high-side current monitor ixys cop y right ? ix ys corp ora t ion 2004 ds99 183( 1/04) ixi848 features: ? high -side cu rre nt sense a m plifier ? 2.7v to 40v input ra nge ? 0.7% typical full scale accuracy ? scalabl e out put voltage ? soic packag e type applications: ? powe r mana gement syste m s ? smart battery pac k s ? battery chargers ? battery powe red porta b le equipme n t ? dc moto r c o ntrol general description the ixi848 i s a p r e c isi o n high si de current sen s e monitor. hig h si de po we r-line monito ri ng offe rs the advantag e of allo wing the gro und pla n e to remai n undi sturb ed whe n se nsi n g load cu rrents. an external sen s e resi st or set s the range of the amplified ground -refere n c ed outp u t monito ring voltage. th e output volt age i s amp lified by a sele ctabl e fixed gain of e i ther 10 o r 5 0 . with an input voltage rang e exceed ing 37v, an d output gai n of up to 50, the ixi848 i s de sig ned t o add re ss a wide vari ety of current se nse appli c ation s . the ixi848 operates ove r a tempe r at ure ra nge of -40 c to +85 c. the ixi8 48 is availa b l e in an 8- lead soic p a ckag e. figure 1. ix i848 func tional block diagram figure 2. ix i848 soic pin confi guration and general application circuit 5 4 1 3 2 8 r10 r50 vo u t gn d loa d in il loa d / ba t t e ry rs r 10r 40r vio zm + - r g r g 8 - le ad s o ic 1 2 3 4 8 7 6 5 vo u t r10 r50 gn d in l o ad in = positive s upp l y term ina l r s = sense re sistor lo ad = load side termi nal z m = external voltag e monit o r imped ance r g = o u tput gain setting res i stors r10, r5 0 = selectabl e outp u t gai n termina l s vo ut = amplified o u tput mon i torin g voltag e
ixys 2 ixi848 absolute maximum ratings parameter rati n g voltag e to an y pin -0.3v to + 40v differenti a l inp u t voltage (v se n s e ) + 0.4v input curre nt to an y pi n t b d o peratin g amb i ent t e mp ran ge -40c to + 85c o peratin g junc tion t e mp ran ge -40c to + 125 c j a 1 5 0 c/w jc 40c/w storage t e mp ran ge -65c to + 150 c lea d t e mperature (sol deri ng, 10 sec) + 300c a bsol ute maxi mu m r a tin g s are stress ratings. stresses in e x cess of thes e ratin g s ca n caus e p er ma nent d a mag e to th e dev ice. f u nction a l oper ation of t he devic e at these or an y othe r cond itions bey ond th ose i n d i c a ted i n the o p e r ation a l sections of this data s heet is not i m p l ie d. ex posur e of the device t o the abso l ute maxi mu m rati ngs fo r an exte nd ed p erio d may deg rade th e d e vic e an d affect its reliabi lity. esd w a rning esd (electrostatic discharge) sensitive dev ice. e l e c trostatic charges can readily accumulate on test equipment and t he human bo dy in excess of 40 00 volts. this energ y can discharge w i thou t det ection. although the ixi848 feat ure proprieta ry esd protecti o n circuitry , perman ent damage ma y be sustained i f subjected to hi gh energ y electrostatic discharges . proper esd precautions are recommended to avoid performan ce degradation o r loss of functionality . electrical characteristics t a = 25c, v in = 2.7v to 40v, unl ess other w i se noted parameter sy mbol conditio n s min ty p max uni t o peratin g volt age ran ge v in 2 . 7 40 v supp l y curre nt i dd v in = 20v, v sen se = 0 v , i load = 0 a . 0 6 5 m a g a in = 10v/v 150 f u ll scal e sen s e voltag e v sen se g a in = 50v/v 150 mv input o ffset voltag e v os v in = 12v 0.5 mv f u ll scal e accurac y v sen se = 100mv, v in = 12v t a = +2 5 c 0 . 7 % t a = +2 5 c 0 .7 v sen se = 100mv v in = 12v ? @ t a = -40 to +85c 0.3 % t a = +2 5 c 0 .8 t o tal o u t voltage error (note 1, note 2 ) v sen se = 100mv v in = 40v ? @ t a = -40 to +85c 0.4 % t a = +2 5 c 0.5 gain accurac y (note 2) v sen se = 20mv to 100mv v in = 12v, 40v ? @ t a = -40 to + 85c 0.1 % g a in = 10v/v 33 k ? o u t output resistanc e r out v in = 12v v sen se = 100mv g a in = 50v/v 165 k ? note 1: t o tal ou t voltage error is the sum of gain and offset voltage erro rs. note 2: pro duction tested at t a = 25c.
