LTC69-7 Linear Phase 8th Order Lowpass Fiter FEATURES n 8th Order, Linear Phase Fiter in SO-8 Package n Raised Cosine Ampitude Response n 43 Attenuation at 2 f CUTOFF n Wideband Noise: 4μV RMS n Operates from Singe 5V Suppy to ±5V Power Suppies n Cock-Tunabe to 2kHz with ±5V Suppies n Cock-Tunabe to 2kHz with Singe 5V Suppy APPLICATIONS n Digita Communication Fiter n Antiaiasing Fiter with Linear Phase n Smoothing Fiters DESCRIPTION The LTC 69-7 is a monoithic, cock-tunabe, inear phase, 8th order owpass fiter. The ampitude response of the fi ter approximates a raised cosine fi ter with an apha of one. The gain at the cutoff frequency is 3 and the attenuation at twice the cutoff frequency is 43. The cutoff frequency of the LTC69-7 is set by an externa cock and is equa to the cock frequency divided by 25. The ratio of the interna samping frequency to the cutoff frequency is 5: that is, the input signa is samped twice per cock cyce to ower the risk of aiasing. The LTC69-7 can be operated from a singe 5V suppy up to dua ±5V suppies. The gain and phase response of the LTC69-7 can be used in digita communication systems where puse shaping and channe bandwidth imiting must be carried out. Any system that requires an anaog fiter with inear phase and sharper ro off than conventiona Besse fiters can use the LTC69-7. The LTC69-7 has a wide dynamic range. With ±5V suppies and an input range of.v RMS to 2V RMS, the signa-to-(noise + THD) ratio is 6. The wideband noise of the LTC69-7 is 4μV RMS. Unike other LTC69-X fiters, the typica passband gain of the LTC69-7 is equa to V/V. The LTC69-7 is avaiabe in an SO-8 package. Other fiter responses with ower power/speed specifications can be obtained. Pease contact LTC Marketing. L, LT, LTC and LTM are registered trademarks of Linear Technoogy Corporation. TYPICAL APPLICATION Singe 5V Suppy, Linear Phase khz Lowpass Fiter Frequency Response.47μF.μF 5V V IN AGND V OUT V + V LTC69-7 NC NC V IN CLK V OUT 69-7 TA GAIN () 2 3 4 5 6 7 69-7 TA2 697fa
LTC69-7 ABSOLUTE MAXIMUM RATINGS Tota Suppy Votage (V + to V )... 2V Power Dissipation... 4mW Operating Temperature Range LTC69-7C... C to 7 C LTC69-7I... 4 C to 85 C Storage Temperature... 65 C to 5 C Lead Temperature (Sodering, sec)... 3 C PIN CONFIGURATION AGND V + 2 NC 3 V IN 4 TOP VIEW 8 7 6 5 S8 PACKAGE 8-LEAD PLASTIC SO T JMAX = 25 C, θ JA = 3 C/W V OUT V NC CLK ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC69-7CS8#PBF LTC69-7CS8#TRPBF 697 8-Lead Pastic SO C to 7 C LTC69-7IS8#PBF LTC69-7IS8#TRPBF 697I 8-Lead Pastic SO 4 C to 85 C Consut LTC Marketing for parts specifi ed with wider operating temperature ranges. Consut LTC Marketing for information on non-standard ead based fi nish parts. For more information on ead free part marking, go to: http://www.inear.com/eadfree/ For more information on tape and ree specifications, go to: http://www.inear.com/tapeandree/ ELECTRICAL CHARACTERISTICS The denotes specifi cations which appy over the fu operating temperature range. f CUTOFF is the fi ter s cutoff frequency and is equa to f CLK /25. The f CLK signa eve is TTL or CMOS (max cock rise or fa time μs), R L = k, T A = 25 