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ina326 ina327 sbos222d C november 2001 C revised november 2004 www.ti.com description the ina326 and ina327 (with shutdown) are high-perfor- mance, low-cost, precision instrumentation amplifiers with rail-to-rail input and output. they are true single-supply instrumentation amplifiers with very low dc errors and input common-mode ranges that extends beyond the positive and negative rails. these features make them suitable for appli- cations ranging from general-purpose to high-accuracy. excellent long-term stability and very low 1/f noise assure low offset voltage and drift throughout the life of the product. the ina326 (without shutdown) comes in the msop-8 pack- age. the ina327 (with shutdown) is offered in an msop-10. both are specified over the industrial temperature range, C40 c to +85 c, with operation from C40 c to +125 c. features precision low offset: 100 v (max) low offset drift: 0.4 v/ c (max) excellent long-term stability very-low 1/f noise true rail-to-rail i/o input common-mode range: 20mv below negative rail to 100mv above positive rail wide output swing: within 10mv of rails supply range: single +2.7v to +5.5v small size micro package: msop-8, msop-10 low cost 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 ? 2001-2004, texas instruments incorporated precision, rail-to-rail i/o instrumentation amplifier 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. applications low-level transducer amplifier for bridges, load cells, thermocouples wide dynamic range sensor measurements high-resolution test systems weigh scales multi-channel data acquisition systems medical instrumentation general-purpose ina326 and ina327 related products product features ina337 precision, 0.4 v/ c drift, specified C40 c to +125 c ina114 50 v v os , 0.5na i b , 115db cmr, 3ma i q , 0.25 v/ c drift ina118 50 v v os , 1na i b , 120db cmr, 385 a i q , 0.5 v/ c drift ina122 250 v v os , C10na i b , 85 a i q , rail-to-rail output, 3 v/ c drift ina128 50 v v os , 2na i b , 125db cmr, 750 a i q , 0.5 v/ c drift ina321 500 v v os , 0.5pa i b , 94db cmrr, 60 a i q , rail-to-rail output ina326 r 1 r 2 c 2 v in ? v in+ 7 v+ 4 v ? v o 5 6 2 1 8 3 g = 2(r 2 /r 1 ) i n a 3 2 7 i n a 3 2 6
ina326, ina327 2 sbos222d www.ti.com specified package temperature package ordering transport product package-lead designator range marking number media, quantity ina326 msop-8 dgk C 40 c to +85 c b26 ina326ea/250 tape and reel, 250 " """" ina326ea/2k5 tape and reel, 2500 ina327 msop-10 dgs C 40 c to +85 c b27 ina327ea/250 tape and reel, 250 " """" ina327ea/2k5 tape and reel, 2500 note: (1) for the most current package and ordering information, download the latest version of this data sheet and see the pac kage option addendum located at the end of the data sheet. package/ordering information (1) absolute maximum ratings (1) supply voltage .................................................................................. +5.5v signal input terminals: voltage (2) .............................. C 0.5v to (v+) + 0.5v current (2) ................................................... 10ma output short-circuit ................................................................. continuous operating temperature range ....................................... C 40 c to +125 c storage temperature range .......................................... C 65 c to +150 c junction temperature .................................................................... +150 c lead temperature (soldering, 10s) ............................................... +300 c notes: (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. (2) input terminals are diode clamped to the power-supply rails. input signals that can swing more than 0.5v beyond the supply rails should be current limited to 10ma or less. electrostatic discharge sensitivity this integrated circuit can be damaged by esd. texas instruments recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper han- dling and installation procedures can cause damage. esd damage can range from subtle performance degrada- tion 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. 1 2 3 4 8 7 6 5 r 1 v+ v o r 2 r 1 v in ? v in+ v ? ina326 msop- 8 1 2 3 4 5 10 9 8 7 6 r 1 v+ v o r 2 enable r 1 v in ? v in+ v ? (connect to v+) ina327 msop- 10 top view pin configuration
