LTC1164-5 Low Power 8th Order Pin Selectable Butterworth or Bessel Lowpass Filter DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 U APPLICATIO S ■ ■ ■ ■ 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. Anti-Aliasing Filters Battery-Operated Instruments Telecommunications Filters Smoothing Filters , LTC and LT are registered trademarks of Linear Technology Corporation. U Frequency Response TYPICAL APPLICATIO Butterworth 20kHz Anti-Aliasing Filter 0 –10 8V NC 14 –20 2 13 –30 3 12 4 11 LTC1164-5 5 10 6 9 7 8 –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) VIN 1 –40 –50 –60 –70 –80 1 10 FREQUENCY (kHz) 100 LTC1164-5 TA02 1 LTC1164-5 U W W W ABSOLUTE AXI U RATI GS + (Note 1) – 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 Operating Temperature Range LTC1164-5C ...................................... – 40°C to 85°C LTC1164-5M .................................... – 55°C to 125°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO TOP VIEW 50:1 MODE 1 14 CONNECT 2 VIN 2 13 50:1 MODE V– GND 3 12 V+ 4 11 CLK GND 5 10 BUTT/BESS LP6 CONNECT 1 6 9 7 J PACKAGE 14-LEAD CERDIP 8 ORDER PART NUMBER TOP VIEW 50:1 MODE 1 16 CONNECT 2 VIN 2 15 50:1 MODE LTC1164-5CN LTC1164-5CJ LTC1164-5MJ GND 3 14 V – V+ 4 13 NC GND 5 11 BUTT/BESS LP6 7 NC 10 NC CONNECT 1 8 N PACKAGE 14-LEAD PDIP LTC1164-5CS 12 CLK NC 6 VOUT ORDER PART NUMBER 9 VOUT S PACKAGE 16-LEAD PLASTIC SW TJMAX = 150°C, θJA = 65°C/W (J) TJMAX = 110°C, θJA = 65°C/W (N) TJMAX = 110°C, θJA = 85°C/W Consult factory for Industrial grade parts. ELECTRICAL CHARACTERISTICS VS = ±7.5V, RL = 10k, fCLK = 400kHz, TA = Operating Temperature Range, unless otherwise specified. MIN LTC1164-5C TYP MAX UNITS ● ● – 0.5 – 0.5 – 0.10 0.10 0.25 0.25 dB dB fIN = 2kHz, (fCLK/fC) = 100:1 fIN = 4kHz, (fCLK/fC) = 50:1 ● ● – 0.45 – 0.35 – 0.20 – 0.10 0.17 0.40 dB dB Gain at 0.90fCUTOFF (Note 3) fIN = 3.6kHz, (fCLK/fC) = 100:1 ● – 2.50 –1.90 –1.0 dB Gain at 0.95fCUTOFF (Note 3) fIN = 3.8kHz, (fCLK/fC) = 100:1 Gain at fCUTOFF (Note 3) fIN = 4kHz, (fCLK/fC) = 100:1 fIN = 8kHz, (fCLK/fC) = 50:1 ● ● – 4.10 – 4.20 – 3.40 – 3.80 – 2.75 – 2.75 dB dB Gain at 1.44fCUTOFF (Note 3) fIN = 5.76kHz, (fCLK/fC) = 100:1 ● – 20.5 –19.0 –17.0 dB Gain at 2.0fCUTOFF (Note 3) fIN = 8kHz, (fCLK/fC) = 100:1 ● – 45.0 – 43.0 – 41.0 dB Gain with fCLK = 20kHz (Note 3) fIN = 200Hz, (fCLK/fC) = 100:1 ● – 4.50 – 3.40 – 2.75 dB Gain with VS = 2.375V (Note 3) fIN = 400kHz, fIN = 2kHz, (fCLK/fC) = 100:1 fIN = 400kHz, fIN = 4kHz, (fCLK/fC) = 100:1 – 0.50 – 4.20 – 0.10 – 3.40 0.35 – 2.00 dB dB Input Frequency Range (fCLK/fC) = 100:1 (fCLK/fC) = 50:1 PARAMETER CONDITIONS Passband Gain 0.1Hz at 0.25fCUTOFF (Note 3) fIN = 1kHz, (fCLK/fC) = 100:1 fIN = 1kHz, (fCLK/fC) = 50:1 Gain