www.ti.com production data information is current as of publication date. products conform to specifications per the terms of texas instruments standard warranty. production processing does not necessarily include testing of all parameters. copyright ?2001, texas instruments incorporated please be aware that an important notice concerning availability, standard warranty, and use in critical applications of texas instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. features complete bidirectional current measurement circuit wide supply range: 2.7v to 40v supply-independent common-mode voltage: 2.7v to 60v resistor programmable gain set low quiescent current: 75 a (typ) msop-8 package high-side, bidirectional current shunt monitor description the ina170 is a high-side, bidirectional current shunt monitor featuring a wide input common-mode voltage range, low quiescent current, and a tiny msop-8 package. bidirectional current measurement is accomplished by out- put offsetting. the offset voltage level is set with an external resistor and voltage reference. this permits measurement of a bidirectional shunt current while using a single supply for the ina170. input common-mode and power-supply voltages are inde- pendent. input voltage can range from +2.7v to +60v on any supply voltage from +2.7v to +40v. low 10 a input bias current adds minimal error to the shunt current. the ina170 converts a differential input voltage to a current output. this current develops a voltage across an external load resistor, setting any gain from 1 to over 100. the ina170 is available in an msop-8 package, and is specified over the extended industrial temperature range, ?0 c to +85 c with operation from ?5 c to +125 c. applications current shunt measurement: automotive, telephone, computers, power systems, test, general instrumentation portable & battery-backup systems battery chargers power management cell phones ina170 sbos193 ?march 2001 2 1 3 out gnd ina170 q1 a1 a2 q2 6 4 i s v ref v+ v supply r os 8 5 load r l r g1 1k ? r g2 1k ? r s v in v in + r os
ina170 2 sbos193 electrostatic discharge sensitivity this integrated circuit can be damaged by esd. texas instru- ments recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper handling and installation procedures can cause damage. esd damage can range from subtle performance degradation to complete device failure. precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. supply voltage, v+ to gnd ................................................. 0.3v to 40v analog inputs, common mode ............................................ 0.3v to 60v differential (v in + ) (v in ) .................................. 40v to 2v analog output, out .............................................................. 0.3v to 40v operating temperature .................................................. 55 c to +125 c storage temperature ..................................................... 65 c to +150 c junction temperature .................................................................... +150 c lead temperature (soldering, 10s) ............................................... +300 c note: (1) stresses above these ratings may cause permanent damage. exposure to absolute maximum conditions for extended periods may degrade device reliability. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not implied. absolute maximum ratings (1) package specified drawing temperature package ordering transport product package number range marking number (1) media ina170ea msop-8 337 40 c to +85 c ina170ea ina170ea/250 tape and reel """"" ina170ea/2k5 tape and reel note: (1) models with a slash (/) are available only in tape and reel in the quantities indicated (e.g., /2k5 indicates 2500 de vices per reel). ordering 2500 pieces of ina170na/2k5 will get a single 2500-piece tape and reel. package/ordering information
