LTC1560-1 1MHz/500kHz Continuous Time, Low Noise, Lowpass Elliptic Filter either 500kHz (Pin 5 to V +) or 1MHz (Pin 5 to V –). When programmed for 1MHz, the passband ripple is typically ±0.2dB up to 0.55fCUTOFF and ±0.3dB to 0.9fCUTOFF. The transition band gain is – 24dB at 1.4fCUTOFF and – 51dB at 2fCUTOFF. Stopband attenuation is 63dB at 2.43fCUTOFF and above, remaining at least 60dB to 10MHz with proper board layout. When the LTC1560-1 is programmed for fCUTOFF = 500kHz, the filter response closely follows the 1MHz case with the exception of passband flatness near the cutoff frequency; the gain at fCUTOFF is – 1.3dB. FEATURES ■ ■ ■ ■ ■ ■ ■ 5th Order, 1MHz Elliptic Filter in SO-8 Package Pin Selectable 1MHz/500kHz Cutoff Frequency Signal-to-Noise Ratio (SNR): 75dB Signal-to-Noise Ratio with – 63dB THD: 69dB Passband Ripple (fCUTOFF = 1MHz): ±0.3dB Stopband Attenuation Better Than 60dB No External Components Required U APPLICATIONS ■ ■ ■ The LTC1560-1, unlike other high frequency filters, is designed for low noise and low distortion. With a 1VRMS input signal, the signal-to-noise ratio is 69dB and the THD is – 63dB. The maximum SNR of 75dB is obtained with a 2.1VRMS input signal. This results in – 46dB THD. Antialiasing Filters Smoothing or Reconstruction Filters Communication Filters The LTC1560-1 operates with ±5V supplies, has a power saving mode and is available in an SO-8 surface mount package. U DESCRIPTION The LTC ®1560-1 is a 5th order, continuous-time, lowpass filter. The elliptic transfer function of the LTC1560-1 was carefully chosen to reach a compromise between selectivity, for antialiasing applications, and transient response. The filter cutoff frequency, fCUTOFF, is pin selectable to Other cutoff frequencies from 450kHz to 1.5MHz can be obtained. Demo board DC135A is available for the LTC1560-1. For more information please contact LTC Marketing. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION Frequency Response 10 1MHz/500kHz Elliptic Lowpass Filter 0 VIN – 5V 0.1µF 2 GND VOUT VIN SHDN 8 7 LTC1560-1 3 GND V+ 6 4 5 V– 0.5fC /fC –10 VOUT –20 (OR – 5V) 5V 0.1µF 0.01µF GAIN (dB) 1 –30 –40 –50 – 60 –70 0.01µF – 5V 1MHz 5V 500kHz 1560-1 TA01 – 80 fCUTOFF = 1MHz/500kHz – 90 1 0.1 FREQUENCY (MHz) 10 1560-1 TA02 1 LTC1560-1 U W U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION Total Supply Voltage (V + to V –) ............................. 12V Power Dissipation............................................. 400mW Burn-In Voltage ................................................... ±5.5V Operating Temperature Range LTC1560-1C ........................................... 0°C to 70°C LTC1560-1I ....................................... – 40°C to 85°C Maximum Junction Temperature ......................... 150°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW GND 1 8 VOUT VIN 2 7 SHDN GND 3 6 V+ V– 4 5 0.5fC/fC LTC1560-1CS8 LTC1560-1IS8 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO 15601 15601I TJMAX = 150°C, θJA = 125°C/ W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS VS = ±5V, TA = 25°C, Pin 5 = – 5V (fCUTOFF = 1MHz), Pin 7 = 0V unless otherwise specified. PARAMETER CONDITIONS Operating Supply Voltage Range Passband Gain (fCUTOFF = 1MHz) Transition Band Gain (Note 1) VIN = 0.5VRMS, fIN = 