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LTC1560-1 1MHz/500kHz Continuous Time, Low Noise, Lowpass Elliptic Filter
FEATURES
s s s s s s s
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
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. 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. The LTC1560-1 operates with 5V supplies, has a power saving mode and is available in an SO-8 surface mount package. 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.
APPLICATIONS
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Antialiasing Filters Smoothing or Reconstruction Filters Communication Filters
DESCRIPTION
The LTC (R)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
TYPICAL APPLICATION
Frequency Response 1MHz/500kHz Elliptic Lowpass Filter
1 2 GND VIN VOUT SHDN 8 7 6 5 0.1F VOUT
GAIN (dB)
10 0 -10 -20 -30 -40 -50 - 60 -70
VIN
LTC1560-1 3 GND V+ - 5V 0.1F 0.01F 4 V- 0.5fC /fC
U
U
U
(OR - 5V) 5V 0.01F
- 5V 1MHz 5V 500kHz
1560-1 TA01
- 80
fCUTOFF = 1MHz/500kHz - 90 1 0.1 FREQUENCY (MHz)
10
1560-1 TA02
1
LTC1560-1
ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V + to V -) ............................. 12V Power Dissipation............................................. 400mW Burn-In Voltage ................................................... 5.5V Operating Temperature Range LTC1560-1C ........................................... 0C to 70C LTC1560-1I ....................................... - 40C to 85C Maximum Junction Temperature ......................... 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
PACKAGE/ORDER INFORMATION
TOP VIEW GND 1 VIN 2 GND 3 V- 4 8 7 6 5 VOUT SHDN V+ 0.5fC/fC
ORDER PART NUMBER LTC1560-1CS8 LTC1560-1IS8 S8 PART MARKING 15601 15601I
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 150C, JA = 125C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER Operating Supply Voltage Range Passband Gain (fCUTOFF = 1MHz) CONDITIONS
VS = 5V, TA = 25C, Pin 5 = - 5V (fCUTOFF = 1MHz), Pin 7 = 0V unless otherwise specified.
MIN 4.5 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 fIN = 2.44MHz fIN = 3.0MHz fIN = 6.0MHz fIN = 100kHz, Pin 5 = 5V fIN = fCUTOFF = 500kHz fIN = 1.4MHz RL = 5k
q q q q q q
TYP 5.0 0.17 0.18 0.08 0.05 - 0.3 0.6 - 1.0 - 24 - 42 - 51 - 70 - 68 - 66.1
MAX 5.5 0.6 0.3 0 0.5 1.0 -18
UNITS V dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB dB V mV
- 0.3 - 0.35 - 0.8 - 3.0 - 5.0
Transition Band Gain (Note 1)
Stopband Gain (fCUTOFF = 1MHz) (Note 2)
q
- 65
Passband Gain (fCUTOFF = 500kHz)
q q
-4 1.9
0.14 - 1.6 - 45 3 250 22 1 350 322 - 63 - 61 - 62 - 62 - 63
0.5
Output Voltage Swing Output DC Offset (VOS) Power Supply Current (IS) Power Supply Current in Shutdown Mode Total Output Noise Total Harmonic Distortion (THD)
q
29
Pin 7 at 5V VIN (Pin 2) Tied to Ground, fCUTOFF = 1MHz, BW = 2MHz VIN (Pin 2) Tied to Ground, fCUTOFF = 0.5MHz, BW = 1MHz VIN = 1VRMS, fIN = 200kHz, fCUTOFF = 1MHz, BW = 1MHz fIN = 300kHz, fCUTOFF = 1MHz, BW = 1MHz fIN = 1MHz, fCUTOFF = 1MHz, BW = 2MHz fIN = 300kHz, fCUTOFF = 0.5MHz, BW = 1MHz fIN = 500kHz, fCUTOFF = 0.5MHz, BW = 1MHz
VRMS VRMS dB dB dB dB dB 10 k
Input Resistance (RIN) The q 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
q
6
8
connection diagram, Figure 2. A small resistor (e.g. 100) 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.
