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general description the max9918/max9919/MAX9920 are single-supply, high-accuracy current-sense amplifiers with a high input common-mode range that extends from -20v to +75v. these amplifiers are well suited for current moni- toring of inductive loads such as motors and solenoids, where common-mode voltages can become negative due to inductive kickback, reverse-battery conditions, or transient events. the max9918/MAX9920 feature adjustable gain set by an external resistive-divider network. the max9919 fea- tures fixed gains of 45v/v (max9919f) and 90v/v (max9919n). the max9918/max9919/MAX9920 oper- ate as unidirectional amplifiers when v refin = gnd and as bidirectional amplifiers when v refin = v cc /2. the MAX9920 attenuates the input signal by a factor of 4 at the input level-shifting stage allowing the device to sense voltages up to 200mv (unidirectional operation) or 100mv (bidirectional operation). the max9918/max9919/MAX9920 operate with a sin- gle 5v supply voltage, are fully specified over the -40c to +125c automotive temperature range, and are available in an 8-pin soic package. applications h-bridge motor current sensing solenoid current sensing current monitoring of inductive loads high- and low-side precision current sensing 4x4 transmission control electronic throttle control super-capacitor charge/discharge monitoring in hybrid cars precision high-voltage current monitoring features -20v to +75v input common-mode voltage range 400? (max) input offset voltage 0.6% (max) gain accuracy error uni- or bidirectional current sensing reference input for bidirectional out 120khz, -3db bandwidth (max9919n) single-supply operation (4.5v to 5.5v) 1ma supply current 0.5? (typ) shutdown current rail-to-rail output -40? to +125? automotive temperature range max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers ________________________________________________________________ maxim integrated products 1 19-5015; rev 0; 11/09 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 m 2b 1b adc ref a input stage level shifter r sense v batt adjustable gain v cc v cc rs+ rs- fb out refin r2 r1 gnd gnd shdn 2b 1a max9918 MAX9920 c typical operating circuit ordering information/ selector guide part v sense (mv) gain (v/v) pin-package max9918 asa+ 50 adjustable 8 soic-ep* max9919 fasa+ 50 45 8 soic-ep* max9919nasa+ 50 90 8 soic-ep* MAX9920 asa+ 200 adjustable 8 soic-ep* note: all devices operate over the -40c to +125c tempera- ture range. + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad.
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 5v, v rs+ = v rs- = +14v, v sense = (v rs+ - v rs- ) = 0v, v shdn = v gnd = 0v, v refin = v cc /2, r l = 100k ? ; for max9918, a v = 90v/v, r2/r1 = 89k ? /1k ? ; for MAX9920, a v = 20v/v, r2/r1 = 79k ? /1k ? ; t a = -40c to +125c, unless otherwise noted. typical val- ues are at t a = +25c.) (note 1) stresses beyond those listed under absolute 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 +6v rs+, rs- to gnd (v cc = 5v) ..................................-30v to +80v rs+, rs- to gnd (v cc = 0v) .............-15v to +80v (15 minutes) differential input voltage (v rs+ - v rs- ) (max9918/max9919).................................15v (continuous) differential input voltage (v rs+ - v rs- ) (MAX9920) .............................5v (continuous) refin, fb, out to gnd.............................-0.3v to (v cc + 0.3v) shdn to gnd.........................................................-0.3v to +20v output short circuit to v cc or gnd...........................continuous continuous current into any pin (not to exceed package power dissipation) ................20ma continuous power dissipation (t a = +70c) 8-pin soic-ep (derate 24.4mw/c above +70c) . 1951.2mw** soic package junction-to-ambient thermal resistance ( ja ) (note 1)...............................41c/w junction temperature ......................................................+150c storage temperature range .............................-65c to +150c reflow soldering temperature ........................................+260c lead temperature (soldering, 10s) .................................+300c parameter symbol conditions min typ max units t a = +25c 0.14 0.4 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 0.7 t a = +25c 0.08 0.4 max9918 v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 1.3 t a = +25c 0.18 0.4 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 0.9 t a = +25c 0.11 0.4 max9919_ v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 1.0 t a = +25c 0.48 1.2 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 3.0 t a = +25c 0.10 0.9 input offset voltage (note 2) v os MAX9920 v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 3.5 mv note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . ** as per jedec51 standard (multilayer board).
