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general description the MAX9928/max9929 low-cost, uni-/bidirectional, high-side, current-sense amplifiers are ideal for moni- toring battery charge and discharge currents in note- books, cell phones, and other portable equipment. these devices feature a wide -0.1v to +28v input com- mon-mode voltage range, low 20? supply current with v os less than 0.4mv, and a gain accuracy better than 1.0%. the input common-mode range is independent of the supply voltage, ensuring that the current-sense information remains accurate even when the measure- ment rail is shorted to ground. the MAX9928f/MAX9928t feature a current output with transconductance ratios of 5?/mv and 2?/mv, respec- tively. an external resistor converts the output current to a voltage, allowing adjustable gain so that the input sense voltage can be matched to the maximum adc input swing. the max9929f/max9929t have a voltage output and integrate a 10k output resistor for fixed voltage gains of 50v/v and 20v/v, respectively. a digital sign output indicates direction of current flow, so the user can utilize the full adc input range for mea- suring both charging and discharging currents. the MAX9928/max9929 are fully specified over the -40? to +125? automotive temperature range, and available in 6-bump ucsp (1mm x 1.5mm) and 8-pin ?ax packages. the ucsp package is bump-to-bump com- patible with the max4372_ebt. features ? wide -0.1v to +28v common-mode range, independent of supply voltage ? 2.5v to 5.5v operating supply voltage ? 20 a quiescent supply current ? 0.4mv (max) input offset voltage ? gain accuracy better than 1% (max) ? sign output indicates current polarity ? two i out transconductance versions available 2 a/mv (MAX9928t) 5 a/mv (MAX9928f) ? two v out gain versions available 20v/v (max9929t) 50v/v (max9929f) ? pin compatible with the max4372 in ucsp ? available in ultra-small 3x2 ucsp (1mm x 1.5mm) and 8-pin max packages applications monitoring charge/discharge currents in portable/battery-powered systems notebook computers general-system/board-level current monitoring smart-battery packs/chargers precision current sources smart cell phones super capacitor charge/discharge MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers ________________________________________________________________ maxim integrated products 1 ordering information 19-4251; rev 0; 8/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. note: all devices are specified over the -40? to +125? operating temperature range. + denotes a lead-free/rohs-compliant package. * future product?ontact factory for availability. ? the MAX9928_abt and the max9929_abt use package code r61a1+1 with backside coating to minimize die chipping. part output type gain pin-package top mark pkg code MAX9928 faua+ current g m = 5?/mv 8 ?ax u8-1 MAX9928fabt+t ? current g m = 5?/mv 3x2 ucsp +aaa r61a1+1 MAX9928taua+ current g m = 2?/mv 8 ?ax u8-1 MAX9928tabt+t ? current g m = 2?/mv 3x2 ucsp +aac r61a1+1 max9929 faua+ voltage a v = 50v/v 8 ?ax u8-1 max9929fabt+t ? voltage a v = 50v/v 3x2 ucsp +aab r61a1+1 max9929taua+* voltage a v = 20v/v 8 ?ax u8-1 max9929tabt+* ? voltage a v = 20v/v 3x2 ucsp +aad r61a1+1 pin configurations and typical operating circuit appear at end of data sheet. ucsp is a trademark and ?ax is a registered trademark of maxim integrated products, inc.
