LINER LTC1560-1IS8 1mhz/500khz continuous time, low noise, lowpass elliptic filter Datasheet

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
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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.
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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.
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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
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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
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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
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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
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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
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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
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LTC1560-1
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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
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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
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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
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