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units v rs+ = v rs- = +14v 1.2 max9918 v rs+ = v rs- = -2v 3.3 v rs+ = v rs- = +14v 1.8 max9919_ v rs+ = v rs- = -2v 1.8 v rs+ = v rs- = +14v 2.4 input offset voltage drift (note 3) v osd MAX9920 v rs+ = v rs- = -2v 8.8 v/c common-mode range v cm inferred from cmrr tests -20 +75 v -2v v cm +14v 80 m ax 9918, m ax 9919 -20v v cm +75v 96 -2v v cm +14v 72 common-mode rejection ratio (note 3) cmrr MAX9920 -20v v cm +75v 86 db t a = +25c 175 input bias current i rs+ , i rs- -20v v cm +75v t a = -40c to +125c 250 a input offset current ( i rs + - i rs - ) 0 8 a input leakage current in shutdown -20v v cm +75v, v shdn = v cc = 5v 30 a input leakage current v rs+ = v rs- = +14v, +75v, v cc = 0v 30 a common mode 300 k ? max9918, max9919_ differential 715 ? common mode 330 k ? input resistance MAX9920 differential 224 ? max9918, max9919_ 50 full-scale sense voltage (note 4) v sense inferred from gain error test MAX9920 200 mv max9918, MAX9920 adj max9919f 45 gain (notes 2, 4) g max9919n 90 v/v max9918 30 minimum adjustable gain g adj MAX9920 7.5 v/v electrical characteristics (continued) (v cc = 5v, v rs+ = v rs- = +14v, v sense = (v rs+ - v rs- ) = 0v, v shdn = v gnd = 0v, v refin = v cc /2, r l = 100k ? ; for max9918, a v = 90v/v, r2/r1 = 89k ? /1k ? ; for MAX9920, a v = 20v/v, r2/r1 = 79k ? /1k ? ; t a = -40c to +125c, unless otherwise noted. typical val- ues are at t a = +25c.) (note 1
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 4 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = 5v, v rs+ = v rs- = +14v, v sense = (v rs+ - v rs- ) = 0v, v shdn = v gnd = 0v, v refin = v cc /2, r l = 100k ? ; for max9918, a v = 90v/v, r2/r1 = 89k ? /1k ? ; for MAX9920, a v = 20v/v, r2/r1 = 79k ? /1k ? ; t a = -40c to +125c, unless otherwise noted. typical val- ues are at t a = +25c.) (note 1 parameter symbol conditions min typ max units t a = +25c, v refin = 0v 0.08 0.6 v rs+ = v rs- = +14v t a = -40c to +125c, v refin = 0v 1.2 t a = +25c 0.02 0.6 max9918 v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 1.0 t a = +25c 0.13 0.45 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 1.2 t a = +25c 0.10 0.45 max9919f v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 0.9 t a = +25c 0.16 0.6 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 1.2 t a = +25c 0.11 0.6 max9919n v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 1.0 t a = +25c 0.29 1.0 v rs+ = v rs- = +14v, v refin = 0v t a = -40c to +125c 1.7 t a = +25c 0.24 1.0 gain error (note 2) ge MAX9920 v rs+ = v rs- = -2v, v refin = 0v t a = -40c to +125c 1.7 % fb input bias current i fb max9918, MAX9920 5 15 na r l = 100k ? to gnd 3 10 output-voltage high (note 4) v cc - v oh v sense = 200mv for max9918, max9919_, v sense = 400mv for MAX9920 r l = 10k ? to gnd 12 40 mv r l = 100k ? to v cc 310 output-voltage low (note 4) v ol v sense = -200mv for max9918, max9919_, v sense = -400mv for MAX9920 r l = 10k ? to v cc 10 40 mv out shorted to v cc 44 short-circuit current i sc out shorted to gnd 41 ma output resistance r out 0.1 ? m ax 9918, m ax9919_ 0 v cc /2 v cc - 1.9 refin voltage range inferred from refin cmrr test MAX9920 0 v cc /2 v cc - 2.4 v