ina326, ina327 3 sbos222d www.ti.com electrical characteristics: v s = +2.7v to +5.5v boldface limits apply over the specified temperature range , t a = C 40 c to +85 c at t a = +25 c, r l = 10k ? , g = 100 (r 1 = 2k ? , r 2 = 100k ? ), external gain set resistors, and ia common = v s /2, with external equivalent filter corner of 1khz, unless otherwise noted. ina326ea, ina327ea parameter condition min typ max units input offset voltage, rti v os v s = +5v, v cm = v s /2 20 100 v over temperature 124 v vs temperature dv os /dt 0.1 0.4 v/ c vs power supply psr v s = +2.7v to +5.5v, v cm = v s /2 20 3 v/v long-term stability see note (1) input impedance, differential 10 10 || 2 ? || pf common-mode 10 10 || 14 ? || pf input voltage range (v C ) C 0.02 (v+) + 0.1 v safe input voltage (v C ) C 0.5 (v+) + 0.5 v common-mode rejection cmr v s = +5v, v cm = (v C ) C 0.02v to (v+) + 0.1v 100 114 db over temperature 94 db input bias current v cm = v s /2 bias current i b v s = +5v 0.2 2na vs temperature see typical characteristics offset current i os v s = +5v 0.2 2na noise voltage noise, rti r s = 0 ? , g = 100, r 1 = 2k ? , r 2 = 100k ? f = 10hz 33 nv/ hz f = 100hz 33 nv/ hz f = 1khz 33 nv/ hz f = 0.01hz to 10hz 0.8 vp-p voltage noise, rti r s = 0 ? , g = 10, r 1 = 20k ? , r 2 = 100k ? f = 10hz 120 nv/ hz f = 100hz 97 nv/ hz f = 1khz 97 nv/ hz f = 0.01hz to 10hz 4 vp-p current noise, rti f = 1khz 0.15 pa/ hz f = 0.01hz to 10hz 4.2 pap-p output ripple, v o filtered (2) see applications information gain gain equation g = 2(r 2 /r 1 ) range of gain < 0.1 > 10000 v/v gain error (3) g = 10, 100, v s = +5v, v o = 0.075v to 4.925v 0.08 0.2 % vs temperature g = 10, 100, v s = +5v, v o = 0.075v to 4.925v 6 25 ppm/ c nonlinearity g = 10, 100, v s = +5v, v o = 0.075v to 4.925v 0.004 0.01 % of fs output voltage output swing from rail r l = 100k ? 5mv r l = 10k ? , v s = +5v 75 10 mv over temperature 75 mv capacitive load drive 500 pf short-circuit current i sc 25 ma internal oscillator frequency of auto-correction 90 khz accuracy 20 % frequency response bandwidth (4) , C 3db bw g = 1 to 1k 1 khz slew rate (4) sr v s = +5v, all gains, c l = 100pf filter limited settling time (4) , 0.1% t s 1khz filter, g = 1 to 1k, v o = 2v step, c l = 100pf 0.95 ms 0.01% 1.3 ms 0.1% 10khz filter, g = 1 to 1k, v o = 2v step, c l = 100pf 130 s 0.01% 160 s overload recovery (4) 1khz filter, 50% output overload, g = 1 to 1k 30 s 10khz filter, 50% output overload, g = 1 to 1k 5 s
ina326, ina327 4 sbos222d www.ti.com parameter condition min typ max units power supply specified voltage range +2.7 +5.5 v quiescent current i q i o = 0, diff v in = 0v, v s = +5v 2.4 3.4 ma over temperature 3.7 ma shutdown disable (logic low threshold) 0.25 v enable (logic high threshold) 1.6 v enable time (5) 75 s disable time 100 s shutdown current and enable pin current v s = +5v, disabled 2 5 a temperature range specified range C 40 +85 c operating range C 40 +125 c storage range C 65 +150 c thermal resistance ja msop-8, msop-10 surface-mount 150 c/w notes: (1) 1000-hour life test at 150 c demonstrated randomly distributed variation in the range of measurement limits approximately 10 v. (2) see applications information section, and figures 1 and 3. (3) does not include error and tcr of external gain-setting resistors. (4) dynamic re sponse is limited by filtering. higher bandwidths can be achieved by adjusting the filter. (5) see typical characteristics, input offset voltage vs warm-up time . electrical characteristics: v s = +2.7v to +5.5v (cont.) boldface limits apply over the specified temperature range , t a = C 40 c to +85 c at t a = +25 c, r l = 10k ? , g = 100 (r 1 = 2k ? , r 2 = 100k ? ), external gain set resistors, and ia common = v s /2, with external equivalent filter corner of 1khz, unless otherwise noted. ina326ea, ina327ea
