DESCRIPTION TYPICAL APPLICATION. LTC Ultraselective, Low Power 8th Order Elliptic Bandpass Filter with Adjustable Gain FEATURES APPLICATIONS

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1 FOR INFORMATION PRPOSES ONLY OBSOLETE: Contact Linear Technology for Potential Replacement FEATRES ltraselectivity (db Attenuation at ±% of Center Frequency) Adjustable Passband Gain Noise Independent of Gain Filter Noise: μv RMS, V S = Single Supply Clock-Tunable (Center Frequency = f CLK /) Center Frequencies up to khz, V S = ± (Typical I SPPLY =.ma) Center Frequencies up to khz, V S = Single Supply (Typical I SPPLY =.ma) APPLICATIONS Asynchronous Narrowband Signal Detectors Low Frequency Asynchronous Demodulators Handheld Spectrum Analyzers In-Band Tone Signaling Detectors LTC- ltraselective, Low Power th Order Elliptic Bandpass Filter with Adjustable Gain DESCRIPTION The LTC - is a monolithic ultraselective, th order, elliptic bandpass filter. The passband of the LTC- is tuned with an external clock and the clock-to-center frequency ratio is :. The db pass bandwidth is typically % of the filter center frequency. The stopband attenuation of the LTC- is greater than db. The lower and upper stopband frequencies are less than. center frequency and greater than. center frequency, respectively. The LTC- requires an external op amp and two external resistors (see the circuit below). The filter s gain at center frequency is set by the ratio R IN /R F. For a gain equal to one and an optimum dynamic range, R F should be set to.k and R IN should be k. For gains other than one, R IN = k/gain. Gains up to are obtainable. Setting the filter s gain with input resistor R IN does not increase the filter s wideband noise. The μv RMS wideband noise of the LTC- is independent of the filter s center frequency. The LTC- is available in a -pin PDIP or a -pin surface mount SO Wide package., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION ltranarrow khz Bandpass Filter with Gain = Gain = k/r IN, /(π R F C F ) Center Frequency Frequency Response V IN R IN k LTC- khz C F pf R F.k LT V OT GAIN (db) db SHORT CONNECTION NDER IC AND SHIELDED BY A GROND PLANE LTC- TA FREQEY (khz) - TA fb

2 LTC- ABSOLTE MAXIMM RATINGS W W W Total Supply Voltage (V to V ).... Power Dissipation... mw Burn-In Voltage.... Voltage at Any Input... (V.V) V IN (V.V) Operating Temperature Range*... C to C Storage Temperature Range... C to C Lead Temperature (Soldering, sec)... C Maximum Clock Frequency V S = ±.... khz V S = ±... khz V S = Single... khz *For an extended operating temperature range contact LTC Marketing for details. PACKAGE/ORDER INFORMATION W INVB AGND V AGND INVA TOP VIEW N PACKAGE -LEAD PDIP R(h, l) V f CLK I OT T JMAX = C, θ JA = C/ W ORDER PART NMBER LTC-CN INVB AGND V AGND INVA TOP VIEW SW PACKAGE -LEAD PLASTIC SO WIDE T JMAX = C, θ JA = C/ W R(h, l) V f CLK I OT ORDER PART NMBER LTC-CSW Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS (See Test Circuit) T A = C, Center Frequency = f CLK /, f CLK = khz (the clock signal is a TTL or CMOS square wave, clock rise or fall time μs), the AC test signal level is V RMS for V S = ± or. RMS for V S = ±., unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX NITS Gain at Center Frequency V S = ±. f IN = Hz ±. db ±. db V S = ± f IN = Hz ±. db ±. db Gain at. Center Frequency and V S = ±. f IN = Hz db. Center Frequency f IN = Hz db (Referenced to Gain at Center Frequency) V S = ± f IN = Hz ± db f IN = Hz ± db Lower Stopband Attenuation V S = ±. f IN = Hz (Note ) db (Referenced to Gain at Center Frequency) f IN = Hz db db V S = ± f IN = Hz (Note ) db f IN = Hz db fb