2
U
W
U
U
WW
W
mA mA
LTC1560-1 TYPICAL PERFORMANCE CHARACTERISTICS
Frequency Response
10 0 -10 -20 fCUTOFF = 1MHz 10 0 -10 -20
GAIN (dB)
GAIN (dB)
-30 - 40 -50 - 60 -70 - 80 0 1 2 FREQUENCY (MHz)
1560-1 G01
- 40 -50 - 60 -70 - 80 -90
GAIN (dB)
Passband Gain
0.4 0.2 0
fCUTOFF = 500kHz
GROUP DELAY (s)
- 0.2
GROUP DELAY (s)
GAIN (dB)
- 0.4 - 0.6 - 0.8 -1.0 -1.2 -1.4 0.1 0.2 0.3 0.4 FREQUENCY (MHz) 0.5
1560-1 G04
Phase vs Frequency
45 0 - 45 - 90
0
fCUTOFF = 500kHz
- 45 - 90
PHASE (DEG)
PHASE (DEG)
-135 -180 -225
20
100
UW
3
Frequency Response
fCUTOFF = 500kHz 0.6 0.4 0.2 0 - 0.2 - 0.4 - 0.6 0 0.5 1.0 FREQUENCY (MHz)
1560-1 G02
Passband Gain
fCUTOFF = 1MHz
-30
4
1.5
2.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FREQUENCY (MHz)
1560-1 G03
Group Delay
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 0.25 0.50 0.75 1.0 1.25 1.50 1.75 2.0 FREQUENCY (MHz)
1560-1 G05
Group Delay
2.25 fCUTOFF = 500kHz 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 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 G06
fCUTOFF = 1MHz
Phase vs Frequency
fCUTOFF = 1MHz
-135 -180
-225 -270
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 TYPICAL PERFORMANCE CHARACTERISTICS
Transient Response Transient Response
60 54 48
OUTPUT NOISE (VRMS)
1V/DIV
1V/DIV
fCUTOFF = 0.5MHz VIN = 5VP-P fIN = 50kHz
2s/DIV
Output Noise vs Frequency
60 54 48
OUTPUT NOISE (VRMS)
fCUTOFF = 0.5MHz TOTAL OUTPUT NOISE = 198VRMS
42 36 30 24 18 12 6 0 50 100 200 400 FREQUENCY (kHz) 600
1560-1 G12
THD + NOISE
THD + Noise vs Input Frequency
- 52 - 54 - 56 - 58
THD (dB) THD (dB)
fCUTOFF = 500kHz
- 60 - 62 - 64 - 66 - 68 -70 -72 40 60
80 100 120 140 160 180 200 INPUT FREQUENCY (kHz)
1560-1 G14
4
UW
1560-1 G09
Output Noise vs Frequency
fCUTOFF = 1MHz TOTAL OUTPUT NOISE = 232VRMS
42 36 30 24 18 12 6 0 0.1 0.5 FREQUENCY (MHz) 1.0 1.5
fCUTOFF = 1MHz VIN = 5V P-P fIN = 50kHz
2s/DIV
1560-1 G10
1560-1 G11
Dynamic Range
- 20 - 30 - 40 - 50 - 60 - 70 - 80 - 90 0.1 fCUTOFF = 500kHz OR 1MHz fIN = 45kHz
1 INPUT VOLTAGE (VRMS)
1560-1 G13
3
THD + Noise vs Input Frequency
- 52 - 54 - 56 - 58 fCUTOFF = 1MHz
VIN = 1VRMS S/N = 74dB
- 60 - 62 - 64 - 66 - 68 -70 -72 40 60 80 100 120 140 160 180 200 INPUT FREQUENCY (kHz)
1560-1 G15
VIN = 1VRMS S/N = 72dB
VIN = 0.6VRMS S/N = 69.5dB
VIN = 0.6VRMS S/N = 68dB
LTC1560-1
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). VIN (Pin 2): The filter input is internally connected to the inverting input of a high frequency op amp through an 8k 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 0.1F capacitor in parallel with a 0.01F. 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 degradation. 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. 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. 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. 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.
U
U
U
V+ 10k 0.1F 0.01F 1 1F 0.01F 2 3 4 GND VIN VOUT SHDN 8 7 6 5 GND OR V+ VOUT
10k
VIN
LTC1560-1 GND V+ V- 0.5fC /fC
ANALOG GROUND PLANE
SYSTEM GROUND
DIGITAL GROUND PLANE
1560-1 F01
Figure 1. Connections for Single Supply Operation
5
LTC1560-1
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 (R)1360 op amp. The buffering can be bypassed by using jumper JP1. Figure 3 shows the demo board layout.
