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lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 lmh6551q differential, high speed op amp check for samples: lmh6551q 1 features description the lmh ? 6551q is a high performance voltage 23 ? 370 mhz ? 3 db bandwidth (v out = 0.5 v pp ) feedback differential amplifier. the lmh6551q has ? 50 mhz 0.1 db bandwidth the high speed and low distortion necessary for ? 2400 v/ s slew rate driving high performance adcs as well as the current handling capability to drive signals over balanced ? 18 ns settling time to 0.05% transmission lines like cat 5 data cables. the ? ? 94/ ? 96 db hd2/hd3 @ 5 mhz lmh6551q can handle a wide range of video and ? lmh6551q is aec-q100 grade 1 qualified and data formats. is manufactured on an automotive grade flow with external gain set resistors, the lmh6551q can be used at any desired gain. gain flexibility coupled applications with high speed makes the lmh6551q suitable for ? differential ad driver use as an if amplifier in high performance communications equipment. ? video over twisted pair the lmh6551q is available in the vssop package. ? differential line driver ? single end to differential converter ? high speed differential signaling ? if/rf amplifier ? saw filter buffer/driver ? automotive typical application 1 please be aware that an important notice concerning availability, standard warranty, and use in critical applications of texas instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. 2 lmh is a trademark of texas instruments. 3 all other trademarks are the property of their respective owners. production data information is current as of publication date. copyright ? 2011 ? 2013, texas instruments incorporated products conform to specifications per the terms of the texas instruments standard warranty. production processing does not necessarily include testing of all parameters.
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com connection diagram figure 1. top view 8-pin vssop see package number dgk these devices have limited built-in esd protection. the leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the mos gates. absolute maximum ratings (1) (2) esd tolerance (3) human body model 2000v machine model 200v supply voltage 13.2v common mode input voltage vs maximum input current (pins 1, 2, 7, 8) 30ma maximum output current (pins 4, 5) (4) maximum junction temperature 150 c soldering information: http://www.ti.com/lit/snoa549 (1) absolute maximum ratings indicate limits beyond which damage to the device may occur. operating ratings indicate conditions for which the device is intended to be functional, but specific performance is not ensured. for ensured specifications, see the electrical characteristics tables. (2) if military/aerospace specified devices are required, please contact the texas instruments sales office/ distributors for availability and specifications. (3) human body model: 1.5 k ? in series with 100 pf. machine model: 0 ? in series with 200pf. (4) the maximum output current (i out ) is determined by device power dissipation limitations. operating ratings (1) operating temperature range ? 40 c to +125 c storage temperature range ? 65 c to +150 c total supply voltage 3v to 11v package thermal resistance ( ja ) (2) 8-pin vssop 159 c/w (1) absolute maximum ratings indicate limits beyond which damage to the device may occur. operating ratings indicate conditions for which the device is intended to be functional, but specific performance is not ensured. for ensured specifications, see the electrical characteristics tables. (2) the maximum power dissipation is a function of t j(max) , ja and t a . the maximum allowable power dissipation at any ambient temperature is p d = (t j(max) ? t a )/ ja . all numbers apply for package soldered directly into a 4 layer pc board with zero air flow. 2 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q - 4 +out 5 -out 3 6 v+ v- nc 2 7 v cm + 1 8 -in +in
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 5v electrical characteristics (1) single ended in differential out, t a = 25 c, g = +1, v s = 5v, v cm = 0v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units ac performance (differential) ssbw small signal ? 3 db bandwidth v out = 0.5 v pp 370 mhz lsbw large signal ? 3 db bandwidth v out = 2 v pp 340 mhz large signal ? 3 db bandwidth v out = 4 v pp 320 mhz 0.1 db bandwidth v out = 2 v pp 50 mhz slew rate 4v step (4) 2400 v/ s rise/fall time 2v step 1.8 ns settling time 2v step, 0.05% 18 ns v cm pin ac performance (common mode feedback amplifier) common mode small signal v cm bypass capacitor removed 200 mhz bandwidth distortion and noise response hd2 v o = 2 v pp , f = 5 mhz, r l =800 ? ? 94 dbc hd2 v o = 2 v pp , f = 20mhz, r l =800 ? ? 85 dbc hd3 v o = 2 v pp , f = 5 mhz, r l =800 ? ? 96 dbc hd3 v o = 2 v pp , f = 20 mhz, r l =800 ? ? 72 dbc e n input referred voltage noise freq 1 mhz 6.0 nv/ hz i n input referred noise current freq 1 mhz 1.5 pa/ hz input characteristics (differential) v osd input offset voltage differential mode, v id = 0, v cm = 0 0.5 4 mv 6 input offset voltage average (5) ? 0.8 v/ c temperature drift i bi input bias current (6) -4 0 a -10 input bias current average (5) ? 