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 5 electrical characteristics (continued) (v cc = 5v, v rs+ = v rs- = +14v, v sense = (v rs+ - v rs- ) = 0v, v shdn = v gnd = 0v, v refin = v cc /2, r l = 100k ? ; for max9918, a v = 90v/v, r2/r1 = 89k ? /1k ? ; for MAX9920, a v = 20v/v, r2/r1 = 79k ? /1k ? ; t a = -40c to +125c, unless otherwise noted. typical val- ues are at t a = +25c.) (note 1 parameter symbol conditions min typ max units max9918, max9919_ 0v v refin (v cc - 1.9v) 82 103 refin common-mode rejection ratio re fin c m r r MAX9920 0v v refin (v cc - 2.4v) 75 90 db m ax 9918, m ax 9919_, v rs + = v rs - = 50m v 100 refin current i refin MAX9920, v rs+ = v rs- = 200mv 100 a shdn logic-high v ih 2.0 v shdn logic-low v il 0.8 v shdn logic-input current 0v v shdn v cc 5a supply voltage range v cc inferred from psrr test 4.5 5.5 v max9918, max9919_ 4.5v v cc 5.5v 74 103 power-supply rejection ratio (note 3) psrr MAX9920 4.5v v cc 5.5v 68 100 db t a = +25c 0.7 1.2 v rs+ = v rs- = +14v t a = - 40c to + 125c 1.5 t a = +25c 1.0 1.6 supply current i cc v rs+ = v rs- = -2v t a = - 40c to + 125c 2.2 ma shutdown supply current i cc_shdn v shdn = v cc = 5v 0.5 10 a max9918, v sense = 50mv 75 max9919f, v sense = 50mv 250 max9919n, v sense = 50mv 120 small-signal -3db bandwidth bw MAX9920, v sense = 200mv 230 khz max9918 0.6 max9919f 0.9 max9919n 3.0 slew rate sr MAX9920 1.5 v/s v sense = 5mv to 50mv step 12 max9918 v sense = 50mv to 5mv step 7 v sense = 5mv to 50mv step 3.5 max9919f v sense = 50mv to 5mv step 2.5 v sense = 5mv to 50mv step 3.5 max9919n v sense = 50mv to 5mv step 3 v s e n s e = 20m v to 200m v step 5 1% settling time from v sense step MAX9920 v s e ns e = 200mv to 20mv step 3 s
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 6 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = 5v, v rs+ = v rs- = +14v, v sense = (v rs+ - v rs- ) = 0v, v shdn = v gnd = 0v, v refin = v cc /2, r l = 100k ? ; for max9918, a v = 90v/v, r2/r1 = 89k ? /1k ? ; for MAX9920, a v = 20v/v, r2/r1 = 79k ? /1k ? ; t a = -40c to +125c, unless otherwise noted. typical val- ues are at t a = +25c.) (note 1 parameter symbol conditions min typ max units v cm = -2v to +14v step 2.5 max9918, v sense = 50mv v cm = +14v to -2v step 0.5 v cm = -2v to +14v step 2.5 max9919f, v sense = 50mv v cm = +14v to -2v step 0.5 v cm = -2v to +14v step 3.5 max9919n, v sense = 50mv v cm = +14v to -2v step 3.5 v cm = -2v to +14v step 0.25 1% settling time from v cm step MAX9920, v sense = 200mv v cm = +14v to -2v step 2.5 s max9918, v sense = 50mv, 1% settling 4.5 max9919f, v sense = 50mv, 1% settling 5 max9919n, v sense = 50mv, 1% settling 6 power-up time MAX9920, v sense = 200mv, 1% settling 5 s m axi m um c ap aci ti ve load s tab i l i ty no sustained oscillations (note 5) 50 pf max9918, max9919_ 60 input referred noise voltage density e n 10khz MAX9920 174 nv/ hz note 1: all devices are 100% production tested at t a = +25c. all temperature limits are guaranteed by design. note 2: v os is extrapolated from two point gain error tests. measurements are made at v sense = 5mv and 50mv for max9918/max9919n/max9919f, and v sense = 20mv and 200mv for MAX9920. note 3: extrapolated v os as described above in note 2 is used to calculate v os drift, cmrr, and psrr. note 4: out should be 100mv away from either rail to achieve rated accuracy, or limited by a v sense of 50mv for the max9918/max9919n/max9919f and 200mv for the MAX9920. note 5: not production tested. guaranteed by design.