20kHz fIN = 100kHz fIN = 300kHz fIN = 550kHz (Gain Relative to 100kHz) fIN = 850kHz (Gain Relative to 100kHz) fIN = 950kHz (Gain Relative to 100kHz) fIN = fCUTOFF = 1MHz (Gain Relative to 100kHz) VIN = 0.5VRMS, fIN = 1.4MHz fIN = 1.9MHz fIN = 2.0MHz Stopband Gain (fCUTOFF = 1MHz) (Note 2) fIN = 2.44MHz fIN = 3.0MHz fIN = 6.0MHz Passband Gain (fCUTOFF = 500kHz) fIN = 100kHz, Pin 5 = 5V fIN = fCUTOFF = 500kHz fIN = 1.4MHz Output Voltage Swing RL = 5k MIN TYP MAX ±4.5 ±5.0 ±5.5 ● – 0.3 ● ● ● ● – 0.35 – 0.8 – 3.0 – 5.0 0.17 0.18 0.08 0.05 – 0.3 0.6 – 1.0 V dB dB dB dB dB dB dB 0.6 0.3 0 0.5 1.0 ● – 24 – 42 – 51 –18 dB dB dB ● – 70 – 68 – 66.1 – 65 dB dB dB ● –4 0.14 – 1.6 – 45 ● ±1.9 ±3 22 ● dB dB dB 0.5 V ±250 Output DC Offset (VOS) Power Supply Current (IS) UNITS mV 29 1 mA Power Supply Current in Shutdown Mode Pin 7 at 5V Total Output Noise VIN (Pin 2) Tied to Ground, fCUTOFF = 1MHz, BW = 2MHz VIN (Pin 2) Tied to Ground, fCUTOFF = 0.5MHz, BW = 1MHz 350 322 µVRMS µVRMS Total Harmonic Distortion (THD) VIN = 1VRMS, fIN = 200kHz, fCUTOFF = 1MHz, BW = 1MHz fIN = 300kHz, fCUTOFF = 1MHz, BW = 1MHz fIN = 1MHz, fCUTOFF = 1MHz, BW = 2MHz – 63 – 61 – 62 dB dB dB – 62 – 63 dB dB fIN = 300kHz, fCUTOFF = 0.5MHz, BW = 1MHz fIN = 500kHz, fCUTOFF = 0.5MHz, BW = 1MHz Input Resistance (RIN) The ● denotes specifications which apply over the full operating temperature range. Note 1: To properly measure high frequency characteristics of the filter, a noninverting output buffer is recommended as shown on the demo board 2 ● 6 8 mA 10 kΩ connection diagram, Figure 2. A small resistor (e.g. 100Ω) can also be used instead of the buffer to isolate any high capacitive load (CL > 10pF) from the filter output. Note 2: The stopband gain at 2.44MHz is guaranteed by design. LTC1560-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Frequency Response 10 Frequency Response 10 fCUTOFF = 1MHz 0 0 –10 –10 fCUTOFF = 500kHz – 40 –50 0.2 –30 GAIN (dB) GAIN (dB) –30 – 40 –50 –70 –70 – 80 – 0.4 –90 – 80 0 2 1 4 3 – 0.6 0 1.0 0.5 FREQUENCY (MHz) FREQUENCY (MHz) Group Delay 1.6 Group Delay 2.25 fCUTOFF = 1MHz fCUTOFF = 500kHz fCUTOFF = 500kHz 2.00 0 1.2 1.75 – 0.4 – 0.6 – 0.8 GROUP DELAY (µs) 1.4 GROUP DELAY (µs) 0.2 – 0.2 1.0 0.8 0.6 0.4 –1.0 –1.2 0.2 –1.4 0 0.2 0.3 0.4 FREQUENCY (MHz) 0.5 1.25 1.00 0.75 0.25 0 0 0.25 0.50 0.75 1.0 1.25 1.50 1.75 2.0 FREQUENCY (MHz) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FREQUENCY (MHz) 1560-1 G05 Phase vs Frequency 1560-1 G06 Phase vs Frequency 0 45 fCUTOFF = 1MHz fCUTOFF = 500kHz – 45 – 45 – 90 PHASE (DEG) 0 –135 – 90 –135 –180 –180 –225 –225 1.50 0.50 1560-1 G04 PHASE (DEG) GAIN (dB) 1560-1 G03 1560-1 G02 Passband Gain 0.1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FREQUENCY (MHz) 2.0 1.5 1560-1 G01 0.4 0 – 0.2 – 60 – 60 fCUTOFF = 1MHz 0.4 –20 –20 GAIN (dB) Passband Gain 0.6 –270 20 100 180 260 340 420 FREQUENCY (kHz) 500 1560-1 G07 20 180 340 500 660 820 FREQUENCY (kHz) 980 1560-1 G08 3 LTC1560-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Transient Response Output Noise vs Frequency Transient Response 60 54 fCUTOFF = 1MHz TOTAL OUTPUT NOISE = 232µVRMS OUTPUT NOISE (µVRMS) 1V/DIV 1V/DIV 48 fCUTOFF = 0.5MHz VIN = 5VP-P fIN = 50kHz 1560-1 G09 2µs/DIV fCUTOFF = 1MHz VIN = 5V P-P fIN = 50kHz 36 30 24 18 