lt1568 Linear Technology Corporation, lt1568 Datasheet
lt1568
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lt1568 Summary of contents
Page 1
... Unequal noise op amps are trimmed such that consistent and repeat- able filter responses can be achieved. With a single resis- tor value, the LT1568 provides a pair of matched 2-pole Butterworth lowpass filters with unity gain suitable for I/Q channels. By using unequal-valued external resistors, the two 2-pole ...
Page 2
... Output Short-Circuit Duration on OUTA, OUTB, OUTA and OUTB Pins ............................................... Indefinite Maximum Continuous Output Current (Note 3) DC ............................................................... 100mA Specified Temperature Range (Note 9) LT1568C ............................................ – LT1568I ............................................. – Junction Temperature .......................................... 150 C Storage Temperature Range ................ – 150 C Lead Temperature (Soldering, 10 sec)................. 300 C ...
Page 3
... R = 1.28k S C FIL 1MHz 1.28k S C FIL ) 1MHz 1.28k FIL LT1568 = single 5V, EN pin to logic “low,” 400 , L MIN TYP MAX 0.5 2 0.4 2 –0 –0.2 0.01 0.2 0.01 0.27 180 179 176 1.9 –3.4 to 2.7 2 – 2.1 ...
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... LT1568 FILTER ELECTRICAL CHARACTERISTICS Specifications are for the output (OUTA or OUTB single 2nd order section ( with respect to V gain = – R11 = R21 = R31 = R12 = R22 = R32, (see Block Diagram). The FIL full operating temperature range, otherwise specifications and typical values are 400 connected to midsupply, unless otherwise noted ...
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... Test Frequency = 2MHz (2 • Test Frequency = 4MHz (4 • Test Frequency = 1MHz (0.1 • f Test Frequency = 7.5MHz (0.75 • f Test Frequency = 10MHz (1 • f Test Frequency = 20MHz (2 • f Test Frequency = 40MHz (4 • f LT1568 = gain = 1, GND GNDA GNDB = single 5V, EN pin to logic “low,” ...
Page 6
... Note 8: With equal-sized resistors, the differential DC gain through either a single section or cascaded sections is 6dB. Note 9: The LT1568C is guaranteed to meet specified performance from The LT1568C is designed, characterized and expected to meet specified performance from – but is not tested or QA sampled at these temperatures. The LT1568I is guaranteed to meet specified performance from – ...
Page 7
... S CUTOFF – 400 2.5MHz IN –40 –50 –60 2ND –70 3RD –80 – OUTA (V ) P-P LT1568 Crosstalk vs Frequency f = 10MHz CUTOFF – P –60 –70 –80 OUTA, OUTB –90 OUTA, OUTB –100 –110 10k 100k 1M 10M FREQUENCY (Hz) ...
Page 8
... IC connected to V through an internal pull-up resistor of approximately 40k. This defaults the LT1568 to the shutdown state if the EN pin is left floating. Therefore, the user must connect the EN pin to a voltage equal to or less + than (V – ...
Page 9
... C2A – – V LT1568 ANALOG GROUND PLANE 0.1 F INVA INVB LT1568 4 13 OUTA OUTB 5 12 OUTA OUTB 6 11 GNDA GNDB – – SINGLE POINT DIGITAL GROUND PLANE SYSTEM GROUND (IF ANY) + ...
Page 10
... SYSTEM GROUND Figure 1. Dual and Single Supply and Ground Plane Connections SIMPLE FILTER IMPLEMENTATIONS The basic 2nd order filter block of the LT1568, with three external resistors connected as shown in the Block Dia- gram, has the following lowpass transfer function: e OUT e IN ...
Page 11
... For each filer, a table of external resistor values (standard 1% tolerance) is provided. These resistor values have been adjusted to compensate for the finite gain bandwidth product of the LT1568 amplifiers. To implement a filter, simply connect the resistor values shown in the table for the cutoff frequency desired. If the ...
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... INPUT 500mV/DIV OUTPUT 200mV/DIV 10 20 1568 TA07 U Dual 2nd Order Lowpass Filter, Single Supply Operation + 2.7V V 10V R31 R32 2 15 INVA INVB 3 LT1568 R21 R22 4 13 OUTA OUTB 5 12 OUTA OUTB 6 11 GNDA GNDB 0 – – ...
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... R11, R21 CUTOFF 1 866 2 422 3 280 4 210 5 165 6 137 7 115 = 1MHz 500mV/DIV OUTPUT 200mV/DIV 10 20 1568 TA11 LT1568 U R31 825 412 274 205 165 137 118 0.25dB Passband Ripple 1MHz CUTOFF INPUT 1 s/DIV 1568 TA10 R31 1180 590 383 287 232 191 ...
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... Order Lowpass Butterworth Lowpass, f CUTOFF INPUT 500mV/DIV OUTPUT 200mV/DIV 10 20 1568 TA13 4th Order Lowpass Filter, Single Supply Operation + R31 R32 2 15 INVA INVB 3 LT1568 R21 R22 4 13 OUTA OUTB 5 12 OUTA OUTB 6 11 GNDA GNDB 0 – ...
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... CUTOFF 500mV/DIV OUTPUT 200mV/DIV 10 20 1568 TA17 LT1568 R12, R22 R32 2.21k 634 1.10k 324 698 205 499 154 383 121 309 100 255 86.6 215 76.8 182 66.5 158 61.9 0.25dB Passband Ripple, f ...
Page 16
... LT1568 U TYPICAL APPLICATIO S 4th Order Bandpass Filter f = 10MHz, –3dB Passband = f CENTER 5V C IN1 0.1 F 39pF LT1568 R11 93 INVA INVB R21 113 4 13 OUTA OUTB 5 12 OUTA OUTB 6 11 GNDA GNDB – – PACKAGE DESCRIPTIO ...