C, uness otherwise specifi ed. A AC gains are measured reative to the passband gain. SYMBOL CONDITIONS MIN TYP MAX UNITS Passband Gain (f IN.2f CUTOFF ) Gain at.25f CUTOFF Gain at.5f CUTOFF Gain at.75f CUTOFF Gain at f CUTOFF, f TEST = khz, V IN = V RMS V S = 4.75V, f CLK = 5kHz f TEST = khz, V IN =.5V RMS, f TEST = 25kHz, V IN = V RMS.55 V S = 4.75V, f CLK = 5kHz f TEST = 5kHz, V IN =.5V RMS.3, f TEST = 5kHz, V IN = V RMS.4 V S = 4.75V, f CLK = 5kHz f TEST = khz, V IN =.5V RMS.6, f TEST = 75kHz, V IN = V RMS 2. V S = 4.75V, f CLK = 5kHz f TEST = 5kHz, V IN =.5V RMS.5, f TEST = khz, V IN = V RMS 4. V S = 4.75V, f CLK = 5kHz f TEST = 2kHz, V IN =.5V RMS 3.3. ±.75 ±.9. ±.75 ±.9.3..5.5..35.3.65.8.75.25 3.5 2.7 2.9 2.4 2 697fa
LTC69-7 ELECTRICAL CHARACTERISTICS The denotes specifi cations which appy over the fu operating temperature range. f CUTOFF is the fi ter s cutoff frequency and is equa to f CLK /25. The f CLK signa eve is TTL or CMOS (max cock rise or fa time μs), R L = k, T A = 25 C, uness otherwise specifi ed. A AC gains are measured reative to the passband gain. SYMBOL CONDITIONS MIN TYP MAX UNITS Gain at.5f CUTOFF Gain at 2.f CUTOFF Gain at 5.f CUTOFF Gain at f CUTOFF (6kHz) Phase at.5f CUTOFF Phase at f CUTOFF Passband Phase Deviation from Linear Phase (Note ) Output DC Offset (Input at GND) Output Votage Swing Power Suppy Current, f TEST = 5kHz, V IN = V RMS 9 V S = 4.75V, f CLK = 5kHz f TEST = 3kHz, V IN =.5V RMS 2, f TEST = 2kHz, V IN = V RMS 55 V S = 4.75V, f CLK = 5kHz f TEST = 4kHz, V IN =.5V RMS 48 6.5 8. V S = 4.75V, f CLK = 5kHz f TEST = khz, V IN =.5V RMS 7 59 55, f CLK = 4MHz 2. f TEST = 6kHz, V IN = V RMS, 35 3.5 25 Deg f TEST = 5kHz, 24 235 23 Deg f TEST = khz, f CLK = 5kHz 3. Deg, f CLK = 5kHz V S = 4.75V, f CLK = 4kHz, I SOURCE /I SINK ma, R L = k V S = 4.75V, I SOURCE /I SINK ma, R L = k, f CLK = 5kHz V S = 4.75V, f CLK = 4kHz ±3.5 2.6 43 4 4 7 38 39 5 25 25 ±4. 3.6 8 26 29 3 5 6.5 mv mv V V P-P ma ma ma ma Note : Stresses beyond those isted under Absoute Maximum Ratings may cause permanent damage to the device. Exposure to any Absoute Maximum Rating condition for extended periods may affect device reiabiity and ifetime. Note 2: Phase Deviation = /2(Phase at Hz Phase at f CUTOFF ) (Phase at Hz Phase at.5f CUTOFF ) Phase at Hz = 8 (guaranteed by design) Exampe: An LTC69-7 has Phase at.5f CUTOFF = 3.5 and Phase at f CUTOFF = 235. Passband Phase Deviation from Linear Phase = /2[8 ( 235 )] [(8 ( 3.5 )] = 3 697fa 3
LTC69-7 TYPICAL PERFORMANCE CHARACTERISTICS GAIN ()..5.5..5 2. 2.5 3. 3.5 4. Passband Gain vs Frequency f CLK = 5kHz f C = 2kHz V IN = 2V RMS 3 5 7 9 3 5 7 9 2 69-7 G GAIN () 2 3 4 Transition Band Gain vs Frequency f CLK = 5kHz f C = 2kHz V IN = 2V RMS 5 2 23 25 27 29 3 33 35 37 39 4 69-7 G2 GAIN () 4 42 44 46 48 5 52 54 56 58 Stopband Gain vs Frequency f CLK = 5kHz f C = 2kHz V IN = 2V RMS 6 4 45 49 53 57 6 65 69 73 77 8 69-7 G3 GAIN () 2 3 4 5 6 Gain vs Frequency f CLK = 25kHz f C = khz V IN = V RMS GAIN () 3 3 6 9 2 5 8 2 Passband Gain vs Cock Frequency V IN = 2V RMS f CLK = 4.5MHz f CLK = 4MHz f CLK = 3.5MHz f CLK = 3MHz f CLK = 5MHz 4 6 8 2 4 6 8 2 GAIN ()..5.5..5 2. 