3 ELECTRICAL CHARACTERISTICS (See Test Circuit) LTC- T A = C, Center Frequency = f CLK /, f CLK = khz ( the clock signal is a TTL or CMOS square wave, clock rise or fall time μs), the AC test signal level is V RMS for V S = ± or. RMS for V S = ±., unless otherwise specified. PARAMETER CONDITIONS MIN TYP MAX NITS pper Stopband Attenuation V S = ±. f IN = Hz (Note ) db (Referenced to Gain at Center Frequency) f IN = Hz db db V S = ± f IN = Hz (Note ) db f IN = Hz db Maximum Output for <.% V S = ±. f IN = Hz. V RMS Total Harmonic Distortion V S = ± f IN = Hz. V RMS Output DC Offset V S = ±. (At the Output of External Op Amp) ± mv V S = ± ± mv Power Supply Current (Note ) V S = ±... ma. ma V S = ±.. ma. ma V S = ±... ma. ma Power Supply Range ±. ± V The denotes specifications which apply over the full operating temperature range. Note : The minimum stopband attenuation at Hz and Hz is guaranteed by design and test correlation. Note : The maximum current over temperature is at C. At C the maximum current is less than its maximum value at C. TYPICAL PERFORMAE CHARACTERISTICS W GAIN (db) Gain vs Frequency T A = C V S = ± f CLK = khz GAIN (db) Passband Variations vs Power Supply fclk = khz GAIN = R IN = k R F =.k V S = ± V S = ±. V S = ±. GAIN (db) Passband Gain and Phase vs Frequency T A = C V S = ± f CLK = khz PHASE (DEG) FREQEY (Hz) FREQEY (Hz) FREQEY (Hz) LTC- TPC LTC- TPC LTC- TPC fb

4 LTC- TYPICAL PERFORMAE CHARACTERISTICS W GAIN (db) Passband Gain and Delay vs Frequency T A = C V S = ± f CLK = khz FREQEY (Hz) LTC- TPC DELAY (ms) LOG (THD NOISE/V IN ) (db). THD Noise vs Input Voltage T A = C V S = ± f IN = khz f CLK = khz FILTER GAIN AT f CENTER = OTPT OP AMP IS LT. INPT VOLTAGE (V RMS ) LTC- TPC LOG (THD NOISE/V IN ) (db). THD Noise vs Input Voltage T A = C V S = SINGLE f IN = khz f CLK = khz FILTER GAIN AT f CENTER = OTPT OP AMP IS LT AGND =. AGND = V. INPT VOLTAGE (V RMS ) LTC- TPC LOG (THD NOISE/V IN ) (db) THD Noise vs Input Voltage T A = C V S = SINGLE f IN = khz f CLK = khz FILTER GAIN AT f CENTER = OTPT OP AMP IS LT AGND AT. AGND AT V POWER SPPLY CRRENT (ma)..... Power Supply Current vs Power Supply Voltage C C OTPT LEVEL (dbv) Output vs Input f CLK = khz f CENTER = khz f IN = khz V S = SINGLE (PINS, AT V) V S = ±..... INPT VOLTAGE (V P-P ) POWER SPPLY VOLTAGE (V OR V ) INPT LEVEL (dbv) LTC- TPC LTC- TPC LTC- TPC fb