at 0.50fCUTOFF (Note 3) 2 – 2.60 0 – <fCLK/2 0 – <fCLK dB kHz kHz LTC1164-5 ELECTRICAL CHARACTERISTICS VS = ±7.5V, RL = 10k, fCLK = 400kHz, TA = Operating Temperature Range, unless otherwise specified. MIN LTC1164-5C TYP PARAMETER CONDITIONS Maximum fCLK VS ≥ ±7.5V VS = ±5.0V VS = Single 5V (GND = 2V) 1.5 1.0 1.0 MHz MHz MHz Clock Feedthrough Input at GND, f = fCLK, Square Wave ±5V, (fCLK/fC) = 100:1 ±5V, (fCLK/fC) = 50:1 200 100 µVRMS µVRMS 100 ±5% 115 ±5% µVRMS µVRMS Input at GND, 1Hz ≥ f < fCLK ±5V, (fCLK/fC) = 100:1 ±5V, (fCLK/fC) = 50:1 Wideband Noise Input Impedance 70 100 ±1.25 ±3.70 ±5.40 ±1.50 ±4.10 ±5.90 Output DC Voltage Swing VS = ±2.375V VS = ±5.0V VS = ±7.5V Output DC Offset VS = ±5V, (fCLK/fC) = 100:1 ± 50 Output DC Offset TempCo VS = ±5V, (fCLK/fC) = 100:1 ±100 Power Supply Current VS = ±2.375V, TA ≥ 25°C ● ● ● ±160 4.5 7.0 ● ±2.375 The ● denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which life of the device may be impaired. mV µV/°C ● Power Supply Range kΩ V V V 2.5 VS = ±7.5V, TA ≥ 25°C UNITS 160 ● VS = ±5.0V, TA ≥ 25°C MAX 4.0 4.5 7.0 8.0 11.0 12.5 mA mA mA mA mA mA ±8 V Note 2: Connecting any pin to voltages greater than V + or less than V – may cause latchup. It is recommended that no sources operating from external supplies be applied prior to power-up of the LTC1164-5. Note 3: All gains are measured relative to passband gain. The filter cutoff frequency is abbreviated as fCUTOFF or fC. U W TYPICAL PERFOR A CE CHARACTERISTICS Passband Gain and Phase vs Frequency Gain vs Frequency B C GAIN (dB) –20 –30 –40 –50 GAIN –80 –10 0.1 –15 VS = ±5V TA = 25°C 1 10 FREQUENCY (kHz) 50 LTC1164-5 • G01 –90 –5 –60 –70 0 0 GAIN (dB) A –10 VS = ±5V fCLK = 50kHz fCUTOFF = 1kHz (50:1, PIN 10 TO V +, PINS 1-13 SHORTED) TA = 25°C 0.2 –180 PHASE (DEG) A. fCLK = 100kHz fCUTOFF = 1kHz (100:1, PIN 10 TO V –) B. fCLK = 375kHz fCUTOFF = 2.68kHz (140:1, PIN 10 GND) C. fCLK = 500kHz fCUTOFF = 10kHz (50:1, PIN 10 TO V +, PINS 1-13 SHORTED) 0 PHASE 0.4 0.8 0.6 FREQUENCY (kHz) –270 1.0 LTC1164-5 • G02 3 LTC1164-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Passband Gain and Phase vs Frequency Passband Gain and Phase vs Frequency 0 0 0 0 –180 VS = ±5V fCLK = 100kHz fCUTOFF = 1kHz (100:1, PIN 10 TO V –) TA = 25°C –15 –20 0.2 0.4 0.8 0.6 FREQUENCY (kHz) GAIN (dB) –10 –5 –90 PHASE –10 –270 –15 –360 –20 –180 VS = ±5V fCLK = 150kHz fCUTOFF = 1.07kHz (140:1, PIN 10 TO GND) TA = 25°C 0.2 1.0 –270 0.4 0.8 0.6 FREQUENCY (kHz) Group Delay vs Frequency Passband vs Frequency and fCLK A. fCLK = 500kHz (BUTTERWORTH 100:1) fCUTOFF = 5kHz B. fCLK = 750kHz (BESSEL 140:1) fCUTOFF = 5.36kHz VS = ±7.5V TA = 25°C 450 350 300 250 200 0 C D E –1.0 –1.5 –2.0 –3.0 B –3.5 –4.0 0 1.5 2.5 3.5 