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 7 typical operating characteristics (v cc = 5v, t a = +25c, unless otherwise noted.) v os (v rs+ = +14v) max9918 toc01 offset voltage ( f v) n (%) 240 320 -240-160 -80 0 80 160 -320 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0 -400 400 v os drift (v rs+ = +14v) m ax9918 toc02 offset voltage ( f v/ c) n (%) 3 2 1 0 -1 -2 -3 0.05 0.10 0.15 0.20 0.25 0.30 0 -4 4 v os (v rs+ = -2v) m ax9918 toc03 offset voltage ( f v) n (%) 320 240 160 80 0 -80 -160 -240 -320 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0 -400 400 v os drift (v rs+ = -2v) m ax9918 toc04 offset voltage ( f v/ c) n (%) 8 46 -6 -4 -2 0 2 -8 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0 -10 10 v os vs. v cm m ax9918 toc05 v c m (v) v os (uv) 70 60 40 50 0 10 20 30 -10 -400 -300 -200 -100 0 100 200 300 400 500 -500 -20 80 t a = -40c t a = +25c max9918asa v cc = 5v v ref = gnd t a = +125c v os vs. v cc max9918 toc06 v cc (v) vos ( f v) 5.4 5.3 5.1 5.2 4.7 4.8 4.9 5.0 4.6 -75 -50 -25 0 25 50 75 100 125 -100 4.5 5.5 max9918asa v cc = 5v v ref = gnd v cm = -2v v cm = 14v 0 0.1 0.2 0.3 -0.4 -0.3 -0.2 -0.1 0.4 gain error (v rs+ = +14v, max9919f, a v = +45v/v) max9918 toc07 gain error (%) n (%) 0.1 0.2 0.3 0.4 0.5 0.6 0 0 0.1 0.2 0.3 -0.4 -0.3 -0.2 -0.1 0.4 gain error (%) max9918 toc08 n (%) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 gain error (v rs+ = +14v, max9919n, a v = +90v/v) 0 0.1 0.2 0.3 -0.4 -0.3 -0.2 -0.1 0.4 gain error (v rs+ = -2v, max9919f, a v = +45v/v) max9918 toc09 gain error (%) n (%) 0.1 0.2 0.3 0.4 0.5 0.6 0
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 8 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = 5v, t a = +25c, unless otherwise noted.) 0 0.1 0.2 0.3 -0.4 -0.3 -0.2 -0.1 0.4 gain error (v rs+ = -2v, max9919n, a v = +90v/v) max9918 toc10 gain error (%) n (%) 0.1 0.2 0.3 0.4 0.5 0.6 0 gain error vs. v cm max9918 toc11 v cm (v) ge (%) 70 60 40 50 0 10 20 30 -10 -1.6 -1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6 2.0 -2.0 -20 80 max9918asa v cc = 5v v ref = gnd t a = +125 n c t a = +25 n c t a = -40 n c gain error vs. v cc max9918 toc12 v cc (v) gain error (%) 5.3 5.1 4.9 4.7 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 -0.5 4.5 5.5 v cm = -2v v cm = 14v linearity vs. v sense max9918 toc13 linearity (%) 20 10 0 -10 -20 -0.20 -0.15 -0.10 -0.05 0 0.05 0.10 0.15 0.20 0.25 -0.25 -30 30 v cm = -2v v cc = 5v v refin = v cc /2 a v = 90v/v bidirectional t a = -40c v sense (mv) t a = +25c t a = +125c linearity vs. v sense max9918 toc14 linearity (%) 20 10 0 -10 -20 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 -0.10 -30 30 v cm = +14v v cc = 5v v refin = v cc /2 a v = 90v/v bidirectional t a = -40c t a = +25c t a = +125c v sense (mv) linearity vs. v sense max9918 toc15 linearity (%) 70 60 40 50 20 30 10 080 v cm = -2v v cc = 5v v refin = gnd a v = 90v/v unidirectional t a = -40c t a = +25c t a = +125c -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 -0.10 v sense (mv)
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 9 typical operating characteristics (continued) (v cc = 5v, t a = +25c, unless otherwise noted.) v out - v refin vs. v sense max9918 toc19 v out - v refin (v) 70 60 40 50 0 10 20 30 -10 -1 0 1 1 2 2 3 3 4 4 5 5 6 6 -1 -20 80 max9918, v refin = 0v unidirectional, gain = 90v/v -2v v cm : solid line 14v v cm : dashed line v sense (mv) v out - v refin vs. v sense max9918 toc20 v sense (mv) v out - v refin (v) 30 20 0 10 -20 -10 -30 -3 -2 -2 -1 -1 0 1 1 2 2 3 3 -3 -40 40 max9918, v refin = v cc /2 bidirectional, gain = 90v/v -2v v cm : solid line 14v v cm : dashed line v oh /v ol vs. i oh max9918 toc21 i oh (ma) v oh and v ol (mv) 9 8 7 6 5 4 3 2 1 50 100 150 200 250 300 350 0 010 v cc - v oh v cm = +14v v ol linearity vs. v sense max9918 toc16 linearity (%) 65 60 50 55 15 20 25 30 35 40 45 5 10 -0.06 -0.08 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 -0.10 070 v cm = +14v v cc = 5v v refin = gnd a v = 90v/v unidirectional t a = -40c t a = +125c t a = +25c v sense (mv) linearity vs. v sense max9918 toc17 linearity (%) 80 60 20 40 -60 -40 -20 0 -80 -0.20 -0.15 -0.10 -0.05 0 0.05 0.10 0.15 0.20 0.25 -0.25 -100 100 v cm = -2v v cc = 5v v refin = v cc /2 a v = 30v/v bidirectional t a = -40c t a = +125c t a = +25c v sense (mv) linearity vs. v sense max9918 toc18 linearity (%) 80 60 20 40 -60 -40 -20 0 -80 -100 100 v cm = +14v v cc = 5v v refin = v cc /2 a v = 30v/v bidirectional t a = +25c t a = -40c t a = +125c -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.10 -0.10 v sense (mv)
