LTC1061MJ

LTC1061 High Performance Triple Universal Filter Building Block FEATURES s s s s DESCRIPTIO s s s s s s Up to 6th Order Filter Functions with a Single 20-Pin 0.3" Wide Package Center Frequency Range up to 35kHz fO × Q Product up to 1MHz Guaranteed Center Frequency and Q Accuracy Over Temperature Guaranteed Low Offset Voltages Over Temperature 90dB Signal-to-Noise Ratio Filter Operates from Single 4.7V Supply and up to ±8V Supplies Guaranteed Filter Specifications with ± 5V Supply and ±2.37V Supply Low Power Consumption with Single 5V Supply Clock Inputs T 2L and CMOS Compatible The LTC1061 consists of three high performance, universal filter building blocks. Each filter building block together with an external clock and 2 to 5 resistors can produce various second order functions which are available at its three output pins. Two out of three always provide lowpass and bandpass functions while the third output pin can produce highpass or notch or allpass. The center frequency of these functions can be tuned with an external clock or an external clock and a resistor ratio. For Q < 5, the center frequency ranges from 0.1Hz to 35kHz. For Qs of 10 or above, the center frequency ranges from 0.1Hz to 28kHz. The LTC1061 can be used with single or dual supplies ranging from ±2.37V to ± 8V (or 4.74V to 16V). When the filter operates with supplies of ± 5V and above, it can handle input frequencies up to 100kHz. The LTC1061 is compatible with the LTC1059 single universal filter and the LTC1060 dual. Higher than 6th order functions can be obtained by cascading the LTC1061 with the LTC1059 or LTC1060. Any classical filter realization can be obtained. The LTC1061 is manufactured by using Linear Technology’s enhanced LTCMOSTM silicon gate process. APPLICATI s s S s s High Order, Wide Frequency Range Bandpass, Lowpass, Notch Filters Low Power Consumption, Single 5V Supply, Clock-Tunable Filters Tracking Filters Antialiasing Filters LTCMOSTM is a trademark of Linear Technology Corp. TYPICAL APPLICATI 6th Order, Clock-Tunable, 0.5dB Ripple Chebyshev BP Filter fCLK = 1MHz 2kHz 9.31k 1k 165k 4.99k 165k VIN < 100kHz 1 2 3 4 5 6 7.5V T CLK IN < 1.2MHz 2 20 19 18 17 LTC1061 16 15 14 13 12 11 VOUT 1061 TA01 78.7k 4.99k 23.7k 49.9k V – = –7.5V 4.99k 165k 5.49k –20 FILTER GAIN (dB) –40 –60 7 8 9 –80 V + = 7.5V 10 –100 0 10 20 30 40 INPUT FREQUENCY GAIN (kHz) 50 LTC1061 • TA02 U Amplitude Response 0 UO UO 1 LTC1061 ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW LPA BPA NA INVA S1A AGND 50/100/HOLD CLK LSh 1 2 3 4 5 6 7 8 9 20 LPB 19 BPB 18 NB 17 INVB 16 S1B 15 V – 14 LPC 13 BPC 12 HPC 11 INVC Supply Voltage ....................................................... 18V Power Dissipation............................................. 500mW Operating Temperature Range LTC1061AC, LTC1061C ............ –40°C ≤ TA ≤ 85°C LTC1061AM, LTC1061M ......... –55°C ≤ TA ≤ 125°C Storage Temperature Range ................ –65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C ORDER PART NUMBER LTC1061AMJ LTC1061MJ LTC1061ACJ LTC1061CJ LTC1061ACN LTC1061CN LTC1061CS V + 10 N PACKAGE J PACKAGE 20-LEAD CERAMIC DIP 20-LEAD PLASTIC DIP S PACKAGE 20-LEAD PLASTIC SOL TJMAX = 125°C, θJA = 100°C/W (J) TJMAX = 100°C, θJA = 100°C/W (N) TJMAX = 100°C, θJA = 85°C/W (S) Consult factory for Industrial grade parts ELECTRICAL CHARACTERISTICS (Complete Filter)VS = ±5V, TA = 25°C, T2L clock input level, unless otherwise specified. PARAMETER Center Frequency Range, fO CONDITIONS fO × Q ≤ 175kHz, Mode 1, VS = ± 7.5V fO × Q ≤ 1.6MHz, Mode 1, VS = ± 7.5V fO × Q ≤ 75kHz, Mode 3, VS = ± 7.5V fO × Q ≤ 1MHz, Mode 3, VS = ± 7.5V MIN TYP 0.1–35k 0.1–25k 0.1–25k 0.1–17k 0–200k Sides A, B: Mode 1, R1 = R3 = 50k R2 = 5k, Q = 10, fCLK = 250kHz Pin 7 High. Side C: Mode 3, R1 = R3 = 50k R2 = R4 = 5k, fCLK = 250kHz Same as Above, Pin 7 at Mid-Supplies, fCLK = 500kHz q q MAX UNITS Hz Hz Hz Hz Hz Input Frequency Range Clock-to-Center Frequency Ratio, fCLK /fO LTC1061A LTC1061 50 ± 0.6% 50 ± 1.2% 100 ± 0.6% 100 ±1.2% LTC1061A LTC1061 Clock-to-Center Frequency Ratio, Side-to-Side Matching LTC1061 Q Accuracy LTC1061A LTC1061 fO Temperature Coefficient Q Temperature Coefficient q q 1.2% Sides A, B, Mode 1 Side C, Mode 3 fO × Q ≤ 50kHz, fO × ≤ 5kHz Mode 1, 50:1, fCLK < 300kHz Mode 1, 100:1, fCLK < 500kHz Mode 3, fCLK < 500kHz q q ±2 ±3 ±1 ±5 ±5 5 5 ppm/°C ppm/°C ppm/°C 2 U % % W U U WW W LTC1061 ELECTRICAL CHARACTERISTICS (Complete Filter)VS = ± 5V, TA = 25°C, T2L clock input level, unless otherwise specified. PARAMETER DC Offset Voltage VOS1, Figure 23 VOS2 VOS2 VOS3, LTC1061CN, ACN/LTC1061CS VOS3, LTC1061CN, ACN/LTC1061CS Clock Feedthrough Maximum Clock Frequency Power Supply Current q CONDITIONS q q q q q MIN TYP 2 3 6 3 6 0.4 2.5 MAX 15 30 60 20/25 40/50 UNITS mV mV mV mV mV mVRMS MHz fCLK = 250kHz, 50:1 fCLK = 500kHz, 100:1 fCLK = 250kHz, 50:1 fCLK = 500kHz, 100:1 fCLK < 1MHz Mode 1, Q < 5, VS ≥ ± 5 6 8 11 15 mA mA (Complete Filter)VS = ±2.37V, TA = 25°C, unless otherwise specified. Center Frequency Range, fO Input Frequency Range Clock-to-Center Frequency Ratio LTC1061A LTC1061 LT1061A LT1061 Q Accuracy LTC1061A LTC1061 Maximum Clock Frequency Power Supply Current 50:1, fCLK = 250kHz, Q = 10 Sides A, B: Mode 1 Side C, Mode 3, 250kHz 100:1, fCLK = 500kHz, Q = 10 Sides A, B: Mode 1 Side C: Mode 3 Same as Above fO × Q ≤ 120kHz, Mode 1, 50:1 fO × Q ≤ 120kHz, Mode 3, 50:1 0.1– 12k 0.1– 10k 0 – 20k 50 ± 0.6% 50 ± 1.0% 100 ± 0.6% 100 ± 1.0% Hz Hz Hz ±2 ±3 700 4.5 6 % % kHz mA (Internal Op Amps) TA = 25°C, unless otherwise specified. Supply Voltage Range Voltage Swings LTC1061A LTC1061 LTC1061, LTC1061A Output Short-Circuit Current Source/Sink DC Open-Loop Gain GBW Product Slew Rate VS = ± 5V, RL = 5k (Pins 1,2,13,14,19,20) VS = ± 5V, RL = 3.5k (Pins 3,12,18) q ± 2.37 ± 4.0 ± 3.8 ± 3.6 ± 4.2 ± 4.2 ±9 V V V V mA dB MHz V/µs VS = ± 5V VS = ± 5V, RL = 5k VS = ± 5V VS = ± 5V 40/3 80 3 7 The q denotes the specifications which apply over the full operating temperature range. 