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ltc6101/ltc6101hv 1 6101fg typical application features applications description high voltage, high-side current sense ampli er in sot-23 to p 6101 ta01 ltc2433-1 ltc6101hv r out 4.99k r in 100 v out v + v C out Cin +in v sense i load 5v to 105v 1f 5v l o a d C + C + v out = ? v sense = 49.9 v sense r out r in 16-bit resolution unidirectional output into ltc2433 adc step response 5.5v 5v 0.5v 0v 500ns/div 6101 ta01b t a = 25c v + = 12v r in = 100 r out = 5k v sense + = v + v out v sense C v sense C = 100mv i out = 100a i out = 0 the ltc ? 6101/ltc6101hv are versatile, high voltage, high side current sense ampli? ers. design ? exibility is provided by the excellent device characteristics; 300v max offset and only 375a (typical at 60v) of current consumption. the ltc6101 operates on supplies from 4v to 60v and ltc6101hv operates on supplies from 5v to 100v. the ltc6101 monitors current via the voltage across an external sense resistor (shunt resistor). internal circuitry converts input voltage to output current, allowing for a small sense signal on a high common mode voltage to be translated into a ground referenced signal. low dc offset allows the use of a small shunt resistor and large gain-setting resistors. as a result, power loss in the shunt is reduced. the wide operating supply range and high accuracy make the ltc6101 ideal for a large array of applications from automotive to industrial and power management. a maxi- mum input sense voltage of 500mv allows a wide range of currents to be monitored. the fast response makes the ltc6101 the perfect choice for load current warnings and shutoff protection control. with very low supply current, the ltc6101 is suitable for power sensitive applications. the ltc6101 is available in 5-lead sot-23 and 8-lead msop packages. n current shunt measurement n battery monitoring n remote sensing n power management , lt, ltc and ltm are registered trademarks of linear technology corporation. thinsot is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. n supply range: 5v to 100v, 105v absolute maximum (ltc6101hv) 4v to 60v, 70v absolute maximum (ltc6101) n low offset voltage: 300v max n fast response: 1s response time (0v to 2.5v on a 5v output step) n gain con? gurable with 2 resistors n low input bias current: 170na max n psrr: 118db min n output current: 1ma max n low supply current: 250a, v s = 12v n operating temperature range: C40c to 125c n low pro? le (1mm) sot-23 (thinsot?) package
ltc6101/ltc6101hv 2 6101fg absolute maximum ratings package/order information total supply voltage (v + to v ? ) ltc6101 ............................................................... 70v ltc6101hv ........................................................ 105v minimum input voltage (?in pin) .................... (v + ? 4v) maximum output voltage (out pin) ............................9v input current ....................................................... 10ma output short-circuit duration (to v ? ) .............. inde? nite operating temperature range ltc6101c/ltc6101hvc .......................? 40c to 85c ltc6101i/ltc6101hvi ......................... ?40c to 85c ltc6101h/ltc6101hvh ................... ?40c to 125c speci? ed temperature range (note 2) ltc6101c/ltc6101hvc ........................... 0c to 70c ltc6101i/ltc6101hvi ......................... ?40c to 85c ltc6101h/ltc6101hvh ................... ?40c to 125c storage temperature range .................. ?65c to 150c lead temperature (soldering, 10 sec) ................. 300c (note 1) ltc6101acms8 ltc6101aims8 ltc6101ahms8 ltc6101hvacms8 ltc6101hvaims8 ltc6101hvahms8 consult ltc marketing for parts speci? ed with wider operating temperature ranges. *the temperature grades and parametric grades are identi? ed by a label on the shipping container. order part number ms8 part marking* ltbsb ltbsb ltbsb ltbsx ltbsx ltbsx t jmax = 150c, e ja = 300c/ w ltc6101acs5 ltc6101ais5 ltc6101ahs5 ltc6101bcs5 ltc6101ccs5 ltc6101bis5 ltc6101cis5 ltc6101bhs5 ltc6101chs5 ltc6101hvacs5 ltc6101hvais5 ltc6101hvahs5 ltc6101hvbcs5 ltc6101hvccs5 ltc6101hvbis5 ltc6101hvcis5 ltc6101hvbhs5 ltc6101hvchs5 order part number s5 part marking* ltbnd ltbnd ltbnd ltbnd ltbnd ltbnd ltbnd ltbnd ltbnd ltbsz ltbsz ltbsz ltbsz ltbsz ltbsz ltbsz ltbsz ltbsz t jmax = 150c, e ja = 250c/ w out 1 v ? 2 top view s5 package 5-lead plastic tsot-23 ?in 3 5 v + 4 +in 1 2 3 4 ?in nc nc out 8 7 6 5 +in v + nc v ? top view ms8 package 8-lead plastic msop order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marketing: http://www.linear.com/leadfree/
