LTC1164-5

FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ LTC1164-5 Low Power 8th Order Pin Selectable Butterworth or Bessel Lowpass Filter DESCRIPTIO The LTC®1164-5 is a monolithic 8th order filter; it approximates either a Butterworth or a Bessel lowpass response. The LTC1164-5 features clock-tunable cutoff frequency and low power consumption (4.5mA with ± 5V supplies and 2.5mA with single 5V supply). Low power operation is achieved without compromising noise or distortion performance. With ± 5V supplies and 10kHz cutoff frequency, the operating signal-to-noise ratio is 86dB and the THD throughout the passband is 0.015%. Under the same conditions, a 77dB signal-tonoise ratio and distortion is obtained with a single 5V supply while the clock feedthrough is kept below the noise level. The maximum signal-to-noise ratio is 92dB. The LTC1164-5 approximates an 8th order Butterworth response with a clock-to-cutoff frequency ratio of 100:1 (Pin 10 to V –) or 50:1 double-sampled (Pin 10 to V + and Pin 1 shorted to Pin 13). Double-sampling allows the input signal frequency to reach the clock frequency before any aliasing occurrence. An 8th order Bessel response can also be approximated with a clock-to-cutoff frequency ratio of 140:1 (Pin 10 to ground). With ± 7.5V supply, ± 5V supply and single 5V supply, the maximum clock frequency of the LTC1164-5 is 1.5MHz, 1MHz and 1MHz respectively. The LTC1164-5 is pin-compatible with the LTC1064-2 and LTC-1064-3. Pin Selectable Butterworth or Bessel Response 4mA Supply Current with ± 5V Supplies fCUTOFF up to 20kHz 100µVRMS Wideband Noise THD < 0.02% (50:1, VS = ± 7.5V, VIN = 2VRMS) Operates with a Single 5V Supply (1VRMS Input Range) 60µVRMS Clock Feedthrough (Single 5V Supply) Operates up to ± 8V Supplies TTL/CMOS-Compatible Clock Input No External Components Available in 14-Pin DIP and 16-Pin SO Wide Packages APPLICATIO S ■ ■ ■ ■ Anti-Aliasing Filters Battery-Operated Instruments Telecommunications Filters Smoothing Filters , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 1 VIN 2 3 8V 4 5 NC 6 7 LTC1164-5 14 13 12 11 10 9 8 Butterworth 20kHz Anti-Aliasing Filter –8V CLK = 1MHz TO V + VOUT 1164-5 TA01 WIDEBAND NOISE = 110µVRMS THD IN PASSBAND < 0.02% AT VIN = 2VRMS NOTE: THE CONNECTION FROM PIN 7 TO PIN 14 SHOULD BE MADE UNDER THE PACKAGE. FOR 50:1 OPERATION CONNECT PIN 1 TO PIN 13 AS SHOWN. FOR 100:1 OR 150:1 OPERATION PINS 1 AND 13 SHOULD FLOAT. THE POWER SUPPLIES SHOULD BE BYPASSED BY A 0.1µF CAPACITOR AS CLOSE TO THE PACKAGE AS POSSIBLE. GAIN (dB) U U U Frequency Response 0 –10 –20 –30 –40 –50 –60 –70 –80 1 10 FREQUENCY (kHz) 100 1164-5 TA02 11645fc 1 LTC1164-5 ABSOLUTE AXI U RATI GS + – Total Supply Voltage (V to V ) ............................. 16V Input Voltage (Note 2) ......... (V ++ 0.3V) to (V – – 0.3V) Output Short-Circuit Duration ......................... Indefinite Power Dissipation ............................................. 400mW Burn-In Voltage ...................................................... 