1 lt1311 n four complete current-to-voltage converters n 14-lead small outline package n accurate gain: 20mv/ m a, 4% n low offset error: 250na max n low offset drift: 2.5na/ c max n fast settling: 145ns to 0.1% for a 2v step n wide bandwidth: 12mhz n low noise: 5pa/ ? hz n low quiescent current: 11ma max n wide supply range: 2v to 18v or 4v to 36v the lt ? 1311 is a quad current-to-voltage converter de- signed for the demanding requirements of photo diode amplification. a new approach to current-to-voltage con- version provides excellent dc and ac performance with- out external dc trims or ac frequency compensation. the lt1311 is ideal for converting multiple photo diode cur- rents to voltages and for general purpose matched invert- ing amplifier applications. the lt1311 contains four current feedback amplifiers, each with an internal 20k feedback resistor. a supply bypass capacitor is the only external component required to convert four signal currents to voltages. unlike voltage feedback-based current-to-voltage converters that oper- ate with only a specified value of input capacitance, the current feedback lt1311 settles cleanly with any input capacitance up to 50pf. only in the most demanding applications will the lt1311 need to be mounted close to the photo diodes. quad 12mhz, 145ns settling precision current-to-voltage converter for optical disk drives features descriptio n u typical applicatio n u applicatio n s u n optical disk drive photo diode amplifiers focus and tracking summing amplifiers n color scanners rgb amplifiers selectable gain amplifiers n matched inverting amplifiers , ltc and lt are registered trademarks of linear technology corporation. c in = 1pf c in = 20pf c in = 50pf input = 100 m a step v s = 5v 1311 ta02 1
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14 13 12 10 9 8 1311 ta01 11 + + + + 5v in a
in b
bias
in c
in d out a
out b out c v cc
10v out d lt1311 0.1 m f transient response photo diode current-to-voltage converter
2 lt1311 total supply voltage (v + to v C ) ............................. 36v input current ..................................................... 15ma output short-circuit duration (note 1) ........ continuous operating temperature range ............... C 40 c to 85 c specified temperature range ...................... 0 c to 70 c junction temperature.......................................... 150 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c absolute m axi m u m ratings w ww u package/order i n for m atio n w u u t jmax = 150 c, q ja = 160 c/ w order part number lt1311cs consult factory for industrial and military grade parts. symbol parameter conditions min typ max units current to voltage gain v out = 2v to 8v, r l = 2k to 5v l 19.2 20 20.8 mv/ m a current to voltage gain drift l C 70 ppm/ c current to voltage gain mismatch between amplifiers ( d g/20k) 100% l 0.1 1.0 % v os input offset voltage with respect to v bias l 150 500 m v d v os / d t input offset voltage drift 1 m v/ c output offset voltage with respect to v bias l 1.5 5mv v s = 15v, v bias = 0v l 3 10 mv output offset voltage drift l 10 50 m v/ c (a + b) C (c + d) l 80 m v/ c output offset voltage mismatch between amplifiers l 2 4mv bias input current pin 4 l 5 20 m a output noise voltage density f = 1khz 100 nv/ ? hz i n input noise current density f = 1khz 5 pa/ ? hz e n input noise voltage density f = 1khz, a v = 40db 4.5 nv/ ? hz input impedance d v os / d i in , dc, d v out = 2v to 8v (i in = 150 m a) l 0.2 2 w d v os / d i in , f = 10mhz 400 w bias voltage range l v C + 2v v + C 2v v bias rejection ratio d v out / d v bias , v bias = 2v to 8v l 55 64 db bias input resistance v bias = 2v to 8v l 250 500 k w bias input capacitance f = 100khz 18 pf psrr power supply rejection ratio v s = 2v to 15v, v bias = 0v l 90 103 db minimum supply voltage v bias = 2v l 4v voltage gain d v