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ltc6400-14 1 640014fb frequency (mhz) 050 output ip3 (dbm) 70 60 50 40 30 20 10 0 100 150 200 640020 ta01b 250 300 (note 7) typical application features applications description 2.4ghz low noise, low distortion differential adc driver for 300mhz if the ltc ? 6400-14 is a high-speed differential ampli? er targeted at processing signals from dc to 300mhz. the part has been speci? cally designed to drive 12-, 14- and 16-bit adcs with low noise and low distortion, but can also be used as a general-purpose broadband gain block. the ltc6400-14 is easy to use, with minimal support circuitry required. the output common mode voltage is set using an external pin, independent of the inputs, which eliminates the need for transformers or ac-coupling ca- pacitors in many applications. the gain is internally ? xed at 14db (5v/v). the ltc6400-14 saves space and power compared to alternative solutions using if gain blocks and transformers. the ltc6400-14 is packaged in a compact 16-lead 3mm 3mm qfn package and operates over the C 40c to 85c temperature range. equivalent output ip3 vs frequency n 2.4ghz C3db bandwidth n fixed gain of 5v/v (14db) n C97dbc imd3 at 70mhz (equivalent oip3 = 52.4dbm) n C66dbc imd3 at 300mhz (equivalent oip3 = 36.9dbm) n 1.1nv/ hz internal op amp noise n 2.5nv/ hz total input noise n 7.5db noise figure n differential inputs and outputs n 200 input impedance n 2.85v to 3.5v supply voltage n 85ma supply current (255mw) n 1v to 1.6v output common mode voltage, adjustable n dc- or ac-coupled operation n max differential output swing 4.8v p-p n small 16-lead 3mm 3mm 0.75mm qfn package n differential adc driver n differential driver/receiver n single ended to differential conversion n if sampling receivers n saw filter interfacing r2 29 r1 68.5 c4 0.1f c3 0.1f 64014 ta01a ltc6400-14 ltc2208 r s1 15 c2 0.1f v in c1 1000pf 3.3v 3.3v r s2 15 r s3 10 r s4 10 r3 100 v ocm c5 0.1f 1.25v c f2 33pf coilcraft 0603cs c f1 33pf l1 24nh c f3 33pf v + Cin +in +out Cout v C ain + ain C v cm v dd ltc2208 130msps 16-bit adc single-ended to differential adc driver l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners.
ltc6400-14 2 640014fb absolute maximum ratings supply voltage (v + C v C ) .........................................3.6v input current (note 2) ..........................................10ma operating temperature range (note 3) ...............................................C 40c to 85c speci? ed temperature range (note 4) ...............................................C 40c to 85c storage temperature range ...................C 65c to 150c maximum junction temperature........................... 150c lead temperature (soldering, 10 sec) .................. 300c (note 1) 16 15 14 13 5 6 7 8 top view ud package 16-lead (3mm s 3mm) plastic qfn 9 10 11 17 12 4 3 2 1 v + v ocm v + v C v C enabl e v + v C Cin Cin +in +in Cout Coutf +outf +out t jmax = 150c, ja = 68c/w, jc = 4.2c/w exposed pad (pin 17) is v C , must be soldered to pcb order information ltc6400 and ltc6401 selector guide please check each datasheet for complete details. pin configuration lead free finish tape and reel part marking* package description specified temperature range ltc6400cud-14#pbf ltc6400cud-14#trpbf lccr 16-lead (3mm 3mm) plastic qfn 0c to 70c ltc6400iud-14#pbf ltc6400iud-14#trpbf lccr 16-lead (3mm 3mm) plastic qfn C 40c to 85c 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. consult ltc marketing for information on non-standard lead based ? nish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/ part number gain (db) gain (v/v) z in (differential) () i cc (ma) ltc6400-8 8 2.5 400 85 ltc6400-14 14 5 200 85 ltc6400-20 20 10 200 90 ltc6400-26 26 20 50 85 ltc6401-8 8 2.5 400 45 ltc6401-14 14 5 200 45 ltc6401-20 20 10 200 50 ltc6401-26 26 20 50 45 in addition to the ltc6400 family of ampli? ers, a lower power ltc6401 family is available. the ltc6401 is pin compatible to th e ltc6400, and has the same low noise performance. the lower power consumption of the ltc6401 comes at the expense of slightly higher non-linearity, e specially at input frequencies above 140mhz. please refer to the separate ltc6401 data sheets for complete details.