ina326, ina327 5 sbos222d www.ti.com typical characteristics at t a = 25 c, v s = +5v, gain = 100, and r l = 10k ? with external equivalent filter corner of 1khz, unless otherwise noted. gain vs frequency 1khz filter frequency (hz) 10 100 1k 10k 100k 1m gain (db) 80 60 40 20 0 ? 20 ? 40 g = 1k g = 100 g = 10 g = 1 gain vs frequency 10khz filter frequency (hz) 10 100 1k 10k 100k 1m gain (db) 80 60 40 20 0 ? 20 ? 40 g = 1k g = 100 g = 10 g = 1 common- mode rejection vs frequency 1khz filter frequency (hz) 10 100 1k 10k 100k 1m cmr (db) 160 140 120 100 80 60 40 20 g = 1k g = 100 g = 10 g = 1 common- mode rejection vs frequency 10khz filter frequency (hz) 10 100 1k 10k 100k 1m cmr (db) 160 140 120 100 80 60 40 20 g = 100 g = 10 g = 1 g = 1k power- supply rejection vs frequency frequency (hz) 10 100 1k 10k 100k psr (db) 120 100 80 60 40 20 0 g = 100, 1k g = 10 g = 1 filter frequency 10khz 1khz input- referred voltage noise and input bias current noise vs frequency 10khz filter 1 10k 1k 100 10 1 0.1 0.01 0.001 10 100 1k 10k frequency (hz) input-referred voltage noise (nv/ hz) input bias current noise (pa/ hz) g = 1 g = 100 current noise (all gains) g = 10 g = 1000
ina326, ina327 6 sbos222d www.ti.com typical characteristics (cont.) at t a = 25 c, v s = +5v, gain = 100, and r l = 10k ? with external equivalent filter corner of 1khz, unless otherwise noted. small- signal response g = 1, 10, and 100 50mv/div 500 s/div 1khz filter 10khz filter small- signal step response g = 1000 50mv/div 500 s/div 1khz filter large- signal response g = 1 to 1000 2v/div 500 s/div 1khz filter 10khz filter input offset voltage vs turn- on time 1khz filter, g = 100 input offset voltage (20 v/div) 1 02 turn- on time (ms) filter settling time device turn- on time (75 s) input offset voltage vs warm- up time 10khz filter, g = 100 input offset voltage (20 v/div) 0.2 0.3 0 0.1 0.4 warm- up time (ms) filter settling time device turn- on time 0.01hz to 10hz voltage noise 200nv/div 10s/div
ina326, ina327 7 sbos222d www.ti.com typical characteristics (cont.) at t a = 25 c, v s = +5v, gain = 100, and r l = 10k ? with external equivalent filter corner of 1khz, unless otherwise noted. offset voltage drift production distribution g = 1 offset voltage drift ( v/ c) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 population offset voltage production distribution g = 1 offset voltage ( v) ? 10,000 ? 9000 ? 8000 ? 7000 ? 6000 ? 5000 ? 4000 ? 3000 ? 2000 ? 1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10,000 population offset voltage drift production distribution g = 10 offset voltage drift ( v/ c) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 population offset voltage production distribution g = 10 offset voltage ( v) ? 1000 ? 900 ? 800 ? 700 ? 600 ? 500 ? 400 ? 300 ? 200 ? 100 0 100 200 300 400 500 600 700 800 900 1000 population offset voltage drift production distribution g = 100, 1000 offset voltage drift ( v/ c) 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 population offset voltage production distribution g = 100, 1000 offset voltage ( v) ? 100 ? 90 ? 80 ? 70 ? 60 ? 50 ? 40 ? 30 ? 20 ? 10 0 10 20 30 40 50 60 70 80 90 100 population
ina326, ina327 8 sbos222d www.ti.com typical characteristics (cont.) at t a = 25 c, v s = +5v, gain = 100, and r l = 10k ? with external equivalent filter corner of 1khz, unless otherwise noted. input bias current vs temperature temperature ( c) ? 50 ? 25 0 25 50 75 100 125 i b (na) 2.0 1.5 1.0 0.5 0 ? 0.5 ? 1.0 ? 1.5 ? 2.0 i b+ i b ? quiescent current vs temperature temperature ( c) ? 50 ? 25 0 25 50 75 100 125 i q (ma) 3.0 2.5 2.0 1.5 1.0 0.5 0 v s = +2.7v v s = +5v gain error production distribution g = 100 gain error (m%) ? 200 ? 180 ? 160 ? 140 ? 120 ? 100 ? 80 ? 60 ? 40 ? 20 0 20 40 60 80 100 120 140 160 180 200 population input- referred ripple spectrum g = 100 frequency (hz) 0 200k 400k 600k 800k 1m v out (dbv) ? 100 ? 110 ? 120 ? 130 ? 140 ? 150 ? 160 ? 170 ? 180 v out ( vrms) 100.000 31.600 1.000 0.316 0.100 0.030 0.010 0.003 0.001
ina326, ina327 9 sbos222d www.ti.com ia common (2) ina326 r 1 v in ? v in+ v o filtered v o 6 2 1 8 3 g = 2(r 2 /r 1 ) f o = 1khz r o 100 ? c o (1) 1 f r 2 c 2 (1) 7 +2.5v 4 0.1 f ? 2.5v 5 (1) c 2 and c o combine to form a 2-pole response that is ? 