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ltc6911-1/ltc6911-2 1 sn691112 691112fs , ltc and lt are registered trademarks of linear technology corporation. n 3-bit digital gain control: (inverting gains of 0, 1, 2, 5, 10, 20, 50 and 100v/v) -1 option (inverting gains of 0, 1, 2, 4, 8, 16, 32 and 64v/v) -2 option n two matched programmable gain amplifiers n channel-to-channel gain matching of 0.1db (max) n rail-to-rail input range n rail-to-rail output swing n single or dual supply: 2.7v to 10.5v total n 11mhz gain bandwidth product n input noise: 10nv/ ? hz n total system dynamic range to 120db n input offset voltage: 2mv, gain of 10 n low profile 10-lead msop package dual matched amplifiers with digitally programmable gain in msop n data acquisition systems n dynamic gain changing n automatic ranging circuits n automatic gain control frequency response (ltc6911-1) the ltc ? 6911 is a family of low noise digitally program- mable gain amplifiers (pgas) that are easy to use and occupy very little pc board space. the matched gain of both channels is adjustable using a 3-bit parallel interface to select voltage gains of 0, 1, 2, 5, 10, 20, 50 and 100v/ v (ltc6911-1) and 0, 1, 2, 4, 8, 16, 32 and 64v/v (ltc6911-2). all gains are inverting. the ltc6911 family consists of two matched inverting amplifiers with rail-to-rail outputs. when operated with unity gain, they will also process rail-to-rail input signals. a half-supply reference generated internally at the agnd pin supports single power supply applications. operating from single or split supplies from 2.7v to 10.5v, the ltc6911 family is offered in a 10-lead msop package. features descriptio u applicatio s u typical applicatio u ltc6911-x 10 79 v outb = gain ?v inb v outa = gain ?v ina 8 1 v ina agnd v inb 3 2 3 1 f 0.1 f v + 2.7v to 10.5v 456 691112 ta01 g0 g1 g2 g2 0 0 0 0 1 1 1 1 g1 0 0 1 1 0 0 1 1 g0 0 1 0 1 0 1 0 1 ltc6911-1 0 ? ? ? ?0 ?0 ?0 ?00 ltc6911-2 0 ? ? ? ? ?6 ?2 ?4 digital input gain in v/v frequency (hz) 10 gain (db) 30 50 0 20 40 100 10k 100k 1m 10m 691112 ta02 ?0 1k gain of ?00 (digital input 111) gain of ? (digital input 001) gain of ? (digital input 010) gain of ? (digital input 011) gain of ?0 (digital input 100) gain of ?0 (digital input 101) gain of 50 (digital input 110) v s = 10v, v in = 5mv rms
ltc6911-1/ltc6911-2 2 sn691112 691112fs total supply voltage (v + to v C ) .............................. 11v input current ..................................................... 10ma operating temperature range (note 2) ltc6911c-1/ltc6911c-2 .................. C 40 c to 85 c ltc6911i-1/ltc6911i-2 .................... C 40 c to 85 c ltc6911h-1/ltc6911h-2 ................ C 40 c to 125 c specified temperature range (note 3) ltc6911c-1/ltc6911c-2 .................. C 40 c to 85 c ltc6911i-1/ltc6911i-2 .................... C 40 c to 85 c ltc6911h-1/ltc6911h-2 ................ C 40 c to 125 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c order part number t jmax = 150 c, q ja = 230 c/w ltc6911cms-1 ltc6911ims-1 ltc6911hms-1 ltc6911cms-2 ltc6911ims-2 ltc6911hms-2 (note 1) absolute axi u rati gs w ww u package/order i for atio uu w table 1 (ltc6911-1) nominal nominal input digital inputs voltage gain dual 5v single 5v single 3v impedance g2 g1 g0 volts/volt (db) supply supply supply (k w ) 0 0 0 0 C120 10 5 3 (open) 0 0 1 C1 0 10 5 3 10 0 1 0 C2 6 5 2.5 1.5 5 0 1 1 C5 14 2 1 0.6 2 1 0 0 C10 20 1 0.5 0.3 1 1 0 1 C20 26 0.5 0.25 0.15 1 1 1 0 C50 34 0.2 0.1 0.06 1 1 1 1 C100 40 0.1 0.05 0.03 1 gai setti gs a d properties u uu 1 2 3 4 5 ina agnd inb g0 g1 10 9 8 7 6 outa v outb v + g2 top view ms package 10-lead plastic msop consult ltc marketing for parts specified with wider operating temperature ranges. maximum linear input range (v p-p ) ms part marking ltahk ltahm ltbcf ltahh ltahj ltbcg table 2 (ltc6911-2) nominal nominal input digital inputs voltage gain dual 5v single 5v single 3v impedance g2 g1 g0 volts/volt (db) supply supply supply (k w ) 0 0 0 0 C120 10 5 3 (open) 0 0 1 C1 0 10 5 3 10 0 1 0 C2 6 5 2.5 1.5 5 0 1 1 C4 12 2.5 1.25 0.75 2.5 1 0 0 C8 18.1 1.25 0.625 0.375 1.25 1 0 1 C16 24.1 0.625 0.3125 0.188 1.25 1 1 0 C32 30.1 0.3125 0.156 0.094 1.25 1 1 1 C64 36.1 0.156 0.078 0.047 1.25 maximum linear input range (v p-p )
ltc6911-1/ltc6911-2 3 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics c/i grades h grade parameter conditions min typ max min typ max units ltc6911-1/ltc6911-2 total supply voltage (v s ) l 2.7 10.5 2.7 10.5 v supply current per channel v s = 2.7v, v ina = v inb = v agnd l 2.1 3.15 2.1 3.25 ma v s = 5v, v ina = v inb = v agnd l 2.5 3.75 2.5 4.00 ma v s = 5v, v ina = v inb = 0v, pins 4, 5, 6 = C4.5v or 5v l 3.1 4.65 3.1 5.00 ma v s = 5v, v ina = v inb = 0v, pin 4 = 4.5v, l 3.1 4.65 3.1 5.00 ma pins 5, 6 = 0.5v output voltage swing low (note 4) v s = 2.7v, r l = 10k tied to mid supply l 12 30 12 35 mv v s = 2.7v, r l = 500 w tied to mid supply l 60 110 60 125 mv v s = 5v, r l = 10k tied to mid supply l 20 40 20 45 mv v s = 5v, r l = 500 w tied to mid supply l 100 170 100 190 mv v s = 5v, r l = 10k tied to 0v l 30 50 30 60 mv v s = 5v, r l = 500 w tied to 0v l 190 260 190 290 mv output voltage swing high (note 4) v s = 2.7v, r l = 10k tied to mid supply l 10 20 10 25 mv v s = 2.7v, r l = 500 w tied to mid supply l 50 80 50 90 mv v s = 5v, r l = 10k tied to mid supply l 10 30 10 35 mv v s = 5v, r l = 500 w tied to mid supply l 90 160 90 175 mv v s = 5v, r l = 10k tied to 0v l 20 40 20 45 mv v s = 5v, r l = 500 w tied to 0v l 180 250 180 270 mv output short-circuit current (note 5) v s = 2.7v l 27 27 ma v s = 5v l 35 35 ma agnd open-circuit voltage v s = 5v l 2.45 2.5 2.55 2.45 2.5 2.55 v agnd (common