View LTC1061AM_3303963.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

1 ltc1061 the ltc1061 consists of three high performance, univer- sal filter building blocks. each filter building block together with an external clock and 2 to 5 resistors can produce various second order functions which are available at its three output pins. two out of three always provide low- pass and bandpass functions while the third output pin can produce highpass or notch or allpass. the center frequency of these functions can be tuned with an external clock or an external clock and a resistor ratio. for q < 5, the center frequency ranges from 0.1hz to 35khz. for qs of 10 or above, the center frequency ranges from 0.1hz to 28khz. the ltc1061 can be used with single or dual supplies ranging from 2.37v to 8v (or 4.74v to 16v). when the filter operates with supplies of 5v and above, it can handle input frequencies up to 100khz. the ltc1061 is compatible with the ltc1059 single universal filter and the ltc1060 dual. higher than 6th order functions can be obtained by cascading the ltc1061 with the ltc1059 or ltc1060. any classical filter realiza- tion can be obtained. the ltc1061 is manufactured by using linear technologys enhanced ltcmos tm silicon gate process. high performance triple universal filter building block d u escriptio s f ea t u re n up to 6th order filter functions with a single 20-pin 0.3" wide package n center frequency range up to 35khz n f o q product up to 1mhz n guaranteed center frequency and q accuracy over temperature n guaranteed low offset voltages over temperature n 90db signal-to-noise ratio n filter operates from single 4.7v supply and up to 8v supplies n guaranteed filter specifications with 5v supply and 2.37v supply n low power consumption with single 5v supply n clock inputs t 2 l and cmos compatible input frequency gain (khz) 100 filter gain (db) ?0 ?0 ?0 ?0 0 10 20 30 40 ltc1061 ?ta02 50 2khz f clk = 1mhz 0 amplitude response u s a o pp l ic at i n high order, wide frequency range bandpass, lowpass, notch filters n low power consumption, single 5v supply, clock-tunable filters n tracking filters n antialiasing filters ltcmos tm is a trademark of linear technology corp. 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 78.7k 4.99k 23.7k 4.99k 165k 5.49k 49.9k v = ?.5v 165k 4.99k 1k 9.31k 165k v in < 100khz 7.5v t 2 clk in < 1.2mhz v + = 7.5v 1061 ta01 ltc1061 v out 6th order, clock-tunable, 0.5db ripple chebyshev bp filter u a o pp l ic at i ty p i ca l
2 ltc1061 wu u package / o rder i for atio a u g w a w u w a r b s o lu t exi t i s supply voltage ....................................................... 18v power dissipation ............................................. 500mw operating temperature range ltc1061ac, ltc1061c ............ C40 c t a 85 c LTC1061AM, ltc1061m ......... C55 c t a 125 c storage temperature range ................ C65 c to 150 c lead temperature (soldering, 10 sec.)................ 300 c 1 2 3 4 5 6 7 8 9 10 top view j package 20-lead ceramic dip n package 20-lead plastic dip 20 19 18 17 16 15 14 13 12 11 lp a bp a n a inv a s1 a agnd 50/100/hold clk ls h v + lp b bp b n b inv b s1 b v lp c bp c hp c inv c s package 20-lead plastic sol LTC1061AMj ltc1061mj ltc1061acj ltc1061cj ltc1061acn ltc1061cn ltc1061cs order part number t jmax = 125 c, q ja = 100 c/w (j) t jmax = 100 c, q ja = 100 c/w (n) t jmax = 100 c, q ja = 85 c/w (s) consult factory for industrial grade parts parameter conditions min typ max units center frequency range, f o f o q 175khz, mode 1, v s = 7.5v 0.1C35k hz f o q 1.6mhz, mode 1, v s = 7.5v 0.1C25k hz f o q 75khz, mode 3, v s = 7.5v 0.1C25k hz f o q 1mhz, mode 3, v s = 7.5v 0.1C17k hz input frequency range 0C200k hz clock-to-center frequency ratio, f clk /f o sides a, b: mode 1, r1 = r3 = 50k ltc1061a r2 = 5k, q = 10, f clk = 250khz l 50 0.6% ltc1061 pin 7 high. l 50 1.2% side c: mode 3, r1 = r3 = 50k r2 = r4 = 5k, f clk = 250khz ltc1061a same as above, pin 7 at l 100 0.6% ltc1061 mid-supplies, f clk = 500khz l 100 1.2% clock-to-center frequency ratio, side-to-side matching ltc1061 1.2% q accuracy sides a, b, mode 1 ltc1061a side c, mode 3 l 25 % ltc1061 f o q 50khz, f o 5khz l 35 % f o temperature coefficient mode 1, 50:1, f clk < 300khz 1ppm/ c q temperature coefficient mode 1, 100:1, f clk < 500khz 5ppm/ c mode 3, f clk < 500khz 5ppm/ c e lectr ic al c c hara terist ics (complete filter)v s = 5v, t a = 25 c, t 2 l clock input level, unless otherwise specified.