ltc6400-14 3 640014fb dc electrical characteristics symbol parameter conditions min typ max units input/output characteristic g diff gain v in = 200mv differential l 13.5 14 14.5 db tc gain gain temperature drift v in = 200mv differential l C0.9 mdb/c v swingmin output swing low each output, v in = 800mv differential l 77 160 mv v swingmax output swing high each output, v in = 800mv differential l 2.35 2.48 v v outdiffmax maximum differential output swing 1db compressed l 4.8 v p-p i out output current drive each output l 20 ma v osdiff input differential offset voltage l C3 3 mv tcv osdiff input differential offset voltage drift t min to t max l 0.7 v/c i vrmin input common mode voltage range, min 1 v i vrmax input common mode voltage range, max 1.8 v r indiff input resistance (+in, Cin) differential l 170 200 230 c indiff input capacitance (+in, Cin) differential, includes parasitic 1 pf r outdiff output resistance (+out, Cout) differential l 18 25 32 r outfdiff filtered output resistance (+outf, Coutf) differential l 85 100 115 c outfdiff filtered output capacitance (+outf, Coutf) differential, includes parasitic 2.7 pf cmrr common mode rejection ratio input common mode voltage 1.1v~1.7v l 40 62 db output common mode voltage control g cm common mode gain v ocm = 1v to 1.6v 1 v/v v ocmmin output common mode range, min l 1 1.1 v v v ocmmax output common mode range, max l 1.6 1.5 v v v oscm common mode offset voltage v ocm = 1.1v to 1.5v l C15 15 mv tcv oscm common mode offset voltage drift t min to t max l 9v/c iv ocm v ocm input current l 415 a enable pin v il enable input low voltage l 0.8 v v ih enable input high voltage l 2.4 v i il enable input low current enable = 0.8v l 0.5 a i ih enable input high current enable = 2.4v l 1.3 3 a power supply v s operating supply range l 2.85 3 3.5 v i s supply current enable = 0.8v l 70 85 96 ma i shdn shutdown supply current enable = 2.4v, input and output floating l 0.9 3 ma psrr power supply rejection ratio (differential outputs) v + = 2.85v to 3.5v l 55 76 db the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v + = 3v, v C = 0v, +in = C in = v ocm = 1.25v, enable = 0v, no r l unless otherwise noted.
ltc6400-14 4 640014fb ac electrical characteristics speci? cations are at t a = 25c. v + = 3v, v C = 0v, v ocm = 1.25v, enable = 0v, no r l unless otherwise noted. symbol parameter conditions min typ max units C3dbbw C3db bandwidth 200mv p-p, out (note 6) 1.2 2.37 ghz 0.1dbbw bandwidth for 0.1db flatness 200mv p-p, out (note 6) 200 mhz 0.5dbbw bandwidth for 0.5db flatness 200mv p-p, out (note 6) 377 mhz 1/f 1/f noise corner 15 khz sr slew rate differential (note 6) 6000 v/s t s1% 1% settling time 2v p-p, out (note 6) 1.7 ns t ovdr overdrive recovery time 1.9v p-p, out (note 6) 17 ns t on turn-on time differential output reaches 90% of steady state value 10 ns t off turn-off time differential output drops to 10% of original value 12 ns C3dbbw vocm v ocm pin small signal C3db bw 0.1v p-p at v ocm , measured single-ended at output (note 6) 16 mhz 10mhz input signal hd2,10m/hd3,10m second/third order harmonic distortion 2v p-p, out , r l = 200 C107/C96 dbc 2v p-p, out , no r l C110/C108 dbc imd3,10m third-order intermodulation (f1 = 9.5mhz f2 = 10.5mhz) 2v p-p, out composite, r l = 200 C99 dbc 2v p-p, out composite, no r l C110 dbc oip3,10m third-order output intercept point (f1 = 9.5mhz f2 = 10.5mhz) 2v p-p, out composite, no r l (note 7) 59.1 dbm p1db,10m 1db compression point r l = 375 (notes 5, 7) 17.8 dbm nf10m noise figure r l = 375 (note 5) 7.5 db e in,10m input referred voltage noise density includes resistors (short inputs) 2.5 nv/ hz e on,10m output referred voltage noise density includes resistors (short inputs) 13 nv/ hz 70mhz input signal hd2,70m/hd3,70m second/third order harmonic distortion 2v p-p, out , r l = 200 C86/C85 dbc 2v p-p, out , no r l C89/C94 dbc imd3,70m third-order intermodulation (f1 = 69.5mhz f2 = 70.5mhz) 2v p-p, out composite, r l = 200 C91 dbc 2v p-p, out composite, no r l C97 dbc oip3,70m third-order output intercept point (f1 = 69.5mhz f2 = 70.5mhz) 2v p-p, out composite, no r l (note 7) 52.4 dbm p1db,70m 1db compression point r l = 375 (notes 5, 7) 18.5 dbm nf70m noise figure r l = 375 (note 5) 7.5 db e in,70m input referred voltage noise density includes resistors (short inputs) 2.5 nv/ hz e on,70m output referred voltage noise density includes resistors (short inputs) 12.5 nv/ hz