mode) v s = 2.7v l 0.55 1.60 0.55 1.60 v input voltage range v s = 5v l 0.75 3.65 0.75 3.65 v v s = 5v l C 4.30 3.20 C 4.30 3.20 v agnd rejection (i.e., common v s = 2.7v, v agnd = 1.1v to 1.6v l 55 80 50 80 db mode rejection or cmrr) v s = 5v, v agnd = C 2.5v to 2.5v l 55 75 50 75 db power supply rejection ratio (psrr) v s = 2.7v to 5v l 60 80 57 80 db slew rate v s = 5v, v outa = v outb = 1.1v to 3.9v 12 12 v/ m s v s = 5v, v outa = v outb = 1.4v 16 16 v/ m s signal attenuation at gain = 0 setting gain = 0 (digital inputs 000), f = 20khz l C 120 C 120 db digital input high voltage v s = 2.7v l 2.43 2.43 v v s = 5v l 4.50 4.50 v v s = 5v l 4.50 4.50 v digital input low voltage v s = 2.7v l 0.27 0.27 v v s = 5v l 0.50 0.50 v v s = 5v l 0.50 0.50 v digital input high current v s = 2.7v, pins 4, 5, 6 = 2.43v l 11 m a v s = 5v, pins 4, 5, 6 = 4.5v l 55 m a v s = 5v, pins 4, 5, 6 = 4.5v l 10 10 m a digital input low current v s = 2.7v, pins 4, 5, 6 = 0.27v l 11 m a v s = 5v, pins 4, 5, 6 = 0.5v l 55 m a v s = 5v, pins 4, 5, 6 = 0.5v l 10 10 m a
ltc6911-1/ltc6911-2 4 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics ltc6911-1 only voltage gain (note 6) v s = 2.7v, gain = 1, r l = 10k l C0.07 0 0.07 C0.08 0 0.07 db v s = 2.7v, gain = 1, r l = 500 w l C0.11 C0.02 0.07 C0.13 C0.02 0.07 db v s = 2.7v, gain = 2, r l = 10k l 5.94 6.01 6.08 5.93 6.01 6.08 db v s = 2.7v, gain = 5, r l = 10k l 13.85 13.95 14.05 13.8 13.95 14.05 db v s = 2.7v, gain = 10, r l = 10k l 19.7 19.93 20.1 19.65 19.93 20.1 db v s = 2.7v, gain = 10, r l = 500 w l 19.6 19.85 20.1 19.45 19.85 20.1 db v s = 2.7v, gain = 20, r l = 10k l 25.75 25.94 26.1 25.65 25.94 26.1 db v s = 2.7v, gain = 50, r l = 10k l 33.5 33.8 34.1 33.4 33.8 34.1 db v s = 2.7v, gain = 100, r l = 10k l 39.0 39.6 40.1 38.8 39.6 40.1 db v s = 2.7v, gain = 100, r l = 500 w l 37.4 38.9 40.1 36.5 38.9 40.1 db v s = 5v, gain = 1, r l = 10k l C0.08 0.01 0.08 C0.09 0.01 0.08 db v s = 5v, gain = 1, r l = 500 w l C0.11 C0.01 0.07 C0.13 C0.01 0.07 db v s = 5v, gain = 2, r l = 10k l 5.95 6.02 6.09 5.94 6.02 6.09 db v s = 5v, gain = 5, r l = 10k l 13.8 13.96 14.1 13.78 13.96 14.1 db v s = 5v, gain = 10, r l = 10k l 19.8 19.94 20.1 19.75 19.94 20.1 db v s = 5v, gain = 10, r l = 500 w l 19.6 19.87 20.1 19.45 19.87 20.1 db v s = 5v, gain = 20, r l = 10k l 25.8 25.94 26.1 25.75 25.94 26.1 db v s = 5v, gain = 50, r l = 10k l 33.5 33.84 34.1 33.4 33.84 34.1 db v s = 5v, gain = 100, r l = 10k l 39.3 39.7 40.1 39.1 39.7 40.1 db v s = 5v, gain = 100, r l = 500 w l 38.0 39.2 40.1 37.0 39.2 40.1 db v s = 5v, gain = 1, r l = 10k l C0.06 0.01 0.08 C0.07 0.01 0.08 db v s = 5v, gain = 1, r l = 500 w l C0.10 0.00 0.08 C0.11 0.00 0.08 db v s = 5v, gain = 2, r l = 10k l 5.95 6.02 6.09 5.94 6.02 6.09 db v s = 5v, gain = 5, r l = 10k l 13.8 13.96 14.1 13.79 13.96 14.1 db v s = 5v, gain = 10, r l = 10k l 19.8 19.94 20.1 19.75 19.94 20.1 db v s = 5v, gain = 10, r l = 500 w l 19.7 19.91 20.1 19.60 19.91 20.1 db v s = 5v, gain = 20, r l = 10k l 25.8 25.95 26.1 25.75 25.95 26.1 db v s = 5v, gain = 50, r l = 10k l 33.7 33.87 34.1 33.60 33.87 34.1 db v s = 5v, gain = 100, r l = 10k l 39.4 39.8 40.2 39.25 39.8 40.2 db v s = 5v, gain = 100, r l = 500 w l 38.8 39.5 40.1 38.00 39.5 40.1 db channel-to-channel voltage v s = 2.7v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db gain match v s = 2.7v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 2.7v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 2.7v, gain = 5, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 10, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 10, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 20, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 50, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 100, r l = 10k l C0.20 0.02 0.20 C0.20 0.02 0.20 db v s = 2.7v, gain = 100, r l = 500 w l C1.00 0.02 1.00 C1.50 0.02 1.50 db c/i grades h grade parameter conditions min typ max min typ max units
ltc6911-1/ltc6911-2 5 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics c/i grades h grade parameter conditions min typ max min typ max units ltc6911-1 only channel-to-channel voltage v s = 5v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db gain match v s = 5v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 5, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 10, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 10, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 20, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 50, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 100, r l = 10k l C0.2 0.02 0.2 C0.2 0.02 0.2 db v s = 5v, gain = 100, r l = 500 w l C0.8 0.02 0.8 C1.2 0.02 1.2 db v s = 5v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 5, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 10, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 10, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 20, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 50, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 100, r l = 10k l C0.2 0.02 0.2 C0.2 0.02 0.2 db v s = 5v, gain = 100, r l = 500 w l C0.6 0.02 0.6 C0.9 0.02 0.9 db gain temperature coefficient v s = 5v, gain = 1, r l = open 2 2 ppm/ c v s = 5v, gain = 2, r l = open C1.5 C1.5 ppm/ c- v s = 5v, gain = 5, r l = open C11 C11 ppm/ c v s = 5v, gain = 10, r l = open C30 C30 ppm/ c v s = 5v, gain = 20, r l = open C38 C38 ppm/ c v s = 5v, gain = 50, r l = open C70 C70 ppm/ c v s = 5v, gain = 100, r l = open C140 C140 ppm/ c channel-to-channel gain temperature v s = 5v, gain = 1, r l = open 1.0 1.0 ppm/ c coefficient match v s = 5v, gain = 2, r l = open 1.0 1.0 ppm/ c v s = 5v, gain = 5, r l = open 0.2 0.2 ppm/ c v s = 5v, gain = 10, r l = open 1.0 1.0 ppm/ c v s = 5v, gain = 20, r l = open 0.4 0.4 ppm/ c v s = 5v, gain = 50, r l = open 3.0 3.0 ppm/ c v s = 5v, gain = 100, r l = open 3.0 3.0 ppm/ c channel-to-channel isolation (note 7) f = 200khz v s = 5v, gain = 1, r l = 10k 108 108 db v s = 5v, gain = 10, r l = 10k 107 107 db v s = 5v, gain = 100, r l = 10k 93 93 db offset voltage magnitude referred gain = 1 l 2.0 22 2.0 22 mv to ina or inb pins (note 8) gain = 10 l 1.1 12 1.1 14 mv offset voltage magnitude drift gain = 1 12 20 m v/ c referred to ina or inb pins (note 8) gain = 10 6.6 11 m v/ c