4.5 5.5 FREQUENCY (kHz) 6.5 VS = ±7.5V 50:1 TA = 25°C 0.1 7.5 1 FREQUENCY (kHz) Maximum Passband over Temperature for VS = ±7.5V, 50:1 0.5 0 GAIN (dB) GAIN (dB) 0 –1.5 –2.0 –2.5 –3.5 LTC1164-5 • G07 E –2.0 –3.0 30 C D –1.5 –3.0 VS = ±7.5V fCLK = 1.5MHz (50:1) fCUTOFF = 30kHz B –1.0 –2.5 –4.0 4 A –0.5 –1.0 10 FREQUENCY (kHz) A. fCLK = 200kHz fCUTOFF = 2kHz B. fCLK = 500kHz fCUTOFF = 5kHz C. fCLK = 750kHz fCUTOFF = 7.5kHz D. fCLK = 1MHz fCUTOFF = 10kHz E. fCLK = 1.5MHz fCUTOFF = 15kHz 0.5 TA = –40°C 1 30 Passband vs Frequency and fCLK TA = 70°C –0.5 10 LTC1164-5 • G06 LTC1164-5 • G05 –3.5 F –2.5 100 0.5 A B –0.5 A 50 A. fCLK = 200kHz fCUTOFF = 4kHz B. fCLK = 300kHz fCUTOFF = 6kHz C. fCLK = 500kHz fCUTOFF = 10kHz D. fCLK = 750kHz fCUTOFF = 15kHz E. fCLK = 1MHz fCUTOFF = 20kHz F. fCLK = 1.5MHz fCUTOFF = 30kHz 0.5 GAIN (dB) GROUP DELAY (µs) 400 150 –360 1.0 LTC1164-5 • G04 LTC1164-5 • G03 500 PHASE (DEG) –90 PHASE (DEG) GAIN (dB) GAIN –5 VS = ±7.5V 100:1 TA = 25°C –4.0 0.1 1 FREQUENCY (kHz) 10 20 LTC1164-5 • G08 LTC1164-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Passband vs Frequency and fCLK Passband vs Frequency and fCLK 0 GAIN (dB) – 0.5 –1.0 –1.5 –2.0 A –2.5 – 3.0 B C D E 0 – 4.0 0.1 A –0.5 C –1.5 –2.0 VS = ±5V 50:1 TA = 25°C –3.5 –4.0 10 10 1 LTC1164-5 • G10 Maximum Passband over Temperature for VS = ±5V, 50:1 0 0 TA = –40°C A –0.5 –1.0 –1.5 –2.0 –2.5 B C D E –1.0 –1.5 –2.0 –2.5 –3.0 –3.0 VS = ±5V fCLK = 1MHz fCUTOFF = 20kHz –3.5 –4.0 VS = ±5V 100:1 TA = 25°C –3.5 1 10 –4.0 0.1 20 FREQUENCY (kHz) 1 FREQUENCY (kHz) LTC1164-5 • G011 0.5 Passband vs Frequency and fCLK 0 TA = –40°C –0.5 –1.0 –1.0 GAIN (dB) –0.5 –1.5 –2.0 –3.5 –4.0 0.5 A C B D –1.5 –2.0 –2.5 –2.5 –3.0 A. fCLK = 250kHz fCUTOFF = 5kHz B. fCLK = 500kHz fCUTOFF = 10kHz C. fCLK = 750kHz fCUTOFF = 15kHz D. fCLK = 1MHz fCUTOFF = 20kHz 0.5 TA = 70°C 0 10 LTC1164-5 • G12 Maximum Passband over Temperature for VS = ±5V, 100:1 GAIN (dB) A. fCLK = 200kHz fCUTOFF = 2kHz B. fCLK = 300kHz fCUTOFF = 3kHz C. fCLK = 500kHz fCUTOFF = 5kHz D. fCLK = 750kHz fCUTOFF = 7.5kHz E. fCLK = 1MHz fCUTOFF = 10kHz 0.5 GAIN (dB) GAIN (dB) Passband vs Frequency and fCLK TA = 70°C –0.5 20 FREQUENCY (kHz) LTC1164-5 • G09 0.5 D –1.0 –3.0 1 FREQUENCY (kHz) B –2.5 VS = ±7.5V, 140:1 (BESSEL RESPONSE) TA = 25°C – 3.5 A. fCLK = 250kHz fCUTOFF = 5kHz B. fCLK = 500kHz fCUTOFF = 10kHz C. fCLK = 750kHz fCUTOFF = 15kHz D. fCLK = 1MHz fCUTOFF = 20kHz 0.5 GAIN (dB) A. fCLK = 150kHz fCUTOFF = 1.07kHz B. fCLK = 450kHz fCUTOFF = 3.21kHz C. fCLK = 750kHz fCUTOFF = 5.36kHz D. fCLK = 1MHz fCUTOFF= 7.14kHz E. fCLK = 1.5MHz fCUTOFF = 10.71kHz 0.5 –3.0 VS = ±5V fCLK = 1MHz (100:1) fCUTOFF = 10kHz 1 VS = SINGLE 5V 50:1 TA = 25°C –3.5 –4.0 10 10 1 20 FREQUENCY (kHz) FREQUENCY (kHz) LTC1164-5 • G13 LTC1164-5 • G14 5 LTC1164-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Maximum Passband over Temperature for Single 5V, 50:1* THD + Noise vs RMS Input, 50:1 THD + Noise vs RMS Input, 100:1 –40 –40 TA = 70°C 0 TA = –40°C –50 THD + NOISE (dB) –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 VS = SINGLE 5V fCLK = 1MHz (50:1) fCUTOFF = 20kHz –3.5 –4.0 1 SINGLE 5V –60 –70 ±7.5V –80 –100 0.1 1 FREQUENCY (kHz) LTC1164-5 • G015 THD + Noise vs Frequency THD + Noise vs Frequency VIN = 2VRMS ±7.5V, 100:1 fCLK = 500kHz (5 REPRESENTATIVE UNITS) –60 –70 –80 –90 –90 1 10 1 20 –60 –70 –80 –90 –100 –100 3 2 FREQUENCY (kHz) FREQUENCY (kHz) 4 5 –100 THD + Noise vs Frequency THD + Noise vs Frequency –40 –40 –50 VIN = 0.7VRMS SINGLE 5V SUPPLY 50:1, fCLK = 500kHz fC = 10kHz (5 REPRESENTATIVE UNITS) –50 THD + NOISE (dB) –60 –70 –80 –60 –54 –58 –70 –80 –90 –90 –100 –100 10 LTC1164-5 • G20 THD + Noise vs Frequency VIN = 1VRMS ±5V, 100:1 fCLK = 500kHz (5 REPRESENTATIVE UNITS) 5 FREQUENCY (kHz) 1 LTC1164-5 • G19 LTC1164-5 • G18 –50 VIN = 1VRMS ±5V, 50:1 fCLK = 500kHz (5 REPRESENTATIVE UNITS) –50 THD + NOISE (dB) THD + NOISE (dB) THD + NOISE (dB) –80 5 –40 –50 –70 1 FREQUENCY (kHz) LTC1164-5 • G17 THD + Noise vs Frequency VIN = 2VRMS ±7.5V, 50:1 fCLK = 1MHz (5 REPRESENTATIVE UNITS) –60 ±7.5V –80 –100 0.1 5 –40 –50 –70 LTC1164-5 • G16 –40 ±5V –60 –90 FREQUENCY (kHz) THD + NOISE (dB) SINGLE 5V ±5V –90 10 fIN = 1kHz fCLK = 500kHz –50 THD + NOISE (dB) GAIN (dB) fIN = 1kHz fCLK = 500kHz THD + NOISE (dB) 0.5 –62 –66 VIN = 2VRMS VS = ±7.5V, 140:1 fCLK = 750kHz fC = 5.36kHz (5 REPRESENTATIVE UNITS) –70 –74 –78 –82 –86 1 3 2 FREQUENCY (kHz) 4 5 1 5 FREQUENCY (kHz) LTC1164-5 • G21 10 LTC1164-5 • G22 * See also Passband vs Frequency and fCLK for Single 5V, 50:1; THD + Noise vs RMS Input for Single 5V, 50:1; and Maximum Passband for Single 5V, 50:1, for Two Ground Bias Levels. 6 –90 0.5 1 FREQUENCY (kHz) 5 LTC1164-5 • G23 LTC1164-5 U W TYPICAL PERFOR A CE CHARACTERISTICS Maximum Passband for Single 5V, 50:1, for Two Ground Bias Levels THD + Noise vs Input Voltage –50 2.0 1.5 –58 1.0 –62 0.5 PHASE (DEG) VS = ±2.5V –66 VS = ±5V –70 –40 TA = 70°C fCLK = 1MHz –74 –78 –45 0 –0.5 GND = 2V –1.0 –1.5 –82 –2.0 VS = ±7.5V –86 –90 0.1 1 INPUT VOLTAGE (VRMS) 5 –70 GND = 2.5V –75 –85 –90 0.50 2 4 6 8 10 12 14 16 18 20 22 FREQUENCY (kHz) 0.75 1.00 1.25 INPUT (VRMS) LTC1164-5 • TPC25 1.50 LTC1164-5 G26 Power Supply Rejection Ratio vs Frequency 10 A. BUTTERWORTH (fCLK / fCUTOFF = 100:1 OR 50:1) B. BESSEL (fCLK /fCUTOFF = 140:1) MAXIMUM PHASE DIFFERENCE BETWEEN ANY TWO UNITS (SAMPLE OF 50 UNITS) VS ≥ ±5V TA ≤ 70°C fCLK ≤ 500KHz fCUTOFF = 1kHz 0 –10 –20 PSRR (dB) TOTAL PHASE DIFFERENCE (DEG) GND = 2V –3.0 10 4 A –30 V+ –40 V– –50 –60 B 2 –60 –65 –80 Phase Matching vs Frequency 6 –55 –2.5 LTC1164-5 • G24 8 fCLK = 1MHz TA =25°C –50 GND = 2.5V THD + NOISE (dB) fIN = 1kHz, 140:1 fCLK = 750kHz –54 THD + WIDEBAND NOISE (dB) THD + Noise vs RMS Input for Single 5V, 50:1 –70 –80 0 0 1.0 0.4 0.6 0.8 0.2 FREQUENCY (FREQUENCY/fCUTOFF) –90 1.2 20 100 1k FREQUENCY (Hz) 10k LTC1164-5 • G28 LTC1164-5 • G27 Power Supply Current vs Power Supply Voltage 50k Transient Response VIN = ±3V, 500Hz Square Wave Transient Response VIN = ±3V, 500Hz Square Wave 12 11 –55°C 10 25°C 7 125°C 6 2V/DIV 8 2V/DIV CURRENT (mA) 9 5 4 3 2 500µs/DIV 1 0 0 1 2 3 4 5 6 7 8 POWER SUPPLY (V + OR V –) 9 10 LTC1164-5 • G29 BUTTERWORTH RATIO = 100:1 fCLK = 500kHz fC = 5kHz VS = ±7.5V 1164-5 G30 500µs/DIV 1164-5 G31 BESSEL RATIO = 140:1 fCLK = 700kHz fC = 5kHz VS = ±7.5V 7 LTC1164-5 U U U PI FU CTIO S Power Supply (Pins 4, 12) Clock Input (Pin 11) The V + (Pin 4) and the V – (Pin 12) should be bypassed with a 0.1µF capacitor to an adequate analog ground. The filter’s power supplies should be isolated from other digital or high voltage analog supplies. A low noise linear supply is recommended. Using a switching power supply will lower the signal-to-noise ratio of the filter. The supply during power-up should have a slew rate less than 1V/µs. When V + is applied before V –, and V – can be more positive than ground, a signal diode must be used to clamp V –. Figures 1 and 2 show typical connections for dual and single supply operation. 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 be the filter’s power supply. The analog ground for the filter should be connected to clock’s ground at a single point only. Table 1 shows the clock’s 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 0.5µs. Sine waves are not recommended for clock input frequencies less than 100kHz, since excessively slow clock rise or fall times generate internal clock jitter (maximum clock rise or fall time ≤1µs). 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 clock source and Pin 11 will slow down the rise and fall times of the clock to further reduce charge coupling, Figures 1 and 2. V– VIN 1 14 2 13 3 12 4 V+ 0.1µF LTC1164-5 * 0.1µF 1k 11 5 10 6 9 7 8 CLOCK SOURCE + GND DIGITAL SUPPLY * OPTIONAL (SEE TEXT) VOUT 1164-5 F01 Figure 1. Dual Supply Operation for fCLK/fCUTOFF = 100:1 VIN 14 2 13 3 12 4 5V ≤ V + ≤ 16V 0.1µF 10k 10k 1 LTC1164-5 11 5 10 6 9 7 8 POWER SUPPLY Dual Supply > ±3.4V Dual Supply ≤ ±3.4V Single Supply V+ > 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 Analog Ground (Pins 3, 5) 1k CLOCK SOURCE + GND DIGITAL SUPPLY + 1µF VOUT 1164-5 F02 Figure 2. Single Supply Operation for fCLK/fCUTOFF = 100:1 8 