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LT1993-10 1 199310fb 4-tone wcdma waveform, LT1993-10 driving ltc2255 14-bit adc at 92.16msps 700mhz low distortion, low noise differential ampli er/ adc driver (a v = 10 v / v) the lt ? 1993-10 is a low distortion, low noise differential ampli? er/adc driver for use in applications from dc to 700mhz. the LT1993-10 has been designed for ease of use, with minimal support circuitry required. exception- ally low input-referred noise and low distortion products (with either single-ended or differential inputs) make the LT1993-10 an excellent solution for driving high speed 12-bit and 14-bit adcs. in addition to the normal un? ltered outputs (+out and Cout), the LT1993-10 has a built-in 175mhz differential lowpass ? lter and an additional pair of ? ltered outputs (+outfiltered, Coutfiltered) to reduce external ? ltering components when driving high speed adcs. the output common mode voltage is easily set via the v ocm pin, eliminating either an output transformer or ac-coupling capacitors in many applications. the LT1993-10 is designed to meet the demanding require- ments of communications transceiver applications. it can be used as a differential adc driver, a general-purpose differential gain block, or in any other application requir- ing differential drive. the LT1993-10 can be used in data acquisition systems required to function at frequencies down to dc. the LT1993-10 operates on a 5v supply and consumes 100ma. it comes in a compact 16-lead 3 3 qfn package and operates over a C40c to 85c temperature range. differential adc driver for: imaging communications differential driver/receiver single ended to differential conversion differential to single ended conversion level shifting if sampling receivers saw filter interfacing/buffering 700mhz C3db bandwidth fixed gain of 10v/v (20db) low distortion: 40dbm oip3, C70dbc hd3 (70mhz 2v p-p ) 50.5dbm oip3, C91dbc (10mhz 2v p-p ) low noise: 12.7db nf, e n = 1.9nv/hz differential inputs and outputs additional filtered outputs adjustable output common mode voltage dc- or ac-coupled operation minimal support circuitry required small 0.75mm tall 16-lead 3 3 qfn package 4-channel wcdma receive channel applicatio s u features descriptio u typical applicatio u , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. 2.2v 20db gain 199310 ta01 ma/com etc 1-1-13 1:1 z-ratio ltc2255 125msps 14-bit adc sampling at 92.16msps 70mhz if in 52.3pf 82nh LT1993-10 ?na ?nb ?utfiltered ?ut +outfiltered +out +inb +ina v ocm enable ltc2255 adc ain ain+ frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 25 199310 ?ta02 35 20 30 40 45 ?0 ?10 ?0 ?0 ?0 ?0 ?0 32768 point fft tone center frequencies at 62.5mhz, 67.5mhz, 72.5mhz, 77.5mhz
LT1993-10 2 199310fb 16 15 14 13 5 6 7 8 top view ud package 16-lead (3mm 3mm) plastic qfn 9 10 17 11 12 4 3 2 1 v ccc v ocm v cca v eea v eec enable v ccb v eeb +ina +inb ?na ?nb +out +outfiltered ?utfiltered ?ut total supply voltage (v cca /v ccb /v ccc to v eea /v eeb /v eec ) ...................................................5.5v input current (+ina, Cina, +inb, Cinb, v ocm , enable) ................................................10ma output current (continuous) (note 6) +out, Cout (dc) ..........................................100ma (ac) ..........................................100ma +outfiltered, Coutfiltered (dc) .............15ma (ac) .............45ma output short circuit duration (note 2) ............ inde? nite operating temperature range (note 3) ... C40c to 85c speci? ed temperature range (note 4) .... C40c to 85c storage temperature range ................... C65c to 125c junction temperature ........................................... 125c lead temperature range (soldering 10 sec) ........ 300c order part number ud part marking* consult ltc marketing for parts speci? ed with wider operating temperature ranges. *the temperature grade is identi? ed by a label on the shipping container. lbnt lbnt lt1993cud-10 lt1993iud-10 (note 1) the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v cca = v ccb = v ccc = 5v, v eea = v eeb = v eec = 0v, enable = 0.8v, +ina shorted to +inb (+in), Cina shorted to Cinb (Cin), v ocm = 2.2v, input common mode voltage = 2.2v, no r load unless otherwise noted. symbol parameter conditions min typ max units input/output characteristics (+ina, +inb, Cina, Cinb, +out, Cout, +outfiltered, Coutfiltered) gdiff gain differential (+out, Cout), v in = 160mv differential 18.9 19.7 20.9 db v swingmin single-ended +out, Cout, +outfiltered, Coutfiltered. v in = 600mv differential 0.25 0.35 0.5 v v v swingmax single-ended +out, Cout, +outfiltered, Coutfiltered. v in = 600mv differential 3.6 3.5 3.75 v v v swingdiff output