ltc6911-1/ltc6911-2 6 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics c/i grades h grade parameter conditions min typ max min typ max units ltc6911-1 only dc input resistance at dc v ina or v inb = 0v ina or inb pins (note 9) gain = 0 l >100 >100 m w gain = 1 l 10 10 k w gain = 2 l 55k w gain = 5 l 22k w gain > 5 l 11k w dc input resistance match gain = 1 l 10 10 w r ina C r inb gain = 2 l 55 w gain = 5 l 22 w gain > 5 l 11 w dc small-signal output resistance dc v ina or v inb = 0v at outa or outb pins gain = 0 0.4 0.4 w gain = 1 0.7 0.7 w gain = 2 1.0 1.0 w gain = 5 1.9 1.9 w gain = 10 3.4 3.4 w gain = 20 6.4 6.4 w gain = 50 15 15 w gain = 100 30 30 w gain-bandwidth product gain = 100, f in = 200khz l 7 11 18 6 11 18 mhz wideband noise (referred to input) f = 1khz to 200khz gain = 0 (output noise only) 7.5 7.5 m v rms gain = 1 12.3 12.3 m v rms gain = 2 8.5 8.5 m v rms gain = 5 6.1 6.1 m v rms gain = 10 5.2 5.2 m v rms gain = 20 5.0 5.0 m v rms gain = 50 4.5 4.5 m v rms gain = 100 3.8 3.8 m v rms voltage noise density f = 50khz (referred to input) gain = 1 28 28 nv/ ? hz gain = 2 19 19 nv/ ? hz gain = 5 14 14 nv/ ? hz gain = 10 12 12 nv/ ? hz gain = 20 11.5 11.5 nv/ ? hz gain = 50 10.8 10.8 nv/ ? hz gain = 100 9.9 9.9 nv/ ? hz total harmonic distortion gain = 10, f in = 10khz, v out = 1v rms C90 C90 db 0.003 0.003 % gain = 10, f in = 100khz, v out = 1v rms C82 C82 db 0.008 0.008 %
ltc6911-1/ltc6911-2 7 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics ltc6911-2 only voltage gain (note 6) v s = 2.7v, gain = 1, r l = 10k l C0.07 0 0.07 C0.08 0 0.07 db v s = 2.7v, gain = 1, r l = 500 w l C0.11 C0.02 0.07 C0.13 C0.02 0.07 db v s = 2.7v, gain = 2, r l = 10k l 5.94 6.01 6.08 5.93 6.01 6.08 db v s = 2.7v, gain = 4, r l = 10k l 11.9 12.02 12.12 11.88 12.02 12.12 db v s = 2.7v, gain = 8, r l = 10k l 17.80 18.00 18.15 17.75 18.00 18.15 db v s = 2.7v, gain = 8, r l = 500 w l 17.65 17.94 18.15 17.55 17.94 18.15 db v s = 2.7v, gain = 16, r l = 10k l 23.8 24.01 24.25 23.75 24.01 24.25 db v s = 2.7v, gain = 32, r l = 10k l 29.7 30 30.2 29.65 30 30.2 db v s = 2.7v, gain = 64, r l = 10k l 35.3 35.8 36.2 35.15 35.8 36.2 db v s = 2.7v, gain = 64, r l = 500 w l 34.2 35.3 36.2 33.65 35.3 36.2 db v s = 5v, gain = 1, r l = 10k l C0.08 0.00 0.08 C0.09 0.00 0.08 db v s = 5v, gain = 1, r l = 500 w l C0.10 C0.01 0.08 C0.12 C0.01 0.08 db v s = 5v, gain = 2, r l = 10k l 5.96 6.02 6.1 5.95 6.02 6.1 db v s = 5v, gain = 4, r l = 10k l 11.85 12.02 12.15 11.83 12.02 12.15 db v s = 5v, gain = 8, r l = 10k l 17.85 18.01 18.15 17.83 18.01 18.15 db v s = 5v, gain = 8, r l = 500 w l 17.65 17.96 18.15 17.50 17.96 18.15 db v s = 5v, gain = 16, r l = 10k l 23.85 24.02 24.15 23.80 24.02 24.15 db v s = 5v, gain = 32, r l = 10k l 29.70 30.02 30.2 29.65 30.02 30.2 db v s = 5v, gain = 64, r l = 10k l 35.5 35.9 36.3 35.40 35.9 36.3 db v s = 5v, gain = 64, r l = 500 w l 34.7 35.6 36.1 34.20 35.6 36.1 db v s = 5v, gain = 1, r l = 10k l C0.06 0.01 0.08 C0.07 0.01 0.08 db v s = 5v, gain = 1, r l = 500 w l C0.10 0.00 0.08 C0.11 0.00 0.08 db v s = 5v, gain = 2, r l = 10k l 5.96 6.02 6.1 5.95 6.02 6.1 db v s = 5v, gain = 4, r l = 10k l 11.9 12.03 12.15 11.88 12.03 12.15 db v s = 5v, gain = 8, r l = 10k l 17.85 18.02 18.15 17.83 18.02 18.15 db v s = 5v, gain = 8, r l = 500 w l 17.80 17.99 18.15 17.73 17.99 18.15 db v s = 5v, gain = 16, r l = 10k l 23.85 24.03 24.15 23.82 24.03 24.15 db v s = 5v, gain = 32, r l = 10k l 29.85 30 30.2 29.8 30 30.2 db v s = 5v, gain = 64, r l = 10k l 35.65 36.0 36.20 35.55 36.0 36.20 db v s = 5v, gain = 64, r l = 500 w l 35.20 35.8 36.20 34.80 35.8 36.20 db channel-to-channel v s = 2.7v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db voltage gain match v s = 2.7v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 2.7v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 2.7v, gain = 4, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 8, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 8, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 16, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 32, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 2.7v, gain = 64, r l = 10k l C0.2 0.02 0.2 C0.2 0.02 0.2 db v s = 2.7v, gain = 64, r l = 500 w l C0.7 0.02 0.7 C1.0 0.02 1.0 db c/i grades h grade parameter conditions min typ max min typ max units