2.6 na/ c temperature drift input bias difference difference in bias currents between the 0.03 a two inputs cmrr common mode rejection ratio dc, v cm = 0v, v id = 0v 70 80 dbc r in input resistance differential 5 m ? c in input capacitance differential 1 pf cmvr input common mode voltage range cmrr > 53db +3.1 +3.2 v ? 4.6 ? 4.7 (1) electrical table values apply only for factory testing conditions at the temperature indicated. factory testing conditions result in very limited self-heating of the device such that t j = t a . no specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where t j > t a . (2) limits are 100% production tested at 25 c. limits over the operating temperature range are ensured through correlation using statistical quality control (sqc) methods. (3) typical numbers are the most likely parametric norm. (4) slew rate is the average of the rising and falling edges. (5) drift determined by dividing the change in parameter at temperature extremes by the total temperature change. (6) negative input current implies current flowing out of the device. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 3 product folder links: lmh6551q
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com 5v electrical characteristics (1) (continued) single ended in differential out, t a = 25 c, g = +1, v s = 5v, v cm = 0v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units v cm pin input characteristics (common mode feedback amplifier) v osc input offset voltage common mode, v id = 0 0.5 5 mv 8 input offset voltage average (7) 8.2 v/ c temperature drift input bias current (8) ? 2 a v cm cmrr v id = 0v, 1v step on v cm pin, measure 70 75 db v od input resistance 25 k ? common mode gain v o,cm / v cm 0.995 0.999 1.005 v/v output performance output voltage swing single ended, peak to peak 7.38 7.8 v 7.18 output common mode voltage range v id = 0 v, 3.69 3.8 v i out linear output current v out = 0v 50 65 ma i sc short circuit current output shorted to ground 140 ma v in = 3v single ended (9) l output balance error v out common mode ? 70 db / v out differential, v out = 0.5 vpp differential, f = 10 mhz miscellaneous performance a vol open loop gain differential 70 db psrr power supply rejection ratio dc, v s = 1v 71 90 db supply current r l = 11 12.5 14.5 ma 16.5 (7) drift determined by dividing the change in parameter at temperature extremes by the total temperature change. (8) negative input current implies current flowing out of the device. (9) the maximum output current (i out ) is determined by device power dissipation limitations. 5v electrical characteristics (1) single ended in differential out, t a = 25 c, g = +1, v s = 5v, v cm = 2.5v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units ssbw small signal ? 3 db bandwidth r l = 500 ? , v out = 0.5 v pp 350 mhz lsbw large signal ? 3 db bandwidth r l = 500 ? , v out = 2 v pp 300 mhz 0.1 db bandwidth v out = 2 v pp 50 mhz slew rate 4v step (4) 1800 v/ s rise/fall time, 10% to 90% 4v step 2 ns settling time 4v step, 0.05% 17 ns v cm pin ac performance (common mode feedback amplifier) common mode small signal 170 mhz bandwidth (1) electrical table values apply only for factory testing conditions at the temperature indicated. factory testing conditions result in very limited self-heating of the device such that t j = t a . no specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where t j > t a . (2) limits are 100% production tested at 25 c. limits over the operating temperature range are ensured through correlation using statistical quality control (sqc) methods. (3) typical numbers are the most likely parametric norm. (4) slew rate is the average of the rising and falling edges. 4 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 5v electrical characteristics (1) (continued) single ended in differential out, t a = 25 c, g = +1, v s = 5v, v cm = 2.5v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units distortion and noise response hd2 2 nd harmonic distortion v o = 2 v pp , f = 5 mhz, r l =800 ? ? 84 dbc hd2 v o = 2 v pp , f = 20 mhz, r l =800 ? ? 69 dbc hd3 3 rd harmonic distortion v o = 2 v pp , f = 5 mhz, r l =800 ? ? 93 dbc hd3 v o = 2 v pp , f = 20 mhz, r l =800 ? ? 67 dbc e n input referred noise voltage freq 1 mhz 6.0 nv/ hz i n input referred noise current freq 1 mhz 1.5 pa/ hz input characteristics (differential) v osd input offset voltage differential mode, v id = 0, v cm = 0 0.5 4 mv 6 input offset voltage average (5) ? 0.8 v/ c temperature drift i bias input bias current (6) ? 4 0 a -10 input bias current average (5) ? 3 na/ c temperature drift input bias current difference difference in bias currents between the 0.03 a two inputs cmrr common-mode rejection ratio dc, v id = 0v 70 78 dbc input resistance differential 5 m ? input capacitance differential 1 pf v icm input common mode range cmrr > 53 db +3.1 +3.2 +0.4 +0.3 v cm pin input characteristics (common mode feedback amplifier) input offset voltage common mode, v id = 0 0.5 5 mv 8 input offset voltage average 5.8 v/ c temperature drift input bias current 3 a v cm cmrr v id = 0, 70 75 db 1v step on v cm pin, measure v od input resistance v cm pin to ground 25 k ? common mode gain v o,cm / v cm 0.995 0.999 1.005 v/v output performance v out output voltage swing single ended, peak to peak, v s = 2.5v, 2.4 2.8 v v cm = 0v i out linear output current v out = 0v differential 45 60 ma i sc output short circuit current output shorted to ground 230 ma v in = 3v single ended (7) cmvr output common mode voltage v id = 0, v cm pin = 1.2v and 3.8v 1.23 1.20 v range 3.72 3.80 output balance error v out common mode / v out differential, ? 