ltc6400-14 5 640014fb ac electrical characteristics speci? cations are at t a = 25c. v + = 3v, v C = 0v, v ocm = 1.25v, enable = 0v, no r l unless otherwise noted. symbol parameter conditions min typ max units 140mhz input signal hd2,140m/hd3,140m second/third order harmonic distortion 2v p-p, out , r l = 200 C78/C74 dbc 2v p-p, out , no r l C81/C79 dbc imd3,140m third-order intermodulation (f1 = 139.5mhz f2 = 140.5mhz) 2v p-p, out composite, r l = 200 C80 dbc 2v p-p, out composite, no r l C85 dbc oip3,140m third-order output intercept point (f1 = 139.5mhz f2 = 140.5mhz) 2v p-p, out composite, no r l (notes 7) 46.5 dbm p1db,140m 1db compression point r l = 375 (notes 5, 7) 18.8 dbm nf140m noise figure r l = 375 (note 5) 7.7 db e in,140m input referred voltage noise density includes resistors (short inputs) 2.5 nv/ hz e on,140m output referred voltage noise density includes resistors (short inputs) 12.6 nv/ hz 240mhz input signal hd2,240m/hd3,240m second/ third-order harmonic distortion 2v p-p, out , r l = 200 C63/C57 dbc 2v p-p, out , no r l C67/C63 dbc imd3, 240m third-order intermodulation (f1 = 239.5mhz f2 = 240.5mhz) 2v p-p, out composite, r l = 200 C68 dbc 2v p-p, out composite, no r l C71 dbc oip3, 240m third-order output intercept point (f1 = 239.5mhz f2 = 240.5mhz) 2v p-p, out composite, no r l (note 7) 39.6 dbm p1db, 240m 1db compression point r l = 375 (notes 5, 7) 17.9 dbm nf240m noise figure r l = 375 (note 5) 8db e n, 240m input referred voltage noise density includes resistors (short inputs) 2.5 nv/ hz e on, 240m output referred voltage noise density includes resistors (short inputs) 12.9 nv/ hz
ltc6400-14 6 640014fb ac electrical characteristics speci? cations are at t a = 25c. v + = 3v, v C = 0v, v ocm = 1.25v, enable = 0v, no r l unless otherwise noted. symbol parameter conditions min typ max units 300mhz input signal hd2,300m/hd3,300m second/ third-order harmonic distortion 2v p-p, out , r l = 200 C61/C51 dbc 2v p-p, out , no r l C61/C55 dbc imd3,300m third-order intermodulation (f1 = 299.5mhz f2 = 300.5mhz) 2v p-p, out composite, r l = 200 C62 dbc 2v p-p, out composite, no r l C66 dbc oip3,300m third-order output intercept point (f1 = 299.5mhz f2 = 300.5mhz) 2v p-p, out composite, no r l (note 7) 36.9 dbm p1db,300m 1db compression point r l = 375 (notes 5, 7) 17.4 dbm nf300m noise figure r l = 375 (note 5) 8.2 db e n, 300m input referred voltage noise density includes resistors (short inputs) 2.5 nv/ hz e on, 300m output referred voltage noise density includes resistors (short inputs) 13.9 nv/ hz imd3,280m/320m third-order intermodulation (f1 = 280mhz f2 = 320mhz) measured at 360mhz 2v p-p, out composite, r l = 375 C63 C55 dbc 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: input pins (+in, Cin) are protected by steering diodes to either supply. if the inputs go beyond either supply rail, the input current should be limited to less than 10ma. note 3: the ltc6400c and ltc6400i are guaranteed functional over the operating temperature range of C 40c to 85c. note 4: the ltc6400c is guaranteed to meet speci? ed performance from 0c to 70c. it is designed, characterized and expected to meet speci? ed performance from C 40 to 85c but is not tested or qa sampled at these temperatures. the ltc6400i is guaranteed to meet speci? ed performance from C 40c to 85c. note 5: input and output baluns used. see test circuit a. note 6: measured using test circuit b. note 7: since the ltc6400-14 is a feedback ampli? er with low output impedance, a resistive load is not required when driving an ad converter. therefore, typical output power is very small. in order to compare the ltc6400-14 with ampli? ers that require 50 output load, the ltc6400-14 output voltage swing driving a given r l is converted to oip3 and p 1db as if it were driving a 50 load. using this modi? ed convention, 2v p-p is by de? nition equal to 10dbm, regardless of actual r l .