3 ltc1061 e lectr ic al c c hara terist ics (complete filter)v s = 5v, t a = 25 c, t 2 l clock input level, unless otherwise specified. parameter conditions min typ max units dc offset voltage v os1 , figure 23 l 215 mv v os2 f clk = 250khz, 50:1 l 330 mv v os2 f clk = 500khz, 100:1 l 660 mv v os3 , ltc1061cn, acn/ltc1061cs f clk = 250khz, 50:1 l 3 20/25 mv v os3 , ltc1061cn, acn/ltc1061cs f clk = 500khz, 100:1 l 6 40/50 mv clock feedthrough f clk < 1mhz 0.4 mv rms maximum clock frequency mode 1, q < 5, v s 3 5 2.5 mhz power supply current 6 8 11 ma l 15 ma (internal op amps) t a = 25 c, unless otherwise specified. supply voltage range 2.37 9v voltage swings ltc1061a v s = 5v, r l = 5k (pins 1,2,13,14,19,20) 4.0 4.2 v ltc1061 v s = 5v, r l = 3.5k (pins 3,12,18) 3.8 4.2 v ltc1061, ltc1061a l 3.6 v output short-circuit current source/sink v s = 5v 40/3 ma dc open-loop gain v s = 5v, r l = 5k 80 db gbw product v s = 5v 3 mhz slew rate v s = 5v 7 v/ m s the l denotes the specifications which apply over the full operating temperature range. (complete filter)v s = 2.37v, t a = 25 c, unless otherwise specified. center frequency range, f o f o q 120khz, mode 1, 50:1 0.1C 12k hz f o q 120khz, mode 3, 50:1 0.1C 10k hz input frequency range 0 C 20k hz clock-to-center frequency ratio 50:1, f clk = 250khz, q = 10 ltc1061a sides a, b: mode 1 50 0.6% ltc1061 side c, mode 3, 250khz 50 1.0% lt1061a 100:1, f clk = 500khz, q = 10 100 0.6% lt1061 sides a, b: mode 1 100 1.0% side c: mode 3 q accuracy ltc1061a same as above 2% ltc1061 3% maximum clock frequency 700 khz power supply current 4.5 6 ma
4 ltc1061 cc hara terist ics uw a t y p i ca lper f o r c e mode 1, mode 3 (f clk /f o ) deviation vs q mode 1, mode 3 (f clk /f o ) deviation vs q ideal q 0.1 ?.6 % deviation (f clk /f o ) ?.2 0.8 0.4 0 1 10 100 ltc1061 g01 2.0 2.4 0.4 v s = ?v t a = 25? f clk = 250khz f clk /f o = 50 (test point) ideal q 0.1 0.3 % deviation (f clk /f o ) 0.2 0.1 0 0.1 1 10 100 ltc1061 g02 . 0.4 0.5 0.6 v s = ?v t a = 25? f clk = 500khz f clk /f o = 100 (test point) mode 3: deviation of (f clk /f o ) with respect to q = 10 measurement ideal q 0.1 0.2 deviation of f clk /f o with respect to q = 10 measurement (%) 0.1 0 0.1 1 10 100 ltc1061 g03 . 0.3 0.4 0.5 v s = ?v t a = 25? pin 7 at 100:1 f clk /f o = 500:1 ? r2/r4 = 1/5 (a) (b) ? r2/r4 = 1/2 f clk /f o = 200:1 mode 1: (f clk /f o ) = 50:1 mode 1: (f clk /f o ) = 100:1 mode 3: (f clk /f o ) = 50:1 mode 3: (f clk /f o ) = 100:1 f clk /f o vs f o power supply current vs supply voltage center frequency (khz) 0 deviation from ideal q (%) 32 1061 g04 20 10 0 8 16 24 40 30 0 20 10 30 412 20 28 36 t a = 25? f clk /f o = 50/1 20 50 10 q<5 v s = 2.5v v s = ?.5v 50 20 10 q<5 50 20 10 q<5 t a = 25? f clk /f o = 50/1 v s = 5v center frequency (khz) 0 deviation from ideal q (%) 32 1061 g05 20 10 0 8 16 24 30 0 20 10 30 412 20 28 q=20 v s = 2.5v v s = ?.5v 10 10 10 v s = 5v q=5 q<5 q=20 q=20 q=5 power supply voltage (?) 0 i supply (ma) 8 1061 g09 6 3 0 2 4 6 10 9 15 21 18 24 13 5 7 9 27 30 12 t a = 55? t a = 25? t a = 125? center frequency (khz) 0 error from ideal f clk /f o (%) 32 1061 g08 1.0 0.5 0 8 16 24 40 1.5 0 1.0 0.5 1.5 412 20 28 36 q = 10 t a = 25? f clk /f o = 50/1 mode 1, mode 3 v s = 2.5v v s = ?.5v v s = 5v mode 3 2.0 2.5 mode 3 mode 1 mode 1 v s = 2.5v mode 1,3 v s = 5v mode 1,3 v s = 7.5v mode 1,3 q = 10 t a = 25? f clk /f o = 100/1 center frequency (khz) 0 deviation from ideal q (%) 32 1061 g07 20 10 0 8 16 24 30 0 20 10 30 412 20 28 q=20 v s = 2.5v v s = ?.5v 20 10 10 v s = 5v q=5 q=20 q=5 q=1 10 q=5 q=1 center frequency (khz) 0 deviation from ideal q (%) 32 1061 g06 20 10 0 8 16 24 40 30 0 20 10 30 412 20 28 36 t a = 25? f clk /f o = 50/1 20 5 q=1 v s = 2.5v v s = ?.5v 5 20 10 20 10 t a = 25? f clk /f o = 50:1 v s = 5v 10 2.5 q=1 5 2.5 q=1
5 ltc1061 w i dagra b l o c k s frequencies below 500khz the clock on time can be as low as 300ns. the maximum clock frequency for 5v supplies and above is 2.4mhz. s1 a , s1 b (pins 5, 16) these are voltage input pins. if used, they should be driven with a source impedance below 5k w . when they are not used, they should be tied to the analog ground pin 6. agnd (pin 6) when the ltc1061 operates with dual supplies, pin 6 should be tied to system ground. when the ltc1061 operates with a single positive supply, the analog ground pin should be tied to 1/2 supply, figure 1. the positive input of all the internal op amps, as well as the common reference of all the internal switches, are internally tied to the analog ground pin. because of this, a clean ground is recommended. pi descriptio a d applicatio hi ts u u u u u power supplies (pins 10, 15) they should be bypassed with 0.1 m f disc ceramic. low noise, nonswitching, power supplies are recommended. the device operates with a single 5v supply, figure 1, and with dual supplies. the absolute maximum operating power supply voltage is 9v. clock and level shift (pins 8, 9) when the ltc1061 operates with symmetrical dual sup- plies the level shift pin 9 should be tied to analog ground. for