Table 1. Clock Source High and Low Threshold Levels 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). LTC1164-5 U U U 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. – 1k LT1056 + 1164-5 F03 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. U W U U APPLICATIO S I FOR ATIO Clock Feedthrough 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. Table 2. Output Clock Feedthrough VS 50:1 100:1 ±2.5V 60µVRMS 60µVRMS ±5V 100µVRMS 200µVRMS ±7.5V 150µVRMS 500µVRMS Note: The clock feedthrough at ±2.5V supplies is imbedded in the wideband noise of the filter. The clock waveform is a square wave. 9 LTC1164-5 U W U U 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. 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) MAXIMUM fCLK OUTPUT FREQUENCY (Aliased Frequency) (fCLK/fC) = 100:1, fCUTOFF = 1kHz 97.0kHz 97.5kHz 98.0kHz 98.5kHz 99.0kHz 99.5kHz –102.0dB – 65.0dB – 45.0dB – 23.0dB – 4.0dB – 0.3dB 3.0kHz 2.5kHz 2.0kHz 1.5kHz 1.0kHz 0.5kHz (fCLK/fC) = 50:1, fCUTOFF = 2kHz 197.0kHz 197.5kHz 198.0kHz 198.5kHz 199.0kHz 199.5kHz – 23.0dB –12.0dB – 5.0dB –1.8dB –1.0dB – 0.8dB 3.0kHz 2.5kHz 2.0kHz 1.5kHz 1.0kHz 0.5kHz Table 5. Transient Response of LTC Lowpass Filters MAXIMUM VIN LOWPASS FILTER DELAY TIME* (SEC) LTC1064-3 Bessel LTC1164-5 Bessel LTC1164-6 Bessel 0.50/fC 0.43/fC 0.43/fC 0.34/fC 0.34/fC 0.34/fC 0.80/fC 0.85/fC 1.15/fC 0.5 0 1 LTC1264-7 Linear Phase LTC1164-7 Linear Phase LTC1064-7 Linear Phase 1.15/fC 1.20/fC 1.20/fC 0.36/fC 0.39/fC 0.39/fC 2.05/fC 2.20/fC 2.20/fC 5 5 5 LTC1164-5 Butterworth LTC1164-6 Elliptic 0.80/fC 0.85/fC 0.48/fC 0.54/fC 2.40/fC 4.30/fC 11 18 LTC1064-4 Elliptic LTC1064-1 Elliptic 0.90/fC 0.85/fC 0.54/fC 0.54/fC 4.50/fC 6.50/fC 20 20 Table 3. Maximum VIN vs VS and fCLK POWER SUPPLY OUTPUT LEVEL (Relative to Input) VS = ±7.5V 1.5MHz 1VRMS (fIN > 35kHz) 0.5VRMS (fIN > 250kHz) VS = ±7.5V 1.0MHz 3VRMS (fIN > 25kHz) 0.7VRMS (fIN > 250kHz) VS = ±5.0V 1.0MHz 2.5VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) Single 5V 1.0MHz 0.7VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) RISE TIME** (SEC) SETTLING TIME*** (SEC) OVERSHOOT (%) * To 50% ±5%, ** 10% to 90% ±5%, *** To 1% ±0.5% 10 LTC1164-5 U 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 LTC1164-5 2 3 4 5V 0.1µF 15k + 1µF IC1 14 1 13 2 12 3 11 5 10 6 7 10k 14 LTC1164-5 12 4 5V 10 9 6 9 8 7 8 0.1µF 5V THD + Noise vs Frequency –40 0 –45 –10 –50 –20 –55 THD + NOISE (dB) GAIN (dB) VOUT 1164-5 F04 Gain vs Frequency –30 –40 –50 –60 VS = SINGLE 5V VIN = 0.5VRMS fCLK = 600kHz fC = 10kHz –60 –65 –70 –75 –80 VS = SINGLE 5V fCLK = 600kHz fCUTOFF = 10kHz –85 –90 1 5V 1k 10 –80 11 IC2 5 fCLK –70 13 10 FREQUENCY (kHz) –90 30 5 FREQUENCY (kHz) 1 LTC1164-5 • TA04 LTC1164-5 • TA03 U