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| Final Electrical Specifications LTC1565-31 650kHz Continuous Time, Linear Phase Lowpass Filter March 2000 FEATURES s s s s s s s s s DESCRIPTIO 7th Order, 650kHz Linear Phase Filter in an SO-8 Differential Inputs and Outputs Operates on a Single 5V or a 5V Supply Low Offset: 5mV Typical 75dB THD and SNR 78dB SNR Shutdown Mode Requires No External Components Requires No External Clock Signal APPLICATIO S s s s s s s CDMA Base Stations Data Communications Antialiasing Filters Smoothing or Reconstruction Filters Matched Filter Pairs Replacement for LC Filters The LTC(R)1565-31 is a 7th order, continuous time, linear phase lowpass filter. The selectivity of the LTC1565-31, combined with its linear phase and dynamic range, make it suitable for filtering in data communications or data acquisition systems. The filter attenuation is 37dB at 2x fCUTOFF and at least 72dB for frequencies above 3x fCUTOFF. Unlike comparable LC filters, the LTC1565-31 achieves this selectivity with a linear phase response in the passband. With 5% accuracy of the cutoff frequency, the LTC1565-31 can be used in applications requiring pairs of matched filters, such as transceiver I and Q channels. Furthermore, the differential inputs and outputs provide a simple interface for these wireless systems. With a single 5V supply and a 2VP-P input, the LTC1565-31 features an impressive spurious free dynamic range of 75dB. The maximum signal-to-noise ratio is 78dB and it is achieved with a 2.5VP-P input signal. The LTC1565-31 features a shutdown mode where power supply current is reduced to less than 10A. Other cutoff frequencies and single-ended I/O can be provided upon request. Please contact LTC Marketing. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO Frequency Response 20 2.0 GAIN 1.8 1.6 Single 5V Supply, Differential 650kHz Lowpass Filter ATTENUATION (dB) VIN+ VIN- 1 2 +IN -IN +OUT -OUT 8 7 VOUT+ VOUT- 5V 6 5 5V 0.1F 0 -20 GROUP DELAY -40 -60 -80 1.4 1.2 1.0 0.8 107 1565-31 TA02 LTC1565-31 3 0.1F 4 GND V- V+ SHDN 15645-31 TA01 -100 104 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 DELAY (s) 105 106 FREQUENCY (Hz) U U 1 LTC1565-31 ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW +IN 1 -IN 2 GND 3 V- 4 8 7 6 5 +OUT -OUT V+ SHDN Total Supply Voltage ............................................... 11V Power Dissipation ............................................. 500mW Operating Temperature Range LTC1565-31CS8 ..................................... 0C to 70C LTC1565-31IS8 ................................. - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C ORDER PART NUMBER LTC1565-31CS8 LTC1565-31IS8 S8 PART MARKING 156531 56531I S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 80C/ W (NOTE 5) Consult factory for Military grade parts. The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 5V (V + = 5V, V - = 0V), RLOAD = 10k from each output to AC ground, and Pin 5 open unless otherwise specified. PARAMETER Operating Supply Voltage Filter Gain VIN = 1VP-P, fIN = 25kHz fIN = 200kHz (Gain Relative to 25kHz) fIN = 300kHz (Gain Relative to 25kHz) fIN = 500kHz (Gain Relative to 25kHz) fIN = 650kHz (Gain Relative to 25kHz) fIN = 900kHz (Gain Relative to 25kHz) fIN = 1.3MHz (Gain Relative to 25kHz) fIN = 2.3MHz (Gain Relative to 25kHz) VIN = 1VP-P, fIN = 25kHz fIN = 200kHz fIN = 300kHz fIN = 500kHz fIN = 600kHz fIN = 650kHz fIN = 900kHz Ratio of 600kHz Phase/300kHz Phase Noise BW = DC to 2 * fCUTOFF fIN = 100kHz, 1VP-P (Note 2) Maximum Difference Between Pins 7 and 8 VS = 5V VS = 5V Upper Lower 0.1 Common Mode, VIN = 1.5V to 3.5V Differential VS = 5V VS = 5V (Note 6) q q q q q q q q q ELECTRICAL CHARACTERISTICS CONDITIONS MIN 4.75 - 0.3 - 0.2 - 0.7 - 2.2 -4 TYP 0 0 -0.4 -1.6 -3 -11 -36 -72 -13 -101 -150 113 60 36 - 92 2 115 85 MAX 11 0.3 0.1 - 0.1 - 1.0 -2 -7 - 31 UNITS V dB dB dB dB dB dB dB dB Deg Deg Deg Deg Deg Deg Deg VRMS dB Filter Phase q q - 162 34 - 138 85 Phase