3db at 1khz. each individual pole is at 1.5khz. (2) output voltage is referenced to ia common (see text). desired r 1 r 2 || c 2 gain ( ? )( ? || nf) 0.1 400k 20k || 5 0.2 400k 40k || 2.5 0.5 400k 100k || 1 1 400k 200k || 0.5 2 200k 200k || 0.5 5 80k 200k || 0.5 10 40k 200k || 0.5 20 20k 200k || 0.5 50 8k 200k || 0.5 100 4k 200k || 0.5 200 2k 200k || 0.5 500 2k 500k || 0.2 1000 2k 1m || 0.1 2000 2k 2m || 0.05 5000 2k 5m || 0.02 10000 2k 10m || 0.01 applications information figure 1 shows the basic connections required for operation of the ina326. a 0.1 f capacitor, placed close to and across the power-supply pins is strongly recommended for highest accu- racy. r o c o is an output filter that minimizes auto-correction circuitry noise. this output filter may also serve as an anti- aliasing filter ahead of an analog-to-digital (a/d) converter. it is also optional based on desired precision. the output reference terminal is taken at the low side of r 2 (ia common ). the ina326 uses a unique internal topology to achieve excel- lent common-mode rejection (cmr). unlike conventional instrumentation amplifiers, cmr is not affected by resistance in the reference connections or sockets. see inside the ina326 for further detail. to achieve best high-frequency cmr, minimize capacitance on pins 1 and 8. figure 1. basic connections. note: connections for ina327 differ see pin configuration for detail. setting the gain the ina326 is a 2-stage amplifier with each stage gain set by r 1 and r 2 , respectively (see figure 5, inside the ina326 , for details). overall gain is described by the equation: g r r = 2 2 1 (1) the stability and temperature drift of the external gain-setting resistors will affect gain by an amount that can be directly inferred from the gain equation (1). resistor values for commonly used gains are shown in figure 1. gain-set resistor values for best performance are different for +5v single-supply and for 2.5v dual-supply operation. optimum value for r 1 can be calculated by: r 1 = v in, max /12.5 a (2) where r 1 must be no less than 2k ? . desired r 1 r 2 || c 2 gain ( ? )( ? || nf) 0.1 400k 20k || 5 0.2 400k 40k || 2.5 0.5 400k 100k || 1 1 200k 100k || 1 2 100k 100k || 1 5 40k 100k || 1 10 20k 100k || 1 20 10k 100k || 1 50 4k 100k || 1 100 2k 100k || 1 200 2k 200k || 0.5 500 2k 500k || 0.2 1000 2k 1m || 0.1 2000 2k 2m || 0.05 5000 2k 5m || 0.02 10000 2k 10m || 0.01 notes: (1) c 2 and c o combine to form a 2-pole response that is C 3db at 1khz. each individual pole is at 1.5khz. (2) output voltage is referenced to ia common (see text). (3) output offset voltage required for measurement near zero (see figure 6). ina326 v o filtered v o 6 g = 2(r 2 /r 1 ) f o = 1khz r o 100 ? c o (1) 1 f r 2 c 2 (1) 7 v+ 4 0.1 f 5 ia common (2) r 1 (1) c 2 and c o combine to form a 2-pole response that is ? 3db at 1khz. each individual pole is at 1.5khz. (2) output voltage is referenced to ia common (see text). (3) output offset voltage required for measurement near zero (see figure 28). single-supply operation may require r 2 > 100k ? for full output swing. this may produce higher input referred offset voltage. see offset voltage, drift, and circuit values for detail. 1 8 v in ? v in+ 2 3 (3)
ina326, ina327 10 sbos222d www.ti.com following this design procedure for r 1 produces the maximum possible input stage gain for best accuracy and lowest noise. circuit layout and supply bypassing can affect performance. minimize the stray capacitance on pins 1 and 8. use recom- mended supply bypassing, including a capacitor directly from pin 7 to pin 4 (v+ to v C ), even with dual (split) power supplies (see figure 1). offset voltage, drift, and circuit values as with other multi-stage instrumentation amplifiers, input- referred offset voltage depends on gain and circuit values. the specified offset and drift performance is rated at r 1 = 2k ? , r 2 = 100k ? , and v s = 2.5v. offset voltage and drift for other circuit values can be estimated from the following equations: v os = 10 v + (50na)(r 2 )/g (3) dv os /dt = 0.12 v/ c + (0.16na/ c)(r 2 )/g (4) these equations might imply that offset and drift can be minimized by making the value of r 2 much lower than the values indicated in figure 1. these values, however, have been chosen to assure that the output current into r 2 is kept less than or equal to 25 a, while maintaining r 1 s value greater than or equal to 2k ? . some applications with limited output voltage swing or low power-supply voltage may allow lower values for r 2 , thus providing lower input-referred offset voltage and offset voltage drift. conversely, single-supply operation with r 2 grounded re- quires that r 2 values be