LT1568 Very Low Noise, High Frequency Active RC, Filter Building Block FEATURES DESCRIPTIO n Up to 10MHz Center Frequency on a Single 3V The LT 1568 is an easy-to-use, active-RC filter building Supply block with rail-to-rail inputs and outputs. The internal ca- n Easy to UseA Single Resistor Value Sets Lowpass pacitors of the IC and the GBW product of the internal low Cutoff Frequency (200kHz 5MHz), Unequal noise op amps are trimmed such that consistent and repeat- C Resistor Values Extend Cutoff Frequency Up to able filter responses can be achieved. With a single resis- 10MHz tor value, the LT1568 provides a pair of matched 2-pole n Extremely FlexibleDifferent Resistor Values Butterworth lowpass filters with unity gain suitable for I/Q Allow Lowpass Transfer Functions with or Without channels. Gain (Butterworth, Chebyshev or Custom) By using unequal-valued external resistors, the two 2-pole n SNR = 92dB ( = 2MHz, 2V ) C P-P sections can create different frequency responses or n THD = 84dB ( = 2MHz, 1V ) C P-P gains. In addition, the two stages may be cascaded to n Internal Capacitors Trimmed to 0.75% create a single 4-pole filter with a programmable re- n Single 4-Pole Lowpass Filter or Matched Pair of sponse. Capable of cutoff frequencies up to 10MHz, the 2-Pole Lowpass Filters LT1568 is ideal for antialiasing or channel filtering in high n Can be Connected as a Bandpass Filter speed data communications systems. The LT1568 can n Single-Ended or Differential Output also be used as a bandpass filter. n Operates from Single 3V (2.7V Min) to 5V Supply n The LT1568 features very low noise, supporting signal-to- Rail-to-Rail Input and Output Voltages U noise ratios of over 90dB. It also provides single-ended to APPLICATIO S differential signal conversion for directly driving high n speed A/D converters. The LT1568 has a shutdown mode Replaces Discrete RC Active Filters and LC Filter that reduces supply current to approximately 0.5mA on a Modules n 5V supply. Antialiasing/Reconstruction Filters n Dual or I-and-Q Channels (Two Matched 2nd Order The LT1568 is available in a narrow 16-lead SSOP Filters in One Package) package. n Single-Ended to Differential Conversion , LTC and LT are registered trademarks of Linear Technology Corporation. n Video Signal Processing TYPICAL APPLICATIO Amplitude and Phase Matched Dual Butterworth 2.5MHz Lowpass Amplitude Response Filter with Differential Output. Single 3V Supply Operation 3 0 3V 3 0.1F 1 16 + + 6 V V LT1568 511 511 511 511 2 15 V V 9 INVA INVB INA INB 3 14 12 SA SB V V OUTA OUTB 4 13 OUTA OUTB 15 511 511 5 12 V V 18 OUTA OUTA OUTB OUTB 6 11 GNDA GNDB 21 THE PROPRIETARY ARCHITECTURE 0.1F 7 10 ALLOWS FOR A SIMPLE RESISTOR 24 NC EN CALCULATION: 8 9 V V 27 10MHz R = 128 = CUTOFF FREQUENCY 100k 1M 10M C C 1568 TA01 FREQUENCY (Hz) 1568 TA02 1568f 1 GAIN (dB) U ULT1568 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) + ORDER PART Total Supply Voltage (V to V ) ........................... 11.6V TOP VIEW NUMBER Input Voltage on INVA, INVB, GNDA and + + V 1 + 16 V GNDB Pins ....................................................... V to V LT1568CGN INVA 2 15 INVB Input Current on INVA, INVB, GNDA and LT1568IGN SA 3 14 SB GNDB Pins (Note 2) ........................................... 10mA OUTA 4 13 OUTB Output Short-Circuit Duration on OUTA, OUTB, OUTA OUTA 5 12 OUTB and OUTB Pins ............................................... Indefinite GNDA 6 11 GNDB GN PART Maximum Continuous Output Current (Note 3) NC 7 10 EN MARKING DC ............................................................... 100mA V 8 9 V Specified Temperature Range (Note 9) 1568 GN PACKAGE LT1568C ............................................ 40 C to 85 C 16-LEAD PLASTIC SSOP 1568I T = 150 C, q = 135 C/W LT1568I ............................................. 40 C to 85 C JMAX JA Junction Temperature.......................................... 150 C Consult LTC Marketing for parts specified with wider operating temperature ranges. Storage Temperature Range ................ 65 C to 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications and typical values are at T = 25 C. V = single 5V, EN pin to logic low, R = 400W , A S L connected to midsupply, R = R11 = R21 = R31 = R12 = R22 = R32, unless otherwise noted (see Block Diagram). FIL SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Total Supply Voltage l 2.7 11 V S I Supply Current V = 3V l 24 35 mA S S V = 5V l 26 36 mA S V = 5V l 28 38 mA S Shutdown Supply Current V = 3V, V = 2.4V l 0.3 1.0 mA S EN V = 5V, V = 4.4V l 0.5 1.3 mA S EN V = 5V, V = 4.4V l 1.0 2.5 mA S EN Output Voltage Swing High V = 3V, R = 1.28k, R = 1k l 2.75 2.85 V S FIL L (OUTA, OUTA, OUTB, OUTB Pins) V = 5V, R = 1.28k, R = 1k l 4.60 4.80 V S FIL L V = 5V, R = 128W , R = 400W l 4.50 4.65 V S FIL L V = 5V, R = 1.28k, R = 1k l 4.60 4.75 V S FIL L Output Voltage Swing Low V = 3V, R = 1.28k, R = 1k l 0.05 0.12 V S FIL L (OUTA, OUTA, OUTB, OUTB Pins) V = 5V, R = 1.28k, R = 1k l 0.07 0.15 V S FIL L V = 5V, R = 128W , R = 400W l 0.20 0.40 V S FIL L V = 5V, R = 1.28k, R = 1k l 4.7 V S FIL L I Maximum Output Current 80 mA OUT Op Amp Input Offset Voltage V = 3V l 2.5 0.5 1.5 mV S V = 5V l 2.5 0.2 2.5 mV S V = 5V l 2.0 1.2 4.5 mV S Inverter Output Offset Voltage V = 3V l 2 2.5 7.0 mV S V = 5V l 10 0.6 4.5 mV S V = 5V l 12 4.0 2.0 mV S 1568f 2 U WWW