voltage swing differential (+out, Cout), v in = 600mv differential 6.5 6 7v p-p v p-p i out output current drive (note 5) 40 45 ma v os input offset voltage C6.5 C10 1 6.5 10 mv mv tcv os input offset voltage drift t min to t max 2.5 v/c i vrmin input voltage range, min single-ended 0.9 v i vrmax input voltage range, max single-ended 3.9 v r indiff differential input resistance 77 100 122 c indiff differential input capacitance 1pf absolute axi u rati gs w ww u package/order i for atio uu w dc electrical characteristics t jmax = 125c, ja = 68c/w, jc = 4.2c/w exposed pad is v ee (pin 17) must be soldered to the pcb order options tape and reel: add #tr lead free: add #pbf lead free tape and reel: add #trpbf lead free part marking: http://www.linear.com/leadfree/
LT1993-10 3 199310fb symbol parameter conditions min typ max units input/output characteristics C3dbbw C3db bandwidth 200mv p-p differential (+out, Cout) 500 700 mhz 0.1dbbw bandwidth for 0.1db flatness 200mv p-p differential (+out, Cout) 50 mhz 0.5dbbw bandwidth for 0.5db flatness 200mv p-p differential (+out, Cout) 100 mhz sr slew rate 3.2v p-p differential (+out, Cout) 1100 v/s t s1% 1% settling time 1% settling for a 1v p-p differential step (+out, Cout) 4ns t on turn-on time 40 ns t off turn-off time 250 ns common mode voltage control (v ocm pin) C3dbbw cm common mode small-signal C3db bandwidth 0.1v p-p at v ocm , measured single-ended at +out and Cout 300 mhz symbol parameter conditions min typ max units cmrr common mode rejection ratio input common mode 0.9v to 3.9v 45 70 db r outdiff output resistance 0.3 c outdiff output capacitance 0.8 pf common mode voltage control (v ocm pin) gcm common mode gain differential (+out, Cout), v ocm = 1.2v to 3.6v differential (+out, Cout), v ocm = 1.4v to 3.4v 0.9 0.9 1 1.1 1.1 v/v v/v v ocmmin output common mode voltage adjustment range, min measured single-ended at +out and Cout 1.2 1.4 v v v ocmmax output common mode voltage adjustment range, max measured single-ended at +out and Cout 3.6 3.4 v v v oscm output common mode offset voltage measured from v ocm to average of +out and Cout C30 2 30 mv i biascm v ocm input bias current 515 a r incm v ocm input resistance 0.8 3 m c incm v ocm input capacitance 1pf enable pin v il enable input low voltage 0.8 v v ih enable input high voltage 2v i il enable input low current enable = 0.8v 0.5 a i ih enable input high current enable = 2v 13 a power supply v s operating range 4 5 5.5 v i s supply current enable = 0.8v 88 100 112 ma i sdisabled supply current (disabled) enable = 2v 250 500 a psrr power supply rejection ratio 4v to 5.5v 55 90 db the denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v cca = v ccb = v ccc = 5v, v eea = v eeb = v eec = 0v, enable = 0.8v, +ina shorted to +inb (+in), Cina shorted to Cinb (Cin), v ocm = 2.2v, input common mode voltage = 2.2v, no r load unless otherwise noted. t a = 25c, v cca = v ccb = v ccc = 5v, v eea = v eeb = v eec = 0v, enable = 0.8v, +ina shorted to +inb (+in), Cina shorted to Cinb (Cin), v ocm = 2.2v, input common mode voltage = 2.2v, no r load unless otherwise noted. dc electrical characteristics ac electrical characteristics
LT1993-10 4 199310fb symbol parameter conditions min typ max units srcm common mode slew rate 1.2v to 3.6v step at v ocm 500 v/s noise/harmonic performance input/output characteristics 1khz signal second/third harmonic distortion 2v p-p differential (+outfiltered, Coutfiltered) C100 dbc 2v p-p differential (+out, Cout) C100 dbc 2v p-p differential (+out, Cout), r l = 100 C100 dbc 3.2v p-p differential (+outfiltered, Coutfiltered) C91 dbc 3.2v p-p differential (+out, Cout) C91 dbc 3.2v p-p differential (+out, Cout), r l = 100 C91 dbc third-order imd 2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 0.95khz, f2 = 1.05khz C102 dbc 2v p-p differential composite (+out, Cout), r l = 100 , f1 = 0.95khz, f2 = 1.05khz C102 dbc 3.2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 0.95khz, f2 = 1.05khz C93 dbc oip3 1k output third-order intercept differential (+outfiltered, Coutfiltered), f1 = 0.95khz, f2 = 1.05khz 54 dbm e n1k input referred noise voltage density 1.7 nv/hz 1db compression point 22.7 dbm 10mhz signal second/third harmonic distortion 2v p-p differential (+outfiltered, Coutfiltered) C91 dbc 2v p-p differential (+out, Cout) C91 dbc 2v p-p differential (+out, Cout), r l = 100 C83 dbc 3.2v p-p differential (+outfiltered, Coutfiltered) C82 dbc 3.2v p-p differential (+out, Cout) C82 dbc 3.2v p-p differential (+out, Cout), r l = 100 C74 dbc third-order imd 2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 9.5mhz, f2 = 10.5mhz C95 dbc 2v p-p differential composite (+out, Cout), r l = 100 , f1 = 9.5mhz, f2 = 10.5mhz C94 dbc 