ltc6911-1/ltc6911-2 8 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics c/i grades h grade parameter conditions min typ max min typ max units ltc6911-2 only v s = 5v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 4, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 8, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 8, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 16, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 32, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 64, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 64, r l = 500 w l C0.60 0.02 0.60 C0.80 0.02 0.80 db v s = 5v, gain = 1, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 1, r l = 500 w l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 2, r l = 10k l C0.1 0.02 0.1 C0.1 0.02 0.1 db v s = 5v, gain = 4, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 8, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 8, r l = 500 w l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 16, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 32, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 64, r l = 10k l C0.15 0.02 0.15 C0.15 0.02 0.15 db v s = 5v, gain = 64, r l = 500 w l C0.40 0.02 0.40 C0.60 0.02 0.60 db gain temperature coefficient v s = 5v, gain = 1, r l = open 2 2 ppm/ c v s = 5v, gain = 2, r l = open C1 C1 ppm/ c v s = 5v, gain = 4, r l = open C7 C7 ppm/ c v s = 5v, gain = 8, r l = open C21 C21 ppm/ c v s = 5v, gain = 16, r l = open C28 C28 ppm/ c v s = 5v, gain = 32, r l = open C40 C40 ppm/ c v s = 5v, gain = 64, r l = open C115 C115 ppm/ c channel-to-channel gain v s = 5v, gain = 1, r l = open 0 0 ppm/ c temperature coefficient match v s = 5v, gain = 2, r l = open C0.5 C0.5 ppm/ c v s = 5v, gain = 4, r l = open 0.5 0.5 ppm/ c v s = 5v, gain = 8, r l = open 0.5 0.5 ppm/ c v s = 5v, gain = 16, r l = open 1.0 1.0 ppm/ c v s = 5v, gain = 32, r l = open 4.0 4.0 ppm/ c v s = 5v, gain = 64, r l = open 4.0 4.0 ppm/ c channel-to-channel isolation (note 7) f = 200khz v s = 5v, gain = 1, r l = 10k 110 110 db v s = 5v, gain = 8, r l = 10k 110 110 db v s = 5v, gain = 64, r l = 10k 93 93 db offset voltage magnitude gain = 1 l 2.0 22 2.0 22 mv referred to ina or inb pins (note 8) gain = 8 l 1.1 12 1.1 14 mv offset voltage magnitude drift gain = 1 12 20 m v/ c referred to ina or inb pins (note 8) gain = 8 6.8 11 m v/ c dc input resistance at dc v ina or v inb = 0v ina or inb pins (note 9) gain = 0 l >100 >100 m w gain = 1 l 10 10 k w gain = 2 l 55k w gain = 4 l 2.5 2.5 k w gain > 4 l 1.25 1.25 k w
ltc6911-1/ltc6911-2 9 sn691112 691112fs the l denotes the specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v s = 5v, agnd = 2.5v, gain = 1 (digital inputs 001), r l = 10k to midsupply point, unless otherwise noted. electrical characteristics note 1: absolute maximum ratings are those values beyond which the life of the device may be impaired. note 2: the ltc6911c and ltc6911i are guaranteed functional over the operating temperature range of C 40 c to 85 c. the ltc6911h is guaranteed functional over the operating temperature range of C 40 c to 125 c. note 3: the ltc6911c is guaranteed to meet specified performance from 0 c to 70 c. the ltc6911c is designed, characterized and expected to meet specified performance from C 40 c to 85 c but is not tested or qa sampled at these temperatures. ltc6911i is guaranteed to meet specified performance from C 40 c to 85 c. the ltc6911h is guaranteed to meet specified performance from C40 c to 125 c. note 4: output voltage swings are measured as differences between the output and the respective supply rail. note 5: extended operation with output shorted may cause junction temperature to exceed the 150 c limit and is not recommended. note 6: gain is measured with a dc large-signal test using an output excursion between approximately 30% and 70% of the total supply voltage. note 7: channel-to-channel isolation is measured by applying a 200khz input signal to one channel so that its output varies 1v rms and measuring the output voltage rms of the other channel relative to agnd with its input tied to agnd. isolation is calculated: isolation v v isolation v v a outb outa b outa outb == 20 20 10 10 log , log note 8: offset voltage referred to the ina or inb input is (1 + 1/g) times the offset voltage of the internal op amp, where g is the nominal gain magnitude. see applications information. note 9: input resistance can vary by approximately 30% part-to-part at a given gain setting (input resistance match remains as specified). c/i grades h grade parameter conditions min typ max min typ max units ltc6911-2 only dc input resistance match gain = 1 l 10 10 w r ina C r inb gain = 2 l 55 w gain = 4 l 22 w gain > 4 l 11 w dc small-signal output resistance dc v ina or v inb = 0v at outa or outb pins gain = 0 0.4 0.4 w gain = 1 0.7 0.7 w gain = 2 1.0 1.0 w gain = 4 1.9 1.9 w gain = 8 3.4 3.4 w gain = 16 6.4 6.4 w gain = 32 15 15 w gain = 64 30 30 w wideband noise (referred to input) f = 1khz to 200khz gain = 0 (output noise only) 7.4 7.4 m v rms gain = 1 12.4 12.4 m v rms gain = 2 8.5 8.5 m v rms gain = 4 6.5 6.5 m v rms gain = 8 5.5 5.5 m v rms gain = 16 5.2 5.2 m v rms gain = 32 4.9 4.9 m v rms gain = 64 4.3 4.3 m v rms voltage noise density f = 50khz (referred to input) gain = 1 28.0 28.0 nv/ ? hz gain = 2 19.0 19.0 nv/ ? hz gain = 4 14.8 14.8 nv/ ? hz gain = 8 12.7 12.7 nv/ ? hz gain = 16 11.8 11.8 nv/ ? hz gain = 32 11.5 11.5 nv/ ? hz gain = 64 10.9 10.9 nv/ ? hz total harmonic distortion gain = 8, f in = 10khz, v out = 1v rms C90 C90 db 0.003 0.003 % gain = 8, f in = 100khz, v out = 1v rms C82 C82 db 0.008 0.008 % gain-bandwidth product gain = 64, f in = 200khz l 6 11 17 6 11 17 mhz