ltc6101/ltc6101hv 3 6101fg symbol parameter conditions min typ max units v s supply voltage range 460v v os input offset voltage v sense = 5mv, gain = 100, ltc6101a v sense = 5mv, gain = 100, ltc6101ac, ltc6101ai v sense = 5mv, gain = 100, ltc6101ah 85 300 450 535 v v v v sense = 5mv, gain = 100, ltc6101b 150 450 810 v v v sense = 5mv, gain = 100, ltc6101c 400 800 1200 v v v os /t input offset voltage drift v sense = 5mv, ltc6101a v sense = 5mv, ltc6101b v sense = 5mv, ltc6101c 1 3 5 v/c v/c v/c i b input bias current r in = 1m 100 170 245 na na i os input offset current r in = 1m 2 15 na v sense(max) input sense voltage full scale v os within speci? cation, r in = 1k (note 3) 500 mv psrr power supply rejection ratio v s = 6v to 60v, v sense = 5mv, gain = 100 118 115 140 db db v s = 4v to 60v, v sense = 5mv, gain = 100 110 105 133 db db v out maximum output voltage 12v v s 60v, v sense = 88mv v s = 6v, v sense = 330mv, r in = 1k, r out = 10k v s = 4v, v sense = 550mv, r in = 1k, r out = 2k 8 3 1 v v v v out (0) minimum output voltage v sense = 0v, gain = 100, ltc6101a v sense = 0v, gain = 100, ltc6101ac, ltc6101ai v sense = 0v, gain = 100, ltc6101ah 030 45 53.5 mv mv mv v sense = 0v, gain = 100, ltc6101b 045 81 mv mv v sense = 0v, gain = 100, ltc6101c 0150 250 mv mv i out maximum output current 6v v s 60v, r out = 2k, v sense = 110mv, gain = 20 v s = 4v, v sense = 550mv, gain = 2, r out = 2k 1 0.5 ma ma t r input step response (to 2.5v on a 5v output step) v sense = 100mv transient, 6v v s 60v, gain = 50 v s = 4v 1 1.5 s s bw signal bandwidth i out = 200a, r in = 100, r out = 5k i out = 1ma, r in = 100, r out = 5k 140 200 khz khz i s supply current v s = 4v, i out = 0, r in = 1m 220 450 475 a a v s = 6v, i out = 0, r in = 1m 240 475 525 a a v s = 12v, i out = 0, r in = 1m 250 500 590 a a v s = 60v, i out = 0, r in = 1m ltc6101ai, ltc6101ac, ltc6101bi, ltc6101bc, ltc6101ci, ltc6101cc ltc6101ah, ltc6101bh, ltc6101ch 375 640 690 720 a a a electrical characteristics (ltc6101) the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c, r in = 100, r out = 10k, v sense + = v + (see figure 1 for details), 4v v s 60v unless otherwise noted.
ltc6101/ltc6101hv 4 6101fg symbol parameter conditions min typ max units v s supply voltage range 5 100 v v os input offset voltage v sense = 5mv, gain = 100, ltc6101hva v sense = 5mv, gain = 100, ltc6101hvac, ltc6101hvai v sense = 5mv, gain = 100, ltc6101hvah 85 300 450 535 v v v v sense = 5mv, gain = 100, ltc6101hvb 150 450 810 v v v sense = 5mv, gain = 100, ltc6101hvc 400 800 1200 v v v os /t input offset voltage drift v sense = 5mv, ltc6101hva v sense = 5mv, ltc6101hvb v sense = 5mv, ltc6101hvc 1 3 5 v/c v/c v/c i b input bias current r in = 1m 100 170 245 na na i os input offset current r in = 1m 2 15 na v sense(max) input sense voltage full scale v os within speci? cation, r in = 1k (note 3) 500 mv psrr power supply rejection ratio v s = 6v to 100v, v sense = 5mv, gain = 100 118 115 140 db db v s = 5v to 100v, v sense = 5mv, gain = 100 110 105 133 db db v out maximum output voltage 12v v s 100v, v sense = 88mv v s = 5v, v sense = 330mv, r in = 1k, r out = 10k 8 3 v v v out (0) minimum output voltage v sense = 0v, gain = 100, ltc6101hva v sense = 0v, gain = 100, ltc6101hvac, ltc6101hvai v sense = 0v, gain = 100, ltc6101hvah 030 45 53.5 mv mv mv v sense = 0v, gain = 100, ltc6101hvb 045 81 mv mv v sense = 0v, gain = 100, ltc6101hvc 0 150 250 mv mv i out maximum output current 5v v s 100v, r out = 2k, v sense = 110mv, gain = 20 1 ma t r input step response (to 25v on a 5v output step) v sense = 100mv transient, 6v v s 100v, gain = 50 v s = 5v 1 1.5 s s bw signal bandwidth i out = 200a, r in = 100, r out = 5k i out = 1ma, r in = 100, r out = 5k 140 200 khz khz i s supply current v s = 5v, i out = 0, r in = 1m 200 450 475 a a v s = 6v, i out = 0, r in = 1m 220 475 525 a a v s = 12v, i out = 0, r in = 1m 230 500 590 a a v s = 60v, i out = 0, r in = 1m ltc6101hvi, ltc6101hvc ltc6101hvh 350 640 690 720 a a a v s = 100v, i out = 0, r in = 1m ltc6101hvai, ltc6101hvac, ltc6101hvbi, ltc6101hvbc, ltc6101hvci, ltc6101hvcc ltc6101hvah, ltc6101hvbh, ltc6101hvch 350 640 690 720 a a a electrical characteristics (ltc6101hv) the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c, r in = 100, r out = 10k, v sense + = v + (see figure 1 for details), 5v v s 100v unless otherwise noted.