3.2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 9.5mhz, f2 = 10.5mhz C85 dbc oip3 10m output third-order intercept differential (+outfiltered, Coutfiltered), f1 = 9.5mhz, f2 = 10.5mhz 50.5 dbm nf noise figure measured using dc800a demo board 11.8 dbm e n10m input referred noise voltage density 1.7 nv/hz 1db compression point 22.6 dbm 50mhz signal second/third harmonic distortion 2v p-p differential (+outfiltered, Coutfiltered) C77 dbc 2v p-p differential (+out, Cout) C77 dbc 2v p-p differential (+out, Cout), r l = 100 C73 dbc 3.2v p-p differential (+outfiltered, Coutfiltered) C68 dbc 3.2v p-p differential (+out, Cout) C66 dbc t a = 25c, v cca = v ccb = v ccc = 5v, v eea = v eeb = v eec = 0v, enable = 0.8v, +ina shorted to +inb (+in), Cina shorted to Cinb (Cin), v ocm = 2.2v, input common mode voltage = 2.2v, no r load unless otherwise noted. ac electrical characteristics
LT1993-10 5 199310fb 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: as long as output current and junction temperature are kept below the absolute maximum ratings, no damage to the part will occur. note 3: the lt1993c-10 is guaranteed functional over the operating temperature range of C40c to 85c. note 4: the lt1993c-10 is guaranteed to meet speci? ed performance from 0c to 70c. it is designed, characterized and expected to meet speci? ed performance from C40c and 85c but is not tested or qa sampled at these temperatures. the lt1993i-10 is guaranteed to meet speci? ed performance from C40c to 85c. note 5: this parameter is pulse tested. note 6: this parameter is guaranteed to meet speci? ed performance through design and characterization. it has not been tested. symbol parameter conditions min typ max units 3.2v p-p differential (+out, Cout), r l = 100 C63 dbc third-order imd 2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 49.5mhz, f2 = 50.5mhz C82 dbc 2v p-p differential composite (+out, Cout), r l = 100 , f1 = 49.5mhz, f2 = 50.5mhz C81 dbc 3.2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 49.5mhz, f2 = 50.5mhz C72 dbc oip3 50m output third-order intercept differential (+outfiltered, Coutfiltered), f1 = 49.5mhz, f2 = 50.5mhz 44 dbm nf noise figure measured using dc800a demo board 12.3 db e n50m input referred noise voltage density 1.8 nv/hz 1db compression point 19.7 dbm 70mhz signal second/third harmonic distortion 2v p-p differential (+outfiltered, Coutfiltered) C70 dbc 2v p-p differential (+out, Cout) C67 dbc 2v p-p differential (+out, Cout), r l = 100 C66 dbc third-order imd 2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 69.5mhz, f2 = 70.5mhz C74 dbc 2v p-p differential composite (+out, Cout), r l = 100 , f1 = 69.5mhz, f2 = 70.5mhz C71 dbc oip3 70m output third-order intercept differential (+outfiltered, Coutfiltered), f1 = 69.5mhz, f2 = 70.5mhz 40 dbm nf noise figure measured using dc800a demo board 12.7 db e n70m input referred noise voltage density 1.9 nv/hz 1db compression point 18.5 dbm 100mhz signal second/third harmonic distortion 2v p-p differential (+outfiltered, Coutfiltered) C60 dbc 2v p-p differential (+out, Cout) C55 dbc 2v p-p differential (+out, Cout), r l = 100 C52 dbc third-order imd 2v p-p differential composite (+outfiltered, Coutfiltered), f1 = 99.5mhz, f2 = 100.5mhz C61 dbc 2v p-p differential composite (+out, Cout), r l = 100 , f1 = 99.5mhz, f2 = 100.5mhz C60 dbc oip3 100m output third-order intercept differential (+outfiltered, Coutfiltered), f1 = 99.5mhz, f2 = 100.5mhz 33.5 dbm nf noise figure measured using dc800a demo board 13.2 db e n100m input referred noise voltage density 2.0 nv/hz 1db compression point 17.8 dbm t a = 25c, v cca = v ccb = v ccc = 5v, v eea = v eeb = v eec = 0v, enable = 0.8v, +ina shorted to +inb (+in), Cina shorted to Cinb (Cin), v ocm = 2.2v, input common mode voltage = 2.2v, no r load unless otherwise noted. ac electrical characteristics
LT1993-10 6 199310fb frequency response r load = 400 frequency response vs c load r load = 400 frequency response r load = 100 third order intermodulation distortion vs frequency differential input, no r load third order intermodulation distortion vs frequency differential input, r load = 400 third order intermodulation distortion vs frequency differential input, r load = 100 output third order intercept vs frequency, differential input no r load output third order intercept vs frequency, differential input r load = 400 output third order intercept vs frequency, differential input r load = 100 typical perfor a ce characteristics uw frequency (mhz) 8 gain (db) 14 17 23 26 1 100 1000 10000 199310 g01 2 10 20 11 5 unfiltered outputs filtered outputs v in = 20mv p-p unfiltered: r load = 400 ? filtered: r load = 350 ? (external) + 50 ? (internal, filtered outputs) frequency (mhz) 17 