ltc6911-1/ltc6911-2 10 sn691112 691112fs typical perfor a ce characteristics uw (ltc6911-1) ltc6911-1 gain shift vs temperature temperature ( c) ?0 gain change (db) 0 0.025 0.025 25 75 6911 g01 ?5 0 50 0.050 0.050 0.075 0.075 0.100 0.100 100 gain = 100 gain = 10 gain = 1 v s = 5v output unloaded frequency (hz) 10 gain (db) 30 50 0 20 40 100 10k 100k 1m 10m 6911 g02 ?0 1k gain of 100 (digital input 111) gain of 1 (digital input 001) gain of 2 (digital input 010) gain of 5 (digital input 011) gain of 10 (digital input 100) gain of 20 (digital input 101) gain of 50 (digital input 110) v s = 10v, v in = 5mv rms gain 1 0 ?db frequency (mhz) 2.0 4.0 8.0 7.5 7.0 6.5 5.5 5.0 4.5 3.5 3.0 2.5 1.5 1.0 0.5 10 100 6911 g03 6.0 v in = 5mv rms v s = 2.7v v s = 5v ltc6911-1 frequency response ltc6911-1 C3db bandwidth vs gain setting ltc6911-1 channel isolation vs frequency ltc6911-1 power supply rejection vs frequency ltc6911-1 noise density vs frequency frequency (hz) 85 100 95 90 120 115 110 105 6911 g04 channel-to-channel isolation (db) 100k 1m gain = 100 gain = 1 gain = 10 v s = 5v v out = 1v rms frequency (hz) 20 rejection (db) 40 50 70 90 10k 100k 1m 10m 6911 g05 0 1k 60 30 10 80 +supply ?upply v s = 2.5v gain = 1 frequency (hz) 1k 1 voltage noise density (nv/ hz) 10 100 10k 100k 6911 g06 gain = 1 gain = 10 gain = 100 v s = 2.5v t a = 25 c input referred ltc6911-1 distortion vs frequency with light loading (r l = 10k) ltc6911-1 thd + noise vs input voltage frequency (hz) 0 ?0 ?0 ?0 150k 6911 g07 ?0 ?0 50k 100k 200k ?0 ?00 ?0 thd (amplitude below fundamental) (db) v s = 2.5v v out = 1v rms (2.83v p-p ) gain = 1 gain = 10 gain = 100 ltc6911-1 distortion vs frequency with heavy loading (r l = 500 w ) input voltage (v p-p ) ?0 thd + noise (db) ?0 ?0 ?0 ?0 1m 0.1 1 10 6911 g09 ?10 10n ?0 ?0 ?00 ?0 f in = 1khz v s = 5v bw = 100hz to 22khz gain = 1 gain = 10 gain = 100 frequency (hz) 0 ?0 ?0 ?0 150k 6911 g08 ?0 ?0 50k 100k 200k ?0 ?00 ?0 thd (amplitude below fundamental) (db) v s = 2.5v v out = 1v rms (2.83v p-p ) gain = 1 gain = 10 gain = 100
ltc6911-1/ltc6911-2 11 sn691112 691112fs typical perfor a ce characteristics uw (ltc6911-2) ltc6911-2 gain shift vs temperature ltc6911-2 frequency response ltc6911-2 C3db bandwidth vs gain setting ltc6911-2 channel isolation vs frequency ltc6911-2 power supply rejection vs frequency ltc6911-2 noise density vs frequency ltc6911-2 distortion vs frequency with light loading (r l = 10k) ltc6911-2 thd + noise vs input voltage ltc6911-2 distortion vs frequency with heavy loading (r l = 500 w ) temperature ( c) ?0 gain change (db) 0 0.025 0.025 25 75 ?5 0 50 0.050 0.050 0.075 0.075 0.100 0.100 100 gain = 64 gain = 8 gain = 1 v s = 5v output unloaded 6911 g010 frequency (hz) 10 gain (db) 30 50 0 20 40 100 1k 100k 1m 10m 6911 g11 ?0 10k v s = 5v v in = 10mv rms gain of 64 gain of 32 gain of 16 gain of 4 gain of 8 gain of 2 gain of 1 gain 1 0 ?db frequency (mhz) 2.0 4.0 8.0 7.5 7.0 6.5 5.5 5.0 4.5 3.5 3.0 2.5 1.5 1.0 0.5 10 100 6911 g12 6.0 v in = 10mv rms v s = 2.7v v s = 5v frequency (hz) 85 100 95 90 120 115 110 105 6911 g13 channel-to-channel isolation (db) 100k 1m gain = 64 gain = 1 gain = 8 v s = 5v v out = 1v rms frequency (hz) 20 rejection (db) 40 50 70 90 10k 100k 1m 10m 6911 g14 0 1k 60 30 10 80 +supply ?upply v s = 2.5v gain = 1 frequency (hz) 1k 1 voltage noise density (nv/ hz) 10 100 10k 100k 6911 g15 gain = 1 gain = 8 gain = 64 v s = 2.5v t a = 25 c input referred frequency (hz) 0 ?0 ?0 ?0 150k 6911 g16 ?0 ?0 50k 100k 200k ?0 ?00 ?0 thd (amplitude below fundamental) (db) v s = 2.5v v out = 1v rms (2.83v p-p ) gain = 1 gain = 8 gain = 64 frequency (hz) 0 ?0 ?0 ?0 150k 6911 g17 ?0 ?0 50k 100k 200k ?0 ?00 ?0 thd (amplitude below fundamental) (db) v s = 2.5v v out = 1v rms (2.83v p-p ) gain = 1 gain = 8 gain = 64 input voltage (v p-p ) ?0 thd + noise (db) ?0 ?0 ?0 ?0 1m 0.1 1 10 6911 g18 ?10 10n ?0 ?0 ?00 ?0 f in = 1khz v s = 5v bw = 100hz to 22khz gain = 1 gain = 8 gain = 64
ltc6911-1/ltc6911-2 12 sn691112 691112fs uu u pi fu ctio s ina (pin 1): analog input. the input signal to the a channel amplifier of the ltc6911-x is the voltage difference be- tween the ina and agnd pin. the ina pin connects internally to a digitally controlled resistance whose other end is a current summing point at the same potential as the agnd pin (figure 1). at unity gain (digital input 001), the value of this input resistance is approximately 10k w and the ina pin voltage range is rail-to-rail (v + to v C ). at gain settings above unity, the input resistance falls. the linear input range at ina also falls inversely proportional to the programmed gain. tables 1 and 2 summarize this behav- ior. the higher gains are designed to boost lower level signals with good noise performance. in the zero gain state (digital input 000), analog switches disconnect the ina pin internally and this pin presents a very high input resistance. the input may vary from rail to rail in the zero gain setting, but the output is insensitive to it and is forced to the agnd potential. circuitry driving the ina pin must consider the ltc6911-xs input resistance, its lot-to-lot variance, and the variation of this resistance from gain setting to gain setting. signal sources with significant output resistance may introduce a gain error as the sources output resistance and the ltc6911-xs input resistance form a voltage divider. this is especially true at higher gain settings where the input resistance is the lowest. in single supply voltage applications, it is important to remember that the ltc6911-xs dc ground reference for both input and output is agnd, not v C . with increasing gains, the ltc6911-xs input voltage range for an unclipped output is no longer rail-to-rail but diminishes inversely to gain, centered about the agnd potential. figure 1. block diagram + input r array feedback r array outa mos-input op amp mos-input op amp ina g1 g2 g0 10 v 9 v + 691112 f01 7 + outb 8 1 input r array feedback r array inb 3 agnd v + v 10k 10k 2 cmos logic 5 6 4