3 LTC1061 TYPICAL PERFOR A CE CHARACTERISTICS Mode 1, Mode 3 (fCLK/fO) Deviation vs Q 0.4 0 % DEVIATION (fCLK /fO) 0.1 % DEVIATION (fCLK /fO) VS = ±5V TA = 25°C fCLK = 500kHz DEVIATION OF fCLK /fO WITH RESPECT TO Q = 10 MEASUREMENT (%) VS = ±5V TA = 25°C fCLK = 250kHz fCLK /fO = 50 (TEST POINT) –0.4 –0.8 –1.2 –1.6 –2.0 –2.4 . –0.1 –0.2 –0.3 –0.4 –0.5 –0.6 fCLK /fO = 100 (TEST POINT) . 0.1 1 IDEAL Q 10 Mode 1: (fCLK/fO) = 50:1 TA = 25°C fCLK /fO = 50/1 VS = ± 2.5V 10 50 Q 1MHz, ADD CC SUCH AS CC ≅ Figure 11. Mode 3a: 2nd Order Filter Providing Highpass, Bandpass, Lowpass, Notch U operate with center frequencies up to 24kHz. The speed of the filter could be further improved by using Mode 1 to lock the higher resonant frequency of 1.05 and higher Q or 31.9 to the clock, Figure 10b, thus changing the clock to center frequency ratio to 52.6:1. Mode 3a – This is an extension of Mode 3 where the highpass and lowpass outputs are summed through two external resistors Rh and Rl to create a notch, Figure 11. Mode 3a is very versatile because the notch frequency can be higher or lower than the center frequency of the 2nd order section. The external op amp of Figure 11 is not always required. When cascading the sections of the LTC1061, the highpass and lowpass outputs can be summed directly into the inverting input of the next section. Figure 12 shows an LTC1061 providing a 6th order elliptic bandpass or notch response. Sides C and B are connected in Mode 3a while side A is connected in Mode 1 and uses only two resistors. The resulting filter response is then geometrically symmetrical around either the center frequency of side A (for bandpass responses) or the notch frequency of side A (for notch responses). CC W + Σ – ∫ Rh ∫ Rl Rg – NOTCH + √ EXTERNAL OP AMP OR INPUT OP AMP OF THE LTC1061, SIDES A, B, C ( ) ( ) 1061 F11 9 LTC1061 ODES OF OPERATIO Rl2 1 R33 R23 2 3 4 5 LTC1061 6 7 15 14 13 12 11 20 19 18 17 16 T 2L, CMOS CLOCK INPUT V+ 8 9 10 VOUT/VIN (dB) VIN NOTES: FOR NOTCH RESPONSES, PIN 7 SHOULD BE PREFERABLY CONNECTED TO GROUND AND THE FILTER OUTPUT IS PIN 3. FOR BANDPASS OR LOWPASS RESPONSES, PIN 7 CAN BE EITHER AT GROUND OR POSITIVE SUPPLY, AND THE FILTER OUTPUT IS PIN 2 OR PIN 1. LTC1061 F12 Figure 12. 6th Order Elliptic Bandpass, Lowpass or Notch Topology Figure 13 shows the measured frequency response of the circuit Figure 12 configured to provide a notch function. The filter output is taken out of pin 3. The resistor values are standard 1%. The ratio of the 0dB width, BW1, to the notch width BW2, is 5:1 and matches the theoretical design value. The measured notch depth was –53dB versus –56dB theoretical and the clock-to-center notch