gain (db) 23 26 32 35 1 100 1000 10000 199310 g02 11 10 29 20 14 v in = 20mv p-p unfiltered outputs 10pf 0pf 5pf 1.8pf frequency (mhz) 8 gain (db) 14 17 23 26 1 100 1000 10000 199310 g03 2 10 20 11 5 unfiltered outputs filtered outputs v in = 20mv p-p unfiltered: r load = 100 ? filtered: r load = 50 ? (external) + 50 ? (internal, filtered outputs) frequency (mhz) 0 ?10 third order imd (dbc) ?00 ?0 ?0 ?0 ?0 ?0 40 80 100 199310 g04 ?0 ?0 ?0 ?0 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs frequency (mhz) 0 ?10 third order imd (dbc) ?00 ?0 ?0 ?0 ?0 ?0 40 80 100 199310 g05 ?0 ?0 ?0 ?0 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs frequency (mhz) 0 ?10 third order imd (dbc) ?00 ?0 ?0 ?0 ?0 ?0 40 80 100 199310 g06 ?0 ?0 ?0 ?0 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs frequency (mhz) 0 20 output ip3 (dbm) 25 30 35 60 45 40 80 100 199310 g07 50 55 40 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs frequency (mhz) 0 20 output ip3 (dbm) 25 30 35 60 45 40 80 100 199310 g08 50 55 40 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs frequency (mhz) 0 20 output ip3 (dbm) 25 30 35 60 45 40 80 100 199310 g09 50 55 40 20 60 120 140 2 tones, 2v p-p composite 1mhz tone spacing unfiltered outputs filtered outputs
LT1993-10 7 199310fb distortion (filtered) vs frequency differential input, no r load distortion (un? ltered) vs frequency differential input, no r load distortion vs output amplitude 70mhz differential input, no r load output 1db compression vs frequency noise figure vs frequency input referred noise voltage vs frequency typical perfor a ce characteristics uw frequency (mhz) 1 ?0 distortion (dbc) ?0 ?0 ?0 ?0 10 100 100 0 ?0 ?0 ?00 ?10 ?0 ?0 filtered outputs v out = 2v p-p hd3 hd2 frequency (mhz) 1 ?0 distortion (dbc) ?0 ?0 ?0 ?0 10 100 1000 199310 g11 ?0 ?0 ?00 ?10 ?0 ?0 unfiltered outputs v out = 2v p-p hd3 hd2 output amplitude (dbm) ? ?00 distortion (dbc) ?0 ?0 ?0 1 3 57 199310 g12 9 ?0 ?0 ?5 ?5 ?5 ?5 ?5 11 hd3 unfiltered outputs hd3 filtered outputs hd2 filtered outputs hd2 unfiltered outputs frequency (mhz) 1 output 1db compression (dbm) 30 25 20 15 10 5 0 ? ?0 10 100 100 0 199310 g13 unfiltered outputs r load = 400 ? r load = 100 ? frequency (mhz) input referred noise voltage (nv/ hz) 5 0 3 2 1 4 1000 100 10 reverse isolation vs frequency differential input impedance vs frequency differential output impedance vs frequency frequency (mhz) isolation (db) ?0 ?0 ?0 ?0 ?0 ?0 ?00 ?10 1 100 1000 10000 199310 g16 10 unfiltered outputs frequency (mhz) 1 0 25 50 75 100 10 100 100 0 ?5 ?0 ?5 ?00 125 150 impedance magnitude impedance phase input impedance (magnitude ? , phase ) frequency (mhz) 1 0.1 1 10 100 output impedance ( ? ) 10 100 100 0 unfiltered outputs frequency (mhz) noise figure (db) 25 0 15 10 5 20 1000 100 10 measured using dc800a demo board
LT1993-10 8 199310fb input re? ection coef? cient vs frequency output re? ection coef? cient vs frequency psrr, cmrr vs frequency typical perfor a ce characteristics uw small-signal transient response large-signal transient response overdrive recovery time distortion vs output common mode voltage, lt1933-10 driving ltc2249 14-bit adc turn-on time turn-off time frequency (mhz) 10 input reflection coefficient (s11) 0 ? ?0 ?5 ?0 ?5 ?0 ?5 ?0 ?5 ?0 100 1000 199310 g19 measured using dc800a demo board frequency (mhz) 10 output reflection coefficient (s22) 0 ? ?0 ?5 ?0 ?5 ?0 ?5 ?0 ?5 ?0 100 1000 199310 g20 measured using dc800a demo board frequency (mhz) 1 psrr, cmrr (db) 100 90 80 70 60 50 40 30 20 10 0 10 100 1000 199310 g21 cmrr psrr unfiltered outputs time (ns) 0 output voltage (v) 2.0 2.5 3.0 225 200 250 1.5 1.0 0 50 100 150 175 25 75 125 0.5 4.0 3.5 +out ?ut r load = 100 ? per output output common mode voltage (v) 1.2 distortion (dbc) ?4 ?6 ?8 ?2 ?0 ?4 ?6 199310 g25 1.8 1.6 1.4 2.0 2.2 2.6 2.4 filtered outputs, no r load v out = 70mhz 2v p-p hd3 hd2 time (ns) 0 voltage (v) 1 2 500 625 4 2 ? 125 250 375 0 4 3 0 +out ?ut enable r load = 100 ? per output time (ns) 0 voltage (v) 1 2 500 625 4 2 ? 125 250 375 0 4 3 0 +out ?ut enable r load = 100 ? per output time (ns) 0 2.20 output voltage (v) 2.22 2.24 2.26 15 30 50 10 25 40 45 52035 2.18 2.16 2.14 2.12 2.28 r load = 100 per output time (ns) 0 2.2 output voltage (v) 2.4 2.6 2.8 15 30 50 10 25 40 45 52035 2.0 1.8 1.6 1.4 3.0 r load = 100 per output