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v rs+ = -0.1v to +28v, v cc = 3.3v, v sense = (v rs+ - v rs- ) = 0v, r out = 10k for MAX9928_, t a = -40? to +125?, unless other- wise noted. typical values are at t a = +25?.) (note 1) 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 , sign to gnd ...................................................-0.3v to +6v rs+, rs- to gnd....................................................-0.3v to +30v out to gnd ...............................................-0.3v to (v cc + 0.3v) differential input voltage (v rs+ - v rs- ) .............................. ?0v out, sign short circuit to v cc or gnd ...................continuous current into any pin..........................................................?0ma continuous power dissipation (t a = +70?) 6-bump 1mm x 1.5mm ucsp (derate 3.9mw/? above +70?) ............................308.3mw 8-pin ?ax (derate 4.8mw/? above +70?) .............388mw operating temperature range ........................-40? to +125? storage temperature range ............................-65? to +150? junction temperature .....................................................+150? lead temperature (soldering, 10s) .................................+300? lead temperature (reflow) ..............................................+260? bump temperature (reflow) .............................................+260? parameter symbol conditions min typ max units amplifier dc electrical characteristics t a = +25 c ?.1 ?.4 v rs+ = 3.6v t a = -40 c to +125 c ?.8 t a = +25 c ?.6 ?.0 input offset voltage (note 2) v os v rs+ = -0.1v t a = -40 c to +125 c ?.0 mv common-mode input range v cmr (note 3) -0.1 +28 v t a = +25 c 93 104 2v v rs+ 28v t a = -40 c to +125 c87 t a = +25 c6072 common-mode rejection ratio cmrr -0.1v v rs+ +2v t a = -40 c to +125 c54 db max992_f ?0 full-scale sense voltage (note 2) v sense max992_t ?25 mv max9929f 50 gain (note 2) a v max9929t 20 v/v t a = +25 c ?.3 ?.0 max9929_, v rs+ = 3.6v t a = -40 c to +125 c ?.5 t a = +25 c ?.3 ?.0 gain accuracy (notes 2, 6) max9929_, v rs+ = -0.1v t a = -40 c to +125 c ?.8 % MAX9928f 5 transconductance (note 2) g m MAX9928t 2 ?/mv
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 3 electrical characteristics (continued) (v rs+ = -0.1v to +28v, v cc = 3.3v, v sense = (v rs+ - v rs- ) = 0v, r out = 10k for MAX9928_, t a = -40? to +125?, unless other- wise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units t a = +25 c ?.3 ?.0 MAX9928_, v rs+ = 3.6v t a = -40 c to +125 c ?.5 t a = +25 c ?.3 ?.0 transconductance accuracy (note 2) MAX9928_, v rs+ = -0.1v t a = -40 c to +125 c ?.8 % 2v v rs+ 28v 0 1.6 6 input bias current (note 4) i rs+ , i rs- -0.1v v rs+ +2v -80 +6 ? 2v v rs+ 28v ?.05 ? input offset bias current (note 4) i os -0.1v v rs+ +2v ?.2 ? ? input leakage current i rs+ , i rs- v cc = 0v, v rs+ = v rs- = 28v (note 5) 0.05 1.0 ? MAX9928_ 5 m output resistance r out max9929_ 6.4 10 13.6 k MAX9928_, r out = 10k (v cc - 0.1) (v cc - 0.45) output high voltage (note 6) v oh max9929_ (v cc - 0.1) (v cc - 0.45) v t a = +25 c 0.25 2.0 minimum output voltage (note 7) v ol max9929_ t a = -40 c to +125 c15 mv t a = +25 c 0.025 0.2 minimum output current (note 7) i ol MAX9928_ t a = -40 c to +125 c 1.5 ? sign comparator dc electrical characteristics t a = +25? -1.6 -1.2 -0.5 v rs+ = 3.6v t a = -40? to +125? -2.15 -0.15 t a = +25? -2.5 -1.2 +0.25 discharge to charge trip point (note 8) v tdc v rs+ = -0.1v t a = -40 c to +125 c -4.6 +2.3 mv v rs+ = 3.6v t a = +25 c -1.8 charge to discharge trip point (note 8) v tcd v rs+ = -0.1v t a = +25 c -1.8 mv hysteresis width v hys v rs+ = 3.6v, -0.1v t a = +25 c 0.6 mv
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 4 _______________________________________________________________________________________ electrical characteristics (continued) (v rs+ = -0.1v to +28v, v cc = 3.3v, v sense = (v rs+ - v rs- ) = 0v, r out = 10k for MAX9928_, t a = -40? to +125?, unless other- wise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units common-mode input range (note 9) v cmr -0.1 +28 v 2v v rs+ 28v 102 common-mode rejection ratio (note 9) cmrr -0.1v v rs+ +2v 74 db output low voltage v ol i sink = 100? 0.03 0.1 v output high voltage v oh (v cc - 0.01) (v cc - 0.04) v internal pullup resistor r pull-up 1m power supply t a = +25 c 2.5 5.5 supply voltage range (note 10) v cc t a = -40 c to +125 c 2.8 5.5 v v rs+ = 3.6v 72 90 amplifier power-supply rejection ratio (note 10) psrr a v rs+ = -0.1v 66 86 db v rs+ = 3.6v 90 comparator power-supply rejection ratio psrr c v rs+ = -0.1v 86 db 2v v rs+ 28v 20 30 quiescent supply current i cc -0.1v v rs+ < +2v 115 200 ? ac electrical characteristics max992_f, v sense = 50mv 150 -3db bandwidth bw max992_t, v sense = 125mv 125 khz max992_f, v sense = 5mv to 50mv step 6 max992_f, v sense = 50mv to 5mv step 15 max992_t, v sense = 5mv to 125mv step 8 out settling to 1% of final value t set v rs+ = 3.6v, c load = 10pf, r out = 10k for MAX9928_ max992_t, v sense = 125mv to 5mv step 13 ?