out / d v os , v out = 2v to 8v, r l = 2k to 5v l 10 100 v/mv v out maximum output voltage swing output high, no load, i in = C 250 m a l 8.8 9.0 v output high, i source = 10ma, i in = C 250 m a l 8.5 8.8 v output low, no load, i in = 250 m a l 1.0 1.2 v output low, i sink = 10ma, i in = 250 m a l 1.2 1.5 v output impedance i out = 0ma, f = 10mhz 60 w i out maximum output current i in = 200 m a, v out = 5v l 30 55 ma i s supply current i in = 0 l 711 ma sr slew rate i in = 150 m a, v out at 3v, 7v 80 v/ m s v s = 10v, v bias = 5v, t a = 25 c, unless otherwise noted. electrical characteristics top view s package
14-lead plastic so 1
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in a
nc
in b
bias
in c
v (cd)
in d out a
v (ab)
out b
nc
out c
v +
out d
+ + + +
3 lt1311 v s = 10v, v bias = 5v, t a = 25 c, unless otherwise noted. electrical characteristics symbol parameter conditions min typ max units bw small-signal bandwidth 12 mhz full power bandwidth v out = 2.5v p-p , r in = 20k 10 mhz t r , t f rise time, fall time 10% to 90%, v out = 6v p-p , r in = 20k 65 ns 10% to 90%, v out = 100mv p-p , r in = 20k 35 ns os overshoot v out = 100mv p-p , r in = 20k 0 % t s settling time d v out = 2v, 0.1%, r in = 20k 145 ns v s = 15v, d v out = 10v, 0.1%, r in = 20k 210 ns thd total harmonic distortion v out = 2v rms , 20hz to 20khz, r in = 20k 0.004 % crosstalk v out = 3v to 7v, r l = 2k to 5v, f = 100hz, 110 db 3 channels driven the l denotes specifications which apply over the full specified temperature range of 0 c to 70 c. note 1: a heat sink may be required depending on the power supply voltage and the number of amplifiers that are shorted. typical perfor m a n ce characteristics u w temperature ( c) ?0 short-circuit current (ma) 90
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30 25 75 1311 g04 ?5 0 50 100 125 v s = 15v
i in = 750 m a v s = 5v
i in = 250 m a supply current vs supply voltage total supply voltage (v) 0 supply current (ma) 12
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2 10 20 25 1311 g01 515 30 35 40 t a = 125 c t a = 25 c t a = 55 c short-circuit current vs temperature frequency (hz) output impedance ( w ) 100
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1
0.1
0.01 1k 100k 1m 1311 g06 10k 10m r in = v s = 15v v s = 5v output impedance vs frequency C3db bandwidth vs load resistance load resistance ( w ) 100 3db bandwidth (mhz) 20
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6 1k 10k 1131 g05
v s = 15v r in = 100k v s = 5v bias voltage range vs temperature temperature ( c) ?0 bias voltage range (v) v +
v + ?
v + ?
v +2
v +1
v 25 75 1311 g02 ?5 0 50 100 125 load current (ma) 0.01 output saturation voltage (v) 0.1 1 10 1311 g03 125 c 125 c ?5 c ?5 c v +
v + ?
v + ?
v +2
v +1
v 25 c 25 c output saturation voltage vs load current
4 lt1311 typical perfor m a n ce characteristics u w 0.1% settling time vs input capacitance settling time (ns) 0 output step (v) 10
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0
?
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?0
1311 g07 400 100 200 300
500 1mv 1mv 10mv 10mv 0.1% 0.1% v s = 15v
r in = 20k
r l = 1k
a v = 1 capacitive load (pf) 1 settling time (ns) 240
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10 100 1000 1311 g09 v s = 5v
v out = 2v step
r in = 100k
r l = 1k settling time to 0.1%, 1mv,10mv vs output step input capacitance (pf) 0 settling time (ns) 350
300
250
200
150
100 40 1311 g08 10 20 30 50 v s = 5v
v out = 2v step
r in = 100k
r l = 1k 0.1% settling time vs capacitive load frequency (hz) 100k gain (db) phase shift (deg) 70
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0 1m 10m 40m 1311 g10 v s = 5v
r l = 2k a v = 1 a v = 10 a v = 100 a v = 100, r in = 200 w a v = 10, r in = 2k a v = 1, r in = 20k a v = 0.2, r in = 100k a v = 0.2 gain and phase vs frequency frequency (hz) 100k gain (db) ?
