ltc1069-6 1 10696fa typical application description single supply, very low power, elliptic lowpass filter the ltc ? 1069-6 is a monolithic low power, 8th order lowpass ? lter optimized for single 3v or single 5v supply operation. the ltc1069-6 typically consumes 1ma under single 3v supply operation and 1.2ma under 5v operation. the cutoff frequency of the ltc1069-6 is clock tunable and it is equal to the clock frequency divided by 50. the input signal is sampled twice per clock cycle to lower the risk of aliasing. the typical passband ripple is 0.1db up to 0.9f cutoff . the gain at f cutoff is C0.7db. the transition band of the ltc1069-6 features progressive attenuation reaching 42db at 1.3f cutoff and 70db at 2.1f cutoff . the maximum stopband attenuation is 72db. the ltc1069-6 can be clock tuned for cutoff frequencies up to 20khz (single 5v supply) and for cutoff frequencies up to 14khz (single 3v supply). the low power feature of the ltc1069-6 does not penalize the devices dynamic range. with single 5v supply and an input range of 0.4v rms to 1.4v rms , the signal-to- (noise + thd) ratio is 70db. the wideband noise of the ltc1069-6 is 125v rms . other ? lter responses with higher speed can be obtained. please contact ltc marketing for details. the ltc1069-6 is available in an 8-pin so package. single 3v supply 10khz elliptic lowpass filter l , lt, ltc and ltm are registered trademarks of linear technology corporation. features applications n 8th order elliptic filter in so-8 package n single 3v operation: supply current: 1ma (typ) f cutoff : 14khz (max) s/n ratio: 72db n single 5v operation: supply current: 1.2ma (typ) f cutoff : 20khz (max) s/n ratio: 79db n 0.1db passband ripple up to 0.9f cutoff (typ) n 42db attenuation at 1.3f cutoff n 66db attenuation at 2.0f cutoff n 70db attenuation at 2.1f cutoff n wide dynamic range, 75db or more (s/n + thd), under single 5v operation n wideband noise: 120v rms n clock-to-f cutoff ratio: 50:1 n internal sample rate: 100:1 n handheld instruments n telecommunication filters n antialiasing filters n smoothing filters n audio n multimedia agndv + ncv in v out v C nc clk ltc1069-6 f clk = 500khz 3v 0.47f 0.1f 1069-6 ta01 frequency (khz) 5 C80 gain (db) C70 C50 C40 C30 15 10 1069-6 ta02 C60 10 20 25 C20 C10 0 v in = 500mv rms frequency response downloaded from: http:///
ltc1069-6 2 10696fa pin configuration absolute maximum ratings total supply voltage (v + to v ? ) ................................12v operating temperature range ltc1069-6c ............................................. 0c to 70c ltc1069-6i ..........................................? 40c to 85c storage temperature ..............................? 65c to 150c lead temperature (soldering, 10 sec) .................. 300c 12 3 4 87 6 5 top view v out v C ncclk agnd v + nc v in s8 package 8-lead plastic so t jmax = 125c, ja = 130c/w order information lead free finish tape and reel part marking package description temperature range ltc1069-6cs8#pbf ltc1069-6cs8#trpbf 10696 8-lead plastic so 0c to 70c ltc1069-6is8#pbf ltc1069-6is8#trpbf 10696i 8-lead plastic so C40c to 85c consult ltc marketing for parts speci? ed with wider operating temperature ranges. 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/ electrical characteristics symbol conditions min typ max units passband gain (f in 0.2f cutoff )v s = 5v, f clk = 200khz f test = 0.25khz, v in = 1v rms l C 0.25 C 0.30 0.10.1 0.450.50 dbdb v s = 3v, f clk = 200khz f test = 0.25khz, v in = 0.5v rms l C 0.25 C 0.30 0.10.1 0.450.50 dbdb gain at 0.50f cutoff v s = 5v, f clk = 200khz f test = 2.0khz, v in = 1v rms l C 0.10 C 0.15 0.070.07 0.250.30 dbdb v s = 3v, f clk = 200khz f test = 2.0khz, v in = 0.5v rms l C 0.15 C 0.20 0.070.07 0.250.30 dbdb gain at 0.75f cutoff v s = 5v, f clk = 200khz f test = 3.0khz, v in = 1v rms l C 0.25 C 0.30 00 0.250.30 dbdb v s = 3v, f clk = 200khz f test = 3.0khz, v in = 0.5v rms l C 0.25 C 0.30 00 0.250.30 dbdb gain at 0.90f cutoff v s = 5v, f clk = 200khz f test = 3.6khz, v in = 1v rms l C 0.25 C 0.25 0.10.1 0.450.45 dbdb v s = 3v, f clk = 200khz f test = 3.6khz, v in = 0.5v rms l C 0.25 C 0.30 0.10.1 0.450.50 dbdb gain at 0.95f cutoff v s = 5v, f clk = 200khz f test = 3.8khz, v in = 1v rms l C 0.35 C 0.45 0.050.05 0.250.25 dbdb v s = 3v, f clk = 200khz f test = 3.8khz, v in = 0.5v rms l C 0.45 C 0.55 0.050.05 0.250.35 dbdb the l denotes the speci? cations which apply over the full operating temperature range. f cutoff is the lter s cutoff frequency and is equal to f clk /50. the f clk signal level is ttl or cmos (clock rise or fall time 1?) r l = 10k, v s = 5v, t a = 25?, unless otherwise speci ed. all ac gains are measured relative to the passband gain. downloaded from: http:///
ltc1069-6 3 10696fa electrical characteristics 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: the input offset voltage is measured with respect to agnd (pin 1). the input (pin 4) is also shorted to the agnd pin. the analog ground pin potential is internally set to (0.437)(v supply ). the l denotes the speci? cations which apply over the full operating temperature range. f cutoff is the lter s cutoff frequency and is equal to f clk /50. the f clk signal level is ttl or cmos (clock rise or fall time 1?) r l = 10k, v s = 5v, t a = 25?, unless otherwise speci ed. all ac gains are measured relative to the passband gain. symbol conditions min typ max units gain at f cutoff v s = 5v, f clk = 200khz f test = 4.0khz, v in = 1v rms l C 1.50 C 1.65 C0.07 C0.07 C0.20 C0.25 dbdb v s = 3v, f clk = 200khz f test = 4.0khz, v in = 0.5v rms l C1.5 C1.7 C0.07 C0.07 00 dbdb gain at 1.30f cutoff v s = 5v, f clk = 200khz f test = 5.2khz, v in = 1v rms l C42 C42 C40 C39 dbdb v s = 3v, f clk = 200khz f test = 5.2khz, v in = 0.5v rms l C41 C41 C38 C37 dbdb gain at 2.00f cutoff v s = 5v, f clk = 200khz f test = 8.0khz, v in = 1v rms l C66 C66 C61C60 dbdb v s = 3v, f clk = 200khz f test = 8.0khz, v in = 0.5v rms l C66 C66 C60C59 db db gain at 0.95f cutoff v s = 5v, f clk = 400khz, f test = 7.6khz, v in = 1v rms v s = 3v, f clk = 400khz, f test = 7.6khz, v in = 0.5v rms C0.5 C0.5 0.15 0 0.50.5 dbdb output dc offset (note 1) v s = 5v, f clk = 100khz v s = 3v, f clk = 100khz 5030 175135 mvmv output dc offset tempco v s = 5v, v s = 3v 30 v/c output voltage swing (note 2) v s = 5v, f clk = 100khz l 3.43.2 4.24.2 v p-p v p-p v s = 3v, f clk = 100khz l 1.61.6 2.02.0 v p-p v p-p power supply current v s = 5v, f clk = 100khz l 1.2 1.60 1.65 mama v s = 3v, f clk = 100khz l 1 1.40 1.55 mama maximum clock frequency v s = 5v v s = 3v 1 0.7 mhzmhz input frequency range 0 <(f clk C 2f c ) input resistance 35 50 80 k operating supply voltage (note 3) 31 0 v note 3: the input voltage can swing to either rail (v + or ground); the output typically swings 50mv from ground and 0.8v from v + . note 4: the ltc1069-6 is optimized for 3v and 5v operation. although the device can operate with a single 10v supply or 5v, the total harmonic distortion will be degraded. for single 10v or 5v supply operation we recommend to use the ltc1069-1. downloaded from: http:///