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 5 note 1: all devices are 100% production tested at t a = +25?. all temperature limits are guaranteed by design. note 2: v os is extrapolated from two point transconductance and gain accuracy tests. measurements are made at v sense = +5mv and v sense = +50mv for max992_f and v sense = +5mv and v sense = +125mv for max992_t. these measure- ments are also used to test the full-scale sense voltage, transconductance, and gain. these v os specifications are for the trimmed direction only (v rs+ > v rs- ). for current flowing in the opposite direction (v rs- > v rs+ ), v os is ?mv (max) at +25? and ?.8mv (max) over temperature, when v rs+ is at 3.6v. see the detailed description for more information. note 3: guaranteed by common-mode rejection ratio. extrapolated v os as described in note 2 is used to calculate common-mode rejection ratio. note 4: includes input bias current of sign comparator. note 5: leakage in to rs+ or rs- when v cc = 0v. includes input leakage current of sign comparator. this specification does not add to the bias current. note 6: output voltage should be 650mv below v cc to achieve full accuracy. note 7: i ol is the minimum output current in the v sense - i out transfer characteristics. v ol is the minimum output voltage in the v sense - v out transfer characteristic. note 8: v sense voltage required to switch comparator. note 9: discharge to charge trip point is functionally tested at v cm = -0.1v, +3.6v, and +28v. note 10: guaranteed by psrr test. extrapolated v os as described in note 2 is used to calculate the power-supply rejection ratio. v sense has to be such that the output voltage is 650mv below v cc to achieve full accuracy. electrical characteristics (continued) (v rs+ = -0.1v to +28v, v cc = 3.3v, v sense = (v rs+ - v rs- ) = 0v, r out = 10k , for MAX9928_, t a = -40? to +125?, unless other- wise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units overdrive = 1mv 80 sign comparator propagation delay (low to high) t prop_lh overdrive = 5mv 30 ? overdrive = 1mv 50 sign comparator propagation delay (high to low) t prop_hl overdrive = 5mv 13 ? power-up time to 1% of final value v sense = 50mv for max992_f, v sense = 125mv for max992_t, v rs+ = 3.6v, c load = 10pf 50 ? saturation recovery time 100mv v sense 50mv for max992_f, 250mv v sense 125mv for max992_t, v rs+ = 3.6v, c load = 10pf 4ms
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 6 _______________________________________________________________________________________ v os histogram MAX9928 toc01 v os (mv) frequency (%) 0.30 0.20 0.10 -0.20 -0.10 0 -0.30 5 10 15 20 25 30 35 40 45 0 -0.40 0.40 a v = 50v/v gain accuracy histogram MAX9928 toc02 gain accuracy (%) frequency (%) 0.8 0.6 0.4 -0.6 -0.4 0.2 -0.2 0 -0.8 5 10 15 20 25 30 0 -1.0 1.0 a v = 50v/v offset voltage vs. common-mode voltage MAX9928 toc03 common-mode voltage (v) offset voltage (mv) 3 2 0 1 -1.5 -1.0 -0.5 0 1.0 0.5 1.5 2.0 -2.0 -1 28 offset voltage vs. temperature MAX9928 toc04 temperature ( c) offset voltage (mv) 110 95 65 80 -10 5 20 35 50 -25 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 -40 125 v cm = 3.6v supply current vs. supply voltage MAX9928 toc05 supply voltage (v) supply current ( a) 5.0 4.5 4.0 3.5 3.0 25 50 75 100 125 150 0 2.5 5.5 v rs+ = 0v v sense = 0v v rs+ = 3.6v supply current vs. common-mode voltage MAX9928 toc06 common-mode voltage (v) supply current ( a) 2.0 1.5 1.0 0.5 0 30 60 90 150 120 0 -0.5 28 v cc = 5.5v v cc = 2.5v supply current vs. temperature MAX9928 toc07 temperature ( c) supply current ( a) 75 50 25 0 -25 25 50 75 100 125 150 0 -50 125 100 v rs+ = 0v v sense = 0v v rs+ = 3.6v MAX9928f i out vs. v sense MAX9928 toc09 v sense (v) i out ( a) 0.4 0.3 0.2 0.1 500 1000 1500 2000 2500 0 0 0.5 t a = -40 c t a = +125 c v out = 0v t a = +25 c -80 -60 -70 -30 -40 -50 0 -10 -20 10 -2 2 4 06810 28 input bias current vs. common-mode voltage MAX9928 toc08 common-mode voltage (v) input bias current ( a) -0.1 typical operating characteristics (v cc = 3.3v, v rs+ = 12v, t a = +25?, unless otherwise noted.)