Linearity Wideband Noise THD Filter Differential DC Swing q 1.97 2.03 1.4 2.2 1.7 2.3 V + - 1.5 V - + 0.8 0.3 25 >50 >50 2 5 5 1.9 2.5 Filter DC Common Mode Range (Note 4) Input Bias Current Input Offset Current Input Resistance Input Capacitance Output DC Offset (Note 3) 0.6 12 12 2 U W U U WW W VP VP V V A nA M M pF mV mV LTC1565-31 The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VS = 5V (V + = 5V, V - = 0V), RLOAD = 10k from each output to AC ground, and Pin 5 open unless otherwise specified. PARAMETER Output DC Offset Drift Ground Voltage (Pin 3) in Single Supply Applications SHDN Pin Logic Thresholds CONDITIONS VS = 5V VS = 5V VS = 5V VS = 5V, Minimum Logical "1" VS = 5V, Maximum Logical "0" VS = 5V, Minimum Logical "1" VS = 5V, Maximum Logical "0" SHDN Pin Pull-Up Current Power Supply Current Power Supply Current in Shutdown Mode VS = 5V VS = 5V VS = 5V VS = 5V Shutdown. Includes SHDN Pull-Up Current VS = 5V VS = 5V q q q q q ELECTRICAL CHARACTERISTICS MIN TYP - 400 - 400 MAX UNITS V/C V/C 2.49 2.51 4.2 3.3 2.75 2.50 5 9 24 25 2.52 V V V V V A A 31 33 16 40 mA mA A A 4 10 8 20 Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Input and output voltages expressed as peak-to-peak numbers are assumed to be fully differential. Note 3: Output DC offset is measured between Pin 8 and Pin 7 with Pin 1 and Pin 2 connected to Pin 3. Note 4: A 250mVP-P, 100kHz differential signal is applied to Pins 1 and 2. The DC voltages at Pins 1 and 2 are equal. This is the "common mode voltage." The "common mode range" is the range of common mode voltages for which the 250mVP-P differential output has better than 65dB 2nd or 3rd harmonic distortion. Note 5: Thermal resistance varies depending upon the amount of PC board metal attached to the device. JA is specified for a 3.8 square inch test board covered with 2 oz copper on both sides. Note 6: Output DC offset measurements are performed by automatic test equipment approximately 0.5 seconds after application of power. PIN FUNCTIONS +IN, -IN (Pins 1, 2): Input Pins. Signals can be applied to either or both input pins. The DC gain from differential inputs (Pin 1 to Pin 2) to the differential outputs (Pin 8 to Pin 7) is 1.0V/V. The input range is described in the Applications Information section. GND (Pin 3): Ground. The ground pin is the reference voltage for the filter and is internally biased to one-half the total power supply voltage of the filter, maximizing the dynamic range of the filter. For single supply operation, the ground pin should be bypassed with a quality 0.1F ceramic capacitor to Pin 4. For dual supply operation, connect Pin 3 to a high quality DC ground. A ground plane should be used. A poor ground will increase noise and distortion. The impedance seen at Pin 3 is 2.5k in normal mode. In shutdown, the pin is internally biased to the same levels as normal mode. The impedance in shutdown mode is typically 500k but varies with supply voltage and temperature. V -, V + (Pins 4, 6): Power Supply Pins. For a single 5V supply (Pin 4 grounded), a quality 0.1F ceramic bypass capacitor is required from the positive supply pin (Pin 6) to the negative supply pin (Pin 4). The bypass should be as close as possible to the IC. For dual supply applications (Pin 3 is grounded), bypass Pin 6 to Pin 3 and Pin 4 to Pin 3 with a quality 0.1F ceramic capacitor. The maximum voltage difference between the ground pin (Pin 3) and the positive supply pin (Pin 6) should not exceed 5.5V. U U U 3 LTC1565-31 PIN FUNCTIONS SHDN (Pin 5): Shutdown. When the Pin 5 voltage is low, the LTC1565-31 goes into the current saving shutdown mode. Pin 5 has a 4A pull-up current. Leaving Pin 5 open will place the LTC1565-31 in its normal operating mode. - OUT, + OUT (Pins 7, 8): Output Pins. Pins 7 and 8 are the filter differential output. Each pin can drive 1k or 300pF loads. The common mode voltage at the output pins is the same as the voltage at Pin 3. BLOCK DIAGRA +IN 1 -IN 2 GND 3 5k SHUTDOWN SWITCH