ltc1069-6 4 10696fa typical performance characteristics passband gain vs clock frequency passband gain vs clock frequency amplitude response vs supply voltage phase vs frequency group delay vs frequency transient response passband gain vs frequency transition band gain vs frequency stopband gain vs frequency frequency (khz) 1 gain (db) 1 2 9 1069-6 g01 0 C1C2 3 5 7 11 v s = single 3v f clk = 500khz f cutoff = 10khz v in = 0.5v rms frequency (khz) 10 gain (db) C30 C10 10 18 1069-6 g02 C50 C70 C40 C20 0 C60 C80 C90 12 14 16 20 v s = single 3v f clk = 500khz f cutoff = 10khz v in = 0.5v rms frequency (khz) 20 C80 gain (db) C78 C74 C72 C70 C60 C66 40 60 1069-6 g03 C76 C64 C62 C68 80 100 v s = single 3v f clk = 500khz f cutoff = 10khz v in = 0.5v rms frequency (khz) 1 gain (db) 1 2 17 19 1069-6 g04 0 C1C2 5 9 13 15 3 7 11 21 v s = single 3v v in = 0.5v rms f clk = 500khz f cutoff = 10khz f clk = 750khz f cutoff = 15khz frequency (khz) 1 gain (db) 1 2 17 19 1069-6 g05 0 C1C2 5 9 13 15 3 7 11 21 v s = single 5v v in = 1v rms f clk 500khz f cutoff 10khz f clk 750khz f cutoff 15khz f clk 1mhz f cutoff 20khz frequency (khz) 1 C90 gain (db) C70 C50 C30 C10 10 100 1069-6 g06 10 C80 C60 C40 C20 0 f clk = 500khz v in = 0.5v rms single 5v single 3v frequency (khz) 0 phase (deg) C630 C90 0 90 4 8 10 1069-6 g07 C810 C270 C450 C720 C180 C900 C360 C540 2 6 12 14 v s = single 5v f clk = 500khz f cutoff = 10khz frequency (khz) 0 group delay (sec) 6 10 1069-6 g08 24 8 4.00e-043.50e-04 3.00e-04 2.50e-04 2.00e-04 1.50e-04 1.00e-04 5.00e-05 0.00e+00 12 v s = single 5v f clk = 500khz f cutoff = 10khz 0.5v/div v s = single 5v f clk = 1mhz f in = 1khz 2v p-p square wave 0.1ms/div 1069-6 g09 downloaded from: http:///
ltc1069-6 5 10696fa typical performance characteristics supply current vs supply voltage output voltage swing vs temperature dynamic range thd + noise vs input/output voltage dynamic range thd + noise vs input voltage thd + noise vs frequency input/output voltage (v p-p ) 0.1 C90 thd + noise (db) C80 C70 C60 C50 13 1069-6 g14 C85 C75 C65 C55 C45 C40 f clk = 170khz f cutoff = 3.4khz f in = 1khz v in = 2.945v p-p input voltage (v rms ) 0.1 0.5 0.76 1.43 C90 thd + noise (db) C80 C70 C60 C50 15 1069-6 g10 C85 C75 C65 C55 C45 C40 f clk = 500khz f in = 1khz v s = single 3v v s = single 5v frequency (khz) 15 1 0 1069-6 g11 C90 thd + noise (db) C80 C70 C60 C50 C85 C75 C65 C55 C45 C40 f clk = 500khz f cutoff = 10khz v s = single 3v v in = 0.5v rms v s = single 5v v in = 1v rms total supply voltage (v) 0 0 supply current (ma) 2 5 4 8 10 1069-6 g12 1 4 3 26 12 14 16 85c C40c 25c ambient temperature (c) C40C200 20406080 0 positive swing (v) negative swing (mv) 20 40 60 80 4.52.5 4.0 2.0 1069-6 g13 r l = 10k v s = single 5v v s = single 3v v s = single 3v v s = single 5v pin functions agnd (pin 1): analog ground. the quality of the analog signal ground can affect the ? lter performance. for either single or dual supply operation, an analog ground plane surrounding the package is recommended. the analog ground plane should be connected to any digital ground at a single point. for single supply operation, pin 1 should be bypassed to the analog ground plane with a 0.47f capacitor or larger. an internal resistive divider biases pin 1 to 0.4366 times the total power supply of the device (figure 1). that is, with a single 5v supply, the potential at pin 1 is 2.183v 1%. as the ltc1069-6 is optimized v + ncv in v out v C 12 3 4 87 6 5 nc clk ltc1069-6 1069-6 f01 agnd 11.325k 8.775k figure 1. internal biasing of the analog ground (pin 1) downloaded from: http:///
ltc1069-6 6 10696fa pin functions for single supply operation, the internal biasing of pin 1 allows optimum output swing. the agnd pin should be buffered if used to bias other ics. figure 2 shows the connections for single supply operation. agndv + v + ncv in v in v out v out v C 12 3 4 87 6 5 1k nc clk ltc1069-6 analog ground plane digital ground plane 0.47f 0.1f 1069-6 f02 clock source starsystem ground v + , v C (pins 2, 7): power supply pins. the v + (pin 2) and the v C (pin 7, if used) should be bypassed with a 0.1f capacitor to an adequate analog ground. the ? lters power supplies should be isolated from other digital or high voltage analog supplies. a low noise linear supply is