65 db v out = 1vpp differential, f = 10 mhz miscellaneous performance open loop gain dc, differential 70 db psrr power supply rejection ratio dc, v s = 0.5v 71 88 db i s supply current r l = 10 11.5 13.5 ma 15.5 (5) drift determined by dividing the change in parameter at temperature extremes by the total temperature change. (6) negative input current implies current flowing out of the device. (7) the maximum output current (i out ) is determined by device power dissipation limitations. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 5 product folder links: lmh6551q
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com 3.3v electrical characteristics (1) single ended in differential out, t a = 25 c, g = +1, v s = 3.3v, v cm = 1.65v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units ssbw small signal ? 3 db bandwidth r l = 500 ? , v out = 0.5 v pp 320 mhz lsbw large signal ? 3 db bandwidth r l = 500 ? , v out = 1 v pp 300 mhz slew rate 1v step (4) 700 v/ s rise/fall time, 10% to 90% 1v step 2 ns v cm pin ac performance (common mode feedback amplifier) common mode small signal 95 mhz bandwidth distortion and noise response hd2 2 nd harmonic distortion v o = 1 v pp , f = 5 mhz, r l =800 ? ? 93 dbc hd2 v o = 1 v pp , f = 20 mhz, r l =800 ? ? 74 dbc hd3 3 rd harmonic distortion v o = 1v pp , f = 5 mhz, r l =800 ? ? 85 dbc hd3 v o = 1v pp , f = 20 mhz, r l =800 ? ? 69 dbc (1) electrical table values apply only for factory testing conditions at the temperature indicated. factory testing conditions result in very limited self-heating of the device such that t j = t a . no specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where t j > t a . (2) limits are 100% production tested at 25 c. limits over the operating temperature range are ensured through correlation using statistical quality control (sqc) methods. (3) typical numbers are the most likely parametric norm. (4) slew rate is the average of the rising and falling edges. 6 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 3.3v electrical characteristics (1) (continued) single ended in differential out, t a = 25 c, g = +1, v s = 3.3v, v cm = 1.65v, r f = r g = 365 ? , r l = 500 ? ; unless specified boldface limits apply at the temperature extremes. symbol parameter conditions min (2) typ (3) max (2) units input characteristics (differential) v osd input offset voltage differential mode, v id = 0, v cm = 0 1 mv input offset voltage average (5) 1.6 v/ c temperature drift i bias input bias current (6) ? 8 a input bias current average (5) 9.5 na/ c temperature drift input bias current difference difference in bias currents between the 0.3 a two inputs cmrr common-mode rejection ratio dc, v id = 0v 78 dbc input resistance differential 5 m ? input capacitance differential 1 pf v icm input common mode range cmrr > 53 db +1.5 +0.3 v cm pin input characteristics (common mode feedback amplifier) input offset voltage common mode, v id = 0 1 5 mv input offset voltage average 18.6 v/ c temperature drift input bias current 3 a v cm cmrr v id = 0, 60 db 1v step on v cm pin, measure v od input resistance v cm pin to ground 25 k ? common mode gain v o,cm / v cm 0.999 v/v output performance v out output voltage swing single ended, peak to peak, v s = 3.3v, 0.75 0.9 v v cm = 1.65v i out linear output current v out = 0v differential 30 40 ma i sc output short circuit current output shorted to ground 200 ma v in = 2v single ended (7) cmvr output common mode voltage v id = 0, v cm pin = 1.2v and 2.1v 2.1 v range 1.2 output balance error v out common mode / v out differential, ? 65 db v out = 1vpp differential, f = 10 mhz miscellaneous performance open loop gain dc, differential 70 db psrr power supply rejection ratio dc, v s = 0.5v 75 db i s supply current r l = 8 ma (5) drift determined by dividing the change in parameter at temperature extremes by the total temperature change. (6) negative input current implies current flowing out of the device. (7) the maximum output current (i out ) is determined by device power dissipation limitations. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 7 product folder links: lmh6551q
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com typical performance characteristics (t a = 25 c, v s = 5v, r l = 500 ? , r f = r g = 365 ? ; unless specified). frequency response vs. supply voltage frequency response figure 2. figure 3. frequency response frequency response vs. vs. v out capacitive load figure 4. figure 5. suggested r out suggested r out vs. vs. cap load cap load figure 6. figure 7. 8 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q 1 10 100 1000 frequency (mhz) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 gain (db) single ended input v s = 5v v od = 0.5 v pp v od = 2 v pp 1 10 100 1000 frequency (mhz) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 gain (db) single ended input v s = 5v v od = 0.5 v pp v od = 2 v pp 1 10 100 0 10 20 30 40 50 60 70 suggested r o ( : ) capacitive load (pf) load = 1 k : || cap load v s = 5v 1 10 100 0 10 20 30 40 50 60 70 suggested r o ( : ) capacitive load (pf) load = 1 k : || cap load v s = 5v 1 10 100 1000 frequency (mhz) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 gain (db) single ended input v s = 3.3v v od = 0.5 v pp v od = 1 v pp 1 10 100 1000 frequency (mhz) -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 gain (db) c l = 5.7 pf, r out = 60 : c l = 10 pf, r out = 34 : c l = 27 pf, r out = 20 : c l = 57 pf, r out = 15 : load = (cl || 1 k : ) in series with 2 r outs v out = 0.5 v pp differential v s = 5v