ltc6400-14 7 640014fb frequency (mhz) 10 noise figure (db) 15 10 12 14 6 8 5 11 13 7 9 input referred noise voltage (nv/ hz ) 5.0 4.0 2.0 3.0 1.0 0 4.5 2.5 3.5 1.5 0.5 100 1000 640014 g07 noise figure en r l = 87.5 per output test circuit b time (ns) 0246810 output voltage (v) 1.35 1.30 1.20 1.25 1.15 640014 g08 Cout +out time (ns) 0246810 output voltage (v) 2.50 2.00 0.50 1.50 1.00 0.00 640014 g09 Cout +out r l = 87.5 per output test circuit b frequency (mhz) 10 impedance magnitude () 250 200 150 100 50 225 175 125 75 25 0 phase (degrees) 100 60 20 C20 C60 80 40 0 C40 C80 C100 100 1000 640014 g05 z in z out z in z out phase impedance magnitude frequency (mhz) 0 200 400 600 800 1000 phase (degree) group delay (ns) 0 0.4 0.2 C50 C 150 C100 C200 0.0 640014 g03 test circuit b phase group delay frequency (mhz) 10 100 1000 3000 gain (db) 20 18 16 14 12 10 8 6 4 2 0 640014 g01 test circuit b typical performance characteristics frequency response gain 0.1db flatness s21 phase and group delay vs frequency input and output re? ection and reverse isolation vs frequency input and output impedance vs frequency psrr and cmrr vs frequency frequency (mhz) 10 100 1000 3000 gain flatness (db) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 C 0.1 C 0.2 C 0.3 C 0.4 C 0.5 C 0.6 C 0.7 C 0.8 C 0.9 0 C1 640014 g02 test circuit b noise figure and input referred noise voltage vs frequency small signal transient response large signal transient response frequency (mhz) 10 100 1000 s parameters (db) 0 C10 C20 C30 C50 C70 C60 C40 C80 640014 g04 s11 s22 s11 frequency (mhz) 1 psrr, cmrr (db) 80 70 60 50 40 30 0 10 20 10 100 1000 640014 g06 psrr cmrr
ltc6400-14 8 640014fb frequency (mhz) third order imd (dbc) C40 C50 C60 C80 C90 C70 C110 C100 640014 g13 no r l 200 r l differential input v out = 2v p-p composite 0 50 100 150 200 250 300 time (ns) 0 input voltage (v) output voltage (v) 5 4 3 2 1 C4 C3 C2 C1 0 C5 5.0 2.5 0.5 1.0 2.0 3.5 3.0 4.5 4.0 1.5 0 20 40 60 80 100 640014 g10 +out Cout +in Cin r l = 87.5 per output test circuit b time (ns) 0 settling (%) 5 4 3 2 1 C4 C3 C2 C1 C5 0 12 4 3 5 640014 g11 r l = 87.5 per output test circuit b typical performance characteristics overdrive recovery response 1% settling time for 2v output step harmonic distortion vs frequency third order intermodulation distortion vs frequency third order intermodulation distortion vs frequency frequency (mhz) 050 harmonic distortion (dbc) C40 C50 C60 C80 C90 C70 C110 C100 100 150 200 250 300 640014 g12 hd2 no r l hd2 200 r l hd3 no r l hd3 200 r l differential input v out = 2v p-p harmonic distortion vs frequency frequency (mhz) 050 harmonic distortion (dbc) C40 C50 C60 C80 C90 C70 C110 C100 100 150 200 250 300 640014 g14 hd2 no r l hd2 200 r l hd3 no r l hd3 200 r l single-ended input v out = 2v p-p frequency (mhz) third order imd (dbc) C40 C50 C60 C80 C90 C70 C110 C100 640014 g15 no r l 200 r l single-ended input v out = 2v p-p composite 0 50 100 150 200 250 300
ltc6400-14 9 640014fb time (ns) 0 C20 voltage (v) 3.5 2.0 2.5 1.0 1.5 3.0 C0.5 0.5 0 20 40 60 80 640014 g19 +out Cout enable r l = 87.5 per output voltage (v) 3.5 2.0 2.5 1.0 1.5 3.0 C0.5 0.5 0 640014 g20 Cout +out enable r l = 87.5 per output time (ns) 0 C20 20 40 60 80 typical performance characteristics turn-on time turn-off time equivalent output 1db compression point vs frequency imd3 vs v icm and v ocm equivalent output third order intercept vs frequency common mode voltage (v) 1.0 1.2 1.4 1.6 1.8 640014 g18 imd3 (dbc) C85 C88 C91 C97 C94 C100 v out = 2v p-p composite at 100mhz differential input no r l sweep v icm v ocm = 1.25v sweep v ocm input ac-coupled frequency (mhz) output 1db compression point (dbm) 20 19 18 16 17 15 640014 g16 differential input r l = 375 test circuit a (note 7) 0 50 100 150 200 250 300 frequency (mhz) output ip3 (dbm) 70 60 50 40 20 10 30 0 640014 g17 differential input (note 7) 0 50 100 150 200 250 300 no r l 200 r l