JP1 JUMPER 3 2 1 R1 1k U1 LTC1560-1 1 E1 TP VIN 2 3 4 C3 1F 16V X7R C2 0.22F C1 0.01F GND VIN GND V
-
VOUT SHDN V+ 0.5fC/fC
8 7 6 5 C4 0.01F
S1 GS01MSCKE
- 5V E2 TP
S2 GS01MSCKE
Figure 2. Demo Board 135A Connection Diagram
FILTER INPUT GROUND + 5V FILTER SUPPLY GROUND - 5V FILTER SUPPLY
UNBUFFERED OUTPUT BUFFERED OUTPUT GROUND +15V BUFFER SUPPLY - 15V BUFFER SUPPLY
1560-1 F03
Figure 3. Demo Board 135A Layout
6
+
3
-
U
W
U
U
R2 332
OUT2 15V C9 0.01F C10 1F 25V Y5V
E3 TP E4 TP
2
7 6 OUT1 E5 TP E6 TP
U2 LT1360CS8 4
- 15V C7 0.01F C8 1F 25V Y5V C6 1F 16V X7R GND GND
5V
C5 0.22F
E7 TP
E8 TP E9 TP GND E10 TP
1560-1 F02
LTC1560-1
TYPICAL APPLICATIONS N
Augmenting the LTC1560-1 for Improved Delay Flatness
20k 22pF 5V 40.2k
1 2
GND VIN
VOUT SHDN
8 7 6 5
VIN
LTC1560-1 3 GND V+ -5V 4 V- 0.5fC /fC
0.1F
0.01F
1MHz Lowpass Filter Cascaded with a 30kHz 3rd Order Highpass Filter
5V 0.1F 1 560pF VIN 2 3 4 0.01F 0.1F GND VIN VOUT SHDN 8 7 6 5 0.1F 0.01F - 5V
1560-1 TA09
1k 39pF (OR - 5V)
1/2 LT1364 2
6
GAIN (dB)
LTC1560-1 GND V+ V- 0.5fC /fC
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
9.75k 6.49k 22pF 2
-
1/2 LT1364 1
0.1F 6.65k 6
(OR - 5V) 5V 0.1F 0.01F
- +
8 7 49.9 VOUT
3
+
5
1/2 LT1364 4
0.1F - 5V
1560-1 TA05
2-Level Eye Diagram of the Equalized Filter
2Mbps/s
1560-1 TA06
Gain vs Frequency
10 0 -10
560pF
23.7k 560pF 560pF
- 20 - 30 - 40 - 50 - 60 - 70 - 80 - 90 -100 -110 0.1 1 10 100 1000 FREQUENCY (kHz) 10,000
3
+ -
8 1
-
1/2 LT1364 7
4 0.1F
2.61k
5
+
1560-1 TA10
7
LTC1560-1
TYPICAL APPLICATION
A Simple Highpass/Lowpass Filter
15V 0.1F 1 300pF VIN 8.1k 300pF 2 3 4 GND VIN VOUT SHDN 8 7 6 5 0.1F 1k 3
(OR - 5V) 5V 0.01F
2
LTC1560-1 GND V+ V- 0.5fC /fC
-
GAIN (dB)
-5V
0.1F
0.01F
PACKAGE DESCRIPTION
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254)
0.053 - 0.069 (1.346 - 1.752) 0- 8 TYP
0.016 - 0.050 0.406 - 1.270
*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
RELATED PARTS
PART NUMBER LT1360/LT1361/ LT1362 LTC1562 DESCRIPTION 50MHz, 800V/s Op Amp(s) Active RC Quad Universal Filter COMMENTS Single/Dual/Quad C-LoadTM Op Amps 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 q (408) 432-1900 FAX: (408) 434-0507q TELEX: 499-3977 q www.linear-tech.com
U
U
Measured Frequency Response
10 0 -10 -20
8 VOUT 7 LT1360 4
+
-30 -40 -50 -60
0.1F -15V
1560-1 TA07
-70 -80 -90 20 100 1000 FREQUENCY (kHz) 10000
1560-1 TA08
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) 0.004 - 0.010 (0.101 - 0.254) 8 7 6 5
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) BSC
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
SO8 0695
1
2
3
4
15601f LT/GP 1197 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1997

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