ltc6911-1/ltc6911-2 13 sn691112 691112fs agnd (pin 2): analog ground. the agnd pin is at the midpoint of an internal resistive voltage divider, develop- ing a potential halfway between the v + and v C pins, with an equivalent series resistance to the pin of nominally 5k w (figure 1). agnd is also the noninverting input to both the internal channel a and channel b amplifiers. this makes agnd the ground reference voltage for the ina, inb, outa and outb pins. recommended analog ground plane con- nection depends on how power is applied to the ltc6911-x (see figures 2, 3 and 4). single power supply applications typically use v C for the system signal ground. the analog ground plane in single supply applications should there- fore tie to v C , and the agnd pin should be bypassed to this ground plane by a high quality capacitor of at least 1 m f (figure 2). the agnd pin provides an internal analog reference voltage at half the v + supply voltage. dual supply applications with symmetrical supplies (such as 5v) have a natural system ground plane potential of zero volts, which can be tied directly to the agnd pin, making the zero volt ground plane the input and output reference voltage for the ltc6911-x (figure 3). finally, if dual asymmetrical power supplies are used, the supply ground is still the natural ground plane voltage. to maximize signal swing uu u pi fu ctio s capability with an asymmetrical supply, however, it is often desirable to refer the ltc6911-xs analog input and output to a voltage equidistant from the two supply rails v + and v C . the agnd pin will provide such a potential when open-circuited and bypassed with a capacitor (figure 4). figure 3. dual supply ground plane connection figure 2. single supply ground plane connection ltc6911-x digital ground plane (if any) analog ground plane 1 single-point system ground 2345 691112 f03 10 9 8 7 6 0.1 f v v + 0.1 f figure 4. asymmetrical dual supply ground plane connection ltc6911-x digital ground plane (if any) analog ground plane 1 single-point system ground 2345 691112 f04 10 9 8 7 6 0.1 f v v + 0.1 f 3 1 f reference v + + v 2 digital ground plane (if any) analog ground plane single-point system ground reference v + 2 691112 f02 3 1 f ltc6911-x 12345 10 9 8 7 6 v + 0.1 f
ltc6911-1/ltc6911-2 14 sn691112 691112fs uu u pi fu ctio s in noise sensitive applications where agnd does not directly tie to a ground plane, as in figures 2 and 4, it is important to ac-bypass the agnd pin. otherwise, chan- nel-to-channel isolation is degraded and wideband noise will enter the signal path from the thermal noise of the internal voltage divider resistors that present a thvenin equivalent resistance of approximately 5k w . this noise can reduce snr by at least 3db at high gain settings. an external capacitor from agnd to the ground plane, whose impedance is well below 5k w at frequencies of interest, will filter and suppress this noise. a 1 m f high quality capacitor is effective for frequencies down to 1khz. larger capacitors extend this suppression to lower frequencies. this issue does not arise in dual supply applications because the agnd pin ties directly to ground. in applications requiring an analog ground reference other than half the total supply voltage, the user can override the built-in analog ground reference by tying the agnd pin to a reference voltage within the agnd voltage range speci- fied in the electrical characteristics table. the agnd pin will load the external reference with approximately 5k w returned to the half-supply potential. agnd should still be capacitively bypassed to a ground plane as noted above. do not connect the agnd pin to the v C pin. inb (pin 3): analog input. refer to ina pin description. g0, g1, g2 (pins 4, 5, 6): cmos-level digital gain control inputs. g2 is the most significant bit (msb) and g0 is the least significant bit (lsb). these pins control the voltage gain settings for both channels (see tables 1 and 2). each channels gain cannot be set independent of the other channel. the logic input pins (g pins) are allowed to swing from v C to 10.5v above v C , regardless of v + so long as the logic levels meet the minimum requirements specified in the electrical characteristics table. the g0, g1 and g2 pins are high impedance cmos logic inputs, but have small pull-down current sources (<10 m a) which will force both channels into the zero gain state (digital input 000) if the logic inputs are externally floated. no speed limitation is associated with the digital logic because it is memoryless and much faster than the analog signal path. v C , v + (pins 7, 9): power supply pins. the v + and v C pins should be bypassed with 0.1 m f capacitors to an adequate analog ground plane using the shortest possible wiring. electrically clean supplies and a low impedance ground are important for the high dynamic range available from the ltc6911-x (see further details under the agnd pin description). low noise linear power supplies are recom- mended. switching power supplies require special care to prevent switching noise coupling into the signal path, reducing dynamic range. outb (pin 8): analog output. this is the output of the b channel internal operational amplifier and can swing rail- to-rail (v + to v C ) as specified in the electrical characteris- tics table. the internal op amp remains active at all times, including the zero gain setting (digital input 000). for best performance, loading the output as lightly as possible will minimize signal distortion and gain error. the electrical characteristics table shows performance at output cur- rents up to 10ma, and the current limits which occur when the output is shorted to mid-supply at 2.7v and 5v supplies. signal outputs above 10ma are possible but current-limiting circuitry will begin to affect amplifier performance at approximately 20ma. long-term opera- tion above 20ma output is not recommended. do not exceed a maximum junction temperature of 150 c. the output will drive capacitive loads up to 50pf. capacitances higher than 50pf should be isolated by a series resistor to preserve ac stability. outa (pin 10): analog output. refer to outb pin description.