ltc6101/ltc6101hv 5 6101fg typical performance characteristics electrical characteristics note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the ltc6101c/ltc6101hvc are guaranteed to meet speci? ed performance from 0c to 70c. the ltc6101c/ltc6101hvc are designed, characterized and expected to meet speci? ed performance from C40c to 85c but are not tested or qa sampled at these temperatures. ltc6101i/ ltc6101hvi are guaranteed to meet speci? ed performance from C40c to 85c. the ltc6101h/ltc6101hvh are guaranteed to meet speci? ed performance from C40c to 125c. note 3: r out = 10k for 6v v s 100v, r out = 2k for v s = 4v. ltc6101: i out maximum vs temperature input v os vs temperature input v os vs supply voltage input sense range ltc6101: v out maximum vs temperature ltc6101hv: v out maximum vs temperature 440 10 20 30 50 100 60 70 80 90 v supply (v) maximum v sense (v) 2.5 2 1.5 1 0.5 0 6101 g05 t a = 125c t a = 85c t a = 70c t a = 0c t a = C40c r in = 3k r out = 3k t a = 25c ltc6101 ltc6101hv temperature (c) 12 10 8 6 4 2 0 C40 40 80 120 100 C20 6101 g06 020 60 maximum output (v) v s = 60v v s = 12v v s = 6v v s = 4v temperature (c) 7 6 5 4 3 2 1 0 C40 40 80 120 100 C20 6101 g07 020 60 maximum i out (ma) v s = 12v v s = 60v v s = 6v v s = 4v v supply (v) 40 20 0 C20 C40 C60 C80 C100 C120 C140 6101 g02 432 11 18 25 39 46 53 60 input offset (v) r in = 100 r out = 5k v in = 5mv t a = 125c t a = 85c t a = 45c t a = C40c t a = 0c input offset (v) 800 600 400 200 0 C200 C400 C600 C800 C1000 6101 g01 temperature (c) C40 120 04080 C20 20 60 100 a grade b grade c grade r in = 100 r out = 5k v in = 5mv representative units temperature (c) 12 10 8 6 4 2 0 C40 40 80 120 100 C20 6101 g20 020 60 maximum output (v) v s = 100v v s = 12v v s = 5v v s = 6v v s = 4v
ltc6101/ltc6101hv 6 6101fg typical performance charateristics supply voltage (v) 0 supply current (a) 450 400 350 300 250 200 150 100 50 0 32 6101 g11 816 48 56 24 40 28 412 44 52 20 36 60 C40c 0c 25c 70c 85c 125c v in = 0 r in = 1m v + v + -10mv 0.5v 0v time (10s/div) 6101 g12 t a = 25c v + = 12v r in = 100 r out = 5k v sense + = v + v sense C v out v + -10mv v + -20mv 1v 0.5v time (10s/div) 6101 g13 v out v sense C t a = 25c v + = 12v r in = 100 r out = 5k v sense + = v + ltc6101: supply current vs supply voltage step response 0mv to 10mv step response 10mv to 20mv input bias current vs temperature gain vs frequency gain (db) frequency (hz) 1k 40 35 30 25 20 15 10 5 0 C5 C10 10k 100k 1m 6101 g09 t a = 25c r in = 100 r out = 4.99k i out = 200a i out = 1ma temperature (c) 160 140 120 100 80 60 40 20 0 C40 40 80 120 100 C20 6101 g10 020 60 i b (na) v s = 6v to 100v v s = 4v output error due to input offset vs input voltage ltc6101hv: i out maximum vs temperature input voltage (v) 0.1 output error (%) 1 10 100 0 0.2 0.3 0.4 0.01 0.1 0.5 0.15 0.25 0.35 0.05 0.45 6101 g08 c grade b grade a grade t a = 25c gain =10 temperature (c) 7 6 5 4 3 2 1 0 C40 40 80 120 100 C20 6101 g21 020 60 maximum i out (ma) v s = 12v v s = 100v v s = 6v v s = 5v v s = 4v ltc6101hv: supply current vs supply voltage supply voltage (v) 0 supply current (a) 600 500 400 300 200 100 0 6101 g22 60 10 30 20 40 80 90 50 70 100 C40c 0c 85c 125c v in = 0 r in = 1m 70c 25c
ltc6101/ltc6101hv 7 6101fg typical performance charateristics frequency (hz) psrr (db) 0.1 1 10 100 1k 10k 100k 1m 6101 g19 160 140 120 100 80 60 40 20 0 r in = 100 r out = 10k c out = 5pf gain = 100 i outdc = 100a v inac = 50mvp ltc6101hv, v + = 5v ltc6101, ltc6101hv, v + = 12v ltc6101, v + = 4v v + v + -100mv 5v 0v time (10s/div) 6101 g14 v out c load = 1000pf c load = 10pf v sense C t a = 25c v + = 12v r in = 100 r out = 5k v sense + = v + v + v + -100mv 5v 0v time (100s/div) 6101 g15 v out v sense C t a = 25c v + = 12v c load = 2200pf r in = 100 r out = 5k v sense + = v + 5.5v 5v 0.5v 0v time (500ns/div) 6101 g16 v out v sense ? v sense ? =100mv i out = 100 a i out = 0 t a = 25 c v + = 12v r in = 100 r out = 5k v sense + = v + 5.5v 5v 0.5v 0v time (500ns/div) 6101 g17 v out v sense C =100mv i out = 100 i out = 0 t a = 25c v + = 12v r in = 100 r out = 5k v sense + = v + step response falling edge step response 100mv step response 100mv step response rising edge psrr vs frequency