frequency ratio is 100:1. Figure 14 shows the measured frequency response of the circuit topology, Figure 12, but with pole/zero locations configured to provide a high Q, 6th order elliptic bandpass filter operating with a clock-to-center frequency ratio of 50:1 or 100:1. The theoretical passband ripple, stopband attenuation and stopband to ripple bandwidth ratio are 0.5dB, 56dB, 5:1 respectively. The obtained results with 1% standard resistor values closely match the theoretical frequency response. For this application, the normalized VOUT/VIN (dB) 10 U R h2 R42 R32 R22 W center frequencies, Qs, and notch frequencies are (fO1 = 0.969, Q1 = 54.3, fn1 = 0.84, fO2 = 1.031, Q2 = 54.3, fn2 = 1.187, fO3 = 1, Q3 = 26.2). The output of the filter is the BP output of Side A, Pin 2. Lowpass filters with stopband notches can also be realized by using Figure 12 provided that 6th order lowpass filter approximations with 2 stopband notches can be synthesized. Literature describing elliptic double terminated (RLC) Rl 1 V– R41 R31 R21 Rh1 R11 0 –10 –20 –30 –40 –50 –60 –70 1.0 VS = ± 5V fCLK = 260kHz 1.5 BW2 BW1 STANDARD 1% RESISTOR VALUES R11 = 165k R21 = 10k R31 = 143k R41 = 13k Rh1 = 10k Rl1 = 10.5k R22 = 20k R32 = 221k R42 = 15.4k Rh2 = 10.5k R23 = 84.5k Rl2 = 10k R33 = 169k NOTES: USE A 15pF CAPACITOR BETWEEN PINS 17 AND 18. PIN 7 IS GROUNDED. 2.6kHz 2.5 2.0 fIN (kHz) 3.0 3.5 1061 F13 Figure 13. Resistor Values and Amplitude Response of Figure 12 Topology. The Notch is Centered at 2600Hz. 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 1.0 VS = ±5V fCLK = 130kHz STANDARD 1% RESISTOR VALUES R11 = 576k R21 = 10k R31 = 562k R41 = 10.7k Rh11 = 28.7k Rl11 = 40.2k R22 = 10.7k R32 = 562k R42 = 10k Rh2 = 14k R23 = 2.94k Rl2 = 10k R33 = 75k NOTE: FOR CLOCK FREQUENCIES ABOVE 500kHz, CONNECT A 5pF IN PARALLEL WITH R41 AND R42. 1.5 2.5 2.0 fIN (kHz) 3.0 3.5 1061 F14 Figure 14. Resistor Values and Amplitude Response of Figure 12 Topology. The Bandpass Filter is Centered Around 2600Hz when Operating with a 130kHz Clock. LTC1061 ODES OF OPERATIO 0 –20 VOUT/VIN (dB) –40 –50 –60 –70 –80 –90 0 1 2 3 456 fIN (kHz) 7 8 9 NOTES: USE A 10pF ACROSS R42 FOR fCLK > 1MHz. THE ELLIPTIC LOWPASS FILTER HAS ONLY TWO NOTCHES IN THE STOPBAND, AND IT OPERATES WITH A CLOCK TO CUTOFF FREQUENCY RATIO OF 50:1. 10 1061 F15 R43 R33 R23 1 2 3 4 5 LTC1061 6 7 Figure 15. Resistor Values and Amplitude Response of the Topology of Figure 12. passive ladder filters provide enough data to synthesize the above filters. The measured amplitude response of such a lowpass is shown in Figure 15 where the filter output is taken out of side A’s Pin 1, Figure 12. The clockto-center frequency ratio can be either 50:1 or 100:1 because the last stage of the LTC1061 operates in Mode 1 with a center frequency very close to the overall cutoff frequency of the lowpass filter. In Figure 16, all three sides of