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 7 MAX9928t i out vs. v sense MAX9928 toc10 v sense (v) i out ( a) 0.6 0.4 0.2 400 800 1200 1600 0 0 0.8 v out = 0v t a = +125 c t a = +25 c t a = -40 c max9929f v out vs. v sense MAX9928 toc11 v sense (mv) v out (v) 120 100 80 60 40 20 1 2 3 4 5 6 0 0 140 v cc = 5.5v v cc = 3.3v v cc = 2.7v v cc = 2.5v max9929f v out vs. v sense MAX9928 toc12 v sense (mv) v out (v) 80 70 60 50 40 2.2 2.4 2.6 2.8 3.0 3.2 3.4 2.0 30 90 t a = -40 c t a = +125 c t a = +25 c max9929t v out vs. v sense MAX9928 toc13 v sense (mv) v out (v) 300 250 200 150 100 50 1 2 3 4 5 6 0 0 350 v cc = 5.5v v cc = 3.3v v cc = 2.7v v cc = 2.5v max9929t v out vs. v sense MAX9928 toc14 v sense (mv) v out (v) 200 180 160 140 120 2.2 2.4 2.6 2.8 3.0 3.2 3.4 2.0 100 220 t a = -40 c t a = +125 c t a = +25 c gain accuracy vs. supply voltage MAX9928 toc15 supply voltage (v) gain accurancy (%) 5.0 4.5 4.0 3.5 3.0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 2.5 5.5 minimum output voltage vs. temperature MAX9928 toc16 temperature ( c) minimum output voltage (mv) 110 95 65 80 -10 5 20 35 50 -25 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0 -40 125 gain accuracy vs. temperature MAX9928 toc17 temperature ( c) gain accuracy (%) 110 95 65 80 -10 5 20 35 50 -25 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 -40 125 small-signal gain vs. frequency MAX9928 toc18 frequency (khz) gain (db) 100 10 1 0.1 23 26 29 32 35 20 0.01 1000 v cm = 3.6v max992_t max992_f typical operating characteristics (continued) (v cc = 3.3v, v rs+ = 12v, t a = +25?, unless otherwise noted.)
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 8 _______________________________________________________________________________________ cmrr vs. frequency MAX9928 toc19 frequency (hz) cmrr (db) 100k 10k 1k 100 30 60 90 120 0 10 1m psrr vs. frequency MAX9928 toc20 frequency (hz) psrr (db) 10k 1k 100 10 1 -100 -80 -60 -40 -20 0 20 -120 0.1 100k max9929f large-signal transient response MAX9928 toc21 100 s/div v out v sense 1v/div 50mv/div max9929t large-signal transient response MAX9928 toc22 100 s/div v out v sense 1v/div 20mv/div v sign and v out vs. v sense MAX9928 toc23 v sense (mv) v out (mv) v sign (v) 2 1 -2 -1 0 50 100 150 0 1 2 3 4 0 -3 3 typical operating characteristics (continued) (v cc = 3.3v, v rs+ = 12v, t a = +25?, unless otherwise noted.) overdrive recovery MAX9928 toc24 400 s/div v sense 100mv/div v out 500mv/div comparator propagation delay (rs+ = 3.6v, 5mv overdrive) MAX9928 toc25 40 s/div v sense 2mv/div v out 1v/div power-up delay MAX9928 toc26 40 s/div v cc 1v/div v out 1v/div
detailed description the MAX9928_/max9929_ micropower uni-/bidirectional, current-sense amplifiers feature -0.1v to +28v input common-mode range that is independent of the supply voltage. this wide input voltage range feature allows the monitoring of the current flow out of a power supply dur- ing short-circuit/fault conditions, and also enables high- side current sensing at voltages far in excess of the supply voltage (v cc ). the MAX9928_/max9929_ oper- ate from a 2.5v to 5.5v single supply and draw a low 20? quiescent supply current. current flows through the sense resistor, generating a sense voltage v sense (figure 1). the comparator sens- es the direction of the sense voltage and configures the