16V PACKAGE/ORDER I FOR ATIO TOP VIEW 50:1 MODE VIN GND V+ GND LP6 CONNECT 1 1 2 3 4 5 6 7 14 CONNECT 2 13 50:1 MODE 12 V – 11 CLK 10 BUTT/BESS 9 8 VOUT NC ORDER PART NUMBER LTC1164-5CN N PACKAGE 14-LEAD PDIP TJMAX = 110°C, θJA = 65°C/W J PACKAGE 14-LEAD CERDIP TJMAX = 110°C, θJA = 65°C/W LTC1164-5CJ LTC1164-5MJ OBSOLETE PACKAGE Consider the N Package as an Alternate Source Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = Operating Temperature Range. VS = ± 7.5V, RL = 10k, fCLK = 400kHz, unless otherwise specified. PARAMETER Passband Gain 0.1Hz at 0.25fCUTOFF (Note 3) Gain at 0.50fCUTOFF (Note 3) Gain at 0.90fCUTOFF (Note 3) Gain at 0.95fCUTOFF (Note 3) Gain at fCUTOFF (Note 3) Gain at 1.44fCUTOFF (Note 3) Gain at 2.0fCUTOFF (Note 3) Gain with fCLK = 20kHz (Note 3) Gain with VS = 2.375V (Note 3) Input Frequency Range CONDITIONS fIN = 1kHz, (fCLK/fC) = 100:1 fIN = 1kHz, (fCLK/fC) = 50:1 fIN = 2kHz, (fCLK/fC) = 100:1 fIN = 4kHz, (fCLK/fC) = 50:1 fIN = 3.6kHz, (fCLK/fC) = 100:1 fIN = 3.8kHz, (fCLK/fC) = 100:1 fIN = 4kHz, (fCLK/fC) = 100:1 fIN = 8kHz, (fCLK/fC) = 50:1 fIN = 5.76kHz, (fCLK/fC) = 100:1 fIN = 8kHz, (fCLK/fC) = 100:1 fIN = 200Hz, (fCLK/fC) = 100:1 fIN = 400kHz, fIN = 2kHz, (fCLK/fC) = 100:1 fIN = 400kHz, fIN = 4kHz, (fCLK/fC) = 100:1 (fCLK/fC) = 100:1 (fCLK/fC) = 50:1 ● ● ● ● ● ● ● ● ● ● ELECTRICAL CHARACTERISTICS 2 U U W WW U W (Note 1) Operating Temperature Range LTC1164-5C ...................................... – 40°C to 85°C LTC1164-5M (OBSOLETE) ............... – 55°C to 125°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C TOP VIEW 50:1 MODE 1 VIN 2 GND 3 V+ 4 GND 5 NC 6 LP6 7 CONNECT 1 8 16 CONNECT 2 15 50:1 MODE 14 V – 13 NC 12 CLK 11 BUTT/BESS 10 NC 9 VOUT ORDER PART NUMBER LTC1164-5CSW SW PACKAGE 16-LEAD PLASTIC SO WIDE TJMAX = 110°C, θJA = 85°C/W MIN – 0.5 – 0.5 – 0.45 – 0.35 – 2.50 – 4.10 – 4.20 – 20.5 – 45.0 – 4.50 – 0.50 – 4.20 TYP – 0.10 0.10 – 0.20 – 0.10 –1.90 – 2.60 – 3.40 – 3.80 –19.0 – 43.0 – 3.40 – 0.10 – 3.40 0 – 6.8V, V – = 0V Single Supply V+ < 6.8V, V – = 0V HIGH LEVEL ≥ V +/3 ≥ V +/3 ≥ V +• 0.65 ≥ V +/3 LOW LEVEL ≤ 0.5V ≤ V – + 0.5V ≤ 0.5V + 1/2V + ≤ 0.5V * 0.1µF VOUT 1164-5 F01 14 13 12 LTC1164-5 Analog Ground (Pins 3, 5) 1k CLOCK SOURCE 11 10 9 8 GND + DIGITAL SUPPLY 1µF VOUT 1164-5 F02 The filter performance depends on the quality of the analog signal ground. For either dual or single 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 dual supply operation, Pins 3 and 5 should be connected to the analog ground plane. For single supply operation Pins 3 and 5 should be biased at 1/2 supply and they should be bypassed to the analog ground plane with at least a 1µF capacitor (Figure 2). For single 5V operation at the highest fCLK of 1MHz, Pins 3 and 5 should be biased at 2V. This minimizes passband gain and phase variations (see Typical Performance Characteristics curves: Maximum Passband for Single 5V, 50:1; and THD + Noise vs RMS Input for Single 5V, 50:1). 