12 1560-1 G10 2µs/DIV 42 6 0 0.1 0.5 FREQUENCY (MHz) 1.0 1.5 1560-1 G11 Dynamic Range Output Noise vs Frequency 60 – 20 fCUTOFF = 0.5MHz TOTAL OUTPUT NOISE = 198µVRMS 54 – 30 – 40 42 THD + NOISE OUTPUT NOISE (µVRMS) 48 fCUTOFF = 500kHz OR 1MHz fIN = 45kHz 36 30 24 18 – 50 – 60 – 70 12 – 80 6 0 50 100 200 400 FREQUENCY (kHz) – 90 0.1 600 1560-1 G12 1560-1 G13 THD + Noise vs Input Frequency – 52 – 54 THD + Noise vs Input Frequency – 52 fCUTOFF = 500kHz – 54 – 58 – 58 VIN = 1VRMS S/N = 74dB – 60 THD (dB) THD (dB) fCUTOFF = 1MHz – 56 – 56 – 62 – 64 – 66 – 60 VIN = 1VRMS S/N = 72dB – 62 – 64 – 66 VIN = 0.6VRMS S/N = 69.5dB – 68 VIN = 0.6VRMS S/N = 68dB – 68 –70 –70 –72 –72 40 60 80 100 120 140 160 180 200 INPUT FREQUENCY (kHz) 1560-1 G14 4 3 1 INPUT VOLTAGE (VRMS) 40 60 80 100 120 140 160 180 200 INPUT FREQUENCY (kHz) 1560-1 G15 LTC1560-1 U U U PIN FUNCTIONS GND (Pins 1, 3): Analog Ground Pins. The quality of the analog ground can affect the filter performance. For dual supply operation the analog ground pin should be connected to an analog ground plane surrounding the package. The analog ground plane should be connected to a digital ground plane (if any) at a single point. For single supply operation, the analog ground pin should be biased at one-half the power supply across the device (see Figure 1) and the analog ground plane should then be connected to V – (Pin 4). tion. The power supplies can be applied in any order, that is, the positive supply can be applied before the negative supply and vice versa. Switching power supplies are not recommended. VIN (Pin 2): The filter input is internally connected to the inverting input of a high frequency op amp through an 8k resistor. SHDN (Pin 7): Shutdown. Under normal operating conditions, Pin 7 should be shorted either to the analog ground (Pin 1) or to V – (Pin 4). If Pin 7 is pulled high to V +, the filter operation will stop and the IC will be placed in a power saving mode. The power supply current will then be reduced to 1mA. For a ±5V supply, the logic threshold of Pin 7 is 2.5V. Pin 7 is internally connected to the analog ground pin via a 50k resistor. V –, V + (Pins 4, 6): Power Supply Pins. The negative and positive power supply (Pins 4 and 6 respectively) should be decoupled with a 0.1µF capacitor in parallel with a 0.01µF. Both capacitors should be types designed for decoupling video frequencies and they should be placed as close as possible to the power supply pins of the filter. Parallel routing of high frequency signal paths should be avoided; they will couple into the device’s power supply pins and cause gain inaccuracy and stopband degrada- 0.5fC/fC (Pin 5): By tying Pin 5 high the filter cutoff frequency is internally programmed for 500kHz. By tying Pin 5 low the cutoff frequency will switch to 1MHz. Pin 5 should not be left floating. The logic threshold of Pin 5 is approximately 0.4 times the total power supply across the device. VOUT (Pin 8): The filter output pin can sink or source 1mA. The total harmonic distortion of the filter will degrade when driving coaxial cables or loads less than 10k without an output buffer. V+ 0.1µF 10k 0.01µF 1 1µF 0.01µF 10k VIN 2 3 4 GND VOUT VIN SHDN LTC1560-1 GND V+ V– 0.5fC /fC 8 VOUT 7 6 5 GND OR V+ ANALOG GROUND PLANE SYSTEM