ltc6400-14 10 640014fb block diagram pin functions v + (pins 1, 3, 10): positive power supply (normally tied to 3v or 3.3v). all three pins must be tied to the same voltage. bypass each pin with 1000pf and 0.1f capacitors as close to the pins as possible. v ocm (pin 2): this pin sets the output common mode voltage. a 0.1f external bypass capacitor is recom- mended. v C (pins 4, 9, 12, 17): negative power supply (gnd). all four pins must be connected to same voltage/ground. Cout, +out (pins 5, 8): un? ltered outputs. these pins have series resistors, r out 12.5 . Coutf, +outf (pins 6, 7): filtered outputs. these pins have 50 series resistors and a 2.7pf shunt capacitor. enable (pin 11): this pin is a logic input referenced to v ee . if low, the part is enabled. if high, the part is disabled and draws approximately 1ma supply current. +in (pins 13, 14): positive input. pins 13 and 14 are internally shorted together. Cin (pins 15, 16): negative input. pins 15 and 16 are internally shorted together. exposed pad (pin 17): v C . the exposed pad must be connected to same voltage/ground as pins 4, 9, 12. 13 640014 bd 1 v + 2 v ocm 14 7 15 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 5 16 r g 100 r out 12.5 r f 500 r g 100 2k r f 500 6 4 v C 3 v + 12 v C 11 enable 9 v C 10 v + common mode control bias control 8 r out 12.5 r filt 50 r filt 50 c filt 2.7pf 5.3pf
ltc6400-14 11 640014fb applications information circuit operation the ltc6400-14 is a low noise and low distortion fully differential op amp/adc driver with: ? operation from dc to 2.4ghz (C3db bandwidth) ? fixed gain of 5v/v (14db) ? differential input impedance 200 ? differential output impedance 25 ? on-chip 590mhz output ? lter the ltc6400 is composed of a fully differential ampli? er with on chip feedback and output common mode voltage control circuitry. differential gain and input impedance are set by 100 /1000 resistors in the feedback network. small output resistors of 12.5 improve the circuit stability over various load conditions. they also provide a possible external ? ltering option, which is often desirable when the load is an adc. filter resistors of 50 are available for additional ? ltering. lowpass/bandpass ? lters are easily implemented with just a couple of external components. moreover, they of- fer single-ended 50 matching in wideband applications and no external resistor is needed. the ltc6400-14 is very ? exible in terms of i/o coupling. it can be ac- or dc-coupled at the inputs, the outputs or both. due to the internal connection between input and output, users are advised to keep input common mode voltage between 1v and 1.8v for proper operation. if the inputs are ac-coupled, the input common mode voltage is automatically biased approximately 450mv above v ocm and thus no external circuitry is needed for bias. the ltc6400-14 provides an output common mode voltage set by v ocm , which allows driving an adc directly without external components such as a transformer or ac coupling capacitors. the input signal can be either single-ended or differential with only minor differences in distortion performance. input impedance and matching the differential input impedance of the ltc6400-14 is 200 . if a 200 source impedance is unavailable, then the differential inputs may need to be terminated to a lower value impedance, e.g. 50 , in order to provide an imped- ance match for the source. several choices are available. one approach is to use a differential shunt resistor (figure 1). another approach is to employ a wide band transformer (figure 2). both methods provide a wide band impedance match. the termination resistor or the transformer must be placed close to the input pins in order to minimize the re? ection due to input mismatch. alternatively, one could apply a narrowband impedance match at the inputs of the ltc6400-14 for frequency selection and/or noise reduction. referring to figure 3, ltc6400-14 can be easily con? gured for single-ended input and differential output without a balun. the signal is fed to one of the inputs through a matching network while the other input is connected to the same matching network and a source resistor. because the return ratios of the two feedback paths are equal, the two outputs have the same gain and thus symmetrical swing. figure 1. input termination for differential 50 input impedance using shunt resistor figure 2. input termination for differential 50 input impedance using a 1:4 balun 640014 f01 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 100 66.5 12.5 500 ltc6400-14 100 25 25 v in 500 12.5 50 50 2.7pf 13 14 15 16 7 5 6 8 + C 640014 f02 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 100 12.5 500 ltc6400-14 100 25 25 v in 500 12.5 50 50 2.7pf 13 14 15 16 7 5 6 8 + C 1:4 ? ? mini-circuits tcm4-19