ltc6911-1/ltc6911-2 15 sn691112 691112fs applicatio s i for atio wu uu functional description the ltc6911-1/ltc6911-2 are small outline, wideband inverting 2-channel amplifiers whose voltage gain is digi- tally programmable. each delivers a choice of eight volt- age gains, controlled by the 3-bit digital parallel interface (g pins), which accept cmos logic levels. the gain code is always monotonic; an increase in the 3-bit binary number (g2 g1 g0) causes an increase in the gain. tables 1 and 2 list the nominal voltage gains for ltc6911-1 and ltc6911-2 respectively. gain control within each ampli- fier occurs by switching resistors from a matched array in or out of a closed-loop op amp circuit using mos analog switches (figure 1). bandwidth depends on gain setting. curves in the typical performance characteristics section show measured frequency responses. digital control logic levels for the ltc6911-x digital gain control inputs (pins 4, 5, 6) are nominally rail-to-rail cmos, but can swing above v + so long as the positive swing does not exceed 10.5v with respect to v C . each logic input has a small pull-down current source which can sink up to 10 m a and is used to force the part into a gain of zero if the logic inputs are left unconnected. a logic 1 is nominally v + . a logic 0 is nominally v C or alternatively, 0v when using 5v supplies. the parts are tested with the values listed in the electrical characteristics table. digital input high and low voltages are 10% and 90% of the nominal full excursion on the inputs. that is, the tested logic levels are 0.27v and 2.43v with a 2.7v supply, 0.5v and 4.5v with a 5v supply, and 0.5v and 4.5v with 5v supplies. do not attempt to drive the digital inputs with ttl logic levels. ttl logic sources should be adapted with suitable pull-up resistors to v + keeping in mind the internal pull-down current sources so that for a logic 1 they will swing to the positive rail. timing constraints settling time in the cmos gain-control logic is typically several nanoseconds and is faster than the analog signal path. when amplifier gain changes, the limiting timing is analog, not digital, because the effects of digital input changes are observed only through the analog output (figure 1). the ltc6911-xs logic is static (not latched) and therefore lacks bus timing requirements. however, as with any programmable-gain amplifier, each gain change causes an output transient as the amplifiers output moves, with finite speed, toward a differently scaled version of the input signal. varying the gain faster than the output can settle produces a garbled output signal. the ltc6911-x analog path settles with a characteristic time constant or time scale, t , that is roughly the standard value for a first order band limited response: t = 0.35/(2 p f C3db ) see the C3db bw vs gain setting graph in the typical performance characteristics. offset voltage vs gain setting the electrical characteristics table lists dc gain depen- dent voltage offset error in two gain configurations. the voltage offsets listed, v os(in) , are referred to the input pin (ina or inb). these offsets are directly related to the internal amplifier input voltage offset, v os(oa) , by the magnitude of programmed gain, g: vv g g os oa os in () () = + ? ? ? ? 1 the input referred offset, v os(in) , for any gain setting can be inferred from v os(oa) and the gain magnitude, g. for example, an internal offset v os(oa) of 1mv will appear referred to the ina and inb pins as 2mv at a gain setting
ltc6911-1/ltc6911-2 16 sn691112 691112fs applicatio s i for atio wu uu of 1, or 1.5mv at a gain setting of 2. at high gains, v os(in) approaches v os(oa) . (offset voltage is random and can have either polarity centered on 0v.) the mos input circuitry of the internal op amp in figure 1 draws negligible input currents (unlike some op amps), so only v os(oa) and g affect the overall amplifiers offset. ac-coupled operation adding capacitors in series with the ina and inb pins convert the ltc6911-x into a dual ac-coupled inverting amplifier, suppressing the input signals dc level (and also adding the additional benefit of reducing the offset voltage from the ltc6911-xs amplifier itself). no further compo- nents are required because the input of the ltc6911-x biases itself correctly when a series capacitor is added. the ina and inb analog input pins connect internally to a resistor whose nominal value varies between 10k and 1k depending on the version of ltc6911 used (see the rightmost column of tables 1 and 2). therefore, the low frequency cutoff will vary with capacitor and gain setting. for example, if a low frequency corner of 1khz or lower on the ltc6911-1 is desired, use a series capacitor of 0.16 m f or larger. a 0.16 m f capacitor has a reactance of 1k w at 1khz, giving a 1khz lower C3db frequency for gain settings of 10v/v through 100v/v. if the ltc6911-1 is operated at lower gain settings with an 0.16 m f capacitor, the higher input resistance will reduce the lower corner frequency down to 100hz at a gain setting of 1v/v. these frequencies scale inversely with the value of the input capacitor used. note that operating the ltc6911 family in zero gain mode (digital inputs 000) open circuits the ina and inb pins and this demands some care if employed with a series ac-coupled input capacitor. when the chip enters the zero gain mode, the opened ina or inb pin tends to sample and freeze the voltage across the capacitor to the value it held just before the zero gain state. this can place the ina or inb pin at or near the dc potential of a supply rail (the ina or inb pin may also drift to a supply potential in this state due to small junction leakage currents). to prevent driving the ina or inb pin outside the supply limit and potentially damaging the chip, avoid ac input signals in the zero gain state with an ac-coupled capacitor. also, switching later to a nonzero gain value will cause a transient pulse at the output of the ltc6911-1 (with a time constant set by