the LTC1061 are connected in Mode 3a. This topology is useful for elliptic highpass and notch filters with clock-to-cutoff (or notch) frequency ratio higher than 100:1. This is often required to extend the allowed input signal frequency range and to avoid premature aliasing. Figure 16 is also a versatile, general purpose architecture providing 3 notches and 4 pole pairs, and there is no restriction on the location of the poles with respect to the notch frequencies. The drawbacks, when compared to Figure 12, are the use of an external op amp and the increased number of the required external resistors. Figure 17 shows the measured frequency of a 6th order highpass elliptic filter operating with 250:1 clock-to-cutoff frequency ratio. With a 1MHz clock, for instance, the filter yields a 4kHz cutoff frequency, thus allowing an input frequency range beyond 100kHz. Band limiting can be easily added by placing a capacitor across the feedback resistor of the external op amp of Figure 16. T 2Ll, CMOS CLOCK INPUT V+ 8 9 10 VIN Figure 16. Using an External Op Amp to Connect all 3 Sides of the LTC1061 in Mode 3a. 0 –10 –20 fCLK = 250kHz VOUT/VIN (dB) –30 –40 –50 –60 –70 –80 –90 0 0.5 1.5 1.0 fIN (kHz) 2.0 Figure 17. Measured Amplitude Response of the Topology of Figure 16, Configured to Provide a 6th Order Elliptic Highpass Filter Operating with a Clock-to-Cutoff Frequency Ratio of 250:1. + –30 Rh3 Rl3 – –10 STANDARD 1% RESISTOR VALUES R21 = 10k R11 = 39.2k R41 = 39.2k R31 = 13.7k Rl1 = 12.4k Rh1 = 20.5k R22 = 10k R32 = 26.7k R42 = 14k Rh2 = 32.4k R23 = 10k Rl2 = 11.8k R33 = 100k U Rg LT1056 VOUT 20 19 18 17 16 15 14 13 12 11 Rh1 R11 LTC1061 F16 W Rl2 R42 R32 R22 Rh2 V– Rl1 R41 R31 R21 STANDARD 1% RESISTOR VALUES R21 = 10k R11 = 105k R41 = 45.3k R31 = 47.5k Rl1 = 1.07M Rh1 = 10k R22 = 32.4k R32 = 28.7k R42 = 52.3k Rh2 = 42.2k R23 = 10k Rl2 = 750k R33 = 255k R43 = 63.4k Rh3 = 10k Rl3 = 110k Rg = 140k NOTE: FOR CLOCK FREQUENCIES BELOW 500kHz, USE A CAPACITOR IN PARALLEL WITH R21 SUCH AS (1/2πR21C) ≅ fCLK /3. 2.5 1061 F17 11 LTC1061 ODES OF OPERATIO Figure 18 shows the plotted amplitude responses of a 6th order notch filter operating again with a clock-to-center notch frequency ratio of 250:1. The theoretical notch depth is 70dB and when the notch is centered at 1kHz its width is 50Hz. Two small, noncritical capacitors were used across the R21 and R22 resistors of Figure 16, to bandlimit the first two highpass outputs such that the practical notch depth will approach the theoretical value. With these two fixed capacitors, the notch frequency can be swept within a 3:1 range. When the circuit of Figure 16 is used to realize lowpass elliptic filters, a capacitor across Rg raises the order of the filter and at the same time eliminates any small clock feedthrough. This is shown in Figure 19 where the amplitude response of the filter is plotted for 3 different cutoff