ltc6400-14 12 640014fb in general, the single-ended input impedance and termination resistor r t are determined by the combination of r s , r g and r f . for example, when r s is 50 , it is found that the single-ended input impedance is 202 and r t is 68.5 in order to match to a 50 source impedance. the ltc6400-14 is unconditionally stable under normal bias conditions. however, the overall differential gain is affected by both source impedance and load impedance as shown in figure 4: a v vr r r v out in s l l == ++ 1000 200 25 ? the noise performance of the ltc6400-14 also depends upon the source impedance and termination. for example, an input 1:4 balun transformer in figure 2 improves snr by adding 6db of voltage gain at the inputs. a trade-off between gain and noise is obvious when constant noise ? gure circle and constant gain circle are plotted within the same input smith chart, based on which users can choose the optimal source impedance for a given gain and noise requirement. figure 4. calculate differential gain output match and filter the ltc6400-14 can drive an adc directly without external output impedance matching. alternatively, the differential output impedance of 25 can be matched to higher value impedance, e.g. 50 , by series resistors or an lc network. the internal low pass ? lter outputs at +outf/Coutf have a C3db bandwidth of 590mhz. external capacitors can reduce the low pass ? lter bandwidth as shown in figure 5. a bandpass ? lter is easily implemented with only a few components as shown in figure 6. three 39pf capacitors and a 16nh inductor create a bandpass ? lter with 165mhz center frequency, C3db frequencies at 138mhz and 200mhz. output common mode adjustment the output common mode voltage is set by the v ocm pin, which is a high impedance input. the output common mode voltage is capable of tracking v ocm in a range from 1v to 1.6v. the bandwidth of v ocm control is typically 16mhz, applications information figure 3. input termination for single-ended 50 input impedance figure 5. ltc6400-14 internal filter topology modi? ed for low filter bandwidth (three external capacitors) 640014 f03 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 100 r t 68.5 0.1f 0.1f 12.5 1000 ltc6400-14 100 r s 50 v in 1000 12.5 50 50 2.7pf 13 14 15 16 7 5 6 8 + C 0.1f r t 29 640014 f04 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 100 12.5 500 ltc6400-14 100 1/2 r s 1/2 r s v in v out 500 12.5 50 50 2.7pf 13 14 15 16 7 5 6 8 + C 1/2 r l 1/2 r l 640014 f05 in+ outC inC out+ 100 12.5 500 ltc6400-14 100 500 12.5 50 50 13 14 15 16 7 5 6 8 8.2pf 8.2pf 12pf filtered output (87.5mhz) +out +outf Coutf Cout +in +in Cin Cin 2.7pf figure 6. ltc6400-14 internal filter topology modi? ed for bandpass filtering (three external capacitors, one external inductor) 640014 f06 in+ outC inC out+ 100 12.5 500 ltc6400-14 ltc2208 100 500 12.5 10 10 4.99 4.99 50 50 13 14 15 16 7 5 6 8 39pf 16nh 39pf +out +outf Coutf Cout +in +in Cin Cin 2.7pf 39pf
ltc6400-14 13 640014fb which is dominated by a low pass ? lter connected to the v ocm pin and is aimed to reduce common mode noise generation at the outputs. the internal common mode feedback loop has a C3db bandwidth around 400mhz, allowing fast common mode rejection at the outputs of the ltc6400-14. the v ocm pin should be tied to a dc bias voltage with a 0.1f bypass capacitor. when interfacing with a/d converters such as the ltc22xx families, the v ocm pin can be connected to the v cm pin of the adc. driving a/d converters the ltc6400-14 has been speci? cally designed to inter- face directly with high speed a/d converters. in figure 7, an example schematic shows the ltc6400-14 with a single-ended input driving the ltc2208, which is a 16-bit, 130msps adc. two external 4.99 resistors help eliminate potential resonance associated with stray capacitance of pcb traces and bond wires