made larger to assure that current remains under 25 a. this will increase the input-referred offset voltage and offset voltage drift. circuit conditions that cause more than 25 a to flow in r 2 will not cause damage, but may produce more nonlinearity. ina327 enable function the ina327 adds an enable/shutdown function to the ina326. its pinout differs from the ina326 see the pin configuration for detail. the ina327 can be enabled by applying a logic high voltage level to the enable pin. conversely, a logic low voltage level will disable the amplifier, reducing its supply current from 2.4ma to typically 2 a. for battery-operated applications, this feature may be used to greatly reduce the average current and extend battery life. this pin should be connected to a valid high or low voltage or driven, not left open circuit. the enable pin can be modeled as a cmos input gate as in figure 2. the enable time following shutdown is 75 s plus the settling time due to filters (see typical characteristics, input offset voltage vs warm-up time ). disable time is 100 s. this allows the ina327 to be operated as a gated amplifier, or to have its output multiplexed onto a common output bus. when disabled, the output assumes a high-impedance state. ina327 pin 5 pin 5 of the ina327 should be connected to v+ to ensure proper operation. dynamic performance the typical characteristic gain vs frequency shows that the ina326 has nearly constant bandwidth regardless of gain. this results from the bandwidth limiting from the recom- mended filters. noise performance internal auto-correction circuitry eliminates virtually all 1/f noise (noise that increases at low frequency) in gains of 100 or greater. noise performance is affected by gain-setting resistor values. follow recommendations in the setting gain section for best performance. total noise is a combination of input stage noise and output stage noise. when referred to the input, the total mid-band noise is: vnvhz nv hz g n =+ 33 800 / / (5) the output noise has some 1/f components that affect performance in gains less than 10. see typical characteristic input-referred voltage noise vs frequency. high-frequency noise is created by internal auto-correction circuitry and is highly dependent on the filter characteristics chosen. this may be the dominant source of noise visible when viewing the output on an oscilloscope. low cutoff frequency filters will provide lowest noise. figure 3 shows the typical noise performance as a function of cutoff frequency. figure 2. enable pin model. v+ enable 6 2 a figure 3. total output noise vs required filter cutoff frequency. 100 110 1k10k required filter cutoff frequency (hz) total output noise ( v rms ) 1k 100 10 1 g = 10 g = 1 g = 100 g = 1000
ina326, ina327 11 sbos222d www.ti.com applications sensitive to the spectral characteristics of high- frequency noise may require consideration of the spurious frequencies generated by internal clocking circuitry. spurs occur at approximately 90khz and its harmonics (see typical characteristic input-referred ripple spectrum ) which may be reduced by additional filtering below 1khz. insufficient filtering at pin 5 can cause nonlinearity with large output voltage swings (very near the supply rails). noise must be sufficiently filtered at pin 5 so that noise peaks do not hit the rail and change the average value of the signal. figure 3 shows guidelines for filter cutoff frequency. high-frequency noise c 2 and c o form filters to reduce internally generated auto- correction circuitry noise. filter frequencies can be chosen to optimize the trade-off between noise and frequency re- sponse of the application, as shown in figure 3. the cutoff frequencies of the filters are generally set to the same frequency. figure 3 shows the typical output noise for four gains as a function of the C 3db cutoff frequency of each filter response. small signals may exhibit the addition of internally generated auto-correction circuitry noise at the output. this noise, combined with broadband noise, becomes most evi- dent in higher gains with filters of wider bandwidth. input bias current return path the input impedance of the ina326 is extremely high approximately 10 10 ? . however, a path must be provided for the input bias current of both