frequencies. When the clock frequency equals or exceeds 1MHz, the stopband notches lose their depth due to the finite bandwidth of the internal op amps and to the small crosstalk between the different sides of the LTC1061. The lowpass filter, however, does not lose its passband accuracy and it maintains nearly all of its attenuation slope. The theoretical performance of the 7th order lowpass filter of Figure 19 is 0.2dB passband ripple, 1.5:1 stopband-tocutoff frequency ratio, and 73dB stopband attenuation. Without any tuning, the obtained results closely approximate the textbook response. STANDARD 1% RESISTOR VALUES R11 = 84.5k R21 = 10.2k R31 = 31.6k R41 = 63.4k Rh1 = 48.7k Rl1 = 287k R22 = 10k R32 = 232k R42 = 97.6k Rh2 = 10.2k R23 = 20k Rl2 = 66.5k R33 = 300k R43 = 80.6k Rh3 = 10.2k Rl3 = 63.4k Rg = 210k NOTE: CONNECT 39pF AND 100pF ACROSS R21 AND R22 RESPECTIVELY. VOUT/VIN (dB) 0 –10 VOUT/VIN (dB) –20 –30 –40 –50 –60 fCLK = 250kHz –70 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 fIN (kHz) Figure 18. 6th Order Band Reject Filter Operating with a Clockto-Center Notch Frequency Ratio of 250:1. The Ratio of 0dB to the – 65dB Notch Width is 8:1. 12 U 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 1 4 10 fIN (kHz) 100 fCLK fCLK 200kHz 500kHz fCLK 1MHz STANDARD 1% RESISTOR VALUES R11 = 30.9k R21 = 10k R31 = 16.2k R41 = 26.7k Rh1 = 45.3k Rl1 = 19.6k R22 = 10.5k R32 = 100k R42 = 10k Rh2 = 52.3k R23 = 10k Rl2 = 15.8k R33 = 28.7k R43 = 12.7k Rh3 = 95.3k Rl3 = 10k Rg = 28k NOTE: ADD A CAPACITOR C ACROSS Rg TO CREATE A 7TH ORDER LOWPASS SUCH AS (1/2πRgC) = (CUTOFF FREQUENCY) × 0.38 1061 F19 W Figure 19. Frequency Responses of a 7th Order Lowpass Elliptic Filter Realized with Figure 16 Topology. Mode 2 – This is a combination of Mode 1 and Mode 3, Figure 20. With Mode 2, the clock-to-center frequency ratio, fCLK/fO, is always less than 50:1 or 100:1. When compared to Mode 3 and for applications requiring 2nd order section with fCLK/fO slightly less than 100 or 50:1, Mode 2 provides less sensitivity to resistor tolerances. As in Mode 1, Mode 2 has a notch output which directly depends on the clock frequency and therefore the notch frequency is always less than the center frequency, fO, of the 2nd order section. R4 R3 R2 N VIN R1 S BP LP – + AGND + Σ – ∫ ∫ 1061 F20 1061 F18 fCLK f 1 + R2 ; fn = CLK ; Q = R3 1 + R2 R4 100(50) 100(50) R4 R2 HOLP = –R2/R1 ; HOBP = – R3 R1 1 + (R2/R4) f R2 HON1 (f → 0) = –R2/R1 ; HON2 f → CLK = – R1 2 1 + (R2/R4) fO = √ √ ( ) Figure 20. Mode 2: 2nd Order Filter Providing Notch, Bandpass, Lowpass. LTC1061 ODES OF OPERATIO Figure 21 shows the side A of the LTC1061 connected in Mode 2 while sides B and C are in Mode 3a. This topology can be used to synthesize elliptic bandpass, highpass and notch filters. The elliptic highpass of Figure 17 is synthesized again, Figure 22, but the clock is now locked onto the Rh2 Rl2 R43 R33 R23 1 2 3 4 5 LTC1061 6 7 T 2L, CMOS CLOCK INPUT V+ 8 9 10 15 14 13 12 11 Rh1 R11 VIN LTC1061 F21 20 19 18 17 16 V– Figure 21. LTC1061 with Side A is Connected in Mode 2 While Side B, C are in Mode 3a. Topology is Useful for Elliptic Highpass, Notch and Bandpass Filters. 