of either the adc input or the driver output. v ocm of the ltc6400-14 is connected to v cm of the ltc2208 v cm pin at 1.25v. alternatively, a single- ended input signal can be converted to a differential signal via a balun and fed to the input of the ltc6400-14. figure 8 summarizes the imd3 of the whole system in figure 7. note that figure 7 shows a direct connection to the ltc2208, but in many applications an anti-alias ? lter would be desirable to limit the wideband noise of the ampli? er. this is especially true in high performance 16-bit designs. test circuits due to the fully-differential design of the ltc6400 and its usefulness in applications with differing characteristic figure 7. single-ended input to ltc6400-14 and ltc2208 figure 8. imd3 for the combination of ltc6400-14 and ltc2208 applications information 29 66.5 0.1f 0.1f 640014 f07 ltc6400-14 v ocm enable if in ltc2208 4.99 0.1f ltc2208 130msps 16-bit adc 1.25v 4.99 14db gain ain C ain + v cm Cin +in +out +outf Coutf Cout frequency (mhz) 0 imd3 (dbc) C40 C110 C100 C90 C80 C70 C60 C50 100 150 50 200 640014 f08 250 300 single-ended input f s = 122.8msps driver v out = 2v p-p composite top silkscreen speci? cations, two test circuits are used to generate the information in this datasheet. test circuit a is dc987b, a two-port demonstration circuit for the ltc6400 family. the schematic and silkscreen are shown below. this circuit includes input and output transformers (baluns) for single-ended-to-differential conversion and impedance transformation, allowing direct hook-up to a 2-port
ltc6400-14 14 640014fb typical applications demo circuit 987b schematic (test circuit a) ? ? t1 (2) ? ? ? ? t3 tcm 4-19 1:4 version ic r3 r4 t1 sl1 sl2 sl3 t4 tcm 4-19 1:4 ? ? t2 tcm 4-19 -b ltc6400cud-14 open open mini-circuits tcm4-19 (1:4) 6db 14db 8db 640014 ta03 r10 86.6 r8 (1) r7 (1) r9 86.6 c3 0.1f c4 0.1f c1 0.1f c2 0.1f ltc6400-14 v ocm v + v + v C v C v + v cc v cc v C enable +in +in Cin Cin Cout +outf Coutf +out enable dis 12 11 10 9 1234 5 6 7 8 16 15 14 13 sl1 (2) sl2 (2) j2 Cin j1 +in j5 Cout sl3 (2) j4 +out c22 0.1f c21 0.1f c18 0.1f c13 0.1f c17 1000pf r16 0 tp2 v cc 2.85v to 3.5v 13 2 jp1 v cc v cc v cc c12 1000pf c9 1000pf c10 0.1f c15 1f v cc c14 4.7f c7 0.1f r4 (2) 1 3 2 3 1 2 5 4 4 5 tp5 v ocm r2 (1) r1 0 r3 (2) j6 test in c19 0.1f 1 3 2 5 4 c20 0.1f r21 (1) r22 (1) r20 1k r19 1.5k r14 (1) r13 0 c6 0.1f c5 0.1f c24 0.1f c23 0.1f j7 test out note: unless otherwise specified. (1) do not stuff. (2) sl = signal level sl levels do not include transformer loss in t1 and t2 3 1 2 4 5 tp3 gnd r17 0 r25 0 r18 0 r26 0 r12 0 r11 (1) r24 (1) r6 0 r5 (1) 0db network analyzer. there are also series resistors at the output to present the ltc6400 with a 375 differential load, optimizing distortion performance. due to the input and output transformers, the C3db bandwidth is reduced from 2.4ghz to approximately 1.8ghz. test circuit b uses a 4-port network analyzer to measure s-parameters and gain/phase response. this removes the effects of the wideband baluns and associated circuitry, for a true picture of the >1ghz s-parameters and ac characteristics. applications information
ltc6400-14 15 640014fb information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. package description 3.00 0.10 (4 sides) recommended solder pad pitch and dimensions 1.45 0.05 (4 sides) note: 1. drawing conforms to jedec package outline mo-220 variation (weed-2) 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package pin 1 top mark (note 6) 0.40 0.10 bottom view?exposed pad 1.45 0.10 (4-sides) 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 bsc 0.200 ref 2.10 0.05 3.50 0.05 0.70 0.05 0.00 ? 0.05 (ud16) qfn 0904 0.25 0.05 0.50 bsc package outline ud package 16-lead plastic qfn (3mm 3mm) (reference ltc dwg # 05-08-1691) typical applications test circuit b, 4-port analysis 0.1f 13 640014 ta02 1 v + 2 v ocm 14 7 15 +out +outf Coutf Cout +in in+ outC inC out+ +in Cin Cin 5 16 r g 100 r out 12.5 r f 500 r g 100 r f 500 6 4 v C 3 v + v ocm v + v + 12 v C 11 enable 9 v C 10 v + common mode control 1/2 agilent e5o71a bias control 8 r out 12.5 37.4 37.4 r filt 50 r filt 50 c filt 2.7pf 1000pf 0.1f 0.1f 0.1f port 3 (50) port 4 (50) 1/2 agilent e5o71a 200 0.1f 0.1f port 1 (50) port 2 (50) 0.1f 1000pf ltc6400-14