inputs. this input bias current is approximately 0.2na. high input impedance means that this input bias current changes very little with varying input voltage. input circuitry must provide a path for this input bias current for proper operation. figure 4 shows provision for an input bias current path in a thermocouple application. without a bias current path, the inputs will float to an undefined poten- tial and the output voltage may not be valid. input common-mode range common instrumentation amplifiers do not respond linearly with common-mode signals near the power-supply rails, even if rail- to-rail op amps are used. the ina326 uses a unique topology to achieve true rail-to-rail input behavior (see figure 5, inside the ina326 ). the linear input voltage range of each input terminal extends to 20mv below the negative rail, and 100mv above the positive rail. input protection the inputs of the ina326 are protected with internal diodes connected to the power-supply rails. these diodes will clamp the applied signal to prevent it from damaging the input circuitry. if the input signal voltage can exceed the power supplies by more than 0.5v, the input signal current should be limited to less than 10ma to protect the internal clamp diodes. this can generally be done with a series input resistor. some signal sources are inherently current-limited and do not require limiting resistors. filtering filtering can be adjusted through selection of r 2 c 2 and r o c o for the desired trade-off of noise and bandwidth. adjustment of these components will result in more or less ripple due to auto-correction circuitry noise and will also affect broadband noise. filtering limits slew rate, settling time, and output overload recovery time. it is generally desirable to keep the resistance of r o relatively low to avoid dc gain error created by the subsequent stage loading. this may result in relatively high values for c o to produce the desired filter response. the impedance of r o c o can be scaled higher to produce smaller capacitor values if the load impedance is very high. certain capacitor types greater than 0.1 f may have dielec- tric absorption effects that can significantly increase settling time in high-accuracy applications (settling to 0.01%). polypro- pylene, polystyrene, and polycarbonate types are generally good. certain high-k ceramic types may produce slow settling tails. settling time to 0.1% is not generally affected by high-k ceramic capacitors. electrolytic types are not recommended for c 2 and c o . ina326 thermocouple 5 figure 4. providing input bias current return path.
ina326, ina327 12 sbos222d www.ti.com the ina326 uses a new, unique internal circuit topology that provides true rail-to-rail input. unlike other instrumen- tation amplifiers, it can linearly process inputs up to 20mv below the negative power-supply rail, and 100mv above the positive power-supply rail. conventional instrumenta- tion amplifier circuits cannot deliver such performance, even if rail-to-rail op amps are used. the ability to reject common-mode signals is derived in most instrumentation amplifiers through a combination of amplifier cmr and accurately matched resistor ratios. the ina326 converts the input voltage to a current. current-mode signal processing provides rejection of com- mon-mode input voltage and power-supply variation with- out accurately matched resistors. a simplified diagram shows the basic circuit function. the differential input voltage, (v in+ ) C (v in C ) is applied across r 1 . the signal-generated current through r 1 comes from a1 and a2 s output stages. a2 combines the current in r 1 with a mirrored replica of the current from a1. the result- ing current in a2 s output and associated current mirror is two times the current in r 1 . this current flows in (or out) of pin 5 into r 2 . the resulting gain equation is: g r r = 2 2 1 amplifiers a1, a2, and their associated mirrors are pow- ered from internal charge-pumps that provide voltage supplies that are beyond the positive and negative supply rails. as a result, the voltage developed on r 2 can actually swing 20mv below the negative power-supply rail, and 100mv above the positive supply rail. a3 provides a buffered output of the voltage on r 2 . a3 s input stage is also operated from the charge-pumped power supplies for true rail-to-rail operation. figure 5. simplified circuit diagram. inside the ina326 a1 v+ v ? current mirror current mirror i r1 i r1 i r1 r 1 r 2 c 2 v o v in ? v in+ i r1 2i r1 2i r1 2i r1 2i r1 2i r1 a3 a2 ia common 0.1 f current mirror current mirror 74 6 5 3 8 1 2 ina326