LT1993-10 9 199310fb 30mhz 8192 point fft, LT1993-10 driving lt2249 14-bit adc 50mhz 8192 point fft, LT1993-10 driving ltc2249 14-bit adc 70mhz 8192 point fft, LT1993-10 driving ltc2249 14-bit adc 70mhz 2-tone 32768 point fft LT1993-10 driving ltc2249 14-bit adc 2-tone wcdma waveform LT1993-10 driving ltc2255 14-bit adc at 92.16msps 4-tone wcdma waveform LT1993-10 driving ltc2255 14-bit adc at 92.16msps typical perfor a ce characteristics uw frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 20 199310 g28 30 40 25 35 ?0 ?10 ?0 ?0 ?0 ?0 ?0 8192 point fft f in = 30mhz, ?dbfs filtered outputs frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 20 199310 g30 30 40 25 35 ?0 ?10 ?0 ?0 ?0 ?0 ?0 8192 point fft f in = 70mhz, ?dbfs filtered outputs frequency (mhz) 0 amplitude (dbfs) ?00 ?0 ?0 ?0 0 10 5 15 20 25 30 199310 g31 35 40 ?0 ?10 ?20 ?0 ?0 ?0 ?0 ?0 32768 point fft tone 1 at 69.5mhz, ?dbfs tone 2 at 70.5mhz, ?dbfs filtered outputs frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 25 199310 g32 35 20 30 40 45 ?0 ?10 ?0 ?0 ?0 ?0 ?0 32768 point fft tone center frequencies at 67.5mhz, 72.5mhz frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 25 199310 g33 35 20 30 40 45 ?0 ?10 ?0 ?0 ?0 ?0 ?0 32768 point fft tone center frequencies at 62.5mhz, 67.5mhz, 72.5mhz, 77.5mhz pi fu ctio s uuu v ocm (pin 2): this pin sets the output common mode voltage. without additional biasing, both inputs bias to this voltage as well. this input is high impedance. v cca , v ccb , v ccc (pins 3, 10, 1): positive power supply (normally tied to 5v). all three pins must be tied to the same voltage. bypass each pin with 1000pf and 0.1f capacitors as close to the package as possible. split supplies are possible as long as the voltage between v cc and v ee is 5v. v eea , v eeb , v eec (pins 4, 9, 12): negative power supply (normally tied to ground). all three pins must be tied to the same voltage. split supplies are possible as long as the voltage between v cc and v ee is 5v. if these pins are not tied to ground, bypass each pin with 1000pf and 0.1f capacitors as close to the package as possible. +out, Cout (pins 5, 8): outputs (un? ltered). these pins are high bandwidth, low-impedance outputs. the dc output voltage at these pins is set to the voltage applied at v ocm . frequency (mhz) 0 ?20 amplitude (dbfs) ?00 ?0 ?0 ?0 0 5 10 15 20 199310 g29 30 40 25 35 ?0 ?10 ?0 ?0 ?0 ?0 ?0 8192 point fft f in = 50mhz, ?dbfs filtered outputs
LT1993-10 10 199310fb +outfiltered, Coutfiltered (pins 6, 7): filtered outputs. these pins add a series 25 resistor from the un? ltered outputs and three 12pf capacitors. each output has 12pf to v ee , plus an additional 12pf between each pin (see the block diagram). this ? lter has a C3db bandwidth of 175mhz. enable (pin 11): this pin is a ttl logic input referenced to the v eec pin. if low, the LT1993-10 is enabled and draws typically 100ma of supply current. if high, the LT1993-10 is disabled and draws typically 250a. Cina, Cinb (pins 14, 13): negative inputs. these pins are normally tied together. these inputs may be dc- or ac- coupled. if the inputs are ac-coupled, they will self-bias to the voltage applied to the v ocm pin. +ina, +inb (pins 16, 15): positive inputs. these pins are normally tied together. these inputs may be dc- or ac- coupled. if the inputs are ac-coupled, they will self-bias to the voltage applied to the v ocm pin. exposed pad (pin 17): tie the pad to v eec (pin 12). if split supplies are used, do not tie the pad to ground. pi fu ctio s uuu block diagra w + 14 ina 5 +out 199310 bd 3 v cca 10 v ccb 1 v ccc 11 enable 13 inb 12pf v cca a v eea v eea 100 ? 100 ? 500 ? 500 ? 25 ? 500 ? 6 +outfiltered + 16 +ina 8 ?ut 15 +inb v ccb b v eeb v eeb 100 ? 100 ? 25 ? 500 ? 12pf 12pf 7 ?utfiltered 12 v eec 9 v eeb 4 v eea + v eec c v ccc 2 v ocm bias
LT1993-10 11 199310fb applicatio s i for atio wu u u circuit description the LT1993-10 is a low noise, low distortion differential ampli? er/adc driver with: ? dc to 700mhz C3db bandwidth ? fixed gain of 10v/v (20db) independent of r load ? 100 differential input impedance ? low output impedance ? built-in, user adjustable output ? ltering ? requires minimal support circuitry referring to the block diagram, the LT1993-10 uses a closed-loop topology which incorporates 3 internal am- pli? ers. two of the ampli? ers (a and b) are identical and drive the differential outputs. the third ampli? er (c) is used to set the output common mode voltage. gain and input impedance are set by the 100 / 500 resistors in the internal feedback network. output impedance is low, determined by the inherent output impedance of ampli? ers a and b, and further reduced by internal feedback. the LT1993-10 also includes built-in single-pole output ? ltering. the user has the choice of using the un? ltered outputs, the ? ltered outputs (175mhz C3db lowpass), or modifying the ? ltered outputs to alter frequency response by adding additional components. many lowpass and bandpass ? lters are easily implemented with just one or two additional components. the LT1993-10 has been designed to minimize the need for