PACKAGE DESCRIPTIO 10 Dimensions in inches (millimeters) unless otherwise noted. J Package 14-Lead CERDIP (Narrow 0.300, Hermetic) (LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION 0.005 (0.127) MIN 0.840 (21.336) MAX 16 15 14 13 12 11 10 9 0.220 – 0.310 (5.588 – 7.874) 0.025 (0.635) RAD TYP 1 2 3 4 5 6 7 8 0.200 (5.080) MAX 0.300 BSC (0.762 BSC) 0.015 – 0.060 (0.380 – 1.520) 0.008 – 0.018 (0.203 – 0.457) 0° – 15° NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS 0.125 (3.175) MIN 0.045 – 0.068 (1.143 – 1.727) 0.100 ± 0.010 (2.540 ± 0.254) 0.014 – 0.026 (0.360 – 0.660) J16 1197 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. 11 LTC1164-5 U TYPICAL APPLICATIO S 8th Order Butterworth Lowpass Filter fCLK/fC = 50:1 VIN 1 14 2 13 3 V+ 4 + 0.1µF VIN 12 LTC1164-5 11 5 10 6 9 7 8 V– fCLK 8th Order Linear Phase Lowpass Filter fCLK/fC = 140:1 8th Order Butterworth Lowpass Filter fCLK/fC = 100:1 V 0.1µF + + 0.1µF V+ VOUT 1 14 1 14 2 13 2 13 3 12 3 12 4 11 4 11 LTC1164-5 5 10 6 9 7 8 VIN V– fCLK 0.1µF V+ 0.1µF VOUT LTC1164-5 5 10 6 9 7 8 V– 0.1µF fCLK VOUT 1164-5 TA06 1164-5 TA07 1164-5 TA05 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N Package 14-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.130 ± 0.005 (3.302 ± 0.127) 0.300 – 0.325 (7.620 – 8.255) 0.770* (19.558) MAX 0.045 – 0.065 (1.143 – 1.651) 0.020 (0.508) MIN 0.065 (1.651) TYP 0.009 – 0.015 (0.229 – 0.381) +0.035 0.325 –0.015 0.005 (0.125) MIN 0.100 ± 0.010 (2.540 ± 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) ( 8.255 +0.889 –0.381 ) 13 12 11 10 9 8 1 2 3 4 5 6 7 0.255 ± 0.015* (6.477 ± 0.381) 0.018 ± 0.003 (0.457 ± 0.076) 0.125 (3.175) MIN 14 N14 1197 SW Package 16-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.291 – 0.299** (7.391 – 7.595) 0.010 – 0.029 × 45° (0.254 – 0.737) 0.398 – 0.413* (10.109 – 10.490) 0.093 – 0.104 (2.362 – 2.642) 0.037 – 0.045 (0.940 – 1.143) 16 15 14 13 12 11 10 9 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) 0.050 (1.270) TYP NOTE 1 0.016 – 0.050 (0.406 – 1.270) 0.004 – 0.012 (0.102 – 0.305) 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0.014 – 0.019 (0.356 – 0.482) TYP NOTE: 1. 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 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 1 2 3 4 5 6 7 8 S16 (WIDE) 0396 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1069-1 Low Power, 8th Order Elliptic Lowpass Filter Operates from a Single 3.3V to ±5V Supply LTC1069-6 Very Low Power, 8th Order Elliptic Lowpass Filter Optimized for 3V/5V Single Supply Operation, Consumes 1mA at 3V 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com 11645as, sn11645 LT/TP 1098 2K REV A • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1993