11645fc LTC1164-5 PI FU CTIO S Butterworth/Bessel (Pin 10) The DC level at Pin 10 determines the ratio of the clock frequency to the cutoff frequency of the filter. Pin 10 at V + gives a 50:1 ratio and a Butterworth response (pins 1 to 13 are shorted for 50:1 only). Pin 10 at V – gives a 100:1 Butterworth response. Pin 10 at ground gives a Bessel response and a ratio of 140:1. For single supply operation the ratio is 50:1 when Pin 10 is at V + (Pins 1 to 13 shorted), 100:1 when Pin 10 is at ground, and 140:1 when at 1/2 supply. When Pin 10 is not tied to ground, it should be bypassed to analog ground with a 0.1µF capacitor. If the DC level at Pin 10 is switched mechanically or electrically at slew rates greater than 1V/µs while the device is operating, a 10k resistor should be connected between Pin 10 and the DC source. Filter Input (Pin 2) The input pin is connected internally through a 100k resistor tied to the inverting input of an op amp. Filter Output (Pins 9, 6) Pin 9 is the specified output of the filter; it can typically source or sink 1mA. Driving coaxial cables or resistive loads less than 20k will degrade the total harmonic distortion of the filter. When evaluating the device’s distortion an output buffer is required. A noninverting buffer, Figure 3, can be used provided that its input common mode range is well within the filter’s output swing. Pin 6 is an intermediate filter output providing an unspecified 6th order lowpass filter. Pin 6 should not be loaded. Figure 3. Buffer for Filter Output External Connection (Pins 7, 14 and 1, 13) Pins 7 and 14 should be connected together. In a printed circuit board the connection should be done under the IC package through a short trace surrounded by the analog ground plane. When the clock to cutoff frequency ratio is set at 50:1, Pin 1 should be shorted to Pin 13; if not, the passband will exhibit 1dB of gain peaking and it will deviate from a Butterworth response. Pin 1 is the inverting input of an internal op amp and it should preferably be 0.2 inches away from any other circuit trace. NC (Pin 8) Pin 8 is not connected to any internal circuit point on the device and should be preferably tied to analog ground. APPLICATIO S I FOR ATIO Clock Feedthrough Table 2. Output Clock Feedthrough VS ± 2.5V ± 5V ± 7.5V 50:1 60µVRMS 100µVRMS 150µVRMS 100:1 60µVRMS 200µVRMS 500µVRMS Clock feedthrough is defined as, the RMS value of the clock frequency and its harmonics that are present at the filter’s output pin (Pin 9). The clock feedthrough is tested with the input pin (Pin 2) grounded and, it 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. Note: The clock feedthrough at ±2.5V supplies is imbedded in the wideband noise of the filter. The clock waveform is a square wave. + 1k – U W U U U U U LT1056 1164-5 F03 11645fc 9 LTC1164-5 APPLICATIO S I FOR ATIO Any parasitic switching transients during the rise and fall edges of the incoming clock are not part of the clock feedthrough specifications. 