external support components such as transformers or ac-coupling capacitors. as an adc driver, the LT1993-10 requires no external components except for power-supply bypass capacitors. this allows dc-coupled operation for applications that have frequency ranges including dc. at the outputs, the common mode voltage is set via the v ocm pin, allowing the LT1993-10 to drive adcs directly. no output ac-coupling capacitors or transformers are needed. at the inputs, signals can be differential or single-ended with virtually no difference in performance. furthermore, dc levels at the inputs can be set independently of the output common mode voltage. these input characteristics often eliminate the need for an input transformer and/or ac-coupling capacitors. input impedance and matching networks because of the internal feedback network, calculation of the LT1993-10s input impedance is not straightforward from examination of the block diagram. furthermore, the input impedance when driven differentially is different than when driven single-ended. when driven differentially, the LT1993-10s input impedance is 100 (differential); when driven single-ended, the input impedance is 85.9 . for single-ended 50 applications, a 121 shunt match- ing resistor to ground will result in the proper input termination (figure 1). for differential inputs there are several termination options. if the input source is 50 differential, then input matching can be accomplished by either a 100 shunt resistor across the inputs (figure 3), or a 49.9 shunt resistor on each of the inputs to ground (figure 2). 199310 f01 if in 0.1 f LT1993-10 ?na ?nb ?ut +out 8 5 +inb +ina 14 13 15 121 z in = 50 single-ended 16 figure 1. input termination for single-ended 50 input impedance figure 2. input termination for differential 50 input impedance 199310 f02 if in if in + LT1993-10 ?na ?nb ?ut +out 8 5 +inb +ina 14 13 15 49.9 z in = 50 differential 16 49.9 figure 3. alternate input termination for differential 50 input impedance 199310 f03 if in if in + LT1993-10 ?na ?nb ?ut +out 8 5 +inb +ina 14 13 15 z in = 50 differential 16 100
LT1993-10 12 199310fb applicatio s i for atio wu u u single-ended to differential operation the LT1993-10s performance with single-ended inputs is comparable to its performance with differential inputs. this excellent single-ended performance is largely due to the internal topology of the LT1993-10. referring to the block diagram, if the +ina and +inb pins are driven with a single-ended signal (while Cina and Cinb are tied to ac ground), then the +out and Cout pins are driven differentially without any voltage swing needed from ampli? er c. single-ended to differential conversion using more conventional topologies suffers from performance limitations due to the common mode ampli? er. driving adcs the LT1993-10 has been speci? cally designed to interface directly with high speed analog to digital converters (adcs). in general, these adcs have differential inputs, with an input impedance of 1k or higher. in addition, there is generally some form of lowpass or bandpass ? ltering just prior to the adc to limit input noise at the adc, thereby improving system signal to noise ratio. both the un? ltered and ? ltered outputs of the LT1993-10 can easily drive the high impedance inputs of these differential adcs. if the ? ltered outputs are used, then cutoff frequency and the type of ? lter can be tailored for the speci? c application if needed. wideband applications (using the +out and Cout pins) in applications where the full bandwidth of the LT1993-10 is desired, the un? ltered output pins (+out and Cout) should be used. they have a low output impedance; therefore, gain is unaffected by output load. capacitance in excess of 5pf placed directly on the un? ltered outputs results in additional peaking and reduced performance. when driving an adc directly, a small series resistance is recommended between the LT1993-10s outputs and the adc inputs (figure 4). this resistance helps eliminate any resonances associated with bond wire inductances of either the adc inputs or the LT1993-10s outputs. a value between 10 and 25 gives excellent results. filtered applications (using the +outfiltered and Coutfiltered pins) filtering at the output of the LT1993-10 is often desired to provide either anti-aliasing or improved signal to noise ratio. to simplify this ? ltering, the LT1993-10 includes an additional pair of differential outputs (+outfiltered and Coutfiltered) which incorporate an internal lowpass ? lter network with a C3db bandwidth of 175mhz (figure 5). these pins each have an output impedance of 25 . in- ternal capacitances are 12pf to v ee on each ? ltered output, plus an additional 12pf capacitor