ixys 3 ixi848 t y pical performance characteristics .005 .025 .045 .065 .085 .105 .125 2.7 5 10 1 5 2 0 25 3 0 35 4 0 supp ly c u rren t (ma ) supp ly v o lta ge (v in) . 050 . 055 . 060 . 065 . 070 . 075 . 080 -40 - 15 10 35 60 85 ta (c ) s upply c u rre nt (ma ) vi n = 20v f i g 3. suppl y current vs. vol t age f i g 4. suppl y current vs. t e mperatur e 5mv / div 100 mv 95mv vse n se 20mv / d i v vo ut 1v 0. 95 v 2u s/d i v c l = 8pf vin = 12 v ga in = 1 0 500 mv /d iv 45 m v / d iv vse n se 6mv 100mv c l = 8pf v out 1v 0. 06v v i n= 12 v ga in = 1 0 2us / d iv f i g 5. small si gna l t r ansient resp onse 10 x f i g 6. large si gna l t r ansient resp onse 10 x v s ens e 5mv / d i v vou t 100 mv /d iv c l = 8pf 100 mv 95 m v 5v 4. 75 v v i n= 12 v 10u s / d i v ga in =5 0 v s ens e 45 m v / d iv vou t 2v / d iv 10u s / d i v 1 00mv 6m v 5v 0. 3v c l =8 pf v i n= 12v ga in =5 0 f i g 7. small si gna l t r ansient resp onse 50 x f i g 8. large si gna l t r ansient resp onse 50 x
ixys 4 ixi848 ordering information pin description and configur ation package outline part no . de sc r i ption pack ag e pack q u a n t ity ixi84 8 s 1 8 - p i n so i c 98 (t u b e ) ix i848s1t / r hig h side curre nt sense monit o r 8-pin so ic 250 0 (t ape & reel) soic nam e des c ription 8 r 5 0 con nectin g r5 0 to g nd, (r10= n/c) selects a vo u t voltage that is 50 x the voltag e acr o ss r sen se . 1 g n d g r ound 5 l o a d high im pe da nc e loa d -sid e con nectio n to the ext e rna l sens e resistor. 4 i n positive su ppl y terminal a nd p o w e r co nnecti o n for the ext e rn al sens e resistor. 3 v o u t o u tput voltag e prop ortion al to the voltag e acr o ss r sen se . 2 r 1 0 con nectin g r1 0 to g nd, (r50= n/c) selects a vo u t voltage that is 10 x the voltag e acr o ss r sen se . 6 n / c no co nnect 7 n / c no co nnect 8-lead soi c
ixys 5 ixi848 detailed circuit description the ixi848 is a precision high side current sense monitor featuring an input voltage range of 2.7v to 40v, and a selectable ground referenced fixed gain output of either 10 or 50. a small voltage developed across an external sense resistor (r s ), is converted to an amplified ground referenced voltage output at vout, (figure 1). the amplifier?s non-inverting input is high impedance making the voltage at that terminal equal to v in ? (i l ) (r s ). the amplifier forces the high impedance inverting terminal to equal the non- inverting input voltage by turning on the p-channel mos fet. as the p-channel mos fet is biased on by the amplifier output, current is sourced through r g (10r or 10r+40r), to produce a voltage equal to v in ? (i l ) (r s ) at the inverting input of the amplifier. this develops a voltage across the inverting input resistor, r that matche s the sense voltage across r s , plus any associated in put offset voltage, (v io ). consequently, the voltage at vout corresponds to r g / r. output: vout = g [ (i l ) (r s ) + v io ] gain: g = (r g ) (z m ) / r (r g (r g + z m )) r g = 10r or 50r selectable input offset: v io = + 1.2mv max r = 3.3k ? + 20% temperature coefficient: (all on-chip resistors) r = 700ppm / c typical gain error = + 0.5% typical r sense component selection the r sense value should be selected such that the voltage across r sense is at full-scale for the load current to be monitored. operating the ixi848 at or near the full-scale sense voltage will minimize the error component associated with the input offset voltage of the internal op amp, (0.7% typical at full- scale). the ixi848 can be configured to measure a wide selection of currents by using different r sense values. some common values for typical operation of the ixi848 are listed in the following table. full-scale i l (a) r sense r s ( ?) gain (v/v) vout (v) v sense = 150mv 0.15 1.0 10 1.5 1.5 0.1 10 1.5 5 0.01 50 2.5 100 0.001 50 5 output impedance the vout output is a current source driving a 33k ? resistance to ground for a gain of 10, or a 165k ? resistance to ground for a gain of 50. output gain is reduced by resistive loading of the vout terminal. the impedance of the external monitor load (z m ) should be chosen high enough to maintain the desired accuracy. buffering of the vout terminal with a high-impedance input stage may be required to minimize output errors. the following formulas quantify the percent error introduced by output loading: for a gain of 10 % error = 100 [r load / (33k ? + r load ) ? 1] for a gain of 50 % error = 100 [r load / (165k ? + r load ) ? 1] r load = the external load applied to vout
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