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 typical performance characteristics (continued) (t a = 25 c, v s = 5v, r l = 500 ? , r f = r g = 365 ? ; unless specified). 1 v pp pulse response single ended input 2 v pp pulse response single ended input figure 8. figure 9. large signal pulse response output common mode pulse response figure 10. figure 11. distortion distortion vs. vs. frequency frequency figure 12. figure 13. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 9 product folder links: lmh6551q 0 5 10 15 20 25 30 35 40 frequency (mhz) -110 -100 -90 -80 -70 -60 -50 distortion (dbc) v s = 5v v out = 2 v pp v cm = 0v r l = 800 : hd3 hd2 0 5 10 15 20 25 30 35 40 frequency (mhz) -100 -90 -80 -70 -60 -50 distortion (dbc) v s = 5v v out = 2 v pp v cm = 2.5v r l = 800 : hd2 hd3 0 5 10 15 20 25 30 35 40 45 50 -3 -2 -1 0 1 2 3 v out differential (v) time (ns) v s = 5v r l = 500 : r f = 360 : 0 5 10 15 20 25 30 35 40 45 50 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 common mode v out (v) time (ns) v s = 5v r l = 500 : r f = 360 : v out = 4 v pp 0 5 10 15 20 25 30 35 40 45 50 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 v out differential (v) time (ns) v s = 3.3v r l = 500 : r f = 360 : 0 5 10 15 20 25 30 35 40 45 50 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 v out differential (v) time (ns) v s = 5v r l = 500 : r f = 360 :
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com typical performance characteristics (continued) (t a = 25 c, v s = 5v, r l = 500 ? , r f = r g = 365 ? ; unless specified). distortion distortion vs. vs. frequency supply voltage (split supplies) figure 14. figure 15. distortion maximum v out vs. vs. supply voltage (single supply) i out figure 16. figure 17. minimum v out vs. i out closed loop output impedance figure 18. figure 19. 10 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q 0 10 20 30 40 50 60 70 80 90 100 -4 -3.9 -3.8 -3.7 -3.6 -3.5 -3.4 -3.3 -3.2 -3.1 -3 minimum v out (v) output current (ma) v in = 3.88v single ended v s = 5v a v = 2 r f = 730 : 0.01 0.1 1 10 1000 frequency (mhz) 0.01 0.1 10 100 |z| ( : ) 1 100 v s = 5v v in = 0v 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 -100 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4 maximum v out (v) output current (ma) v in = 3.88v single ended v s = 5v a v = 2 r f = 730 : 6 7 8 9 10 11 12 supply voltage (v) -100 -95 -90 -85 -80 -75 -70 -65 -60 distortion (dbc) hd3 hd2 v out = 4 v pp f = 5 mhz v cm = 0v 0 5 10 15 20 25 30 35 40 frequency (mhz) -100 -90 -80 -70 -60 -50 distortion (dbc) v s = 3.3v v out = 1 v pp v cm = 1.65v r l = 800 : hd2 hd3 3 4 5 6 -100 -90 -80 -70 -60 -50 -40 -30 distortion (dbc) supply voltage (v) v out = 2 v pp f = 5 mhz v cm = v s /2 hd3 hd2
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 typical performance characteristics (continued) (t a = 25 c, v s = 5v, r l = 500 ? , r f = r g = 365 ? ; unless specified). closed loop output impedance closed loop output impedance figure 20. figure 21. psrr psrr figure 22. figure 23. cmrr balance error figure 24. figure 25. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 11 product folder links: lmh6551q 0.1 1 10 100 1000 frequency (mhz) 40 45 50 55 60 65 70 75 80 cmrr (db) v in , cm = 0.5 v pp v s = 5v 1 10 100 1000 frequency (mhz) -90 -80 -40 -25 balance error (dbc) -30 -35 -70 -75 -85 -65 -60 -55 -50 -45 v s = 5v r f = 360 : r l = 500 : v in = 0.5 v pp 0.01 1 1000 frequency (mhz) 0 40 100 psrr (dbc differential) 100 10 0.1 80 60 20 90 70 50 30 10 psrr + psrr - v s = 5v r l = 200 : v cm = 0v 0.01 1 1000 frequency (mhz) 0 40 100 psrr (dbc differential) 100 10 0.1 80 60 20 90 70 50 30 10 v s = +5v r l = 200 : v cm = 2.5v 0.01 0.1 1 10 1000 frequency (mhz) 0.01 0.1 10 100 |z| ( : ) 1 100 v s = 5v v in = 0v 0.01 0.1 1 10 1000 frequency (mhz) 0.01 0.1 10 100 |z| ( : ) 1 100 v s = 3.3v v in = 0v
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com application section the lmh6551q is a fully differential amplifier designed to provide low distortion amplification to wide bandwidth differential signals. the lmh6551q, though fully integrated for ultimate balance and distortion performance, functionally provides three channels. two of these channels are the v + and v ? signal path channels, which function similarly to inverting mode operational amplifiers and are the primary signal paths. the third channel is the common mode feedback circuit. this is the circuit that sets the output common mode as well as driving the v + and v ? outputs to be equal magnitude and opposite phase, even when only one of the two input channels is driven. the common mode feedback circuit allows single ended to differential operation. the lmh6551q is a voltage feedback amplifier with gain set by external