V+ V- 4A SHUTDOWN V- 4 4 W U U U + 8 +OUT - + R 7th ORDER LINEAR PHASE FILTER NETWORK OUTPUT BUFFER R - + V+ SHUTDOWN SWITCH - INPUT BUFFERS WITH COMMON MODE TRANSLATION CIRCUIT OUTPUT BUFFER 7 -OUT ~1M 5k 6 V+ ~1M 5 SHDN 1565-31 BD LTC1565-31 APPLICATIONS INFORMATION Interfacing to the LTC1565-31 The difference between the voltages at Pin 1 and Pin 2 is the "differential input voltage." The average of the voltages at Pin 1 and Pin 2 is the "common mode input voltage." The difference between the voltages at Pin 7 and Pin 8 is the "differential output voltage." The average of the voltages at Pin 7 and Pin 8 is the "common mode output voltage." The input and output common mode voltages are independent. The input common mode voltage is set by the signal source, if DC coupled, or by the biasing network if AC coupled (Figures 1 and 2). The output common mode voltage is equal to the voltage of Pin 3, the GND pin. The GND pin is biased to one-half of the supply voltage by an internal resistive divider (see Block Diagram). To alter the common mode output voltage, Pin 3 can be driven with an external voltage source or resistor network. If external resistors are used, it is important to note that the internal 5k resistors can vary 20% (their ratio only varies 2%). The output can also be AC coupled. 1 2 +IN -IN +OUT -OUT 8 7 VOUT+ VOUT- 5V 6 5 0.1F 15645-31 F01 THD (dB) + - VIN+ + - VIN- 3 LTC1565-31 GND V- V+ SHDN 0.1F 4 DC COUPLED INPUT V + + VIN- VIN (COMMON MODE) = IN 2 V + + VOUT- V+ = VOUT (COMMON MODE) = OUT 2 2 THD (dB) Figure 1 0.1F 1 2 +IN -IN +OUT -OUT 8 7 VOUT+ VOUT- 5V + + - VIN+ + - VIN- 0.1F 100k 1F 100k 3 4 LTC1565-31 GND V- V 6 5 SHDN AC COUPLED INPUT VIN (COMMON MODE) = VOUT (COMMON MODE) = V+ 2 Figure 2 U W U U Input Common Mode and Differential Voltage Range The range of voltage each input can support while operating in its linear region is typically 0.8V to 3.5V for a single 5V supply and - 4.2V to 3.2V for a 5V supply. Therefore, the filter can accept a variety of common mode input voltages. Figures 3 and 4 show the THD of the filter versus common mode input voltage with a 2VP-P differential input signal. -30 -40 -50 -60 -70 -80 -90 VIN = 2VP-P VS = 5V fIN = 100kHz -5 -4 -3 -2 -1 0 1 2 3 4 INPUT COMMON MODE VOLTAGE (V) 5 1565-31 F03 Figure 3. THD vs Common Mode Input Voltage -30 -40 -50 -60 -70 -80 VIN = 2VP-P VS = 5V fIN = 100kHz 0.5 3.0 1.0 2.0 2.5 1.5 INPUT COMMON MODE VOLTAGE (V) 3.5 1565-31 F04 Figure 4. THD vs Common Mode Input Voltage 0.1F 15645-31 F02 Figure 5 shows the THD and S/N ratio versus differential input voltage level for both a single 5V supply and a 5V supply. The common mode voltage of the input signal is one-half the total power supply voltage of the filter. The spurious free dynamic range, where the THD and S/N ratio are equal, is 75dB to 77dB when the differential input voltage level is 2VP-P; that is, for a single 5V supply, the 5 LTC1565-31 APPLICATIONS INFORMATION -30 -40 -50 -60 -70 -80 -90 THD: VS = 5V THD: VS = 5V SNR fIN = 100kHz THD, SNR (dB) 0.5 1.0 3.0 1.5 2.0 2.5 DIFFERENTIAL INPUT (P-P) 3.5 1565-31 F05 Figure 5. Dynamic Range Diff-In, Diff-Out input voltages are Pin 1 = 2.5V DC 0.5V and Pin 2 = 2.5V DC 0.5V. Also note Figure 5 shows a 78dB SNR ratio for higher THD levels. As seen in Figures 3 and 4, the spurious free dynamic range can be optimized by setting the input common mode voltage slightly below one-half of the power supply voltage, i.e., 2V for a single 5V supply and - 0.5V to - 1V for a 5V supply. Figure 6 shows the THD and SNR ratio versus differential input voltage level for both a single 5V supply and a 5V supply when the common mode input voltage is 2V and - 0.5V respectively. For best performance, the inputs should be driven differentially. For single-ended signals, connect the unused input to Pin 3 or a common mode reference. -40 THD: VS = 5V THD: VS = 5V SNR fIN = 100kHz THD (dB) -50 THD, SNR (dB) -60 -30 THD (dB) -70 -80 -90 0.5 3.0 1.5 2.0 2.5 1.0 