recommended. switching power supplies will lower the signal-to-noise ratio of the ? lter. unlike previous monolithic ? lters, the power supplies can be applied in any order, that is, the positive supply can be applied before the negative supply and vice versa. figure 3 shows the connection for dual supply operation. agndv + v + ncv in v in v out v out v C v C 12 3 4 87 6 5 1k nc clk ltc1069-6 analog ground plane digital ground plane starsystem ground 0.1f 0.1f 1069-6 f03 clock source figure 2. connections for single supply operation figure 3. connections for dual supply operation nc (pins 3, 6): no connection. pins 3 and 6 are not connected to any internal circuitry; they should be tied to ground. v in (pin 4): filter input pin. the filter input pin is internally connected to the inverting input of an op amp through a 50k resistor. clk (pin 5): clock input pin. any ttl or cmos clock source with a square wave output and 50% duty cycle (10%) is an adequate clock source for the device. the power supply for the clock source should not necessarily be the ? lters power supply. the analog ground of the ? lter should be connected to the clocks ground at a single point only. table 1 shows the clocks low and high level threshold value for a dual or single supply operation. a pulse generator can be used as a clock source provided the high level on time is greater than 0.42s (v s = 5v). sine waves less than 100khz are not recommended for clock frequencies because, excessive slow clock rise or fall times generate internal clock jitter. the maximum clock rise or fall time is 1s. the clock signal should be routed from the right side of the ic package to avoid coupling into any input or output analog signal path. a 1k resistor between the clock source and the clock input (pin 5) will slow down the rise and fall times of the clock to further reduce charge coupling (figure 1). table 1. clock source high and low thresholds power supply high level low level dual supply = 5v 1.5v 0.5v single supply = 10v 6.5v 5.5v single supply = 5v 1.5v 0.5v single supply = 3.3v 1.2v 0.5v v out (pin 8): filter output pin. pin 8 is the output of the ? lter, and it can source 8ma or sink 1ma. the total harmonic distortion of the ? lter will degrade when driving coaxial cables or loads less than 20k without an output buffer. downloaded from: http:///
ltc1069-6 7 10696fa applications information temperature behavior the power supply current of the ltc1069-6 has a positive temperature coef? cient. the gbw product of its internal op amps is nearly constant and the speed of the device does not degrade at high temperatures. figures 4a, 4b and 4c show the behavior of the passband of the device for various supplies and temperatures. the ? lter has a passband behavior which is temperature independent. clock feedthrough the clock feedthrough is de? ned as the rms value of the clock frequency and its harmonics that are present at the ? lters output (pin 8). the clock feedthrough is tested with the input (pin 4) shorted to agnd (pin 1) and depends on pc board layout and on the value of the power supplies. with proper layout techniques the values of the clock feedthrough are shown in table 2. table 2. clock feedthrough v s clock feedthrough 3.3v 100v rms 5v 170v rms 10v 350v rms any parasitic switching transients during the rising and falling edges of the incoming clock are not part of the clock feedthrough speci? cations. switching transients have frequency contents much higher than the applied clock; their amplitude strongly depends on scope probing techniques as well as grounding and power supply bypassing. the clock feedthrough can be reduced by adding a single rc lowpass ? lter at the output (pin 8). frequency (khz) 1 gain (db) 1 2 17 1069-6 f04a 0 C1 C2 5 9 13 31 9 7 11 15 21 v s = single 3v v in = 0.5v rms f clk = 500khz f cutoff = 10khz 85c C40c figure 4a frequency (khz) 1 gain (db) 1 2 17 1069-6 f04a 0 C1C2 5 9 13 31 9 7 11 15 21 v s = single 5v v in = 1v rms f clk = 750khz f cutoff = 15khz 85c C40c frequency (khz) 1 gain (db) 1 2 25 1069-6 f04c 0 C1C2 7 13 19 42 8 10 16 22 31 v s = 5v v in = 1.5v rms f clk = 1mhz f cutoff = 20khz 85c C40c figure 4b figure 4c downloaded from: http:///