2.5 3. 3.5 4. Passband Gain vs Frequency T A = 4 C T A = 85 C T A = 25 C f CLK = 4MHz f C = 6kHz V IN = 2V RMS 4 7 3 6 69-7 G4 69-7 G5 69-7 G6 GAIN () 2 3 4 5 Gain vs Suppy Votage f CLK = 2MHz f C = 8kHz V IN =.5V RMS 6 3 5 7 9 3 5 7 9 2 69-7 G7 GAIN () 3 3 6 9 2 5 8 2 Passband Gain vs Cock Frequency f CLK = 2MHz f CLK =.5MHz V IN = V RMS f CLK = 3MHz 4 6 8 2 4 6 8 2 69-7 G8 GAIN ()..5.5..5 2. 2.5 3. 3.5 4. Passband Gain vs Frequency f C = khz V IN = V RMS T A = 4 C T A = 25 C T A = 85 C 2 3 4 5 6 7 8 9 69-7 G9 4 697fa
TYPICAL PERFORMANCE CHARACTERISTICS LTC69-7 2 Passband Gain and Phase vs Frequency f C = khz 8 35 9 2 Passband Gain and Deay vs Frequency f C = khz 3.5 3. GAIN () 2 3 4 5 6 PHASE GAIN 45 45 9 35 8 PHASE (DEG) GAIN () 2 3 4 5 6 DELAY GAIN 2.5 2..5 DELAY (μs) 7 225 7 8 27 2 3 4 5 6 7 8 9 8. 2 3 4 5 6 7 8 9 69-7 G 69-7 G2 PHASE DIFFERENCE (DEG) 2.5 2.25 2..75.5.25. Phase Matching vs Frequency THD + Noise vs Input (V P-P ) THD + Noise vs Frequency 7 C 25 C.75 f CLK 2.5MHz.5 PHASE DIFFERENCE BETWEEN.25 ANY TWO UNITS (SAMPLE OF 2 REPRESENTATIVE UNITS)..2.3.4.5.6.7.8.9. FREQUENCY (f CUTOFF /FREQUENCY) 69-7 G THD + NOISE () 4 45 5 55 6 65 7 75. f CLK = MHz f C = 4kHz f IN = khz INPUT (V P-P ) 69-7 G3 THD + NOISE () 4 45 5 55 6 65 7 75 8 f C = khz, V IN = V P-P, V IN = 2V P-P 69-7 G4 Transient Response Output Offset vs Cock Frequency 4.3 Output Votage Swing vs Temperature V/DIV.ms/DIV f CLK = 5kHz f CUTOFF = 2kHz V IN = 4V P-P SQUARE WAVE AT khz 69-7 G5 OUTPUT OFFSET (mv) 5 2 25 3 35 4 45 5.25.25 2.25 3.25 4.25 5.25 CLOCK FREQUENCY (MHz) VOLTAGE SWING (V) 4.2 4..2.. 4 (AGND AT 2.5V) f CLK = 5kHz f CUTOFF = 2kHz R L = k I SOURCE /I SINK ma 2 2 4 6 8 TEMPERATURE ( C) 69-7 G6 69-7 G7 697fa 5
LTC69-7 TYPICAL PERFORMANCE CHARACTERISTICS VOLTAGE SWING (V) 4.2 4. 4. 4.5 4.6 4.7 4 Output Votage Swing vs Temperature f CUTOFF = khz R L = k I SOURCE /I SINK = ma 2 2 4 6 8 TEMPERATURE ( C) SUPPLY CURRENT (ma) 25 2 5 5 Suppy Current vs Suppy Votage f CLK = Hz 25 C 85 C 4 C 2 3 4 5 6 SUPPLY VOLTAGE (±V) SUPPLY CURRENT (ma) 22 2 2 9 8 7 6 5 4 3 2 Suppy Current vs Cock Frequency.25.25 2.25 3.25 4.25 5.25 CLOCK FREQUENCY (MHz) 69-7 G8 69-7 G9 69-7 G2 PIN FUNCTIONS AGND (Pin ): Anaog Ground. The quaity of the anaog signa ground can affect the fiter performance. For either singe or dua suppy operation, an anaog ground pane surrounding the package is recommended. The anaog ground pane shoud be connected to any digita ground at a singe point. For dua suppy operation, Pin shoud be connected to the anaog ground pane. For singe suppy operation, Pin shoud be bypassed to the anaog ground pane with a capacitor.47μf or arger. An interna resistive divider biases Pin to haf the tota power suppy. Pin shoud be buffered if used to bias other ICs. Figure shows the connections for singe suppy operation. V +, V (Pins 2, 7): Power Suppies. The V + (Pin 2) and V (Pin 7) shoud be bypassed with a.μf capacitor to an adequate anaog ground. The fiter s power suppies shoud be isoated from other digita or high votage anaog suppies. A ow noise inear suppy is recommended. Using switching power suppies wi ower the signa-to-noise ratio of the fiter. Unike previous monoithic fi ters, the power suppies can be appied in any order, that is, the positive suppy can be appied before the negative suppy and vice versa. Figure 2 shows the connections for dua suppy operation. 