single 5v supply operation, the level shift pin should be tied to pin 15 which will be the system ground. the typical logic threshold levels of the clock pin are as follows: 1.65v above the level shift pin for 5v supply operation, 1.75v for 7.5v and above, and 1.4v for single 5v supply operation. the logic threshold levels vary 100mv over the full military temperature range. the recommended duty cycle of the input clock is 50% although for clock + s + s level shift level shift level shift clock generator clock generator clock generator clk (8) level shift (9) to filter a to filter b to filter c + + + + + 50/100/ hold (7) agnd (6) v + (10) v (15) hp c (12) s1 b (16) bp c (13) lp c (14) s1 a (5) nb (18) bp b (19) lp b (20) na (3) bp a (2) lp a (1) inv a (4) inv b (17) inv c (11) 1061 bd + + + +
6 ltc1061 pi descriptio a d applicatio hi ts u u u u u figure 1. the 6th order lp butterworth filter of figure 5 operating with a single 5v supply. 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 r3 v out r1 v in 0.1 m f ltc1061 f01 ltc1061 + r2 r1 r3 r2 r4 r1 r3 r2 t 2 l clock in f clk < 1mhz 1 m f 5v 2.49k 2.49k c in clock feedthrough this is defined as the amplitude of the clock frequency appearing at the output pins of the device, figure 2. clock feedthrough is measured with all three sides of the ltc1061 connected as filters. the clock feedthrough mainly de- pends on the magnitude of the power supplies and it is independent from the input clock levels, clock frequency and modes of operation. the table 2 illustrates the typical clock feedthrough num- bers for various power supplies. 50/100/hold (pin 7) by tying pin 7 to v + , the filter operates with a clock-to- center frequency internally set at 50:1. when pin 7 is at mid-supplies, the filter operates with a 100:1 clock-to- center frequency ratio. table 1 shows the allowable varia- tion of the potential at pin 7 when the 100:1 mode is sought. when pin 7 is shorted to the negative supply pin, the filter operation is stopped and the bandpass and lowpass output act as a sample-and-hold circuit holding the last sample of the input voltage. the hold step is around 2mv and the droop rate is 150 m v/sec. table 1 total power supply voltage range of pin 7 (v) for 100:1 operation (v) 5 2.5 0.5 10 5 1 15 7.5 1.5 figure 2. typical clock feedthrogh of the ltc1061 operating with 5v supplies. top trace is the input clock swinging 0v to 5v and bottom trace is one of the lowpass outputs with zero or dc input signals. a = 2v/div b = 10mv/div horizontal = 10 m s/div power supply (v) clock feedthrough (v rms ) 2.5 0.2 5 0.4 8 0.8 table 2 definition of filter functions refer to ltc1060 data sheet.
7 ltc1061 odes of operatio w u description and applications 1. primary modes: there are two basic modes of opera- tion, mode 1 and mode 3. in mode 1, the ratio of the external clock frequency to the center frequency of each 2nd order section is internally fixed at 50:1 or 100:1. in mode 3, this ratio can be adjusted above or below 50:1 or 100:1. the side c of the ltc1061 can be connected only in mode 3. figure 3 illustrates mode 1 providing 2nd order notch, lowpass, and bandpass outputs (for definition of filter functions, refer to the ltc1060 data sheet). mode 1 can be used to make high order butterworth lowpass filters; it can also be used to make low q notches and for cascading 2nd order bandpass functions tuned at the same center frequency and with unity-gain. mode 3, figure 4, is the classical state variable configuration pro- viding highpass, bandpass and lowpass 2nd order filter functions. since the input amplifier is within the resonant loop, its phase shift affects the high frequency operation of the filter and therefore, mode 3 is slower than mode 1. mode 3 can be used to make high order all-pole bandpass, lowpass, highpass and notch filters. mode 3 as well as mode 1 is a straightforward mode to use and the filters dynamics can easily be optimized. figure 5 illustrates a 6th order lowpass butterworth filter operating with up to 40khz cutoff frequency and with up to 200khz input frequency. sides a, b are connected in mode 1 while side c is connected in mode 3. the lower q section was placed in side c, mode 3, to eliminate any early q enhancement. this could happen when the clock approaches 2mhz. the measured frequency response is shown in figure 6. the attenuation floor is limited by the crosstalk between the three different sections operating with a clock frequency above 1mhz. the measured wideband noise was 150 m v rms . for limited temperature range the filter of figure 5 works up to 2.5mhz clock frequency thus yielding a 50khz cutoff. figure 4. mode 3: 2nd order filter providing highpass, bandpass, lowpass figure 3. mode 1: 2nd order filter providing notch, bandpass, lowpass 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 r32 v out r13 v in ltc1061 f05 ltc1061 r22 r12 r31 r21 r41 r33 r23 t 2 l clock < 2.5mhz v r11 v + harmonic distortion with f clk = 2mhz f in 2nd harmonic 10khz, 1v rms 20khz, 1v rms 30khz, 1v rms 40khz, 1v rms 74db 62db 62db 62db standard 1% resistor values r11 = 20k r31 = 11k r12 = 20k r32 = 14k r13 = 10k r21 = 20k r41 = 20k r22 = 20k r23 = 10k r33 = 17.8k figure 5. 6th order butterworth lowpass filter with cutoff frequency up to 45khz + s agnd r1 n bp lp v in 1061 f03 + s 1/3 ltc1061 r2 r3 f o = ; f n = f o h olp = ? ; h obp = ? ; h on1 = ? q = f clk 100(50) r2 r1 r3 r1 r2 r1 r3 r2 + s agnd r1 hp bp lp v in 1061 f04 + s 1/3 ltc1061 r2 r3 r4 f o = ; q = h ohp = ? ; h obp = ? ; h olp = ? f clk 100(50) r2 r1 r3 r1 r4 r1 r3 r2 ? r2 r4 ? r2 r4 c c note: add c c for q > 5 and f clk > 1mhz, such as c c @ 0.16 r4 1.2mhz