connected differentially between the two ? ltered outputs. this resistor/capaci- tor combination creates ? ltered outputs that look like a series 25 resistor with a 36pf capacitor shunting each ? ltered output to ac ground, giving a C3db bandwidth of 175mhz. 199310 f04 LT1993-10 ?ut +out 8 5 10 to 25 10 to 25 adc figure 4. adding small series r at LT1993-10 output the ? lter cutoff frequency is easily modi? ed with just a few external components. to increase the cutoff frequency, simply add 2 equal value resistors, one between +out and +outfiltered and the other between Cout and Coutfil- tered (figure 6). these resistors are in parallel with the internal 25 resistor, lowering the overall resistance and increasing ? lter bandwidth. to double the ? lter bandwidth, for example, add two external 25 resistors to lower the series resistance to 12.5 . the 36pf of capacitance remains unchanged, so ? lter bandwidth doubles. figure 5. LT1993-10 internal filter topology C3db bw 175mhz v ee v ee 199310 f05 25 25 12pf LT1993-10 ?ut +out 25 25 12pf 12pf ?utfiltered filtered output (350mhz) +outfiltered 8 7 6 5
LT1993-10 13 199310fb applicatio s i for atio wu u u to decrease ? lter bandwidth, add two external capaci- tors, one from +outfiltered to ground, and the other from Coutfiltered to ground. a single differential capacitor connected between +outfiltered and Cout- filtered can also be used, but since it is being driven differentially it will appear at each ? ltered output as a single-ended capacitance of twice the value. to halve the ? lter bandwidth, for example, two 36pf capacitors could be added (one from each ? ltered output to ground). al- ternatively one 18pf capacitor could be added between the ? ltered outputs, again halving the ? lter bandwidth. combinations of capacitors could be used as well; a three capacitor solution of 12pf from each ? ltered output to ground plus a 12pf capacitor between the ? ltered outputs would also halve the ? lter bandwidth (figure 7). bandpass ? ltering is also easily implemented with just a few external components. an additional 120pf and 39nh, each added differentially between +outfiltered and Coutfiltered creates a bandpass ? lter with a 71mhz center frequency, C3db points of 55mhz and 87mhz, and 1.6db of insertion loss (figure 8). figure 6. LT1993-10 internal filter topology modi? ed for 2x filter bandwidth (2 external resistors) output common mode adjustment the LT1993-10s output common mode voltage is set by the v ocm pin. it is a high-impedance input, capable of setting the output common mode voltage anywhere in a range from 1.1v to 3.6v. bandwidth of the v ocm pin is typically 300mhz, so for applications where the v ocm pin is tied to a dc bias voltage, a 0.1f capacitor at this pin is recommended. for best distortion performance, the voltage at the v ocm pin should be between 1.8v and 2.6v. when interfacing with most adcs, there is generally a v ocm output pin that is at about half of the supply voltage of the adc. for 5v adcs such as the ltc17xx family, this v ocm output pin should be connected directly (with the addition of a 0.1f capacitor) to the input v ocm pin of the LT1993-10. for 3v adcs such as the ltc22xx families, the lt1993- 10 will function properly using the 1.65v from the adcs v cm reference pin, but improved spurious free dynamic range (sfdr) and distortion performance can be achieved by level-shifting the ltc22xxs v cm reference voltage up to at least 1.8v. this can be accomplished as shown in figure 9 by using a resistor divider between the ltc22xxs v cm output pin and v cc and then bypassing the LT1993-10s v ocm pin with a 0.1f capacitor. for a common mode volt- age above 1.9v, ac coupling capacitors are recommended between the LT1993-10 and the ltc22xx adc because of the input voltage range constraints of the adc. figure 7. LT1993-10 internal filter topology modi? ed for 1/2x filter bandwidth (3 external capacitors) v ee v ee 19932 f06 25 25 12pf LT1993-10 ?ut +out 25 25 12pf 12pf ?utfiltered filtered output (350mhz) +outfiltered 8 7 6 5 v ee v ee 199310 f07 25 12pf LT1993-10 ?ut +out 25 12pf 12pf 12pf 12pf 12pf ?utfiltered +outfiltered 8 7 6 5 filtered output (87.5mhz) figure 8. LT1993-10 output filter topology modi? ed for bandpass filtering (1 external inductor, 1 external capacitor) v ee v ee 199310 f08 25 12pf LT1993-10 ?ut +out 25 12pf 12pf 120pf 39nh ?utfiltered +outfiltered 8 7 6 5 filtered output (71mhz bandpass, ?db @ 55mhz/87mhz)