ltc6101/ltc6101hv 8 6101fg block diagram out: current output. out will source a current that is pro- portional to the sense voltage into an external resistor. v C : negative supply (or ground for single-supply operation). Cin: the internal sense ampli? er will drive in C to the same potential as in + . a resistor (r in ) tied from v + to in C sets the output current i out = v sense /r in . v sense is the voltage developed across the external r sense (figure 1). +in: must be tied to the system load end of the sense resistor, either directly or through a resistor. v + : positive supply pin. supply current is drawn through this pin. the circuit may be con? gured so that the ltc6101 supply current is or is not monitored along with the system load current. to monitor only system load current, connect v + to the more positive side of the sense resistor. to monitor the total current, including the ltc6101 current, connect v + to the more negative side of the sense resistor. the ltc6101 high side current sense ampli? er (figure 1) provides accurate monitoring of current through a user- selected sense resistor. the sense voltage is ampli? ed by a user-selected gain and level shifted from the positive power supply to a ground-referred output. the output signal is analog and may be used as is or processed with an output ? lter. theory of operation an internal sense ampli? er loop forces in C to have the same potential as in + . connecting an external resis- tor, r in , between in C and v + forces a potential across r in that is the same as the sense voltage across r sense . a corresponding current, v sense /r in , will ? ow through r in . the high impedance inputs of the sense ampli? er will not conduct this input current, so it will ? ow through an internal mosfet to the output pin. the output current can be transformed into a voltage by adding a resistor from out to v C . the output voltage is then v o = v C + i out ? r out . C + v + v C 10v out 6101 bd ltc6101/ltc6101hv v battery i out v sense r sense i load r out r in C + l o a d v out = v sense x r out r in 5k 5k 10v Cin +in figure 1. ltc6101/ltc6101hv block diagram and typical connection applications information pin functions
ltc6101/ltc6101hv 9 6101fg applications information figure 2. kelvin input connection preserves accuracy despite large load current ltc6101 r out v out 6101 f02 r in v + load r sense C + v + v C out Cin +in useful gain con? gurations gain r in r out v sense at v out = 5v i out at v out = 5v 20 499 10k 250mv 500a 50 200 10k 100mv 500a 100 100 10k 50mv 500a selection of external current sense resistor the external sense resistor, r sense , has a signi? cant effect on the function of a current sensing system and must be chosen with care. first, the power dissipation in the resistor should be considered. the system load current will cause both heat and voltage loss in r sense . as a result, the sense resis- tor should be as small as possible while still providing the input dynamic range required by the measurement. note that input dynamic range is the difference between the maximum input signal and the minimum accurately reproduced signal, and is limited primarily by input dc offset of the internal ampli? er of the ltc6101. in addition, r sense must be small enough that v sense does not exceed the maximum input voltage speci? ed by the ltc6101, even under peak load conditions. as an example, an application may require that the maximum sense voltage be 100mv. if this application is expected to draw 2a at peak load, r sense should be no more than 50m. once the maximum r sense value is determined, the mini- mum sense resistor value will be set by the resolution or dynamic range required. the minimum signal that can be accurately represented by this sense amp is limited by the input offset. as an example, the ltc6101b has a typical input offset of 150v. if the minimum current is 20ma, a sense resistor of 7.5m will set v sense to 150v. this is the same value as the input offset. a larger sense resistor will reduce the error due to offset by increasing the sense voltage for a given load current. choosing a 50m r sense will maximize the dynamic range and provide a system that has 100mv across the sense resistor at peak load (2a), while input offset causes an error equivalent to only 3ma of load current. peak dissipation is 200mw. if a 5m sense resistor is employed, then the effective current error is 30ma, while the peak sense voltage is reduced to 10mv at 2a, dis- sipating only 20mw. the low offset and corresponding large dynamic range of the ltc6101 make it more ? exible than other solutions in this respect. the 150v typical offset gives 60db of dy- namic range for a sense voltage that is limited to 150mv max, and over 70db of dynamic range if the rated input maximum of 500mv is allowed. sense resistor connection kelvin connection of the in C and in + inputs to the sense resistor should be used in all but the lowest power ap- plications. solder connections and pc board interconnec- tions that carry high current can cause signi? cant error in measurement due to their relatively large resistances. one 10mm x 10mm square trace of one-ounce copper is approximately 0.5m. a 1mv error can be caused by as little as 2a ? owing through this small interconnect. this will cause a 1% error in a 100mv signal. a 10a load current in the same interconnect will cause a 5% error for the same 100mv signal. by isolating the sense traces from the high-current paths, this error can be reduced by orders of magnitude. a sense resistor with integrated kelvin sense terminals will give the best results. figure 2 illustrates the recommended method.