amplifier for either positive or negative sense voltages by controlling the s1 and s2 switches. for positive v sense voltage, the amplifier? inverting input is high impedance and equals v in - v sense. the amplifier? output drives the base of q1, forcing its non- inverting input terminal to (v in - v sense ); this causes a current to flow through r g1 equal to |v sense |/r g1 . transistor q2 and the current mirror amplify the current by a factor of m. for negative v sense voltage, the amplifier? noninvert- ing input is high impedance and the voltage on rs- ter- minal equals v in + v sense. the amplifier? output drives the base of q1 forcing its inverting input terminal to match the voltage at the noninverting input terminal; this causes a current to flow through r g2 equal to |v sense |/r g2 . again, transistor q2 and the current mir- ror amplify the current by a factor of m. +v sense vs. -v sense the amplifier is configured for either positive v sense or negative v sense by the sign comparator. the com- parator has a built-in offset skew of -1.2mv so that ran- dom offsets in the comparator do not affect the precision of i out (v out ) with positive v sense . the comparator has a small amount of hysteresis (typically 0.6mv) to prevent its output from oscillating at the crossover sense voltage. the ideal transfer characteris- tic of i out (v out ) and the output of the comparator (sign) is shown in figure 2. the amplifier v os is only trimmed for the positive v sense voltages (v rs+ > v rs- ). the sign comparator reconfig- ures the internal structure of the amplifier to work with negative v sense voltages (v rs- > v rs+ ) and the preci- sion v os trim is no longer effective and the resulting v os is slightly impacted. see details in the electrical characteristics note 2. the user can choose the direc- tion that needs the best precision to be the direction where v rs+ > v rs- . for example, when monitoring li+ battery currents, the discharge current should be v rs+ > v rs- to give the best accuracy over the largest dynamic range. when the battery charger is plugged in, the charge current flows in the opposite direction and is usually much larger, and a higher v os error can be tolerated. see the typical operating circuit . for applications with unidirectional currents (e.g., bat- tery discharge only), the sign output can be ignored. note that as v sense increases, the output current (i out for the MAX9928 or v out /10k for the max9929) also increases. this additional current is supplied from v cc . MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers _______________________________________________________________________________________ 9 pin description pin bump ?ax ucsp name function 1 b3 rs- negative current-sense input. load-side connection for the external sense resistor. 2 b2 sign sign output. indicates polarity of v sense . sign = h indicates v rs+ > v rs- sign = l indicates v rs+ < v rs- 3 b1 rs+ positive current-sense input. power-side connection to the external sense resistor. 4, 5 n.c. no connection. not internally connected. 6a1v cc supply voltage input. bypass to gnd with a 0.1? capacitor. 7 a2 gnd circuit ground 8 a3 out current-sense output. MAX9928: current output (i out is proportional to |v sense |). max9929: voltage output (v out is proportional to |v sense |).