ina326, ina327 13 sbos222d www.ti.com figure 6. generating output offset voltage. r 1 r 2 5 r 0 r 2 c 2 c 0 v ref v o g = 2 (r 2 || r 2 )/r 1 ina326 r 2 and r 2 are chosen to create a small output offset voltage (e.g., 100mv). gain is determined by the parallel combination of r 2 and r 2 . 2 1 8 3 6 figure 7. output referenced to v ref /2. 2k ? 200k ? 200k ? v ref r o 100 ? 5 6 2 1 8 3 c o 1 f c 2 ina326 a/d converter g = 2(200k ? || 200k ? )/2k ? = 100 figure 8. high-side current shunt measurement. ina326 +5v r l 5 2 1 8 3 6 7 r o 100 ? r s i l r 1 2k ? r 2 c 2 v o c o 1 f note: connection point of v+ will include ( ) or exclude ( ) quiescent current in the measurement as desired. output offset required for measurements near zero (see figure 6). r s must be chosen so that the input voltage does not exceed 100mv beyond the rail. v o = 2(i l r s ) r 2 r 1 application circuits
ina326, ina327 14 sbos222d www.ti.com figure 10. low-side C 48v current shunt monitor. ina326 r l i l 5 4 2 1 8 3 6 7 r i = 2k ? 0.1 f opa336pa 1nf +5v 7 6 2 v cc gnd 3 4 r f = 100k ? r start 100k ? r pull- down 200k ? v o = 2(i l r s ) 8.45k ? zmm5231bdict 5.1v zvn4525g (zetex) (high- voltage n- channel fet) r s v s = 0mv to 50mv max ? + ? 48v note: 0.2% accuracy. current shunt monitor circuit can be designed for ? 250v supply with appropriate selection of high- voltage fet. r f r i figure 11. high-side +48v current shunt monitor. ina326 load 5 7 2 1 8 3 6 4 7 2 3 6 4 r i 2k ? opa336pa 1nf 0.1 f 49.9k ? 75k ? 165k ? v o = 0.1v to 4.9v 8.45k ? zmm5231bdict 5.1v r shunt v shunt = 0mv to 50mv ? + +48v v cc gnd (high- voltage p- channel fet) zvp4525 (zetex) +5v figure 9. low-side current shunt measurement. ina326 +5v r l r s i l r o 100 ? 5 2 1 8 3 6 7 c 2 c o 1 f 2k ? v o r 2 r 1 note: connection point of v ? will include ( ) or exclude ( ) quiescent current in the measurement as desired. output offset required for measurements near zero (see figure 6). r s must be chosen so that the input voltage does not exceed 20mv beyond the rail. v o = 2(i l r s ) r 2 r 1
ina326, ina327 15 sbos222d www.ti.com figure 15. programmable 25 a current source with high output resistance. figure 12. output offset adjustment. 2k ? 100k ? 1nf 5 v o = v in (100) + v dac v dac = 0.075v to 4.925v ina326 2 1 8 3 6 dac + ? v in ina326 4 5 7 2 1 8 3 6 r f = 10k note: output resistance is typically 800m ? . resolution < 5na. recommended values of c f = 1nf to 1 f. +5v c f v ref = +2.5v r 1 200k ? dac i out = ((+v ref ) ? (v dac )) r 1 50na 0v < v dac < +5v figure 14. output from pin 5 to allow swing beyond the rail. ina326 +5v nc (1) v o +15v ? 15v opa277 v d c 2 r 2 r 1 v cm 5 6 7 2 1 8 3 4 4 6 7 2 3 (2) notes: (1) nc denotes no connection. (2) typical swing capability ? 20mv to (+5v + 100mv). figure 13. multiplexed output. ina327 4 7 9 6 2 1 10 3 8 r 1 r 3 r 5 +5v enable note: (1) r 2 , r 4 , and r 6 could be a single, shared resistor to save board space. ina327 4 7 9 6 2 1 10 3 8 r 4 (1) r 2 (1) +5v enable ina327 4 7 9 6 2 1 10 3 8 r 6 (1) +5v enable +1.8v to +5v logic v o 1nf 1nf 1nf
ina326, ina327 16 sbos222d www.ti.com figure 16. programmable 5ma current source. figure 17. 27v output at 200ma amplifier with 100 v offset. ina326 4 5 7 2 1 8 3 6 i o = 5ma with 0.1 a stability. +2.5v ? 2.5v i o 0.1 f v ref = +2.5v r i = 200k ? 10k ? 49.9 ? dac r l i out = 2 v ref ? v dac 200k ? 1 + 10k ? 49.9 ? ina326 4 4 5 7 7 2 1 8 3 2 3 6 6 +5v ? 30v +30v i b 10nf 2k ? 1m ? r i = 1k ? 20k ? v i 20k ? r f = 100k ? opa551 internal charge pump in the ina326 allows this node to swing 20mv below ground without a negative supply. offset of the high- voltage op amp is controlled by the ina326. v o = C 27v v os = C 100 v at 200ma g = ? = ? 100v/v r f r i notes: (1) the opa551 is a 60v op amp. (2) the ina326 does not require a negative supply to correct for negative v os values from the high-voltage op amp. (3) voltage offset contribution of i b (opa551) is 100pa ? 2k ? = 0.2 v.