5 LTC- PIN FTIONS (-Lead PDIP) V, V (Pins, ): Power Supply Pins. The V (Pin ) and the V (Pin ) should be bypassed with a capacitor to a reliable ground plane. The filter s power supplies should be isolated from other digital or high voltage analog supplies. A low noise linear supply is recommended. sing a switching power supply will lower the signal-to-noise ratio of the filter. The power supply during power-up should have a slew rate of less than V/μs. For dual supply operation if the V supply is applied before the V supply or the V supply is applied before the V supply, a signal diode on each supply pin to ground will prevent latchup. Figures and show typical connections for dual and single supply operation. f CLK (Pin ): Clock Input Pin. Any TTL or CMOS clock source with a square wave output and % duty cycle (±%) is an adequate clock source for the device. The power supply for the clock source should not be the filter s power supply. The analog ground for the filter should be connected to the clock s ground at a single point only. Table shows the clock s low and high level threshold values for dual or single supply operation. A pulse generator can be used as a clock source provided the high level on-time is at least μs. Sine waves are not recommended for clock input frequencies less than khz. The clock s rise or fall time should be equal to or less than μs. Table. Clock Source High and Low Threshold Levels POWER SPPLY HIGH LEVEL LOW LEVEL Single Supply = >. <. Single Supply = V >.V <. Dual Supply = ±. >.V <.V Dual Supply = ± >. <. Dual Supply = ±. >.V <. *N OR EQIVALENT V IN R IN k LTC- f CLK N* OR EQIVALENT *FOR SRFACE MONT CIRCITS SE MOTOROLA DIODE MBR OR EQIVALENT R F.k V OT LTC- F Figure. Dual Power Supply Operation (Gain = ) V IN R IN k R F.k μf k k LTC- f CLK V OT LTC- F Figure. Single Power Supply Operation (Gain = ) fb

6 LTC- PIN FTIONS AGND (Pins, ): Analog Ground Pins. For dual supply operation, Pins and (AGND) are connected to an analog ground plane. For single supply operation, Pins and should be biased at / of the V supply and be bypassed to the analog ground plane with a μf (tantalum or better) capacitor (Figure ). For optimum gain linearity and single supply operation, the analog ground Pins and should be biased at V. nder these conditions the typical output AC swing is. to. (please refer to the THD Noise vs Input Voltage graph). The filter performance depends on the quality of the analog ground. For either a dual or a single supply operation, an analog ground plane surrounding the package is necessary. The analog ground plane for the filter should be connected to any digital ground plane at a single point. INVB, INVA, I OT, [R (h, l]) (Pins,,, ): External Connection Pins. Pin (INVB) is the inverting input on an op amp. Pin (I OT ) is the junction of two internal resistors. Pin (INVA) is the inverting input of an op amp, Pin [R (h, l)] is the junction of two internal resistors. For normal filter operation an external input resistor (R IN ) should be connected to input Pin and the output Pin should be connected to the inverting input of an external op amp with a feedback resistor (R F ). Also Pins and should be connected together (Figures and ). On a printed circuit board the external connections should be less than one inch and surrounded by a ground plane. The input resistor and output op amp with feedback resistor determine the filter s gain and dynamic range. Please refer to the Applications Information section for more information. (,,,, ): Pins. Pins,,, and are not connected to any circuit point on the device and should be tied to analog ground for dual or single supply operation. TEST CIRCIT pf V S N V IN R IN k LTC- V S N.k LT V OT f CLK khz LTC- TC fb