ina170 3 sbos193 pin configuration top view msop pin designator description 1v in + noninverting input 2v in inverting input 3v ref reference voltage input 4 gnd ground 5r os offset resistor 6 out output 7 nc no connection 8 v+ supply voltage pin description electrical characteristics at t a = 40 c to +85 c, v s = 5v, v in + = 12v, r out = 25k ? , unless otherwise noted. parameter condition min typ max units input full-scale sense (input) voltage v sense = v in + v in 100 500 mv common-mode input range +2.7 +60 v common-mode rejection v in + = +2.7v to +60v, v sense = 50mv 100 120 db offset voltage (1) rti 0.2 1mv vs temperature t min to t max 1 v/ c vs power supply v+ = +2.7v to +60v, v sense = 50mv 0.1 10 v/v input bias current v in + , v in 10 ua offsetting amplifier offsetting equation v os = (r l /r os ) v ref input voltage 1v s 1v input offset voltage 0.2 1mv vs temperature t min to t max 10 v/ c programming current through r os 01ma input impedance 10 10 || 4 ? || pf input bias current v in + , v in +10 na output transconductance v sense = 10mv to 150mv 0.990 1 1.01 ma/v vs temperature v sense = 100mv 50 na/ c nonlinearity error v sense = 10mv to 150mv 0.01 0.1 % total output error v sense = 100mv 0.5 2% output impedance 1 || 5 g ? || pf voltage output swing to power supply, v+ (v+) 0.9 (v+) 1.2 v swing to common mode, v cm v cm 0.6 v cm 1.0 v frequency response bandwidth r out = 10k ? 400 khz settling time (0.1%) 5v step, r out = 10k ? 3 s noise output-current noise density 20 pa/ hz total output-current noise bw = 100khz 7 na rms power supply operating range v+ +2.7 +60 v quiescent current v sense = 0, i o = 0 75 125 a temperature range specification, t min to t max 40 85 c operating 55 125 c storage 65 150 c thermal resistance, ja 150 c/w note: (1) defined as the amount of input voltage, v sense , to drive the output to zero. ina170ea v in v in v ref gnd v+ nc out r os 1 2 3 4 8 7 6 5 +
ina170 4 sbos193 typical characteristics at t a = +25 c, v+ = 5v, v in + = 12v, r l = 25k ? , unless otherwise noted. 40 30 20 10 0 10 20 100 1k 10k 100k 1m 10m gain (db) frequency (hz) gain vs frequency r l = 10k ? r l = 100k ? r l = 1k ? 120 100 80 60 40 20 0 0.1 1 10 100 1k 10k common-mode rejection (db) frequency (hz) 100k g = 1 g = 10 g = 100 common-mode rejection vs frequency 140 120 100 80 60 40 20 1 10 100 1k 10k 100k power-supply rejection (db) frequency (hz) power-supply rejection vs frequency g = 1 g = 10 g = 100 5 0 5 10 15 0 25 50 75 100 125 total output error (%) v in (mv) total output error vs v in 150 200 55 c +25 c +150 c v in = (v in v in ) + 2 1 0 1 2 0 10 20 30 40 total output error (%) power-supply voltage (v) total output error vs power-supply voltage g = 1 g = 10 g = 25 output error is essentially independent of both v+ supply voltage and input common-mode voltage. 100 80 60 40 20 0 0 10 20 30 40 quiescent current ( a) power-supply voltage (v) quiescent current vs power-supply voltage +150 +125 +25 55
ina170 5 sbos193 typical characteristics (cont.) at t a = +25 c, v+ = 5v, v in + = 12v, r l = 25k ? , unless otherwise noted. step response 20 s/div 1.5v g = 100 0.5v 1v g = 100 0v step response 10 s/div 1v g = 50 0v 2v g = 10 0v
ina170 6 sbos193 operation figure 1 shows the basic circuit diagram for the ina170. load current i s is drawn from supply v s through shunt resistor r s . the voltage drop in shunt resistor v s is forced across r g1 by the internal op-amp, causing current to flow into the collector of q1. external resistor r l converts the output current to a voltage, v out , at the out pin. without offset, the transfer function for the ina170 is: i o = g m (v in + ?v in ? )(1) where g m = 1000 a/v (2) in the circuit of figure 1, the input voltage, (v in + ?v in ? ), is equal to i s ?r s and the output voltage, v out , is equal to i o ?r l . the transconductance, g m , of the ina170 is 1000 a/v. the complete transfer function for the current measurement amplifier in this application is: v out = (i s ) (r s ) (1000 a/v) (r l )(3) applying a positive reference voltage to pin 3 causes a current to flow through r os , forcing output current i o to be offset from zero. the transfer function then becomes: v vr r irr k out ref l os ssl = ? ? ? ? ? ? ? ? ? ? 