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?8 1m 10m 40m 1311 g12 v s = 5v
r in = 100k
r l = 2k c l = 500pf c l = 200pf c l = 0pf c l = 100pf c l = 100pf c l = 50pf frequency (hz) 100k gain (db) ?
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?8 1m 10m 40m 1311 g11 v s = 5v
r in = 100k
r l = 2k c in = 50pf c in = 20pf c in = 10pf c in = 0pf c in = 1pf c in = 5pf frequency response for various input capacitance frequency response for various capacitive loads power supply rejection ratio vs frequency frequency (hz) power supply rejection ratio (db) 90
70
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30
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?0 100k 1m 10m 1311 g13 10k v s = 5v
a v = 1
r l = positive negative frequency (hz) 0.001 total harmonic distortion (%) 0.01 0.1 100 10k 100k 1311 g14 10 1k v s = 15v
v out = 6.5v rms
a v = 1 v s = 5v
v out = 2v rms
a v = 1 total harmonic distortion vs frequency frequency (hz) 10 13
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3 100 i n e n 1k 10k 1311 g15 voltage noise density (nv/ hz) current noise density (pa/ hz) noise spectrum
5 lt1311 typical perfor m a n ce characteristics u w v s = 5v a v = C1 r l = 2k 1311 g16 v s = 15v a v = C1 r l = 2k 1311 g17 small-signal response large-signal response si plified sche atic w w r1
1k r2
2k r3
2k r4
2k q1 q3 q4 q5 r5
1k r6
4.5k r11
1k r12
2k r13
2k r14
2k r15
1k r16
4.5k r9
1.5k r10
1.5k r22
10 w r23
10 w r20
1.5k r19
1.5k v cc out v ee q13 q14 q15 r fb
20k c1
5pf c c
2pf c2
5pf in bias i bias
ptat q28 q33 q44 q41 q39 q40 q17 1311 ss q12 q16 q38 q37 q35 q36 q21 q19 q22 q18 q20 q6 q23 q26 q24 q25 q29 q32 q42 q27 +
6 lt1311 description the lt1311 contains four identical current feedback am- plifiers with their noninverting inputs tied together at pin 4. an external bias voltage is applied to this pin to set the quiescent output voltage of each amplifier. each amplifier has an internal 20k feedback resistor between the output and the inverting input. the amplifiers are packaged in a 14-pin so package with all four inverting inputs on one side and the outputs on the other. none of the inputs (or the outputs) are on adjacent pins for excellent channel separation. the feedback resistors in the lt1311 are laser-trimmed at wafer sort to set the current-to-voltage gain. the gain is set to 20mv/ m a; the change with temperature is typically C 70ppm/ c. the gain matching of the four amplifiers is ten times better. the input offset voltage and bias current are trimmed as well. the trimming also minimizes the resulting output offset drift. for more detailed circuit information, please see the may 1995 (volume 5, number 2) issue of linear technology magazine. supply voltages the lt1311 can be operated on single or split supplies. the total supply voltage must be greater than 4v and less than 36v. the bias voltage applied to pin 4 can be any value from 2v above the negative supply to 2v below the positive supply. the outputs can swing to within 1v of either supply. the lt1311 is trimmed while operating on a single 10v supply with a bias voltage of 5v; this is the equivalent of 5v supplies with the bias at ground. operation on a single 5v supply with a bias voltage of 2.5v results in very similar performance. operation on 15v supplies results in slightly more bandwidth and offset (see the electrical tables and the characteristic curves). bypassing the supplies and bias voltage pins requires no special care. for accurate settling, a 0.1 m f capacitor within an inch or two of the package works well. applicatio n s i n for m atio n wu u u input characteristics the inputs of the lt1311 are low impedance summing nodes. the current feedback amplifiers in the lt1311 have an open-loop input impedance of only a few hundred ohms and therefore the closed-loop response is