sense x r 01 /r g11 . the output voltage v out1 is produced from a second op amp a2 with the gain (1 + r f1 /r 01 ). hence, the v out1 = i load1 x r sense1 (r 01 /r g11 ) x (1 + r f1 / r 01 ) for chan - nel 1 and v out2 = i load2 x r sense2 (r 02 /r g21 ) x (1 + r f2 / r 02 ) for channel 2. internal resistor r 01 = r 02 , r g11 = r g12 = r g21 = r g22 , r f1 = r f2 . the gain-setting resistors r 01 , r 02 , r g11 , r g12 , r g21 , r g22 , r f1, and r f2 are available in table 1): total gain = 12.5v/v for max44285l, 20v/v for the max44285t, 50v/v for the max44285f, and 100v/v for the max44285h. v sense1 p rs1+ rs1- r sense 1 r g11 r g12 a 1 a 2 p1 out1 gnd v sense2 rs2+ rs2- r sense 2 r g21 r g22 a 1 p2 p a 2 out2 gnd r 01 r 02 r 01 r 02 r f1 r f2 v sense1 i load1 i load2 max44285 max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 8 functional diagram downloaded from: http:///
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 x a v where v sense is the full-scale sense voltage, 200mv for gain of 12.5v/v, 125mv for gain of 20v/v, 50mv for gain of 50v/v, 25mv for gain of 100v/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 - tors power dissipation exceeds the nominal value, its value may drift or it may fail altogether. the max44285 senses a wide variety of currents with different sense- resistor values. 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 currents 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 200mv (gain of 12.5v/v), 125mv (gain of 20v/v), or 50mv (gain of 50v/v), 25mv (gain of 100v/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. consider this when choosing the resistor value and its power dissipation (wattage) rating. in addition, the sense resistors value might drift if it heats up excessively. inductance: keep inductance low if i sense has a large high-frequency component. wire-wound resistors have the highest inductance, while metal film is somewhat better. low-inductance, metal-film resistors 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?. take care to eliminate parasitic trace resistance from causing errors in the sense voltage because of the high currents that flow through r sense . either use a four terminal current-sense resistor or use kelvin (force and sense) pcb layout techniques. base station application circuit an example of a typical application ( figure 1 ) of this high-voltage, high-precision current-sense ampliier is in base-station systems where there is a need to monitor the current lowing in the power ampliier. such ampliiers, depending on the technology, can be biased up to 50v or 60v thus requiring a current-sense ampliier like the max44285 with high-voltage common mode. the very low input offset voltage of the max44285 minimizes the value of the external sense resistor thus resulting in system power-saving. table 1. gain-setting resistors gain (v/v) r 01 , r 02 (k ? ) r g11 , r g12 , r g21 , r g22 (k ? ) r f1 , r f2 (k ? ) max44285l 12.5 25 10 100 max44285t 20 25 10 175 max44285f 50 25 10 475 max44285h 100 25 10 975 max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 9 downloaded from: http:///
figure 1. max44285 used in base-station application c rfin v dd = 3.3v v dd = 3.3v ref+ outf outs max6126 max11125 output 20 ? 250 ? 20nf 220nf ref- v drain = 2.7v to 76v rfout max44285 v in max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 10 downloaded from: http:///
+denotes a lead(pb)-free/rohs-compliant package. part gain (v/v) temp range pin-package top mark max44285lawa+ 12.5 -40c to +125c 8 wlp +aaf max44285laua+ 12.5 -40c to +125c 8 max max44285tawa+ 20 -40c to +125c 8 wlp +aag max44285taua+ 20 -40c to +125c 8 max max44285fawa+ 50 -40c to +125c 8 wlp +aah max44285faua+ 50 -40c to +125c 8 max MAX44285HAWA+ 100 -40c to +125c 8 wlp +aai max44285haua+ 100 -40c to +125c 8 max package type package code outline no. land pattern no. 8 wlp w81a2+2 21-0210 refer to application note 1891 8 max u8+1 21-0036 90-0092 max44285 dual-channel, high-precision, high-voltage, current-sense ampliier www.maximintegrated.com maxim integrated 11 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. chip information process: bicmos ordering information downloaded from: http:///
revision number revision date description pages changed 0 1/14 initial release 1 2/14 revised pin description , functional diagram , detailed description and added table 1 7, 8, 9 2 7/14 revised data sheet to change common-mode range from 36v to 76v 1C6. 8C10 3 12/14 released wlp packages and updated electrical characteristics 2, 11 4 4/16 updated unit in toc1 4 maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and speciications without n otice 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 and the maxim integrated logo are trademarks of maxim integrated products, inc. ? 2016 maxim integrated products, inc. 12 max44285 dual-channel, high-precision, high-voltage, current-sense ampliier revision history for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com. downloaded from: http:///

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