ltc6101/ltc6101hv 10 6101fg applications information 6101 f03b C + C + C + r 5 7.5k v in 301 301 v out i load ltc6101 r sense lo 100m m1 si4465 10k cmpz4697 7.5k v in 1.74m 4.7k q1 cmpt5551 40.2k 3 4 5 6 1 2 8 7 619k high range indicator (i load > 1.2a) v logic (3.3v to 5v) low current range out 2.5v/a ( v logic +5v ) v in 60v 0 i load 10a high current range out 250mv/a 301 301 ltc6101 r sense hi 10m v logic bat54c ltc1540 v + v C out Cin +in v + v C out Cin +in selection of external input resistor, r in the external input resistor, r in , controls the transconduc- tance of the current sense circuit. since i out = v sense /r in , transconductance g m = 1/r in . for example, if r in = 100, then i out = v sense /100 or i out = 1ma for v sense = 100mv. r in should be chosen to allow the required resolution while limiting the output current. at low supply voltage, i out may be as much as 1ma. by setting r in such that the largest expected sense voltage gives i out = 1ma, then the maximum output dynamic range is available. output dynamic range is limited by both the maximum allowed output current and the maximum allowed output voltage, as well as the minimum practical output signal. if less dynamic range is required, then r in can be increased accordingly, reducing the max output current and power dissipation. if low sense currents must be resolved accurately in a system that has very wide dynamic range, a smaller r in than the max current spec allows may be used if the max current is limited in another way, such as with a schottky diode across r sense (figure 3a). this will reduce the high current measurement accuracy by limiting the result, while increasing the low current measurement resolution. figure 3b. dual ltc6101s allow high-low current ranging v + load d sense 6101 f03a r sense figure 3a. shunt diode limits maximum input voltage to allow better low input resolution without overranging this approach can be helpful in cases where occasional large burst currents may be ignored. it can also be used in a multirange con? guration where a low current circuit is added to a high current circuit (figure 3b). note that a comparator (ltc1540) is used to select the range, and transistor m1 limits the voltage across r sense lo . care should be taken when designing the board layout for r in, especially for small r in values. all trace and inter- connect impedances will increase the effective r in value, causing a gain error. in addition, internal device resistance will add approximately 0.2 to r in .