8 ltc1061 odes of operatio w u figure 6. measures frequency response of the lowpass butterworth filter of figure 3. 2. secondary modes: mode 1b C it is derived from mode 1. in mode 1b, figure 7, two additional resistors, r5 and r6, are added to attenuate the amount of voltage fed back from the lowpass output into the input of the s a (s b ) switched capacitor summer. this allows the filter clock- to-center frequency ratio to be adjusted beyond 50:1 (or 100:1). mode 1b still maintains the speed advantages of mode 1. figure 8 shows the 3 lowpass sections of the ltc1061 in cascade resulting in a chebyshev lowpass filter. the side a of the ic is connected in mode 1b to provide the first resonant frequency below the cutoff frequency of the filter. the practical ripple, obtained by using a non-a version of the ltc1061 and 1% standard resistor values, was 0.15db. for this 6th order lowpass, the textbook qs and center frequencies normalized to the ripple bandwidth are: q1 = 0.55, f o1 = 0.71, q2 = 1.03, f o2 = 0.969, q3 = 3.4, f o3 = 1.17. the design was done with speed in mind. the higher (q3, f o3 ) section was in mode 1 and placed in the side b of the ltc1061. the remaining two center frequencies were then normalized with respect to the center frequency of side b; this changes the ratio of clock-to-cutoff frequency from 50:1 to 50 1.17 = 58.5:1. as shown in figure 9, the maximum cutoff frequency is about 33khz. the total wideband output noise is 220 m v rms and the measured output dc offset voltage is 60mv. + s agnd r1 n bp lp v in 1061 f07 + s r2 r3 r6 r5 f o = ; f n = f o ; q = h on1 (f ? 0) = h on2 = ? h olp = ; h obp = ? ; (r5//r6) <5k f clk 100(50) r2 r1 r3 r2 r2/r1 r6/(r5 + r6) r3 r1 ? r6 r5 + r6 ? r6 r5 + r6 f clk 2 f ? () f in (hz) 10k ?0 v out /v in (db) ?0 ?0 ?0 ?0 100k 1m 1061 f09 ?0 ?0 0 30k v s > 5v t a = 25? v in = 1v rms f clk = 1.9mhz figure 8. 6th order chebyshev, lowpass filter using 3 different modes of operation for speed optimization figure 9. amplitude response of the 6th order chebyshev lowpass filter of figure 8 figure 7. mode 1b: 2nd order filter providing notch, bandpass, lowpass f in (hz) 10k ?0 gain (db) ?0 ?0 ?0 ?0 100k 1m 1061 f06 ?0 ?0 0 20k 40k 200k v s 3 5v t a = 25? v in = 1v rms f clk = 2mhz f c = 40khz f clk = 1mhz f c = 20khz 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 r32 v out r11 v in ltc1061 f08 ltc1061 r22 r12 r33 r23 r43 r31 r21 f clk < 2mhz v r13 v + r51 r61 standard 1% resistor values r11 = 35.7k r31 = 11.5k r51 = 5.49k r12 = 11k r61 = 2.87k r22 = 11k r23 = 10.5 r43 = 15.8k r32 = 36.5k r13 = 15.8k r33 = 13k r21 = 12.1k
9 ltc1061 another example of mode 1b is illustrated on the front page of the data sheet. the cascading sequence of this 6th order bandpass filter is shown in block diagram form, figure 10a. the filter is geometrically centered around the side b of the ltc1061 connected in mode 1. this dictates a clock-to-center frequency ratio of 50:1 or 100:1. the side a of the ic operates in mode 1b to provide the lower center frequency of 0.95 and still share the same clock with the rest of the filter. with this approach the bandpass filter can operate with center frequencies up to 24khz. the speed of the filter could be further improved by using mode 1 to lock the higher resonant frequency of 1.05 and higher q or 31.9 to the clock, figure 10b, thus changing the clock to center frequency ratio to 52.6:1. mode 3a C this is an extension of mode 3 where the highpass and lowpass outputs are summed through two external resistors r h and r l to create a notch, figure 11. mode 3a is very versatile because the notch frequency can be higher or lower than the center frequency of the 2nd order section. the external op amp of figure 11 is not always required. when cascading the sections of the ltc1061, the highpass and lowpass outputs can be summed directly into the inverting input of the next section. figure 12 shows an ltc1061 providing a 6th order elliptic bandpass or notch response. sides c and b are connected in mode 3a while side a is connected in mode 1 and uses only two resistors. the resulting filter response is then geometrically symmetrical around either the center frequency of side a (for bandpass responses) or the notch frequency of side a (for notch responses). figure 11. mode 3a: 2nd order filter providing highpass, bandpass, lowpass, notch odes of operatio w u figure 10a. cascading sequence of the bandpass filter shown on the front page, with (f clk /f o ) = 50:1 or 100:1 figure 10b. cascading sequence of the same filter for speed optimization, and with (f clk /f o ) = 52.6:1 mode 1b mode 1 mode 3 side a side b side c v in v out f o1 = 0.95 q1 = 31.9 f o2 = 1.05 q2 = 31.9 f o3 = 1 q3 = 15.9 1061 f10b mode 1b mode 1 mode 3 side a side b side c v in v out f o1 = 0.95 q1 = 31.9 f o2 = 1 q2 = 15.9 f o3 = 1.05 q3 = 31.9 1061 f10a + s agnd r1 hp bp lp v in 1061 f11 + s r2 r3 r4 c c note: for q > 5 and f clk > 1mhz, add c c such as c c @ + external op amp or input op amp of the ltc1061, sides a, b, c notch r g r l r h ? r2 r1 r3 r2 r4 r1 r4 r1 f o = ; f n = ; h ohp = ? ; h obp = ? ; h olp = ? h on1 (f ? 