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, if bothersome, can be greatly reduced by adding a simple R/C lowpass network at the output of the filter pin (Pin 9). This R/C will completely eliminate any switching transient. Wideband Noise The wideband noise of the filter is the total RMS value of the device’s noise spectral density and it is used to determine the operating signal-to-noise ratio. Most of its frequency contents lie within the filter passband and it cannot be reduced with post filtering. For instance, the LTC1164-5 wideband noise at ± 2.5V supply is 100µVRMS, 95µVRMS of which have frequency contents from DC up to the filter’s cutoff frequency. The total wideband noise (µRMS) is nearly independent of the value of the clock. The clock feedthrough specifications are not part of the wideband noise. Speed Limitations The LTC1164-5 optimizes AC performance versus power consumption. To avoid op amp slew rate limiting at maximum clock frequencies, the signal amplitude should be kept below a specified level as shown in Table 3. Table 3. Maximum VIN vs VS and fCLK POWER SUPPLY VS = ±7.5V VS = ±7.5V VS = ± 5.0V Single 5V MAXIMUM fCLK 1.5MHz 1.0MHz 1.0MHz 1.0MHz MAXIMUM VIN 1VRMS (fIN > 35kHz) 0.5VRMS (fIN > 250kHz) 3VRMS (fIN > 25kHz) 0.7VRMS (fIN > 250kHz) 2.5VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) 0.7VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) LOWPASS FILTER LTC1064-3 Bessel LTC1164-5 Bessel LTC1164-6 Bessel LTC1264-7 Linear Phase LTC1164-7 Linear Phase LTC1064-7 Linear Phase LTC1164-5 Butterworth LTC1164-6 Elliptic LTC1064-4 Elliptic LTC1064-1 Elliptic 10 U Aliasing Aliasing is an inherent phenomenon of sampled data systems and it occurs when input frequencies close to the sampling frequency are applied. For the LTC1164-5 case at 100:1, an input signal whose frequency is in the range of fCLK ± 2.5% will be aliased back into the filter’s passband. If, for instance, an LTC1164-5 operating with a 100kHz clock and 1kHz cutoff frequency receives a 98kHz 10mV input signal, a 2kHz 56µV alias signal will appear at its output. When the LTC1164-5 operates with a clock-tocutoff frequency of 50:1, aliasing occurs at twice the clock frequency. Table 4 shows details. Table 4. Aliasing Data (fCLK = 100kHz, VS = ±5V) INPUT FREQUENCY (VIN = 1VRMS) 97.0kHz 97.5kHz 98.0kHz 98.5kHz 99.0kHz 99.5kHz 197.0kHz 197.5kHz 198.0kHz 198.5kHz 199.0kHz 199.5kHz OUTPUT LEVEL (Relative to Input) –102.0dB – 65.0dB – 45.0dB – 23.0dB – 4.0dB – 0.3dB – 23.0dB –12.0dB – 5.0dB –1.8dB –1.0dB – 0.8dB OUTPUT FREQUENCY (Aliased Frequency) 3.0kHz 2.5kHz 2.0kHz 1.5kHz 1.0kHz 0.5kHz 3.0kHz 2.5kHz 2.0kHz 1.5kHz 1.0kHz 0.5kHz (fCLK/fC) = 100:1, fCUTOFF = 1kHz (fCLK/fC) = 50:1, fCUTOFF = 2kHz W U U Table 5. Transient Response of LTC Lowpass Filters DELAY TIME* (SEC) 0.50/fC 0.43/fC 0.43/fC 1.15/fC 1.20/fC 1.20/fC 0.80/fC 0.85/fC 0.90/fC 0.85/fC RISE TIME** (SEC) 0.34/fC 0.34/fC 0.34/fC 0.36/fC 0.39/fC 0.39/fC 0.48/fC 0.54/fC 0.54/fC 0.54/fC SETTLING TIME*** (SEC) 0.80/fC 0.85/fC 1.15/fC 2.05/fC 2.20/fC 2.20/fC 2.40/fC 4.30/fC 4.50/fC 6.50/fC OVERSHOOT (%) 0.5 0 1 5 5 5 11 18 20 20 * To 50% ± 5%, ** 10% to 90% ± 5%, *** To 1% ± 0.5% 11645fc LTC1164-5 TYPICAL APPLICATIO S Single 5V, IS = 5.2mA, 16th Order Clock-Tunable Lowpass Filter, fCLK/fCUTOFF = 60:1, –75dB Attenuation at 2.3 fCUTOFF 1 VIN 2 3 5V 0.1µF 15k 4 5 6 1µF IC1 LTC1164-5 14 13 12 11 10 9 8 5V 5V 0.1µF 1 2 3 4 5 6 7 IC2 LTC1164-5 14 13 12 11 10 9 8 5V VOUT + 10k