ltc6400-14 16 640014fb linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2008 lt 0908 rev b ? printed in usa related parts part number description comments high-speed differential ampli? ers/differential op amps lt ? 1993-2 800mhz differential ampli? er/adc driver a v = 2v/v, oip3 = 38dbm at 70mhz lt1993-4 900mhz differential ampli? er/adc driver a v = 4v/v, oip3 = 40dbm at 70mhz lt1993-10 700mhz differential ampli? er/adc driver a v = 10v/v, oip3 = 40dbm at 70mhz lt1994 low noise, low distortion differential op amp 16-bit snr and sfdr at 1mhz, rail-to-rail outputs lt5514 ultralow distortion if ampli? er/adc driver with digitally controlled gain oip3 = 47dbm at 100mhz, gain control range 10.5db to 33db lt5524 low distortion if ampli? er/adc driver with digitally controlled gain oip3 = 40dbm at 100mhz, gain control range 4.5db to 37db ltc6400-8 2.2ghz low noise, low distortion, differential adc driver a v = 8db, 85ma supply current, imd3 = C61dbc at 300mhz ltc6400-20 1.8ghz low noise, low distortion, differential adc driver a v = 20db, 90ma supply current, imd3 = C65dbc at 300mhz ltc6400-26 1.9ghz low noise, low distortion, differential adc driver a v = 26db, 85ma supply current, imd3 = C71dbc at 300mhz ltc6401-8 2.2ghz low noise, low distortion, differential adc driver a v = 8db, 45ma supply current, imd3 = C80dbc at 140mhz ltc6401-14 2ghz low noise, low distortion, differential adc driver a v = 14db, 45ma supply current, imd3 = C81dbc at 140mhz ltc6401-20 1.3ghz low noise, low distortion, differential adc driver a v = 20db, 50ma supply current, imd3 = C74dbc at 140mhz ltc6401-26 1.6ghz low noise, low distortion, differential adc driver a v = 26db, 45ma supply current, imd3 = C72dbc at 140mhz lt6402-6 300mhz differential ampli? er/adc driver a v = 6db, distortion < C80dbc at 25mhz lt6402-12 300mhz differential ampli? er/adc driver a v = 12db, distortion < C80dbc at 25mhz lt6402-20 300mhz differential ampli? er/adc driver a v = 20db, distortion < C80dbc at 25mhz ltc6404-1 600mhz low noise differential adc driver e n = 1.5nv/ hz , rail-to-rail outputs ltc6406 3ghz rail-to-rail input differential op amp 1.6nv/ hz noise, C72dbc distortion at 50mhz, 18ma lt6411 low power differential adc driver/dual selectable gain ampli? er 16ma supply current, imd3 = C83dbc at 70mhz, a v = 1, C1 or 2 high-speed single-ended output op amps lt1812/lt1813/ lt1814 high slew rate low cost single/dual/quad op amps 8nv/ hz noise, 750v/s, 3ma supply current lt1815/lt1816/ lt1817 very high slew rate low cost single/dual/quad op amps 6nv/ hz noise, 1500v/s, 6.5ma supply current lt1818/lt1819 ultra high slew rate low cost single/dual op amps 6nv/ hz noise, 2500v/s, 9ma supply current lt6200/lt6201 rail-to-rail input and output low noise single/dual op amps 0.95nv/ hz noise, 165mhz gbw, distortion = C80dbc at 1mhz lt6202/lt6203/ lt6204 rail-to-rail input and output low noise single/dual/quad op amps 1.9nv/ hz noise, 3ma supply current, 100mhz gbw lt6230/lt6231/ lt6232 rail-to-rail output low noise single/dual/quad op amps 1.1nv/ hz noise, 3.5ma supply current, 215mhz gbw lt6233/lt6234/ lt6235 rail-to-rail output low noise single/dual/quad op amps 1.9nv/ hz noise, 1.2ma supply current, 60mhz gbw integrated filters ltc1562-2 very low noise, 8th order filter building block lowpass and bandpass filters up to 300khz lt1568 very low noise, 4th order filter building block lowpass and bandpass filters up to 10mhz ltc1569-7 linear phase, tunable 10th order lowpass filter single-resistor programmable cut-off to 300khz lt6600-2.5 very low noise differential 2.5mhz lowpass filter snr = 86db at 3v supply, 4th order filter lt6600-5 very low noise differential 5mhz lowpass filter snr = 82db at 3v supply, 4th order filter lt6600-10 very low noise differential 10mhz lowpass filter snr = 82db at 3v supply, 4th order filter lt6600-15 very low noise differential 15mhz lowpass filter snr = 76db at 3v supply, 4th order filter lt6600-20 very low noise differential 20mhz lowpass filter snr = 76db at 3v supply, 4th order filter

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