0) = ; h on2 = ; h on (f = f o ) = q h olp ? h ohp q = f clk 100(50) r2 r1 r3 r1 ? r2 r4 f clk 2 f ? () f clk 100(50) ? r h r l r g r l r g r h () r g r l r g r h r2 r4 0.16 r4 1.2mhz
10 ltc1061 odes of operatio w u center frequencies, qs, and notch frequencies are (f o1 = 0.969, q1 = 54.3, f n1 = 0.84, f o2 = 1.031, q2 = 54.3, f n2 = 1.187, f o3 = 1, q3 = 26.2). the output of the filter is the bp output of side a, pin 2. lowpass filters with stopband notches can also be realized by using figure 12 provided that 6th order lowpass filter approximations with 2 stopband notches can be synthe- sized. literature describing elliptic double terminated (rlc) figure 14. resistor values and amplitude response of figure 12 topology. the bandpass filter is centered around 2600hz when operating with a 130khz clock. figure 13. resistor values and amplitude response of figure 12 topology. the notch is centered at 2600hz. 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 r32 v in ltc1061 f12 ltc1061 r22 r h 2 r31 r41 r33 r23 t 2 l, cmos clock input v r42 v + notes: for notch responses, pin 7 should be preferably connected to ground and the filter output is pin 3. for bandpass or lowpass responses, pin 7 can be either at ground or positive supply, and the filter output is pin 2 or pin 1. r l 2 r l 1 r21 r11 r h 1 figure 12. 6th order elliptic bandpass, lowpass or notch topology figure 13 shows the measured frequency response of the circuit figure 12 configured to provide a notch function. the filter output is taken out of pin 3. the resistor values are standard 1%. the ratio of the 0db width, bw1, to the notch width bw2, is 5:1 and matches the theoretical design value. the measured notch depth was C53db versus C56db theoreti- cal and the clock-to-center notch frequency ratio is 100:1. figure 14 shows the measured frequency response of the circuit topology, figure 12, but with pole/zero locations configured to provide a high q, 6th order elliptic bandpass filter operating with a clock-to-center frequency ratio of 50:1 or 100:1. the theoretical passband ripple, stopband attenuation and stopband to ripple bandwidth ratio are 0.5db, 56db, 5:1 respectively. the obtained results with 1% standard resistor values closely match the theoretical frequency response. for this application, the normalized f in (khz) 1.0 v out /v in (db) ?0 3.0 1061 f14 ?0 ?0 ?0 1.5 2.0 2.5 3.5 ?0 ?0 ?0 0 ?0 ?0 v s = ?v f clk = 130khz r11 = 576k r31 = 562k r h 11 = 28.7k r22 = 10.7k r42 = 10k r l 2 = 10k r33 = 75k r21 = 10k r41 = 10.7k r l 11 = 40.2k r32 = 562k r h 2 = 14k r23 = 2.94k note: for clock frequencies above 500khz, connect a 5pf in parallel with r41 and r42. standard 1% resistor values f in (khz) 1.0 v out /v in (db) ?0 3.0 1061 f13 ?0 ?0 ?0 1.5 2.0 2.5 3.5 ?0 ?0 ?0 0 bw1 bw2 2.6khz standard 1% resistor values r11 = 165k r31 = 143k r h 1 = 10k r22 = 20k r42 = 15.4k r l 2 = 10k r33 = 169k r21 = 10k r41 = 13k r l 1 = 10.5k r32 = 221k r h 2 = 10.5k r23 = 84.5k notes: use a 15pf capacitor between pins 17 and 18. pin 7 is grounded. v s = 5v f clk = 260khz
11 ltc1061 figure 17. measured amplitude response of the topology of figure 16, configured to provide a 6th order elliptic highpass filter operating with a clock-to-cutoff frequency ratio of 250:1. odes of operatio w u figure 15. resistor values and amplitude response of the topology of figure 12. passive ladder filters provide enough data to synthesize the above filters. the measured amplitude response of such a lowpass is shown in figure 15 where the filter output is taken out of side as pin 1, figure 12. the clock- to-center frequency ratio can be either 50:1 or 100:1 because the last stage of the ltc1061 operates in mode 1 with a center frequency very close to the overall cutoff frequency of the lowpass filter. in figure 16, all three sides of the ltc1061 are connected in mode 3a. this topology is useful for elliptic highpass and notch filters with clock-to-cutoff (or notch) frequency ratio higher than 100:1. this is often required to extend the allowed input signal frequency range and to avoid prema- ture aliasing. figure 16 is also a versatile, general purpose architecture providing 3 notches and 4 pole pairs, and there is no restriction on the location of the poles with respect to the notch frequencies. the drawbacks, when compared to figure 12, are the use of an external op amp and the