DIFFERENTIAL INPUT VOLTAGE (VP-P) 3.5 1565-31 F06 Figure 6. THD vs VIN for a Common Mode Input Voltage 0.5V Below Mid Supply 6 U W U U Output Common Mode and Differential Voltage Range The output is a fully differential signal with a common mode level equal to the voltage at Pin 3. The specifications in the Electrical Characteristics table assume the inputs are driven differentially and the output is observed differentially. However, Pin 8 can be used as a single-ended output by simply floating Pin 7. Pin 7 can be used as an inverting single-ended output by floating Pin 8. Using Pins 7 or 8 as single-ended outputs will decrease the performance. The common mode output voltage can be adjusted by overdriving the voltage present on Pin 3. The best performance is achieved using a common mode output voltage that is equal to mid supply (the default Pin 3 voltage). Figures 7 and 8 illustrate the THD versus output common mode voltage for a 2VP-P differential input voltage and a common mode input voltage that is 0.5V below mid supply. 0 -10 -20 -30 -40 -50 -60 -70 -80 1.5 2.0 2.5 3.5 4.0 3.0 COMMON MODE OUTPUT VOLTAGE (V) 1565-31 F07 VIN = 2VP-P 100kHz VS = 5V VIN(CM) = 2V Figure 7. THD vs Common Mode Output Voltage 0 -10 -20 VIN = 2VP-P 100kHz VS = 5V VIN(CM) = -0.5V -40 -50 -60 -70 -80 -90 -4 -2 0 2 4 1565-31 F08 COMMON MODE OUTPUT VOLTAGE (V) Figure 8. THD vs Common Mode Output Voltage LTC1565-31 APPLICATIONS INFORMATION Output Drive Pin 7 and Pin 8 can drive a 1k or 300pF load connected to AC ground with a 0.5V signal (corresponding to a 2VP-P differential signal). For differential loads (loads connected from Pin 7 to Pin 8) the outputs can produce a 2VP-P differential signal across 2k or 150pF. For smaller signal amplitudes the outputs can drive correspondingly larger loads. Noise The wideband noise of the filter is the RMS value of the device's output noise spectral density. The wideband noise data is used to determine the operating signal-tonoise at a given distortion level. Most of the noise is concentrated in the filter passband and cannot be removed with post filtering (Table 1). Table 2 lists the typical change in wideband noise with supply voltage. Table 1. Wideband Noise vs Bandwidth, Single 5V Supply BANDWIDTH DC to fCUTOFF DC to 2 * fCUTOFF TOTAL INTEGRATED NOISE 110VRMS 115VRMS PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 - 0.197* (4.801 - 5.004) 8 7 6 5 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP 0.014 - 0.019 (0.355 - 0.483) TYP *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 0.016 - 0.050 (0.406 - 1.270) U U W U U Table 2. Wideband Noise vs Supply Voltage, fCUTOFF = 650kHz POWER SUPPLY 5V 5V TOTAL INTEGRATED NOISE DC TO 2 * fCUTOFF 115VRMS 117VRMS DC Offset The output DC offset of the LTC1565-31 is trimmed to less than 5mV. The trimming is done with VS = 2.5V. The output DC offset will typically change by 1mV when the power supply varies from 5V to 5V. 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157** (3.810 - 3.988) 1 2 3 4 0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254) 0.050 (1.270) BSC SO8 1298 7 LTC1565-31 TYPICAL APPLICATIO RF/IF SECTION RELATED PARTS PART NUMBER LTC1560-1 LTC1562/LTC1562-2 LTC1563-2/LTC1563-3 LTC1569-6/LTC1569-7 DESCRIPTION 1MHz/500kHz Continuous Time, Low Noise, Lowpass Elliptic Filter Universal 8th Order Active RC Filters 4th Order Active RC Lowpass Filters Self Clocked, 10th Order Linear Phase Lowpass Filters COMMENTS fCUTOFF = 500kHz or 1MHz fCUTOFF(MAX) = 150kHz (LTC1562), fCUTOFF(MAX) = 300kHz (LTC1562-2) fCUTOFF(MAX) = 256kHz fCLK/fCUTOFF = 64/1, fCUTOFF(MAX) = 75kHz (LTC1569-6) fCLK/fCUTOFF = 32/1, fCUTOFF(MAX) = 300kHz (LTC1569-7) 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com U Narrowband Cellular Base Station Receiver 0 LTC1565-31 LPF ADC I 90 LO Q DSP 90 LTC1565-31 LPF ADC 1565-31 TA03 156531i LT/TP 0300 4K * PRINTED IN USA (c) LINEAR TECHNOLOGY CORPORATION 2000 |
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