6 NC (Pins 3, 6): No Connection. Pins 3 and 6 are not connected to any interna circuitry; they shoud be tied to ground. V IN (Pin 4): Fiter Input. The fi ter input pin is internay connected to the inverting inputs of two op amps through a 36k resistor for each op amp. This parae combination creates an 8k input impedance. ANALOG GROUND PLANE.47μF V +.μf STAR SYSTEM GROUND V IN 8 AGND V OUT 2 7 V + V 3 LTC69-7 6 NC NC 4 5 V IN CLK DIGITAL GROUND PLANE V OUT k CLOCK SOURCE 69-7 F Figure. Connections for Singe Suppy Operation 697fa
LTC69-7 PIN FUNCTIONS ANALOG GROUND PLANE V +.μf STAR SYSTEM GROUND V IN 2 3 4 AGND V OUT V + V LTC69-7 NC NC V IN CLK 8 7 6 5 DIGITAL GROUND PLANE V OUT.μF k CLOCK SOURCE V a dua or singe suppy operation. A puse generator can be used as a cock source provided the high eve on-time is greater than.42μs (V S = ± 5V). Sine waves ess than khz are not recommended for cock sources because excessive sow cock rise or fa times generate interna cock jitter. The maximum cock rise or fa time is μs. The cock signa shoud be routed from the right side of the IC package to avoid couping into any input or output anaog signa path. A k resistor between the cock source and the cock input (Pin 5) wi sow down the rise and fa times of the cock to further reduce charge couping, Figure. Figure 2. Connections for Dua Suppy Operation 69 F2 CLK (Pin 5): Cock Input. Any TTL or CMOS cock source with a square wave output and 5% duty cyce (±%) is an adequate cock source for the device. The power suppy for the cock source shoud not necessariy be the fi ter s power suppy. The anaog ground of the fi ter shoud ony be connected to the cock s ground at a singe point. Tabe shows the cock s ow and high eve threshod vaue for Tabe. Cock Source High and Low Threshods POWER SUPPLY HIGH LEVEL LOW LEVEL Dua Suppy = ±5V.5V.5V Singe Suppy = V 6.5V 5.5V Singe Suppy = 5V.5V.5V V OUT (Pin 8): Fiter Output. Pin 8 is the output of the fiter, and it can source 23mA or sink 6mA. The tota harmonic distortion of the fi ter wi degrade when driving coaxia cabes or oads ess than 2k without an output buffer. APPLICATIONS INFORMATION Temperature Behavior The power suppy current of the LTC69-7 has a positive temperature coefficient. The GBW product of its interna op amps is neary constant and the speed of the device does not degrade at high temperatures. Cock Feedthrough The cock feedthrough is defined as the RMS vaue of the cock frequency and its harmonics that are present at the fiter s output (Pin 8). The cock feedthrough is tested with the input (Pin 4) shorted to the AGND pin and depends on PC board ayout and on the vaue of the power suppies. With proper ayout techniques the vaues of the cock feedthrough are shown on Tabe 2. Tabe 2. Cock Feedthrough V S CLOCK FEEDTHROUGH 5V 4μV RMS ±5V 85μV RMS Any parasitic switching transients during the rising and faing edges of the incoming cock are not part of the cock feedthrough specifications. Switching transients have frequency contents much higher than the appied cock; their ampitude strongy depends on scope probing techniques as we as grounding and power suppy bypassing. The cock feedthrough can be reduced by adding a singe RC owpass fiter at the output (Pin 8) of the LTC69-7. 697fa 7