increased number of the required external resis- tors. figure 17 shows the measured frequency of a 6th order highpass elliptic filter operating with 250:1 clock-to-cutoff frequency ratio. with a 1mhz clock, for instance, the filter yields a 4khz cutoff frequency, thus allowing an input frequency range beyond 100khz. band limiting can be easily added by placing a capacitor across the feedback resistor of the external op amp of figure 16. f in (khz) 1 v out /v in (db) ?0 9 1061 f15 ?0 ?0 ?0 3 5 7 0 ?0 ?0 ?0 0 ?0 ?0 2 4 6810 standard 1% resistor values r11 = 39.2k r31 = 13.7k r h 1 = 20.5k r22 = 10k r42 = 14k r l 2 = 11.8k r33 = 100k r21 = 10k r41 = 39.2k r l 1 = 12.4k r32 = 26.7k r h 2 = 32.4k r23 = 10k notes: use a 10pf across r42 for f clk > 1mhz. the elliptic lowpass filter has only two notches in the stopband, and it operates with a clock to cutoff frequency ratio of 50:1. 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 v in ltc1061 f16 ltc1061 r h 2 r43 r33 t 2 l l , cmos clock input v v + r l 2 r32 r22 r42 r31 r41 r l 1 r21 r11 r h 1 r l 3 r h 3 r23 + v out r g lt1056 f in (khz) 0 v out /v in (db) ?0 2.0 1061 f17 ?0 ?0 ?0 0.5 1.0 1.5 2.5 ?0 ?0 ?0 0 ?0 ?0 f clk = 250khz r11 = 105k r31 = 47.5k r h 1 = 10k r22 = 32.4k r42 = 52.3k r l 2 = 750k r33 = 255k r h 3 = 10k r g = 140k r21 = 10k r41 = 45.3k r l 1 = 1.07m r32 = 28.7k r h 2 = 42.2k r23 = 10k r43 = 63.4k r l 3 = 110k note: for clock frequencies below 500khz, use a capaci- tor in parallel with r21 such as (1/2 p r21c) @ f clk /3. standard 1% resistor values figure 16. using an external op amp to connect all 3 sides of the ltc1061 in mode 3a.
12 ltc1061 odes of operatio w u mode 2 C this is a combination of mode 1 and mode 3, figure 20. with mode 2, the clock-to-center frequency ratio, f clk /f o , is always less than 50:1 or 100:1. when compared to mode 3 and for applications requiring 2nd order section with f clk /f o slightly less than 100 or 50:1, mode 2 provides less sensitivity to resistor tolerances. as in mode 1, mode 2 has a notch output which directly depends on the clock frequency and therefore the notch frequency is always less than the center frequency, f o , of the 2nd order section. f in (khz) 1 0 v out /v in (db) ?0 ?0 ?0 ?0 10 100 1061 f19 ?0 ?0 ?0 ?0 ?0 4 standard 1% resistor values r11 = 30.9k r31 = 16.2k r h 1 = 45.3k r22 = 10.5k r42 = 10k r l 2 = 15.8k r33 = 28.7k r h 3 = 95.3k r g = 28k r21 = 10k r41 = 26.7k r l 1 = 19.6k r32 = 100k r h 2 = 52.3k r23 = 10k r43 = 12.7k r l 3 = 10k note: add a capacitor c across r g to create a 7th order lowpass such as (1/2 p r g c) = (cutoff frequency) 0.38 f clk 200khz f clk 500khz f clk 1mhz figure 18 shows the plotted amplitude responses of a 6th order notch filter operating again with a clock-to-center notch frequency ratio of 250:1. the theoretical notch depth is 70db and when the notch is centered at 1khz its width is 50hz. two small, noncritical capacitors were used across the r21 and r22 resistors of figure 16, to band- limit the first two highpass outputs such that the practical notch depth will approach the theoretical value. with these two fixed capacitors, the notch frequency can be swept within a 3:1 range. when the circuit of figure 16 is used to realize lowpass elliptic filters, a capacitor across r g raises the order of the filter and at the same time eliminates any small clock feedthrough. this is shown in figure 19 where the ampli- tude response of the filter is plotted for 3 different cutoff frequencies. when the clock frequency equals or exceeds 1mhz, the stopband notches lose their depth due to the finite bandwidth of the internal op amps and to the small crosstalk between the different sides of the ltc1061. the lowpass filter, however, does not lose its passband accu- racy and it maintains nearly all of its attenuation slope. the theoretical performance of the 7th order lowpass filter of figure 19 is 0.2db passband ripple, 1.5:1 stopband-to- cutoff frequency ratio, and 73db stopband attenuation. without any tuning, the obtained results closely approxi- mate the textbook response. f in (khz) 0 v out /v in (db) ?0 1.6 1061 f18 ?0 ?0 ?0 0.2 0.8 1.2 2.0 ?0 ?0 ?0 0 f clk = 250khz 0.4 0.6 1.0 1.4 1.8 standard 1% resistor values r11 = 84.5k r31 = 31.6k r h 1 = 48.7k r22 = 10k r42 = 97.6k r l 2 = 66.5k r33 = 300k r h 3 = 10.2k r g = 210k r21 = 10.2k r41 = 63.4k r l 1 = 287k r32 = 232k r h 2 = 10.2k r23 = 20k r43 = 80.6k r l 3 = 63.4k note: connect 39pf and 100pf across r21 and r22 respectively. figure 19. frequency responses of a 7th order lowpass elliptic filter realized with figure 16 topology. + s agnd r1 n bp lp v in 1061 f20 + s r2 r3 r4 f o = ; f n = ; q = h olp = ; h obp = ? h on1 (f ? 0) = ; h on2 = ? f clk 100(50) r2 r1 r3 r2 r2/r1 1 + (r2/r4) r3 r1 f clk 2 f ? () ? 1 + r2 r4 f clk 100(50) ? 1 + r2 r4 r2/r1 1 + (r2/r4) figure 18. 6th order band reject filter operating with a clock- to-center notch frequency ratio of 250:1. the ratio of 0db to the C 65db notch width is 8:1. figure 20. mode 2: 2nd order filter providing notch, bandpass, lowpass.