resistors. output common mode voltage is set by the v cm pin. this pin should be driven by a low impedance reference and should be bypassed to ground with a 0.1 f ceramic capacitor. any signal coupling into the v cm will be passed along to the output and will reduce the dynamic range of the amplifier. fully differential operation the lmh6551q will perform best when used with split supplies and in a fully differential configuration. see figure 26 and figure 27 for recommended circuits. figure 26. typical application the circuit shown in figure 26 is a typical fully differential application as might be used to drive an adc. in this circuit closed loop gain, (a v ) = v out / v in = r f /r g . for all the applications in this data sheet v in is presumed to be the voltage presented to the circuit by the signal source. for differential signals this will be the difference of the signals on each input (which will be double the magnitude of each individual signal), while in single ended inputs it will just be the driven input signal. the resistors r o help keep the amplifier stable when presented with a load c l as is typical in an analog to digital converter (adc). when fed with a differential signal, the lmh6551 provides excellent distortion, balance and common mode rejection provided the resistors r f , r g and r o are well matched and strict symmetry is observed in board layout. with a dc cmrr of over 80db, the dc and low frequency cmrr of most circuits will be dominated by the external resistors and board trace resistance. at higher frequencies board layout symmetry becomes a factor as well. precision resistors of at least 0.1% accuracy are recommended and careful board layout will also be required. 12 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q v i r g1 r g2 v cm r l v o r f1 r f2 c l r o r o a + -
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 figure 27. fully differential cable driver with up to 15 v pp differential output voltage swing and 80 ma of linear drive current the lmh6551q makes an excellent cable driver as shown in figure 27 . the lmh6551q is also suitable for driving differential cables from a single ended source. the lmh6551q requires supply bypassing capacitors as shown in figure 28 and figure 29 . the 0.01 f and 0.1 f capacitors should be leadless smt ceramic capacitors and should be no more than 3 mm from the supply pins. the smt capacitors should be connected directly to a ground plane. thin traces or small vias will reduce the effectiveness of bypass capacitors. also shown in both figures is a capacitor from the v cm pin to ground. the v cm pin is a high impedance input to a buffer which sets the output common mode voltage. any noise on this input is transferred directly to the output. output common mode noise will result in loss of dynamic range, degraded cmrr, degraded balance and higher distortion. the v cm pin should be bypassed even if the pin in not used. there is an internal resistive divider on chip to set the output common mode voltage to the mid point of the supply pins. the impedance looking into this pin is approximately 25 k ? . if a different output common mode voltage is desired drive this pin with a clean, accurate voltage reference. figure 28. split supply bypassing capacitors figure 29. single supply bypassing capacitors copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 13 product folder links: lmh6551q v cm 0.1 p f v + v - 0.01 p f 0.01 p f 10 p f 10 p f 0.1 p f + - v cm v + 10 p f 0.1 p f + - 0.01 p f 0.01 p f 2 v pp v cm 100 : twisted pair 50 : 2 v pp 500 500 250 250 gain = 2 50 : a + -
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com single ended input to differential output the lmh6551q provides excellent performance as an active balun transformer. figure 30 shows a typical application where an lmh6551q is used to produce a differential signal from a single ended source. in single ended input operation the output common mode voltage is set by the v cm pin as in fully differential mode. also, in this mode the common mode feedback circuit must recreate the signal that is not present on the unused differential input pin. figure 25 is the measurement of the effectiveness of this process. the common mode feedback circuit is responsible for ensuring balanced output with a single ended input. balance error is defined as the amount of input signal that couples into the output common mode. it is measured as a the undesired output common mode swing divided by the signal on the input. balance error can be caused by either a channel to channel gain error, or phase error. either condition will produce a common mode shift. figure 25 measures the balance error with a single ended input as that is the most demanding mode of operation for the amplifier. supply and v cm pin bypassing are also critical in this mode of operation. see the above section on fully differential operation for bypassing recommendations and also see figure 28 and figure 29 for recommended supply bypassing configurations. figure 30. single ended in to differential out 14 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 single supply operation the input stage of the lmh6551q has a built in offset of 0.7v towards the lower supply to accommodate single supply operation with single ended inputs. as shown in figure 30 , the input common mode voltage is less than the output common voltage. it is set by current flowing through the feedback network from the device output. the input common mode range of 0.4v to 3.2v places constraints on gain settings. possible solutions to this limitation include ac coupling the input signal, using split power supplies and limiting stage gain. ac coupling with single supply is shown in figure 31 . in figure 30 closed loop gain = v o / v i ? r f / r g , where v i =v s / 2, as long as r m < < r g . note that in single ended to differential operation v i is measured single ended while v o is measured differentially. this means that gain is really 1/2 or 6 db less when measured on either of the output pins separately. additionally, note that the input signal at r t (labeled as v i ) is 1/2 of v s when r t is chosen to match r s to r in . v icm = input common mode voltage = (v i1 +v i2 ) / 2. figure 31. ac coupled for single supply operation driving analog to digital converters analog to digital converters (adc) present challenging load conditions. they typically have high impedance inputs with large and often variable capacitive components. as well, there are usually current spikes associated with switched capacitor or sample and hold circuits. figure 32 shows a typical circuit for driving an adc. the two 56 ? resistors serve to isolate the capacitive loading of the adc from the amplifier and ensure stability. in addition, the resistors form part of a low pass filter which helps to provide anti alias and noise reduction functions. the two 39 pf capacitors help to smooth the current spikes associated with the internal switching circuits of the adc and also are a key component in the low pass filtering of the adc input. in the circuit of figure 32 the cutoff frequency of the filter is 1/ (2* *56 ? *(39 pf + 14pf)) = 53mhz (which is slightly less than the sampling frequency). note that the adc input capacitance must be factored into the frequency response of the input filter, and that being a differential input the effective input capacitance is double. also as shown in figure 32 the input capacitance to many adcs is variable based on the clock cycle. see the data sheet for your particular adc for details. copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 15 product folder links: lmh6551q r g r g v cm r l v o r f r f c l r o r o + - v i a v o 1 v o 2 v i 2 v i 1 r m r t r s v icm = v ocm v icm = v i 1 + v i 2 2 *v cm = v o 1 + v o 2 2 *by design
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com figure 32. driving an adc the amplifier and adc should be located as closely together as possible. both devices require that the filter components be in close proximity to them. the amplifier needs to have minimal parasitic loading on the output traces and the adc is sensitive to high frequency noise that may couple in on its input lines. some high performance adcs have an input stage that has a bandwidth of several times its sample rate. the sampling process results in all input signals presented to the input stage mixing down into the nyquist range (dc to fs/2). see an-236 ( snaa079 ) for more details on the subsampling process and the requirements this imposes on the filtering necessary in your system. using transformers transformers are useful for impedance transformation as well as for single to differential, and differential to single ended conversion. a transformer can be used to step up the output voltage of the amplifier to drive very high impedance loads as shown in figure 33 . figure 35 shows the opposite case where the output voltage is stepped down to drive a low impedance load. transformers have limitations that must be considered before choosing to use one. compared to a differential amplifier, the most serious limitations of a transformer are the inability to pass dc and balance error (which causes distortion and gain errors). for most applications the lmh6551q will have adequate output swing and drive current and a transformer will not be desirable. transformers are used primarily to interface differential circuits to 50 ? single ended test equipment to simplify diagnostic testing. figure 33. transformer out high impedance load 16 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q 300 : twisted pair 4 v pp v cm 1:2 (turns) 37.5 : 37.5 : 8 v pp 500 500 250 250 a v = 2 v cm a + - r l = 300 : 1v low impedance voltage reference v i r g1 r g2 v cm r f1 r f2 adc12lo66 56 56 39 pf 39 pf 7 - 8 pf + - a v ref
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 figure 34. calculating transformer circuit net gain figure 35. transformer out low impedance load figure 36. driving 50 ? test equipment copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 17 product folder links: lmh6551q 50 : coax 4 v pp v cm 2:1 (turns) 100 : 100 : 1 v pp 375 375 375 375 gain = 1 c 1 is not required if v cm = ground c 1 a + - 100 : twisted pair 4 v pp v cm 2:1 (turns) 200 : 200 : 1 v pp 375 375 375 375 a v = 1 v cm a + - r l = 100 : where v in = differential input voltage n = transformer turns ratio = a v = closed loop amplifier gain r out = series output matching resistor r l = load resistor v l = voltage across load resistor ? ? secondary primary v l = v in * a v * n 2 r out * n 2 r l + 1 ? ?
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com capacitive drive as noted in driving analog to digital converters , capacitive loads should be isolated from the amplifier output with small valued resistors. this is particularly the case when the load has a resistive component that is 500 ? or higher. a typical adc has capacitive components of around 10 pf and the resistive component could be 1000 ? or higher. if driving a transmission line, such as 50 ? coaxial or 100 ? twisted pair, using matching resistors will be sufficient to isolate any subsequent capacitance. for other applications see figure 6 and figure 7 in typical performance characteristics . power dissipation the lmh6551q is optimized for maximum speed and performance in the small form factor of the standard vssop package, and is essentially a dual channel amplifier. to ensure maximum output drive and highest performance, thermal shutdown is not provided. therefore, it is of utmost importance to make sure that the t jmax of 150 c is never exceeded due to the overall power dissipation. follow these steps to determine the maximum power dissipation for the lmh6551q: 1. calculate the quiescent (no-load) power: p amp = i cc * (v s ) where ? v s = v + - v ? . (be sure to include any current through the feedback network if v ocm is not mid rail.) (1) 2. calculate the rms power dissipated in each of the output stages: p d (rms) = rms ((v s - v + out ) * i + out ) + rms ((v s ? v ? out ) * i ? out ) where ? v out and i out are the voltage and the current measured at the output pins of the differential amplifier as if they were single ended amplifiers and v s is the total supply voltage (2) 3. calculate the total rms power: p t = p amp + p d (3) the maximum power that the lmh6551q package can dissipate at a given temperature can be derived with the following equation: p max = (150 ? t amb )/ ja where ? t amb = ambient temperature ( c) ? ja = thermal resistance, from junction to ambient, for a given package ( c/w) ? ja is 159 c/w for the vssop-8 package (4) note if v cm is not 0v then there will be quiescent current flowing in the feedback network. this current should be included in the thermal calculations and added into the quiescent power dissipation of the amplifier. 18 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q
lmh6551q www.ti.com snosb95e ? november 2011 ? revised march 2013 figure 37 shows the maximum power dissipation vs. ambient temperature for the vssop-8 package when mounted on a 4 layer jedec board. figure 37. maximum power dissipation vs. ambient temperature at high ambient temperatures, the lmh6551q's quiescent power dissipation approaches the maximum power shown in figure 37 , when operated close to the maximum operating supply voltage of 11v. this leaves little room for additional load power dissipation. in such applications, any of the following steps can be taken to alleviate any junction temperature concerns: ? reduce the total supply voltage ? reduce ja by increasing heatsinking possibly by either increasing the pc board area devoted to heatsinking or forced air cooling or both ? reduce maximum ambient temperature esd protection the lmh6551q is protected against electrostatic discharge (esd) on all pins. the lmh6551q will survive 2000v human body model and 200v machine model events. under normal operation the esd diodes have no effect on circuit performance. there are occasions, however, when the esd diodes will be evident. if the lmh6551q is driven by a large signal while the device is powered down the esd diodes will conduct. the current that flows through the esd diodes will either exit the chip through the supply pins or will flow through the device, hence it is possible to power up a chip with a large signal applied to the input pins. board layout the lmh6551q is a very high performance amplifier. in order to get maximum benefit from the differential circuit architecture board layout and component selection is very critical. the circuit board should have low a inductance ground plane and well bypassed broad supply lines. external components should be leadless surface mount types. the feedback network and output matching resistors should be composed of short traces and precision resistors (0.1%). the output matching resistors should be placed within 3-4 mm of the amplifier as should the supply bypass capacitors. the lmh6551q is sensitive to parasitic capacitances on the amplifier inputs and to a lesser extent on the outputs as well. ground and power plane metal should be removed from beneath the amplifier and from beneath r f and r g . with any differential signal path symmetry is very important. even small amounts of asymmetry will contribute to distortion and balance errors. evaluation board texas instruments offers evaluation board(s) to aid in device testing and characterization and as a guide for proper layout. generally, a good high frequency layout will keep power supply and ground traces away from the inverting input and output pins. parasitic capacitances on these nodes to ground will cause frequency response peaking and possible circuit oscillations (see application note oa-15 for more information). copyright ? 2011 ? 2013, texas instruments incorporated submit documentation feedback 19 product folder links: lmh6551q -40 -20 0 20 40 60 80 100 120 140 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 max power dissipation (w) t a (c) vssop