for both positive and negative v sense voltages, the current flowing out of the current mirror is equal to: i out = m x |v sense |/r g1 for the MAX9928f/MAX9928t, the transconductance of the device is trimmed so that i out /|v sense | = 5?/mv and 2?/mv, respectively. for the max9929f/ max9929t, the voltage gain of the device is trimmed so that v out /|v sense | = 50v/v and 20v/v, respectively. the sign output from the comparator indicates the polarity of v sense . current output (MAX9928_) the output voltage equation for the MAX9928_ is given below: v out = (r sense x i load ) x (g m x r out ) where v out = the desired full-scale output voltage, i load = the full-scale current being sensed, r sense = the current-sense resistor, r out = the voltage-setting resistor, and g m = MAX9928f transconductance (5?/mv) or MAX9928t transconductance (2?/mv). the full-scale output voltage range can be set by changing the r out resistor value. the above equation can be modified to determine the r out required for a particular full-scale range: r out = (v out )/(i load x r sense x g m ) MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 10 ______________________________________________________________________________________ current mirror MAX9928_ max9929_ c s2 s1 q1 q2 10k * sign out v cc v in -0.1v to +28v (v batt ) r sense v sense + - 2.5v to 5.5v r g1 80k r g2 80k r c2 80k r c1 80k rs- rs+ to load/charger to adc to c *internal 10k resistor for max9929_ only. gnd a v cc 1m figure 1. functional diagram 0 -1.2 -1.8 -3.0 3.0 2.0 1.0 0 -1.2 -1.8 -3.0 3.0 2.0 1.0 v sense (mv) v sense (mv) sign i out (v out ) ( ) for the max9929_. figure 2. ideal transfer characteristics with 0mv amplifier input offset voltage and -1mv comparator input offset voltage
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers ______________________________________________________________________________________ 11 out is a high-impedance current source and can drive an unlimited amount of capacitance. voltage output (max9929_) the output voltage equation for the max9929_ is given below: v out = (r sense x i load ) x (a v ) where v out = the desired full-scale output voltage, i load = the full-scale current being sensed, r sense = the current-sense resistor, a v = max9929f voltage gain (50v/v) or max9929t voltage gain = (20v/v). sign output the current/voltage at out indicates magnitude. the sign output indicates the current? direction. the sign comparator compares rs+ to rs-. the sign output is high when rs+ is greater than rs- indicating positive current flow. the sign output is low when rs- is greater than rs+ indicating negative current flow. in battery- operated systems, this is useful for determining whether the battery is charging or discharging. the sign output might not correctly indicate the direction of load current when v sense is between -1.8mv to -1.2mv (see figure 2). comparator hysteresis of 0.6mv pre- vents oscillation of sign output. if current direction is not needed, leave sign unconnected. applications information choosing r sense the MAX9928_/max9929_ operate over a wide variety of current ranges with different sense resistors. adjust the r sense value to monitor higher or lower current lev- els. select r sense using these guidelines: ? voltage loss: a high r sense value causes the power-source voltage to drop due to ir loss. for least 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 because offsets become less significant when the sense voltage is larger. ? efficiency and power dissipation: at high current levels, the i 2 r losses in r sense might be significant. take this into consideration when choosing the resis- tor value and power dissipation (wattage) rating. also, if the sense resistor is allowed to heat up exces- sively, its value could drift. ? inductance: if there is a large high-frequency com- ponent to i sense , keep inductance low. wire-wound resistors have the highest inductance, while metal film is somewhat better. low-inductance metal-film resistors are available. instead of being spiral wrapped around a core, as in metal film or wire- wound resistors, these are a straight band of metal. they are made in values under 1 . use in systems with super capacitors since the input common-mode voltage range of the MAX9928/max9929 extends all the way from -0.1v to 28v, they are ideal to use in applications that require use of super capacitors for temporary or emergency energy storage systems. some modern industrial and automotive systems use multifarad (1f?0f) capacitor banks to supply enough energy to keep critical sys- tems alive even if the primary power source is removed or temporarily disabled. unlike batteries, these capaci- tors can discharge all the way down to 0v. the MAX9928/max9929 can continuously help monitor their health and state of charge/discharge. ucsp applications information for the latest application details on ucsp construction, dimensions, tape carrier information, pcb techniques, bump-pad layout, and recommended reflow tempera- ture profile, as well as the latest information on reliability testing results, go to maxim? website at www.maxim- ic.com/ucsp to find application note 1891: understanding the basics of the wafer-level chip- scale package (wl-csp). chip information process: bicmos
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers 12 ______________________________________________________________________________________ 1 2 3 4 8 7 6 5 out gnd v cc n.c. n.c. rs+ sign rs- MAX9928_ max9929_ max top view ucsp (1mm x 1.5mm) top view (bumps on the bottom) v cc gnd out 1 a b 23 rs+ sign rs- MAX9928_ max9929_ + pin configurations c digital input adc gnd gnd r sense 2.5v to 5.5v 0.1 f v in -0.1v to +28v out sign v cc rs+ rs- r out * *for the MAX9928_ only MAX9928_ max9929_ load wall-cube charger typical operating circuit
MAX9928/max9929 -0.1v to +28v input range, micropower, uni-/bidirectional, current-sense amplifiers ______________________________________________________________________________________ 13 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) 8lumaxd.eps
MAX9928/max9929 -0.1v to +28v input range, micropower, 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. 14 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) ucsp.eps

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