13 ltc1061 odes of operatio w u higher frequency notch provided by the side a of the ltc1061. as shown in figure 22, the highpass corner frequency is 3.93khz and the higher notch frequency is 3khz while the filter operates with a 300khz clock. the center frequencies, qs, and notches of figure 22, when normalized to the highpass cutoff frequency, are (f o1 = 1.17, q1 = 2.24, f n1 = 0.242, f o2 = 1.96, q2 = 0.7, f n2 = 0.6, f o3 = 0.987, f n3 = 0.753, q3 = 10). when compared with the topology of figure 16, this approach uses lower and more restricted clock frequencies. the obtained notch in mode 2 is shallower although the topology is more efficient. output noise the wideband rms noise of the ltc1061 outputs is nearly independent from the clock frequency. the ltc1061 noise when operating with 2.5v supply is lower, as table 3 indicates. the noise at the bandpass and lowpass outputs increases rough as the ? q. also the noise in- creases when the clock-to-center frequency ratio is al- tered with external resistors to exceed the internally set 100:1 or 50:1 ratios. under this condition, the noise increases square root-wise. output offsets the equivalent input offsets of the ltc1061 are shown in figure 23. the dc offset at the filter bandpass output is always equal to v os3 . the dc offsets at the remaining two outputs (notch and lp) depend on the mode of operation and external resistor ratios. table 4 illustrates this. it is important to know the value of the dc output offsets, especially when the filter handles input signals with large dynamic range. as a rule of thumb, the output dc offsets increase when: 1. the qs decrease 2. the ratio (f clk /f o ) increases beyond 100:1. this is done by decreasing either the (r2/r4) or the r6/(r5 + r6) resistor ratios. figure 21 shows the side a of the ltc1061 connected in mode 2 while sides b and c are in mode 3a. this topology can be used to synthesize elliptic bandpass, highpass and notch filters. the elliptic highpass of figure 17 is synthe- sized again, figure 22, but the clock is now locked onto the figure 22. 6th order elliptic highpass filter operating with a clock-to-cutoff frequency ratio of 75:1, and using the topology of figure 21. f in (khz) 1 v out /v in (db) ?0 9 1061 f22 ?0 ?0 ?0 3 5 7 0 ?0 ?0 ?0 0 ?0 ?0 2 4 6810 standard 1% resistor values r11 = 54.9k r31 = 34.8k r h 1 = 28.7k r22 = 68.1k r42 = 10k r l 2 = 16.2k r33 = 75k r21 = 24.3k r41 = 10k r l 1 = 280k r32 = 18.2k r h 2 = 10.2k r23 = 10k r43 = 14k note: for clock frequen- cies above 300khz, add a capacitor c across r21 and r22 such as (1/2 p r21c) = f clk 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 v in ltc1061 f21 ltc1061 r h 2 r43 r33 t 2 l, cmos clock input v v + r l 2 r32 r22 r42 r31 r41 r l 1 r21 r11 r h 1 r23 v out figure 21. ltc1061 with side a is connected in mode 2 while side b, c are in mode 3a. topology is useful for elliptic highpass, notch and bandpass filters.