7 LTC- APPLICATIONS INFORMATION W Passband Gain and Dynamic Range The filter s gain at f CENTER is set with an external op amp and resistors R IN and R F (Figure ). The filter s center frequency (f CENTER ) is equal to the clock frequency divided by. The output dynamic range of LTC- is optimized for minimum noise and maximum voltage swing when resistor R F is.k. The value of resistor R IN depends on the filter s gain and it is calculated by the equation R IN = k/gain. Table lists the values of R IN and R F for some typical gains. Increasing the filter s gain with resistor R IN does not increase the noise generated by the filter. Table shows the noise generated by the filter with its input grounded. Table. Passband Gain at Center Frequency, R IN and R F GAIN R IN (±%) R F (±%) GAIN IN db R IN (±%) R F (±%) k.k k.k k.k k.k.k.k.k.k k.k k.k.k.k.k.k.k.k.k.k.k.k.k.k.k.k.k.k Ω.k.k.k Ω.k.k.k Table. LTC- Noise with Its Input Grounded POWER SPPLY NOISE (μv RMS ) ± ±% Single ±% The passband of the LTC- is from. f CENTER to. f CENTER. At the passband s end points the typical filter gain is db ±db relative to the gain at f CENTER. Figure shows typical passband gain variations versus percent of frequency deviation from f CENTER. Outside the filter s passband, signal attenuation increases to db for frequencies less than. f CENTER and greater than. f CENTER. In applications where a signal is to be detected in the presence of wideband noise, the ultraselectivity of the LTC- can improve the output signal-to-noise ratio. When wideband noise (white noise) appears at the input to GAIN (db) VS = ± R IN = k R F =.k.. f CENTER.. PERCENT DEVIATION FROM f CENTER (±% f CENTER ) LTC- F Figure. Typical Passband Variations the filter, only a small amount of input noise will reach the filter s output. If the output noise of the LTC- is neglected, the signal-to-noise ratio at the output of the filter divided by the signal-to-noise ratio at the input of the filter equals: (S/N) OT /(S/N) IN = Log (BW) IN /(BW) f where, (BW) IN = noise bandwidth at the input of the filter (BW) f =. f CENTER = noise equivalent filter bandwidth Example: A small khz signal is sent through a cable that also conducts random noise. The cable bandwidth is.khz. An LTC- is used to detect the khz signal. The signal-to-noise ratio at the output of the filter is.db larger than the signal-to-noise ratio at the input of the filter ( Log (BW) IN /(BW) f = Log.kHz/. khz khz =.db). The AC output swing with ± supplies is ±V, with a single supply it is V to V, when AGND (Pins, ) is biased at.. Table lists op amps that are recommended for use with an LTC-. The LTC- is designed and specified for a dual ± or single supply operation. The filter s passband gain linearity is optimum at single supply and with Pins, (AGND) biased at V. Filter operation at ±. supplies is not tested or specified. At V S =., the filter will operate with center frequencies up to khz. Please refer to the Passband Variations vs Power Supply graph in the Typical Performance Characteristics. fb

8 LTC- APPLICATIONS INFORMATION Aliasing W Table. Recommended Op Amps for LTC- SINGLE DAL QAD LT LT LT LT LT LT LT LT LT LT At the filter s output, alias signals will appear when signals at the filter s input have substantial energy very near the clock frequency or any of its multiples ( f CLK, f CLK,... etc.). For example, if an LTC- filter operates with a khz clock and has a khz, mv signal at its input, a khz, mv alias signal will appear at the filter s output. Table shows details. Clock Feedthrough mv/div LT V S = ± f CLK = khz μs/div LTC- F Figure. Clock Feedthrough at the Output of External Op Amp A. With No Capacitor Across Feedback Resistor R F B. With Capacitor C F Across Feedback Resistor R F /(π R F C F ) = f CENTER A B Table. Aliasing (f CLK = khz) OTPT LEVEL OTPT FREQEY INPT FREQEY (RELATIVE TO INPT) (ALIAS FREQEY).kHz < db Hz (or.khz).khz < db Hz (or.khz).khz <db Hz (or.khz).khz db ±db Hz (or.hz).khz db ±db Hz (or.khz).khz db ±db Hz (or.khz).khz <db Hz (or.khz).khz <db Hz (or.khz).khz <db Hz (or.khz) Transient Response V/DIV FOR INPT mv/div FOR OTPT V S = ± f CLK = khz f CENTER = khz ms/div Figure. Square Wave Input (±.) LTC- F OTPT INPT OTPT V/DIV INPT V S = ± f CLK = khz f CENTER = khz ms/div Figure. Sine Wave Burst Input LTC- F fb