0 –10 –20 VOUT/VIN (dB) –30 –40 –50 –60 –70 –80 –90 0 1 2 3 456 fIN (kHz) 7 8 9 STANDARD 1% RESISTOR VALUES R21 = 24.3k R11 = 54.9k R41 = 10k R31 = 34.8k Rl1 = 280k Rh1 = 28.7k R22 = 68.1k R32 = 18.2k R42 = 10k Rh2 = 10.2k R23 = 10k Rl2 = 16.2k R33 = 75k R43 = 14k NOTE: FOR CLOCK FREQUENCIES ABOVE 300kHz, ADD A CAPACITOR C ACROSS R21 AND R22 SUCH AS (1/2πR21C) = fCLK 10 1061 F22 Figure 22. 6th Order Elliptic Highpass Filter Operating with a Clock-to-Cutoff Frequency Ratio of 75:1, and Using the Topology of Figure 21. U VOUT R42 R32 R22 W higher frequency notch provided by the side A of the LTC1061. As shown in Figure 22, the highpass corner frequency is 3.93kHz and the higher notch frequency is 3kHz while the filter operates with a 300kHz clock. The center frequencies, Qs, and notches of Figure 22, when normalized to the highpass cutoff frequency, are (fO1 = 1.17, Q1 = 2.24, fn1 = 0.242, fO2 = 1.96, Q2 = 0.7, fn2 = 0.6, fO3 = 0.987, fn3 = 0.753, Q3 = 10). When compared with the topology of Figure 16, this approach uses lower and more restricted clock frequencies. The obtained notch in Mode 2 is shallower although the topology is more efficient. Output Noise Rl1 R41 R31 R21 The wideband RMS noise of the LTC1061 outputs is nearly independent from the clock frequency. The LTC1061 noise when operating with ± 2.5V supply is lower, as Table 3 indicates. The noise at the bandpass and lowpass outputs increases rough as the √Q. Also the noise increases when the clock-to-center frequency ratio is altered with external resistors to exceed the internally set 100:1 or 50:1 ratios. Under this condition, the noise increases square root-wise. Output Offsets The equivalent input offsets of the LTC1061 are shown in Figure 23. The DC offset at the filter bandpass output is always equal to VOS3. The DC offsets at the remaining two outputs (Notch and LP) depend on the mode of operation and external resistor ratios. Table 4 illustrates this. It is important to know the value of the DC output offsets, especially when the filter handles input signals with large dynamic range. As a rule of thumb, the output DC offsets increase when: 1. The Qs decrease 2. The ratio (fCLK/fO) increases beyond 100:1. This is done by decreasing either the (R2/R4) or the R6/(R5 + R6) resistor ratios. 