14 ltc1061 odes of operatio w u notch/hp bp lp v s ( v) f clk/ f o ( m v rms )( m v rms )( m v rms ) conditions 5.0 50:1 45 55 70 mode 1, r1 = r2 = r3 5.0 100:1 65 65 85 q = 1 2.5 50:1 30 30 45 2.5 100:1 40 40 60 5.0 50:1 18 150 150 mode 1, q = 10 5.0 100:1 20 200 200 r1 = r3 for bp out 2.5 50:1 15 100 100 r1 = r2 for lp out 2.5 100:1 17 140 140 5.0 50:1 57 57 62 mode 3, r1 = r2 = r3 = r4 5.0 100:1 72 72 80 q = 1 2.5 50:1 40 40 42 2.5 100:1 50 50 53 5.0 50:1 135 120 140 mode 3, r2 = r4, q = 10 5.0 100:1 170 160 185 r3 = r1 for bp out 2.5 50:1 100 88 100 r4 = r1 for lp and hp out 2.5 100:1 125 115 130 table 3. wideband rms noise figure 23. equivalent input offsets of 1/3 ltc1061 filter building block. + 1061 f23 + v os2 v os1 s (12,18) 3 5 + + v os3 2 + + 1 6 (13,19) (14,20) (11,17) + 4 v osn v osbp v oslp mode pin 3 (18) pin 2 (19) pin 1 (20) 1v os1 [(1/q) + 1 + || h olp ||] C v os3 /q v os3 v osn C v os2 1b v os1 [(1/q) + 1 + r2/r1] C v os3 /q v os3 ~(v osn C v os2 )(1 + r5/r6) 2[v os1 (1 + r2/r1 + r2/r3 + r2/r4) C v os3 (r2/r3)] v os3 v osn C v os2 [r4/(r2 + r4)] + v os2 [r2/(r2 + r4)] 3v os2 v os3 v os1 (1 + r4/r1 + r4/r2 + r4/r3) C v os2 (r4/r2) C v os3 (r4/r3) table 4
15 ltc1061 package descriptio u n package 20-lead plastic dip j package 20-lead ceramic dip s package 20-lead plastic sol 0.015 (0.381) min 0.125 (3.175) min 0.130 ?0.005 (3.302 ?0.127) 0.065 (1.651) typ 0.045 ?0.065 (1.143 ?1.651) 0.018 ?0.003 (0.457 ?0.076) 0.065 ?0.015 (1.651 ?0.381) 0.100 ?0.010 (2.540 ?0.254) 0.260 ?0.010 (6.604 ?0.254) 1.040 (26.416) max 12 3 4 5 6 7 8 910 19 11 12 13 14 16 15 17 18 20 0.009 ?0.015 (0.229 ?0.381) 0.300 ?0.325 (7.620 ?8.255) 0.325 +0.025 0.015 +0.635 0.381 8.255 () 3 7 56 10 9 1 4 2 8 11 20 16 15 17 14 13 12 19 18 0.005 (0.127) min 0.025 (0.635) rad typ 0.220 ?0.310 (5.588 ?7.874) 1.060 (26.924) max 0.290 ?0.320 (7.366 ?8.128) 0??15 0.008 ?0.018 (0.203 ?0.457) 0.385 ?0.025 (9.779 ?0.635) 0.015 ?0.060 (0.381 ?1.524) 0.160 (4.064) max 0.125 (3.175) min 0.080 (2.032) typ 0.014 ?0.026 (0.356 ?0.660) 0.038 ?0.068 (0.965 ?1.727) 0.100 ?0.010 (2.540 ?0.254) 0.200 (5.080) max note: pin 1 ident, notch on top and cavities on the bottom of packages are the manufacturing options. the part may be supplied with or without any of the options. see note 0.496 ?0.512 (12.598 ?13.005) 20 19 18 17 16 15 14 13 1 23 4 5 6 78 0.394 ?0.419 (10.007 ?10.643) 910 11 12 0.037 ?0.045 (0.940 ?1.143) 0.004 ?0.012 (0.102 ?0.305) 0.093 ?0.104 (2.362 ?2.642) 0.050 (1.270) typ 0.014 ?0.019 (0.356 ?0.482) typ 0??8?typ see note 0.009 ?0.013 (0.229 ?0.330) 0.016 ?0.050 (0.406 ?1.270) 0.291 ?0.299 (7.391 ?7.595) 45 0.010 ?0.029 (0.254 ?0.737) 0.005 (0.127) rad min dimensions in inches (millimeters) unless otherwise noted. 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.
16 ltc1061 linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7487 (408) 432-1900 l fax : (408) 434-0507 l telex : 499-3977 ? linear technology corporation 1994 lt/gp 0294 2k rev c northeast region linear technology corporation one oxford valley 2300 e. lincoln hwy.,suite 306 langhorne, pa 19047 phone: (215) 757-8578 fax: (215) 757-5631 linear technology corporation 266 lowell st., suite b-8 wilmington, ma 01887 phone: (508) 658-3881 fax: (508) 658-2701 u.s. area sales offices southeast region linear technology corporation 17060 dallas parkway suite 208 dallas, tx 75248 phone: (214) 733-3071 fax: (214) 380-5138 central region linear technology corporation chesapeake square 229 mitchell court, suite a-25 addison, il 60101 phone: (708) 620-6910 fax: (708) 620-6977 southwest region linear technology corporation 22141 ventura blvd. suite 206 woodland hills, ca 91364 phone: (818) 703-0835 fax: (818) 703-0517 northwest region linear technology corporation 782 sycamore dr. milpitas, ca 95035 phone: (408) 428-2050 fax: (408) 432-6331 france linear technology s.a.r.l. immeuble "le quartz" 58 chemin de la justice 92290 chatenay malabry france phone: 33-1-41079555 fax: 33-1-46314613 germany linear techonolgy gmbh untere hauptstr. 9 d-85386 eching germany phone: 49-89-3197410 fax: 49-89-3194821 japan linear technology kk 5f yz bldg. 4-4-12 iidabashi, chiyoda-ku tokyo, 102 japan phone: 81-3-3237-7891 fax: 81-3-3237-8010 taiwan linear technology corporation rm. 801, no. 46, sec. 2 chung shan n. rd. taipei, taiwan, r.o.c. phone: 886-2-521-7575 fax: 886-2-562-2285 united kingdom linear technology (uk) ltd. the coliseum, riverside way camberley, surrey gu15 3yl united kingdom phone: 44-276-677676 fax: 44-276-64851 international sales offices korea linear technology korea branch namsong building, #505 itaewon-dong 260-199 yongsan-ku, seoul korea phone: 82-2-792-1617 fax: 82-2-792-1619 singapore linear technology pte. ltd. 101 boon keng road #02-15 kallang ind. estates singapore 1233 phone: 65-293-5322 fax: 65-292-0398 world headquarters linear technology corporation 1630 mccarthy blvd. milpitas, ca 95035-7487 phone: (408) 432-1900 fax: (408) 434-0507

▲Up To Search▲

Price & Availability of LTC1061AM

	To Download LTC1061AM Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .