Page 1
LTC1560-1
FREQUENCY (MHz)
0.1
–90
GAIN (dB)
–70
–50
–30
–10
110
1560-1 TA02
10
–80
–60
–40
–20
0
f
CUTOFF
= 1MHz/500kHz
1MHz/500kHz
Continuous Time,
Low Noise, Lowpass Elliptic Filter
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 (f
■
Stopband Attenuation Better Than 60dB
■
No External Components Required
= 1MHz): ±0.3dB
CUTOFF
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APPLICATIONS
■
Antialiasing Filters
■
Smoothing or Reconstruction Filters
■
Communication Filters
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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, f
, is pin selectable to
CUTOFF
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 0.55f
transition band gain is –24dB at 1.4f
2f
. Stopband attenuation is 63dB at 2.43f
CUTOFF
and ±0.3dB to 0.9f
CUTOFF
CUTOFF
. The
CUTOFF
and –51dB at
and
CUTOFF
above, remaining at least 60dB to 10MHz with proper
board layout. When the LTC1560-1 is programmed for
f
= 500kHz, the filter response closely follows the
CUTOFF
1MHz case with the exception of passband flatness near
the cutoff frequency; the gain at f
CUTOFF
is –1.3dB.
The LTC1560-1, unlike other high frequency filters, is
designed for low noise and low distortion. With a 1V
RMS
input signal, the signal-to-noise ratio is 69dB and the THD
is –63dB. The maximum SNR of 75dB is obtained with a
2.1V
input signal. This results in –46dB THD.
RMS
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.
TYPICAL APPLICATION
1MHz/500kHz Elliptic Lowpass Filter
1
GND
2
V
3
GND
4
V
–5V
0.1µF
V
IN
0.01µF
IN
LTC1560-1
–
0.5f
V
OUT
SHDN
V
C/fC
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Frequency Response
8
V
OUT
7
(OR –5V)
6
+
5
0.1µF
5V
0.01µF
–5V
1MHz
5V
500kHz
1560-1 TA01
1
Page 2
LTC1560-1
WW
W
ABSOLUTE MAXIMUM RATINGS
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
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U
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PACKAGE/ORDER INFORMATION
TOP VIEW
GND
1
V
2
IN
GND
3
–
V
4
S8 PACKAGE
8-LEAD PLASTIC SO
T
= 150°C, θJA = 125°C/ W
JMAX
Consult factory for Military grade parts.
V
8
OUT
SHDN
7
+
V
6
0.5fC/f
5
C
ORDER PART
NUMBER
LTC1560-1CS8
LTC1560-1IS8
S8 PART MARKING
15601
15601I
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ELECTRICAL CHARACTERISTICS
VS = ±5V, TA = 25°C, Pin 5 = –5V (f
PARAMETER CONDITIONS MIN TYP MAX UNITS
Operating Supply Voltage Range ±4.5 ±5.0 ±5.5 V
Passband Gain (f
Transition Band Gain (Note 1) VIN = 0.5V
Stopband Gain (f
Passband Gain (f
Output Voltage Swing RL = 5k ● ±1.9 ±3V
Output DC Offset (VOS) ±250 mV
Power Supply Current (IS) ● 22 29 mA
Power Supply Current in Shutdown Mode Pin 7 at 5V 1 mA
Total Output Noise VIN (Pin 2) Tied to Ground, f
Total Harmonic Distortion (THD) VIN = 1V
Input Resistance (RIN) ● 6 8 10 kΩ
= 1MHz) VIN = 0.5V
CUTOFF
= 1MHz) (Note 2) fIN = 2.44MHz ● –70 –65 dB
CUTOFF
= 500kHz) fIN = 100kHz, Pin 5 = 5V 0.14 dB
CUTOFF
= 1MHz), Pin 7 = 0V unless otherwise specified.
CUTOFF
= 20kHz 0.17 dB
RMS,fIN
f
= 100kHz ● –0.3 0.18 0.6 dB
IN
f
= 300kHz 0.08 dB
IN
f
= 550kHz (Gain Relative to 100kHz) ● –0.35 0.05 0.3 dB
IN
= 850kHz (Gain Relative to 100kHz) ● –0.8 –0.3 0 dB
f
IN
f
= 950kHz (Gain Relative to 100kHz) ● –3.0 0.6 0.5 dB
IN
f
= f
IN
= 1.4MHz ● –24 –18 dB
RMS,fIN
f
= 1.9MHz –42 dB
IN
f
= 2.0MHz –51 dB
IN
f
= 3.0MHz –68 dB
IN
f
= 6.0MHz –66.1 dB
IN
f
= f
IN
f
= 1.4MHz –45 dB
IN
VIN (Pin 2) Tied to Ground, f
, fIN = 200kHz, f
RMS
f
= 300kHz, f
IN
= 1MHz, f
f
IN
fIN = 300kHz, f
f
= 500kHz, f
IN
= 1MHz (Gain Relative to 100kHz) ● –5.0 – 1.0 1.0 dB
CUTOFF
= 500kHz ● –4 –1.6 0.5 dB
CUTOFF
= 1MHz, BW = 2MHz 350 µV
CUTOFF
= 0.5MHz, BW = 1MHz 322 µV
CUTOFF
= 1MHz, BW = 1MHz –63 dB
CUTOFF
= 1MHz, BW = 1MHz –61 dB
CUTOFF
= 1MHz, BW = 2MHz –62 dB
CUTOFF
= 0.5MHz, BW = 1MHz –62 dB
CUTOFF
= 0.5MHz, BW = 1MHz –63 dB
CUTOFF
RMS
RMS
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
connection diagram, Figure 2. A small resistor (e.g. 100Ω) can also be
used instead of the buffer to isolate any high capacitive load (C
from the filter output.
Note 2: The stopband gain at 2.44MHz is guaranteed by design.
> 10pF)
L
Page 3
FREQUENCY (MHz)
0.1
GAIN (dB)
0
0.2
0.4
0.6
0.5
1560-1 G03
–0.2
–0.4
–0.6
0.2
0.3
0.4
0.6 0.7 0.8 0.9 1.0
f
CUTOFF
= 1MHz
W
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TYPICAL PERFORMANCE CHARACTERISTICS
LTC1560-1
Frequency Response
10
f
= 1MHz
CUTOFF
0
–10
–20
–30
–40
GAIN (dB)
–50
–60
–70
–80
0.4
0.2
0
–0.2
–0.4
–0.6
GAIN (dB)
–0.8
–1.0
–1.2
–1.4
0
f
CUTOFF
1
= 500kHz
2
FREQUENCY (MHz)
0.20.1 0.5
FREQUENCY (MHz)
3
1560-1 G01
0.3 0.4
1560-1 G04
Frequency Response Passband Gain
10
f
= 500kHz
CUTOFF
0
–10
–20
–30
–40
GAIN (dB)
–50
–60
–70
–80
4
–90
0
Group Delay
1.6
f
CUTOFF
1.4
1.2
1.0
0.8
0.6
GROUP DELAY (µs)
0.4
0.2
0
0
0.25
= 1MHz
0.50
0.5
1.0
FREQUENCY (MHz)
1.0
0.75
FREQUENCY (MHz)
1.25
1.5
1.50
1560-1 G02
1.75
1560-1 G05
2.0
2.0
GROUP DELAY (µs)
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
Group DelayPassband Gain
0
0
f
= 500kHz
CUTOFF
0.1 0.3
0.2 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FREQUENCY (MHz)
1560-1 G06
Phase vs Frequency
45
f
CUTOFF
0
–45
–90
PHASE (DEG)
–135
–180
–225
20
= 500kHz
180
FREQUENCY (kHz)
Phase vs Frequency
0
–45
–90
–135
PHASE (DEG)
–180
–225
–270
260100
340
500420
1560-1 G07
20
180
340
FREQUENCY (kHz)
f
= 1MHz
CUTOFF
500 660 820 980
1560-1 G08
3
Page 4
LTC1560-1
FREQUENCY (MHz)
0.1
0
OUTPUT NOISE (µV
RMS
)
12
24
36
48
0.5 1.51.0
1560-1 G11
60
6
18
30
42
54
f
CUTOFF
= 1MHz
TOTAL OUTPUT NOISE = 232µV
RMS
INPUT VOLTAGE (V
RMS
)
–90
–60
–70
–80
–20
–30
–40
–50
1560-1 G13
THD + NOISE
0.1
3
1
f
CUTOFF
= 500kHz OR 1MHz
f
IN
= 45kHz
W
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TYPICAL PERFORMANCE CHARACTERISTICS
Transient Response Transient Response
1V/DIV
CUTOFF
V
= 5V
IN
fIN = 50kHz
= 0.5MHz
P-P
2µs/DIVf
1560-1 G09
1V/DIV
CUTOFF
V
= 5V
IN
fIN = 50kHz
= 1MHz
P-P
2µs/DIVf
Output Noise vs Frequency
60
f
= 0.5MHz
CUTOFF
54
TOTAL OUTPUT NOISE = 198µV
48
)
42
RMS
36
30
24
18
OUTPUT NOISE (µV
12
6
0
50
200 400 600100
FREQUENCY (kHz)
RMS
1560-1 G12
Output Noise vs Frequency
1560-1 G10
Dynamic Range
4
THD + Noise vs Input Frequency
–52
f
= 500kHz
CUTOFF
–54
–56
–58
–60
–62
THD (dB)
–64
–66
–68
–70
–72
40
60 100
80
INPUT FREQUENCY (kHz)
120
VIN = 1V
RMS
S/N = 74dB
VIN = 0.6V
S/N = 69.5dB
160
140
RMS
180
1560-1 G14
200
THD + Noise vs Input Frequency
–52
f
= 1MHz
CUTOFF
–54
–56
–58
–60
–62
THD (dB)
–64
–66
–68
–70
–72
40
60 100
80
120
INPUT FREQUENCY (kHz)
140
VIN = 1V
S/N = 72dB
VIN = 0.6V
S/N = 68dB
160
RMS
RMS
180
1560-1 G15
200
Page 5
UUU
PIN FUNCTIONS
G
ND (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 0.1µF 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-
LTC1560-1
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.