lmh6551q snosb95e ? november 2011 ? revised march 2013 www.ti.com revision history changes from revision d (march 2013) to revision e page ? changed layout of national data sheet to ti format .......................................................................................................... 19 20 submit documentation feedback copyright ? 2011 ? 2013, texas instruments incorporated product folder links: lmh6551q
package option addendum www.ti.com 11-apr-2013 addendum-page 1 packaging information orderable device status (1) package type package drawing pins package qty eco plan (2) lead/ball finish msl peak temp (3) op temp (c) top-side markings (4) samples lmh6551qmm/nopb active vssop dgk 8 1000 green (rohs & no sb/br) cu sn level-1-260c-unlim -40 to 125 au1q lmh6551qmme/nopb active vssop dgk 8 250 green (rohs & no sb/br) cu sn level-1-260c-unlim -40 to 125 au1q lmh6551qmmx/nopb active vssop dgk 8 3500 green (rohs & no sb/br) cu sn level-1-260c-unlim -40 to 125 au1q (1) the marketing status values are defined as follows: active: product device recommended for new designs. lifebuy: ti has announced that the device will be discontinued, and a lifetime-buy period is in effect. nrnd: not recommended for new designs. device is in production to support existing customers, but ti does not recommend using this part in a new design. preview: device has been announced but is not in production. samples may or may not be available. obsolete: ti has discontinued the production of the device. (2) eco plan - the planned eco-friendly classification: pb-free (rohs), pb-free (rohs exempt), or green (rohs & no sb/br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. tbd: the pb-free/green conversion plan has not been defined. pb-free (rohs): ti's terms "lead-free" or "pb-free" mean semiconductor products that are compatible with the current rohs requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. where designed to be soldered at high temperatures, ti pb-free products are suitable for use in specified lead-free processes. pb-free (rohs exempt): this component has a rohs exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. the component is otherwise considered pb-free (rohs compatible) as defined above. green (rohs & no sb/br): ti defines "green" to mean pb-free (rohs compatible), and free of bromine (br) and antimony (sb) based flame retardants (br or sb do not exceed 0.1% by weight in homogeneous material) (3) msl, peak temp. -- the moisture sensitivity level rating according to the jedec industry standard classifications, and peak solder temperature. (4) multiple top-side markings will be inside parentheses. only one top-side marking contained in parentheses and separated by a "~" will appear on a device. if a line is indented then it is a continuation of the previous line and the two combined represent the entire top-side marking for that device. important information and disclaimer: the information provided on this page represents ti's knowledge and belief as of the date that it is provided. ti bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. efforts are underway to better integrate information from third parties. ti has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. ti and ti suppliers consider certain information to be proprietary, and thus cas numbers and other limited information may not be available for release. in no event shall ti's liability arising out of such information exceed the total purchase price of the ti part(s) at issue in this document sold by ti to customer on an annual basis.
tape and reel information *all dimensions are nominal device package type package drawing pins spq reel diameter (mm) reel width w1 (mm) a0 (mm) b0 (mm) k0 (mm) p1 (mm) w (mm) pin1 quadrant lmh6551qmm/nopb vssop dgk 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 q1 lmh6551qmme/nopb vssop dgk 8 250 178.0 12.4 5.3 3.4 1.4 8.0 12.0 q1 lmh6551qmmx/nopb vssop dgk 8 3500 330.0 12.4 5.3 3.4 1.4 8.0 12.0 q1 package materials information www.ti.com 21-mar-2013 pack materials-page 1
*all dimensions are nominal device package type package drawing pins spq length (mm) width (mm) height (mm) lmh6551qmm/nopb vssop dgk 8 1000 210.0 185.0 35.0 lmh6551qmme/nopb vssop dgk 8 250 210.0 185.0 35.0 lmh6551qmmx/nopb vssop dgk 8 3500 367.0 367.0 35.0 package materials information www.ti.com 21-mar-2013 pack materials-page 2

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