ltc6101/ltc6101hv 11 6101fg applications information selection of external output resistor, r out the output resistor, r out , determines how the output cur- rent is converted to voltage. v out is simply i out ? r out . in choosing an output resistor, the max output voltage must ? rst be considered. if the circuit that is driven by the output does not limit the output voltage, then r out must be chosen such that the max output voltage does not exceed the ltc6101 max output voltage rating. if the following circuit is a buffer or adc with limited input range, then r out must be chosen so that i out(max) ? r out is less than the allowed maximum input range of this circuit. in addition, the output impedance is determined by r out . if the circuit to be driven has high enough input imped- ance, then almost any useful output impedance will be acceptable. however, if the driven circuit has relatively low input impedance, or draws spikes of current, such as an adc might do, then a lower r out value may be required in order to preserve the accuracy of the output. as an example, if the input impedance of the driven circuit is 100 times r out , then the accuracy of v out will be reduced by 1% since: v out = i out ? r out ?r in(driven) r out + r in(driven) = i out ?r out ? 100 101 = 0.99 ?i out ?r out error sources the current sense system uses an ampli? er and resistors to apply gain and level shift the result. the output is then dependent on the characteristics of the ampli? er, such as gain and input offset, as well as resistor matching. ideally, the circuit output is: v out = v sense ? r out r in ;v sense = r sense ?i sense in this case, the only error is due to resistor mismatch, which provides an error in gain only. however, offset voltage, bias current and ? nite gain in the ampli? er cause additional errors: output error, e out , due to the ampli? er dc offset voltage, v os e out(vos) = v os ? (r out /r in ) the dc offset voltage of the ampli? er adds directly to the value of the sense voltage, v sense . this is the dominant error of the system and it limits the available dynamic range. the paragraph selection of external current sense resistor provides details. output error, e out , due to the bias currents, i b (+) and i b (C) the bias current i b (+) ? ows into the positive input of the internal op amp. i b (C) ? ows into the negative input. e out(ibias) = r out ((i b (+) ? (r sense /r in ) C i b (C)) since i b (+) i b (C) = i bias , if r sense << r in then, e out(ibias) Cr out ? i bias for instance if i bias is 100na and r out is 1k, the output error is 0.1mv. note that in applications where r sense r in , i b (+) causes a voltage offset in r sense that cancels the error due to i b (C) and e out(ibias) 0. in applications where r sense < r in , the bias current error can be similarly reduced if an external resistor r in (+) = (r in C r sense ) is connected as shown in figure 4 below. under both conditions: e out(ibias) = r out ? i os ; i os = i b (+) C i b (C) ltc6101 r out v out 6101 f04 r in C v + load r sense r in + C + r in + = r in C C r sense v + v C out Cin +in figure 4. second input r minimizes error due to input bias current
ltc6101/ltc6101hv 12 6101fg applications information if the offset current, i os , of the ltc6101 ampli? er is 2na, the 100 microvolt error above is reduced to 2 microvolts. adding r in + as described will maximize the dynamic range of the circuit. for less sensitive designs, r in + is not necessary. example: if an i sense range = (1a to 1ma) and (v out /i sense ) = 3v/1a then, from the electrical characteristics of the ltc6101, r sense v sense (max) / i sense (max) = 500mv/1a = 500m gain = r out /r in = v out (max) / v sense (max) = 3v/500mv = 6 if the maximum output current, i out , is limited to 1ma, r out equals 3v/1ma 3.01 k (1% value) and r in = 3k/6 499 (1% value). the output error due to dc offset is 900volts (typ) and the error due to offset current, i os is 3k x 2na = 6volts (typical), provided r in + = r in C . the maximum output error can therefore reach 906volts or 0.03% (C70db) of the output full scale. considering the system input 60db dynamic range (i sense = 1ma to 1a), the 70db performance of the ltc6101 makes this application feasible. output error, e out , due to the finite dc open loop gain, a ol , of the ltc6101 ampli? er this error is inconsequential as the a ol of the ltc6101 is very large. output current limitations due to power dissipation the ltc6101 can deliver up to 1ma continuous current to the output pin. this current ? ows through r in and enters the current sense amp via the in(C) pin. the power dissipated in the ltc6101 due to the output signal is: p out = (v Cin C v out ) ? i out since v Cin v + , p out (v + C v out ) ? i out there is also power dissipated due to the quiescent sup- ply current: p q = i dd ? v + the total power dissipated is the output dissipation plus the quiescent dissipation: p total = p out + p q at maximum supply and maximum output current, the total power dissipation can exceed 100mw. this will cause signi? cant heating of the ltc6101 die. in order to prevent damage to the ltc6101, the maximum expected dissipation in each application should be calculated. this number can be multiplied by the ja value listed in the package section on page 2 to ? nd the maximum expected die temperature. this must not be allowed to exceed 150c, or performance may be degraded. as an example, if an ltc6101 in the s5 package is to be run at 55v 5v supply with 1ma output current at 80c: p q(max) = i dd(max) ? v + (max) = 41.4mw p out(max) = i out ? v + (max) = 60mw t rise = ja ? p total(max) t max = t ambient + t rise t max must be < 150c p total(max) 96mw and the max die temp will be 104c if this same circuit must run at 125c, the max die temp will increase to 150c. (note that supply current, and therefore p q , is proportional to temperature. refer to typical performance characteristics section.) in this condition, the maximum output current should be reduced to avoid device damage. note that the msop package has a larger ja than the s5, so additional care must be taken when operating the ltc6101a/ltc6101hva at high temperatures and high output currents. the ltc6101hv can be used at voltages up to 105v. this additional voltage requires that more power be dissipated for a given level of current. this will further limit the allowed output current at high ambient temperatures. it is important to note that the ltc6101 has been designed to provide at least 1ma to the output when required, and can deliver more depending on the conditions. care must be taken to limit the maximum output current by proper choice of sense resistor and, if input fault conditions exist, external clamps.