LT1993-10 14 199310fb applicatio s i for atio wu u u large output voltage swings the LT1993-10 has been designed to provide the 3.2v p-p output swing needed by the ltc1748 family of 14-bit low-noise adcs. this additional output swing improves system snr by up to 4db. typical performance curves and ac speci? cations have been included for these applications. input bias voltage and bias current the input pins of the LT1993-10 are internally biased to the voltage applied to the v ocm pin. no external biasing resistors are needed, even for ac-coupled operation. the input bias current is determined by the voltage difference between the input common mode voltage and the v ocm pin (which sets the output common mode voltage). at both the positive and negative inputs, any voltage difference is imposed across 100 , generating an input bias current. for example, if the inputs are tied to 2.5v with the v ocm pin at 2.2v, then a total input bias current of 3ma will ? ow into the LT1993-10s +ina and +inb pins. furthermore, an additional input bias current totaling 3ma will ? ow into the Cina and Cinb inputs. application (demo) boards the dc800a demo board has been created for stand-alone evaluation of the LT1993-10 with either single-ended or differential input and output signals. as shown, it accepts a single-ended input and produces a single-ended output so that the LT1993-10 can be evaluated using standard laboratory test equipment. for more information on this demo board, please refer to the demo board section of this datasheet. there are also additional demo boards available that combine the LT1993-10 with a variety of different linear technology adcs. please contact the factory for more information on these demo boards. 199310 f09 if in LT1993-10 ?na ?nb v ocm 2 31 6 7 1 2 +inb +ina 14 13 15 80.6 16 10 10 ltc22xx 0.1 f 0.1 f +outfiltered ?utfiltered ain + ain 4.02k 11k 1.9v 1.5v 3v v cm figure 9. level shifting 3v adc v cm voltage for improved sfdr 3.00 0.10 (4 s ide s ) note: 1. drawing conform s to jedec package outline mo-220 variation (weed-2) 2. drawing not to s cale 3. all dimen s ion s are in millimeter s pin 1 top mark (note 6) 0.40 0.10 bottom view?xpo s ed pad 1.45 0.10 (4- s ide s ) 0.75 0.05 r = 0.115 typ 0.25 0.05 1 pin 1 notch r = 0.20 typ or 0.25 45 chamfer 15 16 2 0.50 b s c 0.200 ref 0.00 ?0.05 (ud16) qfn 0904 recommended s older pad pitch and dimen s ion s 1.45 0.05 (4 s ide s ) 2.10 0.05 3.50 0.05 0.70 0.05 0.25 0.05 0.50 b s c package outline 4. dimen s ion s of expo s ed pad on bottom of package do not include mold fla s h. mold fla s h, if pre s ent, s hall not exceed 0.15mm on any s ide 5. expo s ed pad s hall be s older plated 6. s haded area i s only a reference for pin 1 location on the top and bottom of package ud package 16-lead plastic qfn (3mm 3mm) (reference ltc dwg # 05-08-1691) package descriptio u
LT1993-10 15 199310fb typical applicatio u 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.
LT1993-10 16 199310fb 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 0406 rev b ? printed in usa part number description comments lt1993-2 800mhz differential ampli? er/adc driver av = 2v/v, nf = 12.3db, oip3 = 38dbm at 70mhz lt1993-4 900mhz differential ampli? er/adc driver av = 4v/v, nf = 14.5db, oip3 = 40dbm at 70mhz lt5514 ultralow distortion if ampli? er/adc driver digitally controlled gain output ip3 47dbm at 100mhz lt6600-2.5 very low noise differential ampli? er and 2.5mhz lowpass filter 86db s/n with 3v supply, so-8 package lt6600-5 very low noise differential ampli? er and 5mhz lowpass filter 82db s/n with 3v supply, so-8 package lt6600-10 very low noise differential ampli? er and 10mhz lowpass filter 82db s/n with 3v supply, so-8 package lt6600-20 very low noise differential ampli? er and 20mhz lowpass filter 76db s/n with 3v supply, so-8 package typical applicatio u related parts demo circuit dc800a schematic (ac test circuit) v cc j6 test in j7 test out j3 v ocm 3 1 2 4 1 5 v cc v cc c9 1000pf 199310 ta03 13 14 15 16 11 10 9 12 v cc v cc gnd sw1 23 4 1 8 7 6 5 r8 [1] r7 [1] r15 [1] +14db 0db notes: unless otherwise specified, [1] do not stuff. t1 1:1 z-ratio ma/com etc1-1-13 t2 4:1 z-ratio c17 1000pf c12 1000pf r22 [1] r21 [1] ?na ?nb +inb +ina v eec v ccb v eeb v ocm v cca v ccc v eea ?utfiltered ?ut +outfiltered +out enable tp1 enable j4 ?ut j5 +out r13 [1] 5 4 2 2 13 3 j1 ?n j2 +in 0db r2 0 r4 50 r6 0 r18 0 r17 0 r16 0 r10 24.9 r12 75 r11 75 r9 24.9 r14 0 c18 0.01 f c4 0.1 f c3 0.1 f c13 0.01 f c5 0.1 f c6 0.1 f c15 1 f c14 4.7 f c19 0.1 f c20 0.1 f c7 0.01 f c10 0.01 f c1 0.1 f c21 0.1 f r3 50 r5 0 r1 [1] c22 0.1 f c2 0.1 f r20 11k r19 14k v cc v cc tp2 v cc t4 4:1 5 4 3 1 2 tp3 gnd LT1993-10 1 2 1 2 1 2 1 2 1 2 1 2 1 1 t3 1:4 5 4 2 3 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 c8 [1] l1 [1] 2 1 c11 [1] 1 2 2 1 1 1 2 1 c16 [1] 1 2 2 1 2 1 +18.8db +8db mini- circuits tcm 4-19 mini- circuits tcm 4-19 mini- circuits tcm 4-19

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