ina326, ina327 17 sbos222d www.ti.com figure 18. single-supply pid temperature control loop. v s v ? v+ v ? v+ r 19 100k ? r 20 5k pot r 17 5k ? pot r 2 100k ? r diff 1m ? differentiator tc: 100ms to 1s r 1 100k ? c 8 0.1 f r 25 10k ? r 22 10k ? r 23 10k ? r 21 10k ? proportional error amplifier bias generator loop gain adjust set temp gain = 100v/v integrator tc: 1s to 10s 1/4 opa4340 1/4 opa4340 1/2 opa2340 1/4 opa4340 1/4 opa4340 c int 1 f r int 10m ? r 18 10k ? r 15 200 ? r 16 2k ? pot c 3 1nf v bias v bias v bias v s v s v bias common output to tec driver common +5v input v bias v bias c diff 1 f summing amplifier ina326 v o 6 r 14 10k ? r 13 20 ? r 10 1k ? c 7 22nf r 8 100k ? r 9 2k ? r 7 1k ? pot r 11 14.3k ? r 12 15k ? r therm 10k r 6 9.53k ? c 5 1nf r 5 20k ? r 4 20k ? c 2 470nf c 6 10 f ref1004- 2.5 d 1 7 v+ 4 0.1 f v ? 5 8 8 4 1 in+ in ? 3 2 + c 4 10 f + 1/2 opa2340 v s v s c 1 1nf v bias
packaging information orderable device status (1) package type package drawing pins package qty eco plan (2) lead/ball finish msl peak temp (3) ina326ea/250 active msop dgk 8 250 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina326ea/250g4 active msop dgk 8 250 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina326ea/2k5 active msop dgk 8 2500 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina326ea/2k5g4 active msop dgk 8 2500 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina327ea/250 active msop dgs 10 250 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina327ea/250g4 active msop dgs 10 250 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina327ea/2k5 active msop dgs 10 2500 green (rohs & no sb/br) cu nipdau level-2-260c-1 year ina327ea/2k5g4 active msop dgs 10 2500 green (rohs & no sb/br) cu nipdau level-2-260c-1 year (1) the marketing status values are defined as follows: active: product device recommended for new designs. lifebuy: ti has announced that the device will be discontinued, and a lifetime-buy period is in effect. nrnd: not recommended for new designs. device is in production to support existing customers, but ti does not recommend using this part in a new design. preview: device has been announced but is not in production. samples may or may not be available. obsolete: ti has discontinued the production of the device. (2) eco plan - the planned eco-friendly classification: pb-free (rohs), pb-free (rohs exempt), or green (rohs & no sb/br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. tbd: the pb-free/green conversion plan has not been defined. pb-free (rohs): ti's terms "lead-free" or "pb-free" mean semiconductor products that are compatible with the current rohs requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. where designed to be soldered at high temperatures, ti pb-free products are suitable for use in specified lead-free processes. pb-free (rohs exempt): this component has a rohs exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. the component is otherwise considered pb-free (rohs compatible) as defined above. green (rohs & no sb/br): ti defines "green" to mean pb-free (rohs compatible), and free of bromine (br) and antimony (sb) based flame retardants (br or sb do not exceed 0.1% by weight in homogeneous material) (3) msl, peak temp. -- the moisture sensitivity level rating according to the jedec industry standard classifications, and peak solder temperature. important information and disclaimer: the information provided on this page represents ti's knowledge and belief as of the date that it is provided. ti bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. efforts are underway to better integrate information from third parties. ti has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. ti and ti suppliers consider certain information to be proprietary, and thus cas numbers and other limited information may not be available for release. in no event shall ti's liability arising out of such information exceed the total purchase price of the ti part(s) at issue in this document sold by ti to customer on an annual basis. package option addendum www.ti.com 18-jul-2006 addendum-page 1
tape and reel box information device package pins site reel diameter (mm) reel width (mm) a0 (mm) b0 (mm) k0 (mm) p1 (mm) w (mm) pin1 quadrant ina326ea/250 dgk 8 site 41 180 12 5.3 3.4 1.4 8 12 q1 ina326ea/2k5 dgk 8 site 41 330 12 5.3 3.4 1.4 8 12 q1 ina327ea/250 dgs 10 site 67 177 12 5.3 3.4 1.4 8 12 q1 ina327ea/2k5 dgs 10 site 67 330 12 5.3 3.4 1.4 8 12 q1 package materials information www.ti.com 5-nov-2007 pack materials-page 1
device package pins site length (mm) width (mm) height (mm) ina326ea/250 dgk 8 site 41 184.0 184.0 50.0 ina326ea/2k5 dgk 8 site 41 346.0 346.0 29.0 ina327ea/250 dgs 10 site 67 187.0 187.0 25.6 ina327ea/2k5 dgs 10 site 67 375.0 340.0 57.0 package materials information www.ti.com 5-nov-2007 pack materials-page 2

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