LTC69-7 APPLICATIONS INFORMATION Wideband Noise The wideband noise of the fiter is the tota RMS vaue of the device s noise spectra density and determines the operating signa-to-noise ratio. Most of the wideband noise frequency contents ie within the fiter passband. The wideband noise cannot be reduced by adding post fitering. The tota wideband noise is neary independent of the cock frequency and depends sighty on the power suppy votage (see Tabe 3). The cock feedthrough specifi cations are not part of the wideband noise. Tabe 3. Wideband Noise V S CLOCK FEEDTHROUGH 4.75V 25μV RMS ±5V 4μV RMS Aiasing Aiasing is an inherent phenomenon of samped data systems and it occurs for input frequencies approaching the samping frequency. The interna samping frequency of the LTC69-7 is 5 times its f CUTOFF frequency. For instance if a 48kHz, mv RMS signa is appied at the input of an LTC69-7 operating with a 5% duty cyce 25kHz cock, a 2kHz, 74μV RMS aias signa wi appear at the fiter output. Tabe 4 shows detais. Tabe 4. Aiasing INPUT FREQUENCY V IN = V RMS OUTPUT LEVEL Reative to Input OUTPUT FREQUENCY Aiased Frequency f CLK /f C = 25:, f CUTOFF = khz 4kHz (or 6kHz) 59.9 khz 47kHz (or 53kHz) 54.2 3kHz 48kHz (or 52kHz) 42.6 2kHz 48.5kHz (or 5.5kHz) 8.3.5kHz 49kHz (or 52kHz) 2.9.kHz 49.5kHz (or 5.5kHz).65.5kHz Speed Limitations To avoid op amp sew rate imiting, the signa ampitude shoud be kept beow a specified eve as shown in Tabe 5. Tabe 5. Maximum V IN vs V S and Cock V S MAXIMUM CLOCK MAXIMUM V IN 5V 2.5MHz 34mV RMS (f IN 2kHz) ±5V 4.5MHz.2V RMS (f IN 4kHz) 8 697fa
PACKAGE DESCRIPTION S8 Package 8-Lead Pastic Sma Outine (Narrow.5) (LTC DWG # 5-8-6) LTC69-7.5 BSC.45 ±.5.89.97 (4.8 5.4) NOTE 3 8 7 6 5.245 MIN.6 ±.5.228.244 (5.79 6.97).5.57 (3.8 3.988) NOTE 3.3 ±.5 TYP RECOMMENDED SOLDER PAD LAYOUT 2 3 4.8. (.23.254)..2 45 (.254.58) 8 TYP.53.69 (.346.752).4. (..254).6.5 (.46.27) NOTE: INCHES. DIMENSIONS IN (MILLIMETERS).4.9 (.355.483) TYP 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED.6" (.5mm).5 (.27) BSC SO8 33 697fa 9
LTC69-7 TYPICAL APPLICATION Cock Tunabe, Noninverting, Linear Phase 8th Order Fiter to 2kHz f CUTOFF 5pF k 5V.μF 5V AGND V OUT V + V LTC69-7 NC NC 5V μf.μf k + LT 354 5V.μF.μF V OUT V IN V IN CLK f CLK 5MHz 69-7 TA3 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC64-3 Linear Phase, Besse 8th Order Fiter f CLK /f C = 75/ or 5/, Very Low Noise LTC64-7 Linear Phase, 8th Order Lowpass Fiter f CLK /f C = 5/ or /, f C(MAX) = khz LTC64-7 Low Power, Linear Phase Lowpass Fiter f CLK /f C = 5/ or /, I S = 2.5mA, LTC264-7 Linear Phase 8th Order Lowpass Fiter f CLK /f C = 25/ or 5/, f C(MAX) = 2kHz LTC 39 REV A PRINTED IN USA Linear Technoogy Corporation 63 McCarthy Bvd., Mipitas, CA 9535-747 (48) 432-9 FAX: (48) 434-57 www.inear.com LINEAR TECHNOLOGY CORPORATION 28 697fa