GROUND DIGITAL GROUND PLANE 1560-1 F01 Figure 1. Connections for Single Supply Operation 5 LTC1560-1 U W U U APPLICATIONS INFORMATION The performance of the LTC1560-1 can be easily evaluated by using demo board 135A which can be obtained through LTC marketing. Figure 2 shows the circuit connection of the LTC1560-1 in demo board 135A. The filter cutoff frequency can be switched via S2 and the power savings mode can also be activated via S1. The output of the filter is buffered by U2, an LT ®1360 op amp. The buffering can be bypassed by using jumper JP1. Figure 3 shows the demo board layout. R2 332Ω OUT2 15V C9 0.01µF JP1 JUMPER 3 2 1 2 R1 1k U1 LTC1560-1 1 E1 TP VIN – 5V E2 TP 2 3 4 C3 1µF 16V X7R C2 0.22µF GND VOUT VIN SHDN GND V – V+ 0.5fC/fC OUT1 6 + – 15V 4 8 C7 0.01µF C8 1µF 25V Y5V C5 0.22µF C6 1µF 16V X7R 7 6 5 E4 TP 7 U2 LT1360CS8 S1 GS01MSCKE C4 0.01µF C1 0.01µF 3 – C10 1µF 25V Y5V E3 TP S2 GS01MSCKE 5V E5 TP E6 TP E7 TP GND E8 TP E9 TP GND E10 TP GND 1560-1 F02 Figure 2. Demo Board 135A Connection Diagram FILTER INPUT UNBUFFERED OUTPUT BUFFERED OUTPUT GROUND + 5V FILTER SUPPLY GROUND GROUND +15V BUFFER SUPPLY – 5V FILTER SUPPLY – 15V BUFFER SUPPLY 1560-1 F03 Figure 3. Demo Board 135A Layout 6 LTC1560-1 U TYPICAL APPLICATIONS N Augmenting the LTC1560-1 for Improved Delay Flatness 40.2k 20k 22pF 5V 9.75k 1 2 VIN –5V GND VIN VOUT SHDN 7 LTC1560-1 3 GND V+ 6 4 5 V– 0.5fC /fC 22pF 6.49k 8 2 0.1µF – 1/2 LT1364 (OR – 5V) 3 6.65k 1 6 + + 49.9Ω 7 1/2 LT1364 5 5V 0.1µF – 8 VOUT 4 0.01µF 0.1µF – 5V 1560-1 TA05 0.01µF 0.1µF 2-Level Eye Diagram of the Equalized Filter 2Mbps/s 1560-1 TA06 1MHz Lowpass Filter Cascaded with a 30kHz 3rd Order Highpass Filter 10 560pF 5V 0 –10 0.1µF 560pF VIN 2 3 4 GND VIN VOUT SHDN LTC1560-1 GND V+ V– 0.5fC /fC 8 1k 7 39pF (OR – 5V) 3 6 5 + 8 1/2 LT1364 2 – 23.7k 560pF 1 – 30 6 – 1/2 LT1364 4 – 20 560pF 2.61k 5 7 + 0.01µF – 90 1560-1 TA09 0.1µF – 50 – 60 – 80 – 5V 0.01µF – 40 – 70 0.1µF 0.1µF GAIN (dB) 1 Gain vs Frequency –100 –110 0.1 1 10 100 1000 FREQUENCY (kHz) 10,000 1560-1 TA10 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. 7 LTC1560-1 U TYPICAL APPLICATION Measured Frequency Response A Simple Highpass/Lowpass Filter 15V 10 0 0.1µF 300pF 300pF 2 VIN 8.1k –5V 3 4 GND VIN VOUT SHDN LTC1560-1 GND V+ V– 0.5fC /fC 1k 8 7 3 7 LT1360 (OR – 5V) 6 + 2 – –20 8 VOUT GAIN (dB) 1 –10 4 5V 5 0.1µF –30 –40 –50 –60 0.01µF –70 0.1µF –80 0.1µF 0.01µF –15V –90 1560-1 TA07 20 100 1000 FREQUENCY (kHz) 10000 1560-1 TA08 U 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) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 8 0.004 – 0.010 (0.101 – 0.254) 7 6 5 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) *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 0.050 (1.270) BSC 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) SO8 0695 1 2 3 4 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1360/LT1361/ LT1362 50MHz, 800V/µs Op Amp(s) Single/Dual/Quad C-LoadTM Op Amps LTC1562 Active RC Quad Universal Filter Very Low Noise, Low Distortion C-Load is a trademark of Linear Technology Corporation 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900 FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com 15601f LT/GP 1197 4K • PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 1997