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 10 ______________________________________________________________________________________ typical operating characteristics (continued) (v cc = 5v, t a = +25c, unless otherwise noted.) i cc vs. v cc max9918 toc22 v cc (v) i cc (ma) 5.4 5.3 5.1 5.2 4.7 4.8 4.9 5.0 4.6 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 4.5 5.5 v cm = 14v v sense = 0v v cm = -2v i cc vs.v cm max9918 toc23 v cm (v) i cc (ma) 70 60 40 50 0 10 20 30 -10 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 0.4 -20 80 t a = +125 n c t a = +25 n c t a = -40 n c v sense = 0v (dash) v sense + 50mv (solid i bias vs. v cm max9918 toc24 v cm (v) i bais ( f a) 70 60 40 50 0 10 20 30 -10 -80 -60 -40 -20 0 20 40 60 80 100 -100 -20 80 max9918 v cc = 5v input leakage current vs. v cm max9918 toc25 v cm (v) input leakage current ( f a) 60 40 20 0 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 -50 -20 80 in+ - in- = 50mv v cc = v shdn = 0v v refin = 0v t a = +125 n c t a = +25 n c t a = -40 n c differential r in vs. v cm max9918 toc26 v cm (v) differential r in ( i ) 55 40 25 10 -5 100 200 300 400 500 600 700 800 900 1000 0 -20 70 gain vs. frequency max9918 toc27 frequency (mhz) gain (db) 1 0.1 0.01 -30 -20 -10 0 10 20 30 40 50 -40 0.001 10 max9918 v cm = 14v gain = 90v/v gain vs . frequency max9918 toc28 frequency (mhz) gain (db) 1 0 . 1 0 . 01 -50 -40 -30 -20 -10 0 10 20 30 40 -60 0 . 001 10 MAX9920 v cm = 14v gain = 20v/v gain vs. frequency max9918 toc29 frequency (mhz) gain (db) 10 1 0.1 0.01 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 -100 0.001 100 max9918 v cm = 14v gain = 90v/v v cm = -2v v cm = 14v psrr vs. frequency max9918 toc30 frequency (khz) psrr (db) 1k 100 10 1 0.1 0.01 0.001 -120 -100 -80 -60 -40 -20 0 -140 0.0001 10k max9918 v cm = 14v v sense = 50mv
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers ______________________________________________________________________________________ 11 typical operating characteristics (continued) (v cc = 5v, t a = +25c, unless otherwise noted.) small-signal transient (gain = 45v/v) max9918 toc31 50mv/div 10 f s/div 5mv/div max9918, v cm = 14v v sense = 10mv to 15mv small-signal transient (gain = 90v/v) max9918 toc32 100mv/div 10 f s/div 5mv/div max9918, v cm = 14v v sense = 10mv to 15mv large-signal transient (gain = 45v/v) max9918 toc33 500mv/div 10 f s/div 50mv/div max9918, v cm = 14v v sense = 0v to 50mv large-signal transient (gain = 90v/v) max9918 toc34 1v/div 10 f s/div 50mv/div max9918, v cm = 14v v sense = 0 to 50mv output response to common-mode transient max9918 toc36 v out 100mv/div v cm 50v/div 0 4s/div output ac-coupled full scale at the input common-mode step response max9918 toc35 1v/div 10 f s/div 10v/div max9918, v cm = 14v s sense = ps (50mv)
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 12 ______________________________________________________________________________________ typical operating characteristics (continued) (v cc = 5v, t a = +25c, unless otherwise noted.) shutdown on/off delay max9918 toc37 1v/div 4 f s/div 5v/div max9918, v cm = 14v v sense = ps (50mv) output overdrive recovery (30v/v) max9918 toc39 2v/div 4 f s/div 200mv/div max9918, v cm = 14v v sense = 2 x ps power-up time max9918 toc38 2v/div 4 f s/div 5v/div max9918, v cm = 14v v sense = ps (50mv) output overdrive recovery (90v/v) max9918 toc40 2v/div 4 f s/div 50mv/div max9918, v cm = 14v v sense = 2 x ps