fairly independent of stray capacitance on the inputs. this is a significant advantage over voltage feedback amplifiers that have to be set up for a particular input capacitance. the lt1311 settles cleanly with any input capacitance from zero to 50pf as shown in the characteristic curves. when the lt1311 is used to convert photo diode currents to signal voltages, the lt1311 does not have to be located close to the diodes. output characteristics the outputs of the lt1311 are complementary emitter followers. the outputs will swing to within 1v of the supplies with no load, 1.2v delivering 10ma. the outputs are short-circuit protected with a 55ma current limit. voltage gain applications when the lt1311 is used with external input resistors to make an inverting voltage gain amplifier, the bandwidth remains fairly constant for gains of 10 or less. at high gains the bandwidth is limited by a gain bandwidth prod- uct of about 250mhz. see the characteristic curves for details. the bandwidth is also influenced by any stray capacitance in parallel with the input resistor. the parallel stray capaci- tance results in a zero that pushes out the bandwidth. this is particularly noticeable with large input resistors that give gains less than one. for example, a single 100k input resistor results in a bandwidth of 14mhz but two 50k resistors in series result in only 10mhz bandwidth. overload recovery when one or more of the outputs is driven into the rail it will not affect the other amplifiers. however, the output that hit the rail will generate a glitch and take one to two microseconds to recover. supply current will increase 2ma to 3ma for each amplifier while it is driven into the rail.
7 lt1311 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. basic optical system focus and tracking signal generation wide common-mode range instrumentation amplifier ?n 1 7 3 5 12 14 8 10 out 1131 ta03 100k +in 100k v s = 5v v cm = 18v
v s = 15v v cm = 68v r2
2k r2
2k trim
for cmrr
20k bw = 5mhz, a v = 20k/r2 = 10 typical applicatio n s u 1
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14 13 12 10 9 8 2k 2k 1311 ta04 v cc
10v tracking
signal
(a + b) ?(c + d) focus
signal
(a + c) ?(b + d) worst-case output drift is 120 m v/ c
bandwidth is 7mhz
0.1% settling is less than 250ns 11 + + + + 5v in a
in b
bias
in c
v ? (cd)
in d out a
out b out c v cc
10v out d lt1311 0.1 m f 2k 8pf 2k 2k 2k 2k 2k 2k 5v 8pf + 1/2 lt1215 + 1/2 lt1215 2k 2k 2k v cc
v ? (ab)
8 lt1311 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7487 (408) 432-1900 l fax : (408) 434-0507 l telex : 499-3977 lt/gp 0595 10k ? printed in usa ? linear technology corporation 1995 dimension in inches (millimeters) unless otherwise noted. package descriptio n u s package 14-lead plastic soic 1 2 3 4 0.150 ?0.157*
(3.810 ?3.988) 14 13 0.337 ?0.344*
(8.560 ?8.738) 0.228 ?0.244
(5.791 ?6.197) 12 11 10 9 5 6 7 8 0.016 ?0.050
0.406 ?1.270 0.010 ?0.020
(0.254 ?0.508) 45 0 ?8 typ 0.008 ?0.010
(0.203 ?0.254) so14 0294 0.053 ?0.069
(1.346 ?1.752) 0.014 ?0.019
(0.355 ?0.483) 0.004 ?0.010
(0.101 ?0.254) 0.050
(1.270)
typ *these dimensions do not include mold flash or protrusions.
mold flash or protrusions shall not exceed 0.006 inch (0.15mm) related parts part number description comments lt1113 dual low noise, precision, jfet input op amp lowest voltage noise fet op amp lt1169 dual low noise, picoampere bias current, 5pa input bias current jfet input op amp lt1213/lt1214 28mhz, 12v/ m s, single supply, dual and quad highest bandwidth, precision single supply op amps precision op amps lt1215/lt1216 23mhz, 50v/ m s single supply, dual and quad fastest settling, precision single supply op amps precision op amps lt1222 low noise, very high speed op amp external compensation and output clamping
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