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.
V
(Pin 8): The filter output pin can sink or source 1mA.
OUT
The total harmonic distortion of the filter will degrade
when driving coaxial cables or loads less than 10k without
an output buffer.
+
V
10k
0.01µF1µF
SYSTEM GROUND DIGITAL GROUND
Figure 1. Connections for Single Supply Operation
10k
ANALOG GROUND PLANE
0.01µF0.1µF
1
GND
2
V
V
IN
3
4
IN
LTC1560-1
GND
–
V
0.5f
V
OUT
SHDN
V
C/fC
+
PLANE
8
7
6
5
V
GND OR V
1560-1 F01
OUT
+
5
Page 6
LTC1560-1
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WUU
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
JP1
JUMPER
3
2
1
U1
LTC1560-1
1
V
IN
E1
TP
–5V
E2
TP
C3
1µF
16V
X7R
C2
0.22µF
C1
0.01µF
GND
2
V
IN
3
GND
4
–
V
SHDN
0.5f
V
OUT
C/fC
8
7
6
+
V
5
C4
0.01µF
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
R1
1k
S1
GS01MSCKE
S2
GS01MSCKE
–
2
LT1360CS8
3
+
C9
0.01µF
7
U2
6
4
C7
0.01µF
C5
0.22µF
C10
1µF
25V
Y5V
C8
1µF
25V
Y5V
C6
1µF
16V
X7R
OUT2
15V
OUT1
–15V
5V
GND
GND
GND
E3
TP
E4
TP
E5
TP
E6
TP
E7
TP
E8
TP
E9
TP
E10
TP
1560-1 F02
6
Figure 2. Demo Board 135A Connection Diagram
GROUND
+5V FILTER SUPPLY
GROUND
–5V FILTER SUPPLY
UNBUFFERED OUTPUTFILTER INPUT
BUFFERED OUTPUT
GROUND
+15V BUFFER SUPPLY
–15V BUFFER SUPPLY
1560-1 F03
Figure 3. Demo Board 135A Layout
Page 7
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FREQUENCY (kHz)
0.1
–60
GAIN (dB)
–50
–40
–30
–20
–10
1 10 100 1000 10,000
1560-1 TA10
–70
–80
–90
–100
–110
0
10
TYPICAL APPLICATIONS N
Augmenting the LTC1560-1 for Improved Delay Flatness
LTC1560-1
–5V
0.1µF
5V
–
1/2 LT1364
+
–5V
40.2k
8
4
0.1µF
7
0.1µF
49.9Ω
V
OUT
1560-1 TA05
20k
22pF
9.75k
1
GND
V
IN
2
3
4
0.01µF
V
IN
LTC1560-1
GND
–
V
0.5f
V
OUT
SHDN
C/fC
8
7
6
+
V
5
6.49k
(OR –5V)
0.1µF
22pF
5V
0.01µF
2
–
1/2 LT1364
3
+
6.65k
1
6
5
2-Level Eye Diagram of the Equalized Filter
1
GND
V
V
IN
LTC1560-1
GND
–
V
SHDN
0.5f
C/fC
OUT
+
V
560pF
V
IN
0.01µF
2
3
4
0.1µF
6
–
1/2 LT1364
5
+
1560-1 TA06
23.7k
1560-1 TA09
2Mbps/s
5V
0.1µF
1k
8
39pF
7
(OR –5V)
6
0.1µF
5
0.01µF
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.
3
+
1/2 LT1364
2
–
8
1
4
0.1µF
–5V
560pF
560pF 560pF
2.61k
Gain vs Frequency1MHz Lowpass Filter Cascaded with a 30kHz 3rd Order Highpass Filter
7
7
Page 8
LTC1560-1
TYPICAL APPLICATION
U
A Simple Highpass/Lowpass Filter
1
300pF
300pF
V
IN
8.1k
–5V
0.1µF
2
3
4
0.01µF
GND
V
IN
LTC1560-1
GND
–
V
0.5f
V
OUT
SHDN
C/fC
8
7
6
+
V
5
PACKAGE DESCRIPTION
Measured Frequency Response
(OR –5V)
0.1µF
15V
0.1µF
1k
5V
0.01µF
3
2
+
–
LT1360
–15V
7
8
V
OUT
4
0.1µF
1560-1 TA07
10
0
–10
–20
–30
–40
GAIN (dB)
–50
–60
–70
–80
–90
20 100 1000
U
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
FREQUENCY (kHz)
10000
1560-1 TA08
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
*
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
× 45°
0.016 – 0.050
0.406 – 1.270
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
(0.355 – 0.483)
0.014 – 0.019
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
0.228 – 0.244
(5.791 – 6.197)
7
8
1
2
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1360/LT1361/ 50MHz, 800V/µs Op Amp(s) Single/Dual/Quad C-LoadTM Op Amps
LT1362
LTC1562 Active RC Quad Universal Filter Very Low Noise, Low Distortion
C-Load is a trademark of Linear Technology Corporation
5
6
0.150 – 0.157**
(3.810 – 3.988)
SO8 0695
3
4
8
Linear Technolog y 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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