detailed description the max9918/max9919/MAX9920 are single-supply, high-accuracy uni-/bidirectional current-sense amplifiers with a high common-mode input range that extends from -20v to +75v. the max9918/max9919/MAX9920s input stage utilizes a pair of level shifters allowing a wide common-mode operating range when measuring the voltage drop (v sense ) across the current-sense resistor. the first level shifter accommodates the upper common- mode operating range from +2v to +75v. when the common-mode voltage falls below +2v, the second level shifter is used to accommodate negative voltages down to -20v. the level shifters translate v sense to an internal refer- ence voltage where it is then amplified with an instru- mentation amplifier. the instrumentation amplifier configuration provides high precision with input offset voltages of 400v (max). indirect feedback of the instrumentation amplifier allows the gain to be adjusted with an external resistive-divider network on the max9918/MAX9920. the max9919 is a fixed gain device available with laser-trimmed resistors for gains of 45v/v (max9919f) and 90v/v (max9919n). the max9918/max9919 operate with a full-scale sense voltage of 50mv. the input stage of the MAX9920 pro- vides an attenuation factor of 4, enabling a full-scale sense voltage of 200mv. max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers ______________________________________________________________________________________ 13 pin description pin name function 1 rs+ positive current-sensing input. power side connects to external sense resistor. 2 rs- negative current-sensing input. load side connects to external sense resistor. 3 shdn active-high shutdown input. connect to gnd for normal operation. 4 gnd ground 5 out current-sense output. v out is proportional to v sense . 6fb feedback input. connect fb to a resistive-divider network to set the gain for the max9918 and MAX9920. see the adjustable gain (max9918/MAX9920) section for more information. leave fb unconnected for the max9919 for proper operation. 7 refin reference input. set refin to v cc /2 for bidirectional operation. set refin to gnd for unidirectional operation. 8v cc 5v supply voltage input. bypass v cc to gnd with 0.1f capacitor. ep exposed pad. connect to a large-area contiguous ground plane for improved power dissipation. do not use as the only ground connection for the part. 8 soic-ep top view max9918 max9919 MAX9920 fb out 8 7 v cc refin 6 5 gnd 1 2 rs- shdn rs+ 3 4 ep* + *exposed pad. connect ep to solid ground for proper thermal and electrical performance. pin configuration
uni-/bidirectional operation the max9918/max9919/MAX9920 support both unidi- rectional and bidirectional operation. the devices oper- ate in unidirectional mode with v refin = gnd. the output is then referenced to ground and the output volt- age v out is proportional to the positive voltage drop (v sense ) from rs+ to rs- (figure 1). the max9918/max9919 operate in bidirectional mode by application of a low-source impedance reference voltage in the 0v to v cc - 1.9v range, (typically v cc /2), to refin. for the MAX9920, the reference voltage range is 0v to v cc - 2.4v (typically v cc /2). the output voltage v out relative to v refin is then proportional to the v sense voltage drop from rs+ to rs- (figure 2). max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 14 ______________________________________________________________________________________ i discharge r sense load to adc v cc gnd rs+ rs- refin out 30mv 10mv 20mv 20mv 0 discharge current 0 . 9v 3 . 6v 2 . 7v g = 90v/v 5v 1 . 8v shdn max9919n v sense v out figure 1. unidirectional operation i discharge r sense i charge load to adc 2 . 5v v cc gnd rs+ rs- refin out -20mv 10mv 20mv 0 discharge current charge current -1 . 8v 1 . 8v 0 . 9v g = 90v/v v sense 5v -0 . 9v -10mv shdn v out - v refin max9919n figure 2. bidirectional operation