ltc6101/ltc6101hv 13 6101fg applications information output filtering the output voltage, v out , is simply i out ? z out . this makes ? ltering straightforward. any circuit may be used which generates the required z out to get the desired ? lter response. for example, a capacitor in parallel with r out will give a low pass response. this will reduce unwanted noise from the output, and may also be useful as a charge reservoir to keep the output steady while driving a switch- ing circuit such as a mux or adc. this output capacitor in parallel with an output resistor will create a pole in the output response at: f ?3db = 1 2? ?r out ?c out useful equations input voltage: v sense = i sense ?r sense voltage gain: v out v sense = r out r in current gain: i out i sense = r sense r in transconductance: i out v sense = 1 r in transimpedance: v out i sense = r sense ? r out r in figure 5. v + powered separately from load supply (v batt ) figure 6. ltc6101 supply current monitored with load ltc6101 r out v out 6101 f05 r in load v + r sense v battery C + v + v C out Cin +in ltc6101 r out v out 6101 f06 r in load v + r sense C + v + v C out Cin +in input common mode range the inputs of the ltc6101 can function from 1.5v below the positive supply to 0.5v above it. not only does this allow a wide v sense range, it also allows the input refer- ence to be separate from the positive supply (figure 5). note that the difference between v batt and v + must be no more than the common mode range listed in the electrical characteristics table. if the maximum v sense is less than 500mv, the ltc6101 may monitor its own supply current, as well as that of the load (figure 6).
ltc6101/ltc6101hv 14 6101fg applications information reverse supply protection some applications may be tested with reverse-polarity supplies due to an expectation of the type of fault during operation. the ltc6101 is not protected internally from external reversal of supply polarity. to prevent damage that may occur during this condition, a schottky diode should be added in series with v C (figure 7). this will limit the reverse current through the ltc6101. note that this diode will limit the low voltage performance of the ltc6101 by effectively reducing the supply voltage to the part by v d . in addition, if the output of the ltc6101 is wired to a device that will effectively short it to high voltage (such as through an esd protection clamp) during a reverse supply condi- tion, the ltc6101s output should be connected through a resistor or schottky diode (figure 8). response time the ltc6101 is designed to exhibit fast response to inputs for the purpose of circuit protection or signal transmission. this response time will be affected by the external circuit in two ways, delay and speed. if the output current is very low and an input transient occurs, there may be an increased delay before the output voltage begins changing. this can be improved by increasing the minimum output current, either by in- creasing r sense or decreasing r in . the effect of increased output current is illustrated in the step response curves in the typical performance characteristics section of this datasheet. note that the curves are labeled with respect to the initial output currents. the speed is also affected by the external circuit. in this case, if the input changes very quickly, the internal ampli- ? er will slew the gate of the internal output fet (figure 1) in order to maintain the internal loop. this results in current ? owing through r in and the internal fet. this current slew rate will be determined by the ampli? er and fet characteristics as well as the input resistor, r in . us- ing a smaller r in will allow the output current to increase more quickly, decreasing the response time at the output. this will also have the effect of increasing the maximum output current. using a larger r out will decrease the re- sponse time, since v out = i out ? r out . reducing r in and increasing r out will both have the effect of increasing the voltage gain of the circuit. figure 7. schottky prevents damage during supply reversal figure 8. additional resistor r3 protects output during supply reversal 6101 f07 ltc6101 r2 4.99k d1 r1 100 v batt r sense l o a d C + v + v C out Cin +in 6101 f08 adc ltc6101 r2 4.99k d1 r1 100 v batt r3 1k r sense l o a d C + v + v C out Cin +in
ltc6101/ltc6101hv 15 6101fg typical applications bidirectional current sense circuit with separate charge/discharge output ltc6101 monitors its own supply current high-side-input transimpedance ampli? er l o a d charger C + C + + C + C v out d = i discharge ? r sense ( ) when i discharge 0 discharging: r out d r in d v out c = i charge ? r sense ( ) when i charge 0 charging: r out c r in c 6101 ta02 v batt r in c 100 ltc6101 r in d 100 r in c 100 ltc6101 v out d r out d 4.99k r out c 4.99k v out c r in d 100 i discharge r sense i charge v + v C out Cin +in v + v C out Cin +in l o a d C + 6101 ta03 r2 4.99k v out r1 100 v batt r sense ltc6101 + C v out = 49.9 ? r sense ( i load + i supply ) i load i supply v + v C out Cin +in C + 6101 ta04 r l v o 4.75k 4.75k v s laser monitor photodiode cmpz4697* (10v) 10k i pd ltc6101 v o = i pd ? r l *v z sets photodiode bias v z + 4 v s v z + 60 v + v C out Cin +in