9 LTC- APPLICATIONS INFORMATION Printed Circuit Layout W For optimum filter performance, an LTC- should be operating on a printed circuit board that has been laid out for precision analog signal processing circuits. On a printed circuit board, an LTC- should be surrounded with an adequate analog signal ground plane and its power supply pins bypassed to ground with capacitors. The ground plane of an LTC- and any digital ground plane should preferably meet at a single point on a system ground (star system ground). The following external filter connections should be one inch or less: N Package Resistor R IN to Pin Pin to Pin Pin to the Inverting Node of an External Op Amp Ground Pins,,,,, and SW Package Resistor R IN to Pin Pin to Pin Pin to the Inverting Node of External Op Amp Ground Pins,,,,,,, and Any signal or power supply printed circuit traces should be at least. inches away from the above mentioned connections (this rule applies also to the routing of the printed circuit trace originating from a clock source in a digital circuit and terminating at a clock input pin of an LTC-). Operating an LTC- in an IC socket is not recommended. TYPICAL APPLICATIONS N Tone Detector and Average Value Circuit N V IN R IN k LTC- N C F R F.k / LT C R k k k N N A B / LT f CLK khz k A k R k C / LT B k R k C k / LT V OT V OT = AVERAGE OF ABS [V PEAK SIN (π f CENTER t)], ±% FROM V P-P TO V P-P R IN = k/gain; f CENTER = f CLK /; /(π R F C F ) f CENTER /(π R C) f CENTER /; /(π R C) f CENTER /; R C = R C LTC- TA fb

10 LTC- PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N Package -Lead PDIP (Narrow.) (LTC DWG # --).* (.) MAX. ±.* (. ±.).. (..). ±. (. ±.).. (..).. (..) ( ). (.) MIN. (.) MIN. ±. (. ±.). ±. (. ±.) *THESE DIMENSIONS DO NOT ILDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. IH (.mm).. (.) TYP. ±. (. ±.) N fb

11 LTC- PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. SW Package -Lead Plastic Small Outline (Wide.) (LTC DWG # --).. (..) (NOTE ) NOTE.. (..). (.) RAD MIN.. (..) (NOTE ).. (..) TYP.. (..).. (..).. (..) NOTE.. (..). (.) TYP.. (..) TYP NOTE:. PIN IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANFACTRING OPTIONS. THE PART MAY BE SPPLIED WITH OR WITHOT ANY OF THE OPTIONS.. THESE DIMENSIONS DO NOT ILDE MOLD FLASH OR PROTRSIONS. MOLD FLASH OR PROTRSIONS SHALL NOT EXCEED. IH (.mm)... (..) SOL 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. fb

12 LTC- TYPICAL APPLICATION Tone Detector Detecting a Low Level Signal Buried in Wideband Noise f CLK R IN V IN μf.k AGND (V) LTC- C F R F.k / LT C R k R k / LT REF.V STROBE LTC COMP k REF (.V).k REF (V) k FOR OPTIMM TONE DETECTION, THE SIGNAL S FREQEY SHOLD BE IN THE FILTER S PASSBAND AND WITHIN ±.% FROM f CENTER. AT V OT, LOGIC HIGH = SIGNAL AT V IN, LOGIC LOW = NO SIGNAL AT V IN. THE MINIMM DETECTABLE SIGNAL AT V IN : V IN(MIN) = mv RMS /GAIN. THE MAXIMM NOISE SPECTRAL DENSITY AT V IN : V IN = mv RMS /[GAIN (BW) f ] WHERE: (BW) f =. f CENTER AND IS THE NOISE EQIVALENT BANDWIDTH OF THE FILTER GAIN = k/r IN AND IS THE FILTER GAIN AT f CENTER R IN = k/gain; f CENTER = f CLK /; /(π R F C F ) f CENTER /(π R C) f CENTER /; /(π R C) f CENTER / R k C REF V COMP LTC- TA V OT RELATED PARTS PART NMBER DESCRIPTION COMMENTS LTC niversal Filter Building Block This Part, with External Resistors, Allows Design of Bandpass Filters Similar to LTC- (p to khz) LTC niversal Filter Building Block This Part, with External Resistors, Allows Design of Bandpass Filters Similar to LTC- (Low Power p to khz) LTC niversal Filter Building Block This Part, with External Resistors, Allows Design of Bandpass Filters Similar to LTC- (p to khz) See Table for additional information Linear Technology Corporation McCarthy Blvd., Milpitas, CA - () - FAX: () - TELEX: - fb LT / REV B PRINTED IN SA LINEAR TECHNOLOGY CORPORATION