shutdown mode drive shdn high to enter low-power shutdown mode. in shutdown mode, the max9918/max9919/MAX9920 draw 0.5a (typ) of quiescent current. adjustable gain (max9918/MAX9920) the max9918/MAX9920 feature externally adjustable gain set by a resistive-divider network circuit using resistors r1 and r2 (see the functional diagram ). the gain frequency compensation is set for a minimum gain of 30v/v for the max9918 and 7.5v/v for the MAX9920. the gain g for the max9918/MAX9920 is given by the following equation: applications information component selection 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 g where v sense is the full-scale sense voltage, 50mv for the max9918/max9919, or 200mv for the MAX9920 and g is the gain of the device. g is externally adjustable for the max9918/MAX9920. the max9919 has a fixed gain version of 45v/v (max9919f) or 90v/v (max9919n). in unidirectional applications (v refin = 0v), select the gain of the max9918/MAX9920 to utilize the full output range between gnd and v cc . in bidirectional applica- tions (v refin = v cc /2), select the gain to allow an output voltage range of v cc /2. v out must be at least 100mv from either rail to achieve the rated gain accuracy. sense resistor, r sense choose r sense based on the following criteria: accuracy: a high r sense value allows lower currents to be measured more accurately. this is because off- sets become less significant when the sense voltage is larger. in the linear region (100mv < v out < v cc - 100mv), there are two components to accuracy: input offset voltage (v os ) and gain error (ge). use the linear equation to calculate total error: v out = (g ge) x (v sense v os ) for best performance, select r sense to provide approximately 50mv (max9918/max9919) or 200mv (MAX9920) of sense voltage for the full-scale current in each application. sense resistors of 5m ? to 100m ? are available with 1% accuracy or better. 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 resistors value might drift if it is allowed to heat up excessively. the precision v os of the max9918/max9919/MAX9920 allows the use of small sense resistors to reduce power dissipation and reduce hot spots. inductance: keep inductance low if i sense has a large high-frequency component by using resistors with low inductance value. power-supply bypassing and grounding bypass the max9918/max9919/MAX9920s v cc to ground with a 0.1f capacitor. grounding these devices requires no special precautions; follow the same cautionary steps that apply to the rest of the sys- tem. high-current systems can experience large volt- age drops across a ground plane, and this drop may add to or subtract from v out . using a differential mea- surement between v out and refin prevents this prob- lem. for highest current-measurement accuracy, use a single-point star ground. connect the exposed pad to a solid ground to ensure optimal thermal performance. ( g r r f =+ ? ? ? ? ? ? 1 2 1 o or max and g 9918 1 ) = + + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? r r for max 2 1 4 9920 () max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers ______________________________________________________________________________________ 15
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 16 ______________________________________________________________________________________ a input input stage/ level shifter fixed gain g = 45v/v or 90v/v v cc rs+ rs- fb out refin r2 r1 gnd shdn max9919f i load 50mv (typ) r sense a input input stage/ level shifter adjustable gain v cc rs+ rs- fb out refin r2 r1 gnd shdn max9918 MAX9920 i load max9918 50mv (typ) MAX9920 200mv (typ) r sense gain is set by external resistors, r1 and r2 g = [1+(r2/r1)] for max9918 g = [1+(r2/r1)]/4 for MAX9920 functional diagram chip information process: bicmos
max9918/max9919/MAX9920 -20v to +75v input range, precision uni-/bidirectional, current-sense amplifiers 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 17 ? 2009 maxim integrated products maaxim is a registered trademark of maxim integrated products, inc. package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 8 soic-ep s8e+14 21-0111 8l, soic exp. pad.eps c 1 1 21-0111 package outline 8l soic, .150" exposed pad

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