the capacitor value and the new ltc6911-1 input resistance value). this occurs because the ina and inb pins return to the agnd potential forcing transient current sourced by the amplifier output to charge the ac-coupling capacitor to its proper dc blocking value. snr and dynamic range the term dynamic range is much used (and abused) with signal paths. signal-to-noise ratio (snr) is an unam- biguous comparison of signal and noise levels, measured in the same way and under the same operating conditions. in a variable gain amplifier, however, further characteriza- tion is useful because both noise and maximum signal level in the amplifier will vary with the gain setting, in general. in the ltc6911-x, maximum output signal is independent of gain (and is near the full power supply voltage, as detailed in the swing sections of the electrical characteristics table). the maximum input level falls with increasing gain, and the input-referred noise falls as well (as also listed in the table). to summarize the useful signal range in such an amplifier, we define dynamic range (dr) as the ratio of maximum input (at unity gain) to minimum input-referred noise (at maximum gain). this dr has a physical interpretation as the range of signal levels that will experience an snr above unity v/v or 0db. at a 10v total power supply, dr in the ltc6911-x (gains 0v/v to 100v/v) is typically 120db (the ratio of a nominal 9.9v p-p , or 3.5v rms (maximum input), to the 3.8 m v rms (high gain input noise). the snr of an amplifier is the ratio of input level to input-referred noise, and can be 110db with the ltc6911 family at unity gain.
ltc6911-1/ltc6911-2 17 sn691112 691112fs construction and instrumentation cautions electrically clean construction is important in applications seeking the full dynamic range of the ltc6911 family of dual amplifiers. it is absolutely critical to have agnd either ac bypassed or wired directly, using the shortest possible wiring, to a low impedance ground return for best channel- to-channel isolation. short, direct wiring will minimize parasitic capacitance and inductance. high quality supply bypass capacitors of 0.1 m f near the chip provide good decoupling from a clean, low inductance power source. but several cm of wire (i.e., a few microhenrys of induc- tance) from the power supplies, unless decoupled by substantial capacitance (>10 m f) near the chip, can create a high-q lc resonance in the hundreds of khz in the chips supplies or ground reference. this may impair circuit performance at those frequencies. a compact, carefully laid out printed circuit board with a good ground plane makes a significant difference in minimizing distortion and maximizing channel isolation. finally, equipment to mea- sure amplifier performance can itself add to distortion or noise floors. checking for these limits with wired shorts from ina to outa and inb to outb in place of the chip is a prudent routine procedure. applicatio s i for atio wu uu
ltc6911-1/ltc6911-2 18 sn691112 691112fs figure 5. expanding a dual channel adcs dynamic range expanding an adcs dynamic range figure 5 shows a compact 2-channel data acquisition system for wide ranging input levels. this figure combines an ltc6911-x programmable amplifier (10-lead msop) with an ltc1865 analog-to-digital converter (adc) in an 8-lead msop. this adc has 16-bit resolution and a maximum sampling rate of 250ksps. an ltc6911-1, for example, expands the adcs input amplitude range by 40db while operating from the same single 5v supply. the 499 w resistor and 270pf capacitor couple cleanly be- tween the ltc6911-xs output and the switched-capacitor inputs of the ltc1865. u typical applicatio ltc6911-x 10 499 270pf 499 79 8 1 v ina agnd v inb 3 2 3 1 f 270pf 0.1 f v + 45 gain control adc interface 6 691112 f05 0.1 f v + 691112 f05 ch0 conv sdi sdo sck v cc ltc1865 gnd ch1
ltc6911-1/ltc6911-2 19 sn691112 691112fs u package descriptio ms package 10-lead plastic msop (reference ltc dwg # 05-08-1661) msop (ms) 0603 0.53 0.152 (.021 .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 0.27 (.007 ?.011) typ 0.127 0.076 (.005 .003) 0.86 (.034) ref 0.50 (.0197) bsc 12 3 45 4.90 0.152 (.193 .006) 0.497 0.076 (.0196 .003) ref 8 9 10 7 6 3.00 0.102 (.118 .004) (note 3) 3.00 0.102 (.118 .004) (note 4) 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 0.254 (.010) 0 ?6 typ detail ? detail ? gauge plane 5.23 (.206) min 3.20 ?3.45 (.126 ?.136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.305 0.038 (.0120 .0015) typ 0.50 (.0197) bsc 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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
ltc6911-1/ltc6911-2 20 sn691112 691112fs linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com ? linear technology corporation 2004 lt/tp 0104 1k ? printed in usa related parts part number description comments lt ? 1228 100mhz gain controlled transconductance amplifier differential input, continuous analog gain control lt1251/lt1256 40mhz video fader and gain controlled amplifier two input, one output, continuous analog gain control ltc1564 10khz to 150khz digitally controlled filter and pga continuous time, low noise 8th order filter and 4-bit pga ltc6910 digitally controlled programmable gain amplifier in sot-23 single channel version of the ltc6911 ltc6915 digitally controlled programmable instrumentation 14 bits of gain control amplifier with spi interface typical applicatio u fully differential amplifier with digitally programmable gain 1 2 3 4 5 10 9 8 7 6 ltc6911-1 or ltc6911-2 g0 g1 digital gain control high dynamic range (pga input) high cmrr (differential input) g2 g0 g1 digital gain control g2 1 2 3 4 8 7 6 5 8 7 6 5 ltc1992-1 or ltc1992-2 or ltc1992-5 or ltc1992-10 1 2 3 4 5 10 9 8 7 6 ltc6911-1 or ltc6911-2 1 2 3 4 ltc1992-1 or ltc1992-2 or ltc1992-5 or ltc1992-10 0.1 f 0.1 f0.1 f 0.1 f v out + v out 5v v in + v in v in + v in ?v 0.1 f 691112 ta03 v out + v out 5v 0.1 f ?v 0.1 f 5v ?v 0.1 f ?v

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