ltc1069-6 8 10696fa wideband noisethe wideband noise of the ? lter is the total rms value of the devices noise spectral density and determines the operating signal-to-noise ratio. the frequency contents of the wideband noise lie within the ? lters passband. the wideband noise cannot be reduced by adding post ? ltering. the total wideband noise is nearly independent of the clock frequency and depends slightly on the power supply voltage (see table 3). the clock feedthrough speci? cations are not part of the wideband noise. table 3. wideband noise v s wideband noise 3.3v 118v rms 5v 123v rms 5v 127v rms applications information aliasingaliasing is an inherent phenomenon of sampled data systems and occurs for input frequencies approaching the sampling frequency. the internal sampling frequency of the ltc1069-6 is 100 times its cutoff frequency. for instance, if a 98.5khz, 100mv rms signal is applied at the input of an ltc1069-6 operating with a 50khz clock, a 1.5khz, 484v rms alias signal will appear at the ? lter output. table 4 shows details. table 4. aliasing (f clk = 50khz) input frequency (v in = 1v rms ) (khz) output level (relative to input) (db) output frequency (aliased frequency) (khz) f clk /f c = 50:1, f cutoff = 1khz 96 (or 104) C78.3 4.0 97 (or 103) C70.4 3.0 98 (or 102) C 80.6 2.0 98.5 (or 101.5) C46.3 1.5 99 (or 101) C2.8 1.0 99.5 (or 100.5) C1.38 0.5 downloaded from: http:///
ltc1069-6 9 10696fa .016 C .050 (0.406 C 1.270) .010 C .020 (0.254 C 0.508) s 45 0C 8 typ .008 C .010 (0.203 C 0.254) so8 0303 .053 C .069 (1.346 C 1.752) .014 C .019 (0.355 C 0.483) typ .004 C .010 (0.101 C 0.254) .050 (1.270) bsc 1 2 3 4 .150 C .157 (3.810 C 3.988) note 3 8 7 6 5 .189 C .197 (4.801 C 5.004) note 3 .228 C .244 (5.791 C 6.197) .245 min .160 .005 recommended solder pad layout .045 .005 .050 bsc .030 .005 typ inches (millimeters) note:1. dimensions in 2. drawing not to scale 3. these dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed .006" (0.15mm) package description s8 package 8-lead plastic small outline (narrow 0.150) (ltc dwg # 05-08-1610) downloaded from: http:///
ltc1069-6 10 10696fa 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 0309 rev a printed in usa related parts typical application part number description comments ltc1068 very low noise, high accuracy, quad universal filter building block user-con? gurable, ssop package ltc1069-1 low power, progressive elliptic lpf f clk /f c ratio 100:1, 8-pin so package ltc1164-5 low power 8th order butterworth lpf f clk /f c ratio 100:1 and 50:1 ltc1164-6 low power 8th order elliptic lpf f clk /f c ratio 100:1 and 50:1 ltc1164-7 low power 8th order linear phase lpf f clk /f c ratio 100:1 and 50:1 12 3 4 87 6 5 v out v C nc clk agndv + ncv in 0.1f 0.47f on shutdown 5v v in v out 1069-6 ta03 ltc1069-6 f clk 750khz 5v0v 12 3 4 87 6 5 v out v C nc clk agndv + ncv in 0.1f 0.47f v in v out 1069-6 ta04 ltc1069-6 f clk 500khz 3.3v0v C + 1/2 lt1366 3.3v 0.1f 56 84 7 12 3 4 87 6 5 v out v C nc clk agndv + ncv in 0.1f 1f 3v 3v 10k 40.2k 1069-6 ta05 ltc1069-6 170khz 56 23 7 8 C + 1/2 lt1366 0.1f 40.2k 1 4 C + 1/2 lt1366 270pf 10k single 5v operation with power shutdown single 3v supply operation with output buffer single 3v supply voice band lowpass filter with rail-to-rail input and output downloaded from: http:///
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