Gain vs Frequency 10 0 –10 THD + NOISE (dB) –20 GAIN (dB) –30 –40 –50 –60 –70 –80 –90 1 10 FREQUENCY (kHz) 30 1164-5 • TA03 VS = SINGLE 5V fCLK = 600kHz fCUTOFF = 10kHz U 7 fCLK 1k 1164-5 F04 THD + Noise vs Frequency –40 –45 –50 –55 –60 –65 –70 –75 –80 –85 –90 1 5 FREQUENCY (kHz) 10 1164-5 ¥ TA04 VS = SINGLE 5V VIN = 0.5VRMS fCLK = 600kHz fC = 10kHz 11645fc 11 LTC1164-5 TYPICAL APPLICATIO S 8th Order Butterworth Lowpass Filter fCLK/fC = 50:1 1 VIN V+ 0.1µF 2 3 4 14 13 12 LTC1164-5 11 10 9 8 fCLK V+ VOUT V– 0.1µF 12 U + 5 6 7 1164-5 TA05 8th Order Butterworth Lowpass Filter fCLK/fC = 100:1 1 VIN V+ 0.1µF 2 3 4 14 13 12 LTC1164-5 11 10 9 8 VOUT fCLK V– 0.1µF + 5 6 7 1164-5 TA06 11645fc LTC1164-5 PACKAGE DESCRIPTIO .300 BSC (7.62 BSC) .008 – .018 (0.203 – 0.457) NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS U J Package 14-Lead CERDIP (Narrow 0.300, Hermetic) (LTC DWG # 05-08-1110) .785 (19.939) MAX 14 13 12 11 10 9 8 .005 (0.127) MIN .025 (0.635) RAD TYP .220 – .310 (5.588 – 7.874) 1 2 3 4 5 6 7 .200 (5.080) MAX .015 – .060 (0.381 – 1.524) 0° – 15° .045 – .065 (1.143 – 1.651) .014 – .026 (0.360 – 0.660) .100 (2.54) BSC .125 (3.175) MIN J14 0801 OBSOLETE PACKAGE 11645fc 13 LTC1164-5 PACKAGE DESCRIPTIO .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) +.035 .325 –.015 .005 (0.127) .100 MIN (2.54) BSC ( +0.889 8.255 –0.381 ) INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) NOTE: 1. DIMENSIONS ARE 14 U N Package 14-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) .770* (19.558) MAX 14 13 12 11 10 9 8 .255 ± .015* (6.477 ± 0.381) 1 .130 ± .005 (3.302 ± 0.127) .020 (0.508) MIN 2 3 4 5 6 7 .045 – .065 (1.143 – 1.651) .065 (1.651) TYP .120 (3.048) MIN .018 ± .003 (0.457 ± 0.076) N14 1103 11645fc LTC1164-5 PACKAGE DESCRIPTIO .030 ±.005 TYP N .420 MIN 1 2 3 RECOMMENDED SOLDER PAD LAYOUT 1 .291 – .299 (7.391 – 7.595) NOTE 4 .010 – .029 × 45° (0.254 – 0.737) 0° – 8° TYP .005 (0.127) RAD MIN .009 – .013 (0.229 – 0.330) NOTE 3 .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. 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 4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U SW Package 16-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) .050 BSC .045 ±.005 .398 – .413 (10.109 – 10.490) NOTE 4 16 15 14 13 12 11 10 9 N .325 ±.005 NOTE 3 .394 – .419 (10.007 – 10.643) N/2 N/2 2 3 4 5 6 7 8 .093 – .104 (2.362 – 2.642) .037 – .045 (0.940 – 1.143) .050 (1.270) BSC .004 – .012 (0.102 – 0.305) .014 – .019 (0.356 – 0.482) TYP S16 (WIDE) 0502 11645fc 15 LTC1164-5 TYPICAL APPLICATION 8th Order Linear Phase Lowpass Filter fCLK/fC = 140:1 1 VIN + RELATED PARTS PART NUMBER LTC1069-1 LTC1069-6 DESCRIPTION Low Power, 8th Order Elliptic Lowpass Filter Very Low Power, 8th Order Elliptic Lowpass Filter COMMENTS Operates from a Single 3.3V to ± 5V Supply Optimized for 3V/5V Single Supply Operation, Consumes 1mA at 3V 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● U 14 13 12 LTC1164-5 11 10 9 8 VOUT fCLK V– 0.1µF 2 3 V 0.1µF 4 5 6 7 1164-5 TA07 11645fc LT/LT 0805 REV C • PRINTED IN USA www.linear.com © LINEAR TECHNOLOGY CORPORATION 1993