1 ? (4) the maximum differential input voltage for accurate mea- surements is 0.5v, which produces a 500 a output current. a differential input voltage of up to 2v will not cause damage. differential measurements (pins 1 and 2) can be bipolar with a more-positive voltage applied to pin 2. if a more-negative voltage is applied to pin 1, output current i o will decrease towards zero. basic connection figure 1 shows the basic connection of the ina170. the input pins, v in + and v in ? , should be connected as closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance. the output resistor, r l , is shown connected between pin 6 and ground. best accuracy is achieved with the output voltage measured directly across r l . this is especially important in high-current systems where load current could flow in the ground connections, affecting the measurement accuracy. no power-supply bypass capacitors are required for stability of the ina170. however, applications with noisy or high impedance power supplies may require de-coupling capaci- tors to reject power-supply noise. connect bypass capacitors close to the device pins. power supplies the input circuitry of the ina170 can accurately measure beyond its power-supply voltage, v+. for example, the v+ power supply can be 5v, while the load power-supply voltage (ina170 input voltage) is up to +60v. however, the output-voltage range of the out terminal (pin 6) is limited by the supply. selecting r s and r l the value chosen for the shunt resistor, r s , depends on the application and is a compromise between small-signal accu- racy and maximum permissible voltage loss in the measure- ment line. high values of r s provide better accuracy at lower figure 1. basic circuit connections. voltage gain exact r l ( ? ) nearest 1% r l ( ? ) 11k 1k 22k 2k 5 5k 4.99k 10 10k 10k 20 20k 20k 50 50k 49k 100 100k 100k shunt r s ina170 4 6 out q1 r l i 0 + v o load r g1 1k ? r g2 1k ? v in v in 2 1 i s v+ v ref 3 8 5 v+ power can be common or indepedent of load supply. 2.7 (v+) 40v v p load power supply +2.7 to 60v + q2 r os
ina170 7 sbos193 figure 2. buffering output to drive a/d converter. figure 3. output filter. figure 4. offsetting the output voltage. currents by minimizing the effects of offset, while low values of r s minimize voltage loss in the supply line. for most applications, best performance is attained with an r s value that provides a full-scale shunt voltage of 50mv to 100mv. maximum input voltage for accurate measurements is 500mv. r l is chosen to provide the desired full-scale output voltage. the output impedance of the ina170 out terminal is very high which permits using values of r l up to 100k ? with excellent accuracy. the input impedance of any additional circuitry at the output should be much higher than the value of r l to avoid degrading accuracy. some analog-to-digital (a/d) converters have input imped- ances that will significantly affect measurement gain. the input impedance of the a/d converter can be included as part of the effective r l if its input can be modeled as a resistor to ground. alternatively, an op-amp can be used to buffer the a/d converter input, as shown in figure 2. see figure 1 for recommended values of r l . output voltage range the output of the ina170 is a current, which is converted to a voltage by the load resistor, r l . the output current remains accurate within the compliance voltage range of the output circuitry. the shunt voltage and the input common-mode and power supply voltages limit the maximum possible output swing. the maximum output voltage compliance is limited by the lower of the two equations below: v out max = (v+) ?0.7v ?(v in + ?v in )(5) or v out max = v in ? ?0.5v (6) (whichever is lower) bandwidth measurement bandwidth is affected by the value of the load resistor, r l . high gain produced by high values of r l will yield a narrower measurement bandwidth (see typical per- formance curves). for widest possible bandwidth, keep the capacitive load on the output to a minimum. if bandwidth limiting (filtering) is desired, a capacitor can be added to the output, as shown in figure 3. this will not cause instability. applications the ina170 is designed for current shunt measurement circuits as shown in figure 1, but its basic function is useful in a wide range of circuitry. a creative engineer will find many unforeseen uses in measurement and level shifting circuits. i s opa340 ina170 2 1 4 6 z in r l buffer of amp drives a/d converter without affecting gain. ina170 f 3db = 1 2 r l c l v o f 3db r l c l 2 1 4 6 v 0 v ref r l 6 gain set by r l output offset current = v ref r os output offset voltage = r l v ref r os ina170 2 1 4 5 3 i s r os
ina170 8 sbos193 figure 5. bipolar current measurement. load 4 5 1 v ref 2 3 0.0125 ? gnd r os out v+ ina170 28v +2.5v i s = 10a i os = 125 a i o = 125 a 125 a v out = 0 to +2.5v full-scale 20k ? 6 r l 10k ? +5v 0.1 f 8 ? v = 125mv full-scale v in v in +
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