13 LTC1061 ODES OF OPERATIO VS (±V) 5.0 5.0 2.5 2.5 5.0 5.0 2.5 2.5 5.0 5.0 2.5 2.5 5.0 5.0 2.5 2.5 fCLK/fO 50:1 100:1 50:1 100:1 50:1 100:1 50:1 100:1 50:1 100:1 50:1 100:1 50:1 100:1 50:1 100:1 NOTCH/HP (µVRMS) 45 65 30 40 18 20 15 17 57 72 40 50 135 170 100 125 (11,17) 4 +V OS1 –– + 6 Figure 23. Equivalent Input Offsets of 1/3 LTC1061 Filter Building Block. MODE 1 1b 2 3 VOSN PIN 3 (18) VOS1 [(1/Q) + 1 + || HOLP ||] – VOS3/Q VOS1 [(1/Q) + 1 + R2/R1] – VOS3/Q [VOS1 (1 + R2/R1 + R2/R3 + R2/R4) – VOS3(R2/R3)] × × [R4/(R2 + R4)] + VOS2[R2/(R2 + R4)] VOS2 14 U Table 3. Wideband RMS Noise BP (µVRMS) 55 65 30 40 150 200 100 140 57 72 40 50 120 160 88 115 LP (µVRMS) 70 85 45 60 150 200 100 140 62 80 42 53 140 185 100 130 CONDITIONS Mode 1, R1 = R2 = R3 Q=1 Mode 1, Q = 10 R1 = R3 for BP Out R1 = R2 for LP Out Mode 3, R1 = R2 = R3 = R4 Q=1 Mode 3, R2 = R4, Q = 10 R3 = R1 for BP Out R4 = R1 for LP and HP Out 3 (12,18) 2 (13,19) 1 (14,20) W + Σ + VOS2 – – 5 – + + VOS3 – – + 1061 F23 Table 4 VOSBP PIN 2 (19) VOS3 VOS3 VOS3 VOS3 VOSLP PIN 1 (20) VOSN – VOS2 ~(VOSN – VOS2)(1 + R5/R6) VOSN – VOS2 VOS1 (1 + R4/R1 + R4/R2 + R4/R3) – VOS2(R4/R2) – VOS3 (R4/R3) LTC1061 PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. J Package 20-Lead Ceramic DIP 0.160 (4.064) MAX 0.015 – 0.060 (0.381 – 1.524) 0.200 (5.080) MAX 1.060 (26.924) MAX 20 19 18 17 16 15 14 13 12 11 0.290 – 0.320 (7.366 – 8.128) 0.220 – 0.310 0.025 (5.588 – 7.874) (0.635) RAD TYP 1 2 0.005 (0.127) MIN 3 4 5 6 7 8 9 10 0.008 – 0.018 (0.203 – 0.457) 0° – 15° 0.385 ± 0.025 (9.779 ± 0.635) 0.125 (3.175) MIN 0.080 (2.032) TYP 0.038 – 0.068 (0.965 – 1.727) 0.014 – 0.026 (0.356 – 0.660) 0.100 ± 0.010 (2.540 ± 0.254) N Package 20-Lead Plastic DIP 0.300 – 0.325 (7.620 – 8.255) 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 1.040 (26.416) MAX 20 19 18 17 16 15 14 13 12 11 0.009 – 0.015 (0.229 – 0.381) 0.015 (0.381) MIN 0.065 (1.651) TYP 0.125 (3.175) MIN 0.260 ± 0.010 (6.604 ± 0.254) ( +0.025 0.325 –0.015 +0.635 8.255 –0.381 1 0.065 ± 0.015 (1.651 ± 0.381) 0.100 ± 0.010 (2.540 ± 0.254) 0.018 ± 0.003 (0.457 ± 0.076) 2 3 4 5 6 7 8 9 10 ) S Package 20-Lead Plastic SOL 0.291 – 0.299 (7.391 – 7.595) 0.005 (0.127) RAD MIN 0.010 – 0.029 × 45° (0.254 – 0.737) 0.496 – 0.512 (12.598 – 13.005) 0.093 – 0.104 (2.362 – 2.642) 0.037 – 0.045 (0.940 – 1.143) 20 19 18 17 16 15 14 13 12 11 0° – 8° TYP 0.050 (1.270) TYP 0.014 – 0.019 (0.356 – 0.482) TYP 2 3 5 7 8 9 10 SEE NOTE 0.004 – 0.012 (0.102 – 0.305) 0.394 – 0.419 (10.007 – 10.643) 0.009 – 0.013 (0.229 – 0.330) SEE NOTE 0.016 – 0.050 (0.406 – 1.270) NOTE: 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. 1 4 6 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. 15 LTC1061 U.S. Area Sales Offices NORTHEAST REGION Linear Technology Corporation One Oxford Valley 2300 E. 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The Coliseum, Riverside Way Camberley, Surrey GU15 3YL United Kingdom Phone: 44-276-677676 FAX: 44-276-64851 World Headquarters Linear Technology Corporation 1630 McCarthy Blvd. Milpitas, CA 95035-7487 Phone: (408) 432-1900 FAX: (408) 434-0507 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 LT/GP 0294 2K REV C © LINEAR TECHNOLOGY CORPORATION 1994