ltc6101/ltc6101hv 16 6101fg to p 6101 ta06 ltc2433-1 ltc6101 r out 4.99k r in 100 v out v sense i load 4v to 60v 1f 5v l o a d C + C + v out = ? v sense = 49.9 v sense r out r in adc full-scale = 2.5v 21 9 8 7 10 6 3 4 5 v cc sck ref + ref C gnd in + in C c c f o sdd v + v C out Cin +in 16-bit resolution unidirectional output into ltc2433 adc 6101 ta07 l o a d fault off on 15 4.99k v o r s 3 4 47k 2 8 6 100 100 1% 10f 63v 1f 14v v logic sub85n06-5 v o = 49.9 ? r s ? i l for r s = 5m, v o = 2.5v at i l = 10a (full scale) lt1910 ltc6101 i l v + v C out Cin +in intelligent high-side switch with current monitor typical applications
ltc6101/ltc6101hv 17 6101fg 6101 ta08 ltc6101hv r in v C v C v sense r sense i sense load + C C+ v out = v logic C i sense ? ? n ? r out r sense r in n = optoisolator current gain v s any optoisolator r out v out v logic v + v C out Cin +in 6101 ta09 ltc6101 r in 100 v out r out 4.99k l o a d C + v out = ? v sense = 49.9 v sense r out r in m1 and m2 are fqd3p50 tm m1 m2 62v cmz5944b 500v 2m v sense r sense i sense +C danger! lethal potentials present use caution danger!! high voltage!! v + v C out Cin +in 48v supply current monitor with isolated output with 105v survivability simple 500v current monitor typical applications
ltc6101/ltc6101hv 18 6101fg package description ms8 package 8-lead plastic msop (reference ltc dwg # 05-08-1660 rev f) msop (ms8) 0307 rev f 0.53 0.152 (.021 .006) seating plane note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.18 (.007) 0.254 (.010) 1.10 (.043) max 0.22 ? 0.38 (.009 ? .015) typ 0.1016 0.0508 (.004 .002) 0.86 (.034) ref 0.65 (.0256) bsc 0 ? 6 typ detail ?a? detail ?a? gauge plane 12 3 4 4.90 0.152 (.193 .006) 8 7 6 5 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) 0.52 (.0205) ref 5.23 (.206) min 3.20 ? 3.45 (.126 ? .136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.42 0.038 (.0165 .0015) typ 0.65 (.0256) bsc
ltc6101/ltc6101hv 19 6101fg information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description 1.50 ? 1.75 (note 4) 2.80 bsc 0.30 ? 0.45 typ 5 plcs (note 3) datum ?a? 0.09 ? 0.20 (note 3) s5 tsot-23 0302 rev b pin one 2.90 bsc (note 4) 0.95 bsc 1.90 bsc 0.80 ? 0.90 1.00 max 0.01 ? 0.10 0.20 bsc 0.30 ? 0.50 ref note: 1. dimensions are in millimeters 2. drawing not to scale 3. dimensions are inclusive of plating 4. dimensions are exclusive of mold flash and metal burr 5. mold flash shall not exceed 0.254mm 6. jedec package reference is mo-193 3.85 max 0.62 max 0.95 ref recommended solder pad layout per ipc calculator 1.4 min 2.62 ref 1.22 ref s5 package 5-lead plastic tsot-23 (reference ltc dwg # 05-08-1635)
ltc6101/ltc6101hv 20 6101fg linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2005 lt 0108 rev g ? printed in usa related parts part number description comments lt1636 rail-to-rail input/output, micropower op amp v cm extends 44v above v ee , 55a supply current, shutdown function lt1637/lt1638/ lt1639 single/dual/quad, rail-to-rail, micropower op amp v cm extends 44v above v ee , 0.4v/s slew rate, >1mhz bandwidth, <250a supply current per ampli? er lt1787/lt1787hv precision, bidirectional, high side current sense ampli? er 2.7v to 60v operation, 75v offset, 60a current draw ltc1921 dual C48v supply and fuse monitor 200v transient protection, drives three optoisolators for status lt1990 high voltage, gain selectable difference ampli? er 250v common mode, micropower, pin selectable gain = 1, 10 lt1991 precision, gain selectable difference ampli? er 2.7v to 18v, micropower, pin selectable gain = C13 to 14 ltc2050/ltc2051/ ltc2052 single/dual/quad zero-drift op amp 3v offset, 30nv/c drift, input extends down to vC ltc4150 coulomb counter/battery gas gauge indicates charge quantity and polarity lt6100 gain-selectable high-side current sense ampli? er 4.1v to 48v operation, pin-selectable gain: 10, 12.5, 20, 25, 40, 50v/v typical application u typical applicatio l o a d charger C + C + + C v out = i discharge ? r sense ( ) when i discharge 0 discharging: r out r in d v out = i charge ? r sense ( ) when i charge 0 charging: r out r in c 6101 ta05 v batt r in c ltc6101 r in d r in c ltc6101 r out v out